Fermentation control in baker’s yeast production

Fermentation Control in Baker’s Yeast Production:Mapping PatentsPierre Gelinas

Abstract: During baker’s yeast manufacturing, the fermentation process must be thoroughly controlled. This review ofthe patent literature provides new information on the early development of industrial fermentation processes. As shownby a review of 199 patents filed between 1900 and 2009, inventors in this field were mainly interested to improve yeastyields through the control of infection and sugar concentration in the growth media. Contrary to common belief, muchattention was also given to continuous culture processes, involving addition and withdrawal of growth media. Thesetechnologies were mainly developed in about 30 y, between 1910 and 1939. In the recent years, inventors gave sustainedattention to the fine tuning of fermentation control, mainly the rapid determination of yeast fermentation by-products inthe exhaust to get rapid feedback on the rate of sugar addition in the fermentation tank. Improved fermentation controlbenefited much the baking industry because baker’s yeast had higher gassing power and was cheaper. However, some ofthese key patents on baker’s yeast technology were later declared invalid in court because it had little intellectual propertyvalue. In the baker’s yeast trade and other sectors, this situation might have encouraged trade secrets while reducing thecredibility of innovative ideas disclosed in the patent literature.

Keywords: baker’s yeast, bread, fermentation control, patents, sugar

IntroductionBaker’s yeast production is one of the oldest food biotechnolo-

gies and may be considered as a “ripened technology.” At theturn of the 20th century, the baker’s yeast industry had developedindependently from distilleries where high alcohol yield gave lit-tle yeast biomass. During the golden age of modern baker’s yeastmanufacturing, from 1910 to 1940, much effort was put in to findthe best and cheapest growth media available (Gelinas 2012). Inaddition, much interest was given to the control of both infectionand sugar concentration in such sugar-rich growth media to in-crease biomass yields and reduce costs. However, little informationhas been published on the development of these critical aspectsof baker’s yeast manufacturing. Part of this situation may be at-tributed to the fact that much technical information is disclosedin trade secrets.

The objective of baker’s yeast manufacturing is to harvest as fastas possible the highest amount of living cell mass at the lowestcost. First, fermentation tanks must be seeded with the strongestand purest microbial starters, otherwise unwanted microorganismswill be harvested instead; both the gassing power and the keep-ing properties of the concentrated yeast biomass will be reduced.Second, such microorganisms must be fed under thoroughly con-trolled conditions to optimize yeast biomass and gassing power,

MS 20140954 Submitted 6/2/2014, Accepted 6/18/2014. Author is with theFood Research and Development Centre, Agriculture and Agri-Food Canada, Saint-Hyacinthe, Quebec, Canada J2 8E3. Direct inquiries to author Gelinas (E-mail:[email protected]).

enough to raise dough, otherwise bakers will experience varia-tions in bread volume. Major steps of baker’s yeast manufacturing,including fermentation control, have been described in Gelinas(2006).

Searching the patent literature is an original way to follow theevolution of specific technologies. This study is a follow-up andcompanion to reviews of the early patent literature from the 19thcentury (Gelinas 2010a), growth media (Gelinas 2012), strains andspecialty ingredients (Gelinas 2009), and yeast management at thebakery plant (Gelinas 2010b). In addition, this study provides someinsight on the true value of patenting activity. For example, prob-lems with double-patenting have been stressed in a companionpaper (Gelinas 2012). This review suggests that, although they hadpreviously been accepted by patent examiners, key patents on fer-mentation control in baker’s yeast production were judged invalidin justice courts for want of invention.

The objective of this review was to study the evolution of fer-mentation control for baker’s yeast production based on patentingactivity. The main objective of such fermentation control was toimprove yield and reduce the cost of commercial baker’s yeast.These technologies were instrumental to the large-scale manufac-turing of high-quality bread.

PatentsBackground information and search criteria

This review is based on the concept of patent families,which combines closely related patented inventions granted be-tween 1900 and 2009 (Gelinas 2012). In addition to grantedpatents, specifications of 5 nonaccepted patents were found and

C© 2014 Her Majesty the Queen in Right of CanadaJournal of Food Science C© 2014 Institute of Food Technologists®

Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

doi: 10.1111/1541-4337.12107 Vol. 13, 2014 � Comprehensive Reviews in Food Science and Food Safety 1141

Fermentation control and baker’s yeast . . .

cited: GB 191007640; GB 191023662; GB 191417009;GB146947; GB 230050. For those not familiar with the patent lit-erature, letter codes correspond to the country where patents werefiled; in the case cited above, patents filed in Great Britain with anapplication date earlier than 1916 had numbers that included theyear of application and the serial number.

For the sake of clarity and simplicity, patents are presented ac-cording to the “priority date.” This corresponds to the filing dateexcept for German patents where the priority date in the publica-tion (“Patentiert vom”) was 1 d later than the “convention date”(filing date) cited in foreign patents. Further details on patents andsearch criteria may be found in Gelinas (2010a, 2012).

Evolution of Patenting Activity According to YearNumber of patents

Table 1 presents the evolution in the number of patent appli-cations filed on the control of fermentation during baker’s yeastproduction. Overall, 225 patents were found, including 26 filedbefore the year 1900 as reported in Gelinas (2010a).

The most important patenting activity was on the control ofsugar concentration in growth media, with 52 patents. That num-ber does not include 38 patents on related inventions on addition-withdrawing of growth media, also called “continuous culture.”Interest of the inventors was similar for seed production and in-fection control during fed-batch fermentation, respectively, with38 and 36 patents. To a lesser extent, some interest was given tonitrogen concentration (26 patents), final conditioning steps (23patents), and temperature control (12 patents).

Compared to patents on growth media for baker’s yeast (Gelinas2012), interest in the control of fermentation parameters camelater, around 1910 rather than 1875; it also lasted for 30 y (1910to 1939) instead of about 70 y (1875 to 1944). For both sub-jects, there was a major drop of patenting activity after 1939. Thisconfirms that selection of growth media and fermentation controlfor baker’s yeast were ripened technologies around that period,enough to be commercially viable for supplying the large-scalebaking industry. This might have been partly caused by the begin-ning of World War II (1939 to 1945) in Europe, although WorldWar I (1914 to 1918) did not appear to have a major negativeeffect on patenting activity (Table 1). As discussed later, there isa possibility that lawsuits dismissing key patents in baker’s yeasttechnology discouraged patent filing in this sector. After 1940, in-ventors showed some interest in the control of sugar concentrationthrough ethanol analyses and, to a lesser extent, infection controland conditioning.

InventorsCountry of origin

Table 2 indicates that German inventors were the most activewith 53 patents, although this number did not include 8 patentapplications by citizens from the German Democratic Republicfiled between 1950 and 1990. These trends confirm those seen foryeast growth media (Gelinas 2012). For both topics (media andfermentation control), patenting activity from Germany peakedaround 1930 to 1934. As was the case for patents on yeast growthmedia (Gelinas 2012), German inventors filed patents in foreigncountries, contrary to U.S. inventors that rarely protected inven-tions outside their own country (data not shown). With 50 patents,or about as many as German inventors, citizens from the UnitedStates and, in particular from the Fleischmann/Standard Brandsgroup, were also very active inventors on fermentation control forbaker’s yeast and their peak activity was around 1925 and 1934.

Except for citizens from Germany and the United States, themost active inventors on fermentation control in baker’s yeastproduction came from France, Japan, Great Britain, Denmark,and Austria. However, among the latter, only Japanese inventorsappeared to show a more recent interest in these technologies, es-pecially those related to the control of sugar concentration duringfermentation.

CompaniesAbout one-half of the patents on yeast fermentation control

were owned by companies or research institutes. This representsa higher proportion than for growth media (about 35%), whichconfirms the economical importance of this subject. Overall, 62companies were interested in getting intellectual property rightson fermentation control for baker’s yeast production. However,according to Table 3, only 12 companies had more than 3 patents,which is about the same as growth media (Gelinas 2012). Thissuggests that the development of both growth media and fermen-tation control was of interest to only a handful of manufacturersthat took control of those topics in the early years of the develop-ment of modern baker’s yeast manufacturing.

As for growth media, the Fleischmann/Standard Brands groupwas the most active with not less than 17 patents on fermentationcontrol. This does not include 3 patents held by the Interna-tional Yeast Co., based in London, and 1 patent filed in 1984by Nabisco Brands, Inc., these companies also being affiliatedwith the same group. As described later, 16 more patents by theFleischmann/Standard Brands group were also obtained under li-cense agreements with various inventors from Europe, includinga German research institute, Verein der Spiritus-Fabrikanten inDeutschland.

LicensesWhen searching the patent literature, it may be difficult to de-

termine inventorship. Especially before 1950, some patents werefiled under different names in different countries (Gelinas 2012). Insome cases, it may be very difficult to trace back the true inventor,the one who was the first to file in patent offices the specifica-tions describing the invention. Some inventions were assigned todifferent applicants, probably in exchange of money, which corre-sponded much to a license. Thorough reading of patent claims isessential to determine or distinguish inventorship from licensees.

According to Table 4, 24 basic patents produced 28 licenseson fermentation control, which is similar to the 21 licenses ongrowth media (Gelinas 2012). In general, most of the licenseswere negotiated between established companies, except in a fewcases where individuals appeared to have sold the rights of their in-ventions. Contrary to patents on growth media where 10 obscurelicense cases were found (no proper citation of the basic patent),no double-patenting situation was found, so each patent specifica-tion corresponded to a license that properly cited the priority file,the first to describe the basic invention. The industrial group con-sisting of The Fleischmann Co. and Standard Brands Inc. (U.S.A.)had the largest share of such licenses (16 over 28) and, around thatperiod, also owned the rights for 3 more patented inventions thatwere licensed to The International Yeast Co. Ltd (Great Britain).Vereinigte Mautner’sche Presshefe-Fabriken G.m.b.H. (Austria)had 4 licenses. For growth media applications, the companies fromthe United States and Austria, respectively, had 5 and 1 licenses(Gelinas 2012).

Table 4 shows that most of the licenses were on the con-trol of sugar concentration as part of the continuous process

1142 Comprehensive Reviews in Food Science and Food Safety � Vol. 13, 2014 C© 2014 Institute of Food Technologists®


Table 1–Categories of patents on fermentation control in baker’s yeast production according to filing date.a

Year Seed Infection Temperature Sugar Continuous culture Nitrogen Conditioning Total

1870 to 1874 1 11875 to 1879 1 1 1 31880 to 1884 1 11885 to 1889 3 3 1 71890 to 1894 2 1 2 51895 to 1899 5 3 1 91900 to 1904 2 5 1 81905 to 1909 1 2 1 2 61910 to 1914 4 3 1 1 3 1 131915 to 1919 3 3 1 6 2 4 1 201920 to 1924 2 3 2 6 2 151925 to 1929 1 2 2 6 9 6 3 291930 to 1934 3 1 3 5 6 3 2 231935 to 1939 1 1 1 3 2 2 1 111940 to 1944 2 1 2 1 61945 to 1949 2 1 3 1 71950 to 1954 1 2 2 1 61955 to 1959 1 3 1 3 81960 to 1964 1 1 1 31965 to 1969 1 1 2 1 51970 to 1974 2 1 1 41975 to 1979 1 2 1 41980 to 1984 1 6 2 1 101985 to 1989 1 1 2 1 51990 to 1994 4 41995 to 1999 1 1 3 52000 to 2004 3 1 42005 to 2009 1 1 1 3Subtotal (before 1900) 10 8 1 3 0 0 4 26Subtotal (1900 to 2009) 28 28 11 49 38 26 19 199Total 38 36 12 52 38 26 23 225aPatents prepared by the same inventor and representing variations or improvements of the same invention were combined into a single patent for invention. Information on patents filed before 1900 wasadapted from Gelinas (2010a).

Table 2–Country of origin of inventors on fermentation control in baker’s yeast production according to filing date of patents.

Year DE US FR JP GB DK AT DD CS BE HU NL SE RU Others Total

Before 1900a 6 4 5 3 3 1 3 1 261900 to 1904 3 3 1 1 81905 to 1909 3 2 1 61910 to 1914 3 2 1 2 3 1 RO 131915 to 1919 6 5 2 2 2 1 1 CH 201920 to 1924 2 5 1 1 5 AU 151925 to 1929 5 11 1 1 4 3 1 1 1 YU 291930 to 1934 10 8 2 2 1 231935 to 1939 2 5 2 1 AU 111940 to 1944 4 1 1 61945 to 1949 3 1 1 2 71950 to 1954 1 1 2 1 1 61955 to 1959 1 3 3 1 81960 to 1964 1 1 1 31965 to 1969 1 1 1 2 51970 to 1974 1 1 1 1 41975 to 1979 4 41980 to 1984 2 5 3 101985 to 1989 1 2 1 1 51990 to 1994 1 2 1 41995 to 1999 1 1 1 1 IE 52000 to 2004 1 1 1 1 42005 to 2009 1 2 3Total 53 50 23 17 16 15 14 8 6 4 4 4 3 2 6 225aThese data were partly adapted from Gelinas (2010a).Based on Recommended Standards of the World Intellectual Property, the following 2-letter codes for the representation of States have been used for patent numbers and country of origin of inventors: AT,Austria; AU, Australia; BE, Belgium; CH, Switzerland; CS, Czechoslovakia; DD, German Democratic Republic; DE, Germany; DK, Denmark; FR, France; GB, Great Britain; HU, Hungary; IE, Ireland; JP, Japan; NL,Netherlands; RO, Romania; RU, Russia; SE, Sweden; US, United States of America; YU, Yugoslavia. For patents with inventors from different countries, only the country of the 1st inventor was considered.

(8) or not (9); to a lesser extent, some interest for licenses wasseen for nitrogen control (4), seed production (3), infection con-trol (2), and temperature control (2). This is also a clear indi-cation of the importance that the yeast industry gave to thesematters.

With Friedrich Hayduck (1880 to 1961) as the inventor, Vereinder Spiritus-Fabrikanten in Deutschland (Berlin, Germany) wasthe most active group to license; these 5 applications were filedon the same day (October 30, 1920) and assigned only in the

United States and Canada to The Fleischmann Co. For fermen-tation control during baker’s yeast production, licenses were filedbetween 1919 and 1947 (with peaks between 1919 to 1920 and1932 to 1935) from patented inventions originally filed between1915 and 1943. This confirms that, over 30 y, improvements ofthe control of fermentation were major concerns for the industry,which corresponds to the golden age of modern yeast technologythat truly began in 1910 to 1915 and ended around 1947, shortlyafter World War II.

C© 2014 Institute of Food Technologists® Vol. 13, 2014 � Comprehensive Reviews in Food Science and Food Safety 1143


Table 3–List of the major industrial assignees on fermentation control in baker’s yeast production for patents filed between 1900 and 2009.

Assignee (city, country) Application (filing year)

Akademie der Wissenschaften der DDR (Berlin, Deutsche Democratic Republic) Infection (1984); sugar (1984, 1985); continuous culture (1983)Aktieselskabet Dansk Gaerings-Industri (Copenhagen, Denmark); Aktieselskabet

de Danske SpritfabrikkerSugar (1919; 1919; 1946; 1954); continuous culture (1936; 1947)

Kanegafuchi Chemical Ind. (Osaka, Japan); Kanegafuchi Kagaku Kogyo KabushikiKaisha

Seed production (2006); infection (1979); sugar (1978; 1982;1992); continuous culture (1976)

Mellemeuropaeisk Patent-Financierings-Selskab Aktieselskab (CopenhagenDenmark)

Seed production (1924); nitrogen (1924); conditioning (1923)

Oriental Yeast Co., Ltd. (Tokyo, Japan); Oriental Yeast Co., Ltd., and Marubishi RikaSochi Kenkyusho

Sugar (1967; 1976; 1980; 1995); conditioning (1986)

Pfeifer & Langen Akt.-Ges. (Cologne, Germany); Rheinischer Actien-Verein furZuckerfabrikation (Dormagen, Germany), a joint-company

Nitrogen (1924; 1933); conditioning (1929)

Rheinischer Actien-Verein fur Zuckerfabrikation; see Pfeifer & Langen Akt.-Ges.Standard Brands Inc. (Dover, Del., USA); see also The Fleischmann Co.; does not

include 1 patent in 1984 by Nabisco Brands, Inc. on continuous cultureSeed production (1932); temperature (1926); continuous culture

(1925; 1927); nitrogen (1921; 1923; 1927; 1931; 1934);conditioning (1932, 1970)

The Distillers Co. (Yeast) Ltd. (London; Morden, Surrey, Great Britain); The DistillersCo. Ltd. (Edinburgh, Scotland, Great Britain)

Seeding conditions (1968); infection (1926); sugar (1954);continuous culture (1926; 1957; 1957; 1957); conditioning(1968)

The Fleischmann Co. (New York, U.S.A.); see also Standard Brands Inc. Continuous culture (1924; 1924; 1925); nitrogen (1919; 1919);conditioning (1925)

The International Yeast Co. Ltd. (London, England) Temperature (1938); nitrogen (1938); continuous culture (1927)Verein der Spiritus-Fabrikanten in Deutschland (Berlin, Germany) Seed production (1915); infection (1900; 1915); sugar (1915);

continuous culture (1915), nitrogen (1915)Wirtschaftliche Vereinigung der Deutschen Hefeindustrie (Berlin, Germany) Continuous culture (1930; 1932; 1932)

Disputing Validity of PatentsContrary to growth media for which infringement of patents

appeared to be less important or more difficult to spot, there weremajor suits in justice courts to truly protect patented inventionson the control of fermentation during baker’s yeast manufacturing.Again, this is an indication to the commercial importance of thismatter for the baker’s yeast industry in the United States.

Table 5 (left column) shows a list of 7 patents on fermentationcontrol during baker’s yeast manufacturing that have been con-tested in courts of the United States. In 1923, when they weregranted, most of these patents were recognized as critical issues inthe development of modern yeast manufacturing, because it wasconsidered that these inventions improved much the yield, cost,and overall quality of the baker’s yeast. During that period, thelatter patented “inventions” appeared to have found major andwidespread applications in the industry, leading to infringementsof the owner’s rights.

Between 1925 and 1930, the first cases were held in court tocontest the validity of 5 patents owned by The Fleischmann Co.,which became Standard Brands Inc. in 1929. These patents werelicenses of German patents originally filed in 1915 by FriedrichHayduck. The defendant was Federal Yeast Corp. (Baltimore,Md.). In courts of the State of Maryland, all 5 patents were con-sidered valid and 4 of them were judged infringed. Costs wereestablished at $92,000 for events between October 1923 and July1926. In a court judgment on U.S. patent 1449103 (District CourtMaryland 1930a), it was estimated that, between 1923 and 1926,The Fleischmann Co. dominated the yeast industry in the UnitedStates with 11 manufacturing plants producing not less than 90%of the yeast consumed in the United States or about 1000 millionspounds annually. Producing about 9 to 12 million pounds of yeastannually, one of the biggest competitors of The Fleischmann Co.was The Liberty Co., which was acquired in 1925 by the former.One of the manufacturers sued by The Fleischmann Co. was TheFederal Yeast Corp., which produced less than 1 million poundsannually. These smaller yeast manufacturers sold yeast at a lowerprice than The Fleischmann Co., 18 to 22 cents compared to 25to 28 cents a pound, respectively.

However, between 1937 and 1939, these court decisions weredismissed in later cases involving Standard Brands Inc. and anothercompany, National Grain Yeast Corp. Now judged in the Stateof New Jersey, the issues involved 3 of the patents previouslyjudged valid in the State of Maryland (US 1449103, 1449105,and 1449106) and 2 other patents (US 1449109 and 1673735).Finally, all these patents were ruled as invalid by the judge. Inaddition, the rights for the first 3 patents were invalidated bythe U.S. Supreme Court. In essence, most of these patents wereinvalidated because of lack of invention due to similarities with aGerman patent, DE 10135, filed in 1879 by Jacques Rainer. Thelatter described a technique to feed progressively yeast starters withnutrient solutions (Gelinas 2010a).

Based on the 7 court case decisions, inventors experienced ma-jor difficulties to protect the intellectual property of key patentsin baker’s yeast technology. Despite the commercial importanceof patents under litigation, very few “inventions” were truly newand patentable. After the negative judgment by the U.S. SupremeCourt on the value of these major patents, baker’s yeast man-ufacturers saw less benefit in patent protection and some mighthave preferred not to disclose publicly their inventions. After 1939,there was a major drop in patenting activity on baker’s yeast manu-facturing in general and also by the Fleischmann/Standard Brandsgroup. Overall, this industrial group filed 49 patents in the UnitedStates on baker’s yeast growth media (Gelinas 2012) and fermen-tation control: 27 inventions + 22 licenses. As shown in Fig-ure 1, most of these patents were filed between 1915 and 1939; in1896, Charles Fleischmann himself also obtained 1 license (Gelinas2010a). It is likely that, after the judgment by the U.S. SupremeCourt in 1939, the above dismissed court cases discouraged Stan-dard Brands, and possibly others also, to patent-protect their newideas because their true novelty aspects might be too difficult toprove.

Criteria for judging novelty aspects were higher for judges ofcourts than patent examiners, who certainly questioned the truevalue of patents and stressed the limits and potential deficiencies ofthe reviewing process of patent applications. This situation high-lights the care required when drafting patent specifications that



Table 4–Cases of licenses (1900 to 2009) in which several patent applicants claimed the same invention on fermentation control in baker’s yeastproduction, with proper citation of the priority file.a

Priority date Inventor or first to file; patent nr. Licensee; patent nr. Subject

January 16,1915

Wohl and Scherdel; DE 310580 (and otherpatents)

The Fleischmann Co.; US 1475215; filed August 31, 1921 Nitrogenconcentration

February 25,March 16,March 20,April 16,and April24, 1915

Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 300663; DE 303251; DE303222; DE 304242; DE 304243; andother FR and GB versions

The Fleischmann Co.; US 1449102(CA 221756); US1449103, invalid (CA 238175); US 1449106, invalid (CA238178); US 1449110 (CA 238179); US 1449109,invalid (CA 238180); filed October 30, 1920

Nitrogenconcentration

March 17,1915

Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 300662 (GB 155284)

The Fleischmann Co.; US 1449105, invalid; CA 238172;filed October 30, 1920

Sugar concentration

April 1 and 13,1915

Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 303221; DE 304241

The Fleischmann Co.; US 1449107 (CA 238173); US1449108 (CA 238174); filed October 30, 1920

Continuous culture

May 8, 1915 Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 303253 (GB 155288)

The Fleischmann Co.; US 1449112; CA 238181; filedOctober 30, 1920

Infection control

December 24,1915

Hayduck; Verein der Spiritus-Fabrikanten inDeutschland; DE 303311 (FR 520523)

The Fleischmann Co.; US 1449111; US 15716, Reissue; CA238181; filed October 30, 1920

Seed production

July 5, 1919 Sak; Aktieselskabet Dansk Gaerings-Industri;DK 28507(GB 153667; FR 515704; CH90954; FI 8842; CA 215671)

#1. Vereinigte Mautner’sche Presshefe-FabrikenGesellschaft m.b.H., and Eugene Fould-Springer; AT102274; AT 105785; filed September 20, 1919

Sugar concentration

#2. The Fleischmann Co.; US 1566431; CA 237963; filedDecember 14, 1920

July 15, 1919 Aktieselskabet Dansk Gaerings-Industri; NO39412 (SE 56428; FR 503808; CH 94210;NL 8737; GB146947, not accepted; AT

#1. Vereinigte Mautner’sche Presshefe-FabrikenGesellschaft m.b.H., and Eugene Fould-Springer; AT105784; filed September 20, 1919

Sugar concentration

105784; CA 209947); FR 503810 (CH94210; CA 209948)

#2. The Fleischmann Co.; CA 237961; CA 237962; filingdate unknown

March 3, 1924(DE)

Hamburger and others; MellemeuropaeiskPatent-Financierings-Selskab Aktieselskab;GB 230051 (DK 35550; FR 593128; CA258456)

Standard Brands Inc.; US 1733962; filed November 11, 1924 Nitrogenconcentration

August 16,1924

Corby and Buhrig; The Fleischmann Co.; US1673735, invalid; US 1730876

The International Yeast Co. Limited; GB 238554 (FR603956; DE 583760); GB 252193 (FR 627701; DE499506); filed August 13, 1925

Continuous culture

October 6,1925

Harrison; Standard Brands Inc.; US 1761789 The International Yeast Co. Limited; GB 259572; filedOctober 5, 1926

Continuous culture

May 4, 1926 Meyer; The Distillers Co. Limited; GB 275328 The Fleischmann Co.; US 1724952; filed April 30, 1927 Continuous cultureJune 8, 1927 Jacobsen; DK 42808 Standard Brands Inc.; US 1752003; filed May 28, 1928 Continuous cultureMay 1, 1929 Meyer; The Distillers Co.; GB 334502 (FR

689238; DK 43822)Standard Brands Inc.; US 1938081; filed May 3, 1930 Infection control

October 22,1929

Jellinek; Vereinigte Mautner-Markhof’schePresshefe Fabriken und

#1. Arthur Koenig (from Germany); DK 46078; filed August13, 1930

Sugar concentration

Aktien-Gesellschaft Ignaz Kuffner & JacobKuffner fur Bauerei, Spiritus- undPresshefefabrikation Ottakring-Dobling;AT 130438 (FR 704113; GB 354118;US1920395)

#2. Hefefabriken A.-G.; CH 153184; filed October13, 1930

July 28, 1931 Daranyi; Invention Gesellschaft furVerwaltung und VerwertungChemischtechnischer Patente G.m.b.H.; GB376038

#1. Jointly licensed to: (1) Vereinigte Mautner Markhof’schePresshefe Fabriken und Aktien-Gesellschaft Ignaz Kuffner& Jacob Kuffner fur Brauerei, Spiritus-undPresshefefabrikation Ottakring-Dobling (Vienna), (2)Erste Ober-Osterreichische Spiritus- & PresshefefabrikJosef Kirchmeir & Sohn (Urfahr-Linz), and (3) BruderReininghaus Aktien-Gesellschaft fur Brauerei undSpiritus-Industrie (Graz-Steinfeld); AT 145684; filed July28, 1932

Continuous culture

#2. Moskovits; DE 659951; filed July 29, 1932January 26,

1932Kirby and Frey; Standard Brands Inc.; US

2029572The International Yeast Co. Limited; GB 390114; filed

December 20, 1932Seed production

March 11,1932

Wirtschaftliche Vereinigung der DeutschenHefeindustrie; DE 618021

Aktien-Gesellschaft Ignaz Kuffner & Jacob Kuffner furBrauerei, Spiritus- und PresshefefabrikationOttakring-Dobling, Aktiengesellschaft fur Spiritus- undPresshefe-Industrie Wolfrum, M. Fischl’s Sohne, andVereinigte Mautner Markhof’sche Presshefe Fabriken; AT141399; filed March 10, 1933

Continuous culture

March 3, 1933 Stich; GB 411611 Standard Brands Inc.; CA 371677; filing date unknown Sugar concentrationMarch 10,

1933Knappe (1937); DE 614753 Brandstrup (from Norway); DK 51473; filed March 8, 1934 Temperature

November23,1934

Effront and Popper; FR 794359 Standard Brands Inc.; US 2083598; filed November 23, 1935 Seed production

February 9,1938

Meyer; The International Yeast Co. Limited;GB 502762

Standard Brands Inc.; US 2214028; filed February 3, 1939 Nitrogenconcentration

December 22,1938

Meyer and Chaffe; The International YeastCo. Limited; GB 523019

Standard Brands Inc.; US 2304471; filed December 8, 1939 Temperature

February 5,1943

Berkel; DE 767347 Aktiengesellschaft Jungbunzlauer Spiritus- und ChemischeFabrik; AT 164248; filed June 10, 1947

Sugar concentration

aWhen identical versions of the same “basic patent” were issued in several countries, patent numbers are given in parentheses and without reference to the publication year. Identification of the country codes isgiven in Table 2.



Table 5–Patents on fermentation control in baker’s yeast production owned by The Fleischmann Co. or Standard Brands Inc., and contested in U.S.justice courts.

Patent nr.; inventor (publication year); details Court case; datea Decision

US 1449103; Hayduck (1923); nitrogen concentration; Case #1; May 9, 1925 Valid and infringedif excessive acidity is neutralized with inorganic Case #2 (Appeal); June 8, Valid and infringed; if other workers had known Hayduckammonium salts and others, yeast grows faster in an 1926 process, they would have made prompt use of itall-sugar medium such as molasses and others, and its Case #3. February 10, 1930 Valid and infringed; damages were set at $92,000quality is improved (fermentation power and keeping Case #5. October 29, 1937 Valid and infringed only for the specific use of aquaproperties) ammonia (not ammonium lactate and di-ammonium

phosphate)Case #6 (Appeal); February 1,

1939Invalid for want of invention over the prior art; it was

known that yeast growth was stimulated byneutralizing the deleterious effect of acid by antacid;this old principle was applied to yeast manufacturing

Case #7 (Supreme Court);November 6, 1939

Invalid for want of invention over the prior art;neutralization of acids was the application of an oldprinciple with no change in the manner of application

US 1449127; Nilsson and Harrison (1923); nitrogen Case #1; May 9, 1925 Invalid because claims are equivalent to US 1449103concentration; aqua ammonia may be used to described aboveneutralize excessive acidity in combination with Case #2 (Appeal); June 8, Valid and infringedammonium phosphate (nutrient) 1926

US 1449102; Hayduck (1923); nitrogen concentration;excessive acidity is controlled with dilution ratherthan neutralization described in US 1449103

Case #4; February 10, 1930 Valid but not infringed

US 1449105; Hayduck (1923); sugar concentration; Case #4; February 10, 1930 Valid and infringed, despite similarities with a patentdilute medium is slowly supplemented with medium of filed in 1879 by Rainerhigher concentration Case #5; October 29, 1937 Invalid because claims are indefinite, vague, and

uncertainCase #6 (Appeal); February 1,

1939Invalid because claims are too vague and indefinite; it is

a mechanical improvement over the prior art mainlydescribed in 1879 by Rainer because it does notascertain the times and manner in which theconcentrated nutrient solution is to be added


Invalid for want of sufficient disclosure (too vague andindefinite); regulated rate of feeding is no more than amechanical improvement over the prior art

US 1449106; Hayduck (1923); sugar concentration; Case #4; February 10, 1930 Valid and infringedcombines disclosures of US 1449103 (neutralization) Case #5; October 29, 1937 Invalid for want of invention over the prior art and basedand US 1449105 (dilution) on US 1449105 which is invalid

Case #6 (Appeal); February 1,1939

Invalid for want of invention and based on US 1449103and US 1449105 which are invalid


Invalid for want of novelty; process is the combination ofUS 1449103 and US 1449105 which are invalid

US 1449109; Hayduck (1923); nitrogen concentration; Case #5; October 29, 1937 Invalid for want of invention compared to US 1449103acid is neutralized with ammonium sulfate Case #6 (Appeal); February 1, Invalid for want of invention; ammonium salts have been

1939 mentioned in other patentsUS 1673735; Corby and Buhrig (1928); sugar Case #5; October 29, 1937 Invalid for want of novelty

concentration; similar to US 1449105 and US Case #6 (Appeal); February 1, Invalid for want of novelty compared to US 14491051449106 except that portion of the growth medium 1939 and 1449106is withdrawn during propagation

aFor sake of clarity, justice court cases are cited as follows:Case #1. District Court of Maryland (1925);Case #2. Circuit Court of Appeals (1926);Case #3. District Court of Maryland (1930a);Case #4. District Court of Maryland (1930b);Case #5. District Court of New Jersey (1937);Case #6. Circuit Court of Appeals (1939);Case #7. U.S. Supreme Court (1939).

truly show novelty aspects compared to prior art (Roberts 2007;Ohly 2008).

In conclusion, drop of patenting activity by the most active in-dustrial in the baker’s yeast industry between 1920 and 1940 mightreflect the artisanal nature of this industry around that period. Didnegative justice court decisions discourage this manufacturer andothers to protect their innovative ideas through patents? This wascertainly not an encouragement to privilege patent filing withcomplete written disclosure of their innovative ideas. In all casesdismissed in justice courts of the United States, patents under liti-gation were not developed by the company but they were ratherlicensed from original German inventions. According to Khan(2005), such rudimentary innovations might be better protectedby trade secrets, as was the case for chocolate composition orproduction. This appeared to be the case for fermentation controlin baker’s yeast production, around 1910 to 1940, the golden age of

the development of this industry that was nevertheless of artisanalnature. This also applied to a large share of patented inventions ongrowth media, which had little commercial value, except for mo-lasses treatment (Gelinas 2012). The risk of reverse engineering iscritical when determining patent or trade secret protection, espe-cially when technology is changing rapidly (Daizadeh and others2002; DuPre and Smith 2011). This appears to have been thecase with several of the early patented inventions on fermentationcontrol in baker’s yeast production.

Seed (Pure Yeast)Table 6 to 9 present patents related to seed yeast. This includes

processes for the preparation of pure yeast starters. Only a fewinventions were patented on the long-term management or keep-ing conditions of yeast starters (Table 6). Much more interest wasgiven to growth conditions, in particular, the acclimatization of



0

2

4

6

8

10

12

14

Licenses

Patents

Figure 1–Number of patents and licenses filed by the Fleischmann/Standard Brands group on growth media (Gelinas 2012) and fermentation controlin baker’s yeast production.

Table 6–Patents published between 1900 and 2009 on seed preservation for the production of baker’s yeast.a

Inventor (publication year); priority date Country Patent nr. Details

Burmann (1917); September 15, 1916 CH CH 74939 A tube or small container contains sterile and solidified media (gelatinemixed with nutritive broth) and is seeded with pure yeast; for keepingand sending pure seed cultures

Hublot and Vallet (1961); August 9, 1960 FR FR 1272116 (BE605492)

To improve its long-term preservation (18 mo), yeast cultures are storedinto plastic packaging material allowing little gas exchange(polyethylene or polyvinyl chloride)

Cowan and others (1976); assigned toTruman Limited; August 3, 1973

GB GB 1425979 Mixed with mannitol (osmotic stabilizer), and β-phenyl ethanol(bactericide); storable seed yeast

aLinked to the inventor and publication year (left column), patent number refers to the earliest publication of the invention. Patents are listed according to filing date of the invention (priority). For Germanpatents, the priority date was based on the information disclosed in the publication (“Patentiert vom”), which was 1 d later than the “convention date” (filing date) cited in foreign patents. In case of multiplepublications and when available, the country of earliest filing is mentioned. For some entries, details of the main invention were published in several “basic patents” forming a “patent family.” When identicalversions of the same “basic patent” were issued in several countries, patent numbers are given in parentheses and without reference to the publication year. Identification of most of the country codes is given atthe bottom of Table 2.

seed yeast cells by growing it under adverse conditions likely to bemet during the large-scale yeast manufacturing process (Table 7).Some effort was also put to boost seed yeast activity so early effortsrecognized the importance of growing conditions that increasedprotein content in yeast gave higher gassing power (Table 7).

In the early days of large-scale baker’s yeast manufacturing, upto 1911, another concern was seed decontamination (Table 8). Afew patents also claimed the best ways to add starters to the maingrowth media (Table 9): as for sugar and nitrogen sources, thestepwise addition of yeast starters was finally recommended in 1943by Stich. Some interest was given on techniques to better estimatethe amount of seed yeast to be added in the fermentation vat.

Historical contextThe pure culture method took long to be adopted by the yeast

industry, so the quality of concentrated yeast available commer-cially remained quite variable until about 1930 (Frey 1930; Gelinas2010a). Up to around 1925, a very critical issue was seed harden-ing to inhibitory chemicals added to control infection during yeastmanufacturing. After that period, both the nature and concentra-tion of such chemical inhibitors probably changed because seedhardening to those toxic compounds was less an issue for inventors.Most of these rudimentary techniques were abandoned when con-trol of pure starter management and infection during large-scalefermentation was better understood by the yeast industry.

Around 1925 to 1935, much was already known on the bestpractice to manage seed yeast for baker’s yeast production. So, in1934, Kitzmeyer stressed the importance of rapid seed transfer onthe quality of final baker’s yeast (Table 7). This might be consideredas a breakthrough because, until then, little interest had been givento the activity of starters for baker’s yeast production, as shown byspecification of Kitzmeyer’s patent: « At one time in the yeastmanufacturing industry it was customary to initiate the growth ofyeast by placing a small portion of previously manufactured yeast ina suitable quantity of nutrient and increase in yeast in quantity bythe regular manufacturing process. Due to the fact that this oftencaused the yeast to become infected with wild yeasts and otherorganisms, this method has been generally abandoned. The presentpractice of handling yeast to be used to start the manufacturingprocess is similar to that employed in the routine handling of otherbacteriological cultures. The pure culture of yeast is obtained byknown methods, and is kept alive by transfer in liquid media suchas malt, other grain, or molasses solutions, or by growth on solidmedia preparations of agar or gelatine. The media are sterilizedand the technique of transfer is well known to bacteriologists. Ifsolid media are employed, they are kept in a tube or small vesselprotected from infection by a cotton plug. The yeast is introducedin very small quantity on a platinum wire, and the medium iskept at proper temperature until yeast growth is complete. Thenthe culture may be transferred to a fresh medium or may be kept



Table 7–Patents published between 1900 and 2009 on seed growth conditions for the production of baker’s yeast.

Inventor (publication year);priority date Country Patent nr. Details

Jacquemin (1903); June 23,1902

FR FR 322381 Acclimatized to inhibitory substances in nontreatedmolasses by growth with increased levels ofsulfuric acid; distillers’ yeast

Molhant (1914, 1921); May25, 1912 (FR)

BE FR 455483 (GB 191311617; AT66474); FR 471775 (GB191417009, not accepted)

Acclimatized to inhibitory substances by growth withincreased levels of hydrochloric acid, formol, orboracic acid

Verein derSpiritus-Fabrikanten inDeutschland (1919);Hayduck (1923); licensedto The Fleischmann Co. (USand CA); December 24,1915 (DE)

DE DE 303311 (FR 520523; US1449111; US 15716, Reissue; CA238181)

Acclimatized to acids by growth in acidic mediacontaining inorganic nutrients and sugar;alternative to sulfuric acid, to adapt seed yeastand protect it against infection

Stein and Reiser (1921);November 30, 1918 (AT)

CS AT 88648 (DE 337282; DK 27783) Acclimatized to inhibitory substances by mixing withsodium disulfide; infection tolerance, high gassingpower, and good keeping properties

Pollak (1923); April 4, 1922(AT)

CS; AT; US AT 102790; AT 105786 (DE480076; FR 564231; GB 195963;US 1677529)

Treated with enzymes to stimulate N-assimilationwhen yeast development slows down; yield

Hamburger and others(1925); MellemeuropaeiskPatent-Financierings-Selskab Aktieselskab(1925); March 3, 1924 (DE)

CS; DK FR 591896 (AT 109526, dependenton AT 83559; CA 258458; GB230050, not accepted)

Grown in diluted, moderately aerated, acidified(lactic acid) and, nitrogen-rich media; yield

Claassen (1928); November19, 1926 (DE)

DE GB 280861 (US 1774546) Grown only with organic nitrogen, then withincreasing quantities of inorganic nitrogen; to getseed with high-protein content and gassing power

Kirby and Frey (1933);assigned to StandardBrands Inc. (US only);licensed to TheInternational Yeast Co.Limited (GB only); January26, 1932 (US)

US US 2029572 (GB 390114) Grown under adverse conditions with large amountsof inorganic nitrogen (30% of total sugar); to gethigh-protein (over 50%) seed yeast; yield, color,gassing power, and keeping properties

Kitzmeyer (1939); November3, 1934a

US US 2150329 (CA 373608) Repeatedly transferred from solution to solution at aperiod between the time the sugar first showsreally appreciable depletion (every 3 or 4 d) andthe time when three-quarters of the growth timehas elapsed; to avoid seed degradation, andimprove yeast yield, color, gassing power, andkeeping properties

Effront and Popper (1936);Effront (1937); licensed toStandard Brands Inc. (USonly); November 23, 1934(FR)

FR; HU FR 794359 (US 2083598) Combination of seeds grown under differentconditions, where alcohol production is high orlow, depending on sugar concentration andaeration conditions; higher gassing power underalcohol-forming conditions

Levin (1947); January 17,1944 (Palestine)

GB; Palestine GB 588374 (US 2439572) Using a specific apparatus, liquid medium isgradually dropped on seed yeast (in cotton);gradual varying growth conditions (temperature,medium composition) harden seed yeast andeliminate contaminants

Shropshire (1949, 1951);assigned to RaytheonManufacturing Co.; October26, 1946

US US 2492128; US 2578491 Treated in a 360 cycles-vibrator and grown for about24 h; faster growth (about 50 times)

Schneider (1954a, 1954b);Backhefe G.m.b.H. (1955);November 1, 1949 (DE)

DE DE 933443 (US 2676137; US2680689; GB 739702)

Grown under conditions hindering cells growth,allowing either low or high alcohol production,with nutrient starving and inhibitors (formalin;sulfurous acid), at low pH and temperature (12 to21 °C), and weak aeration; yield, color, andkeeping properties

Griesbach (1957); February 6,1956

US US 2802776 During growth, acid components are removed withan electrolytic cell; yield

Rost (1972); December 23,1970

DD DD 88927 As part of a continuous process, produced incontinuous (not in batch)

Cauchy (1972); assigned toNordon & Cie; March 11,1971

FR FR 2129018 As part of a continuous process, produced in a batchprocess allowing ethanol production and understrict aseptic conditions (filtered air)

Iwasaki and others (2006);assigned to KanegafuchiChemical Ind.; March 28,2006

JP JP 2006304780 Acclimatized in a synthetic and/or a low-sugarmedium; to limit the effects of varying mediacomposition

aBreakthrough.



Table 8–Patents published between 1900 and 2009 on seed decontamination for the production of baker’s yeast.


Head (1899); April 9, 1899 (DE)a GB AT 457 (GB 189907507;DE 124675)

Grown in concentrated (25%) and highly acidic media;to eliminate putrid ferments in “bud” as part of themanufacture of spirits and yeast

Jansen (1900); July 5, 1899 NL DK 3068 (US 724293; CA68817)

Grown in concentrated (specific gravity of 1.07) andhighly acidic media; to purify seed yeast (“bud”) aspart of yeast manufacturing

Henri and others (1910); November29, 1909

FR GB 190927798 Short treatment with ultra-violet rays to kill mostcontaminants in yeast starters for distilleries orbrewing; cheap alternative to pure cultures

Schimper (1912); partly assigned toA. H. Koeller; October 12, 1911

US US 1020716 Dead yeast, bacteria, small and light cells, and impuritiesare carried off under aeration and with wash water;mainly designed for pitching brewer’s yeast

aPublished before the year 1900 but not included in Gelinas (2010a).

Table 9–Patents published between 1900 and 2009 on seeding conditions for the production of baker’s yeast.


Board and Board (1905); December7, 1904

GB GB 190426698 (DE180338)

Seed is added at 3 stages during the course of the mainfermentation; alternative to 1- or 2 steps for spirits, beer, vinegaror yeast manufacturing

Kamienski (1914); September 20,1912

DE DE 269192 Seed is added in 2 portions: two-thirds in diluted media and the restwith concentrated media; aerated; yield

Roth (1917); April 6, 1914 AT-HU (AT) AT 73173 Very high level of seed yeast (15% to 50%) is added to diluted(twice than normal) molasses-based media; yield and gassingpower

Stich (1952); February 14, 1943 DE DE 752269 (FR891981)

Seed is added at regular intervals to constantly provide highly activecells; gassing power

Burrows (1972); Burrows and Dear(1972); assigned to The DistillersCo. (Yeast) Ltd.; April 11, 1968

GB GB 1262639; GB1278784

To estimate dry matter and cells number in seed, specific gravity(mass of a given volume) or turbidity of a yeast suspensionpreviously separated to retain only large yeast particles isdetermined automatically with a specific turbidimeter; to allowrapid and precise determination of the amount of seed yeast toadd to fermentation tanks, and to determine final yeast yield

Donnelly and Cahill (2000); assignedto Guinness Limited; September14, 1999

IE EP 0987334 The amount and activity of seed yeast is measured by imageanalysis; cell volume decreases during storage, which is correlatedto viability (old cells tend to sediment); brewer’s yeast and baker’syeast

for some time in a cool place before transfer to another similartube, or to the vessel in which is started the first stage of the yeastmanufacturing process. As the yeast grows on the surface of thesolid medium, the increasing cells pile on top of each anotherand crowd along at the side of the colony so that the individualcells of the culture are subjected to a changing and wide varietyof conditions of moisture, nutrient concentration, alcohol, wasteproducts, air, and carbon dioxide. Most of the cells are subjectedduring most of their existence as units to an environment of smallamounts of nutrients and large amounts of yeast metabolic wasteproducts and are not in a state of active reproduction.»

Infection ControlCommercial baker’s yeast contains high levels of contaminat-

ing bacteria and wild yeast that impair its yield, gassing power,and keeping properties (White 1954; Reale and others 2013). Al-though lactic acid bacteria have generally been found in abundance(O’Brien and others 2008), wild yeasts (nonstarter types) appear tobe the most important contaminants of compressed baker’s yeast,consisting up to 10% of the viable biomass (Tracey and others1984; Viljoen and Lues 1993); for example, Candida krusei utilizesethanol excreted during the growth of baker’s yeast strains (Suihkoand Makinen 1981).

Most of the patented inventions for infection control duringyeast production were related to the addition of antimicrobials in

the growth media, including acids (Table 10). Antiseptics such asformalehyde, chlorine, or antibiotics were also proposed but hadsome inhibitory action against yeast itself, which explains whysome interest was put on seed-hardening to such toxic compounds(Table 7). Addition of such preservatives was important in the earlydays of baker’s yeast manufacturing (Gelinas 2010a) but, accordingto Table 10, this practice appeared to have been abandoned inthe early 1920s. However, since the 1950s, there have been afew patented inventions on the decontamination of both growthmedia and yeast itself. According to Table 10, patents were filed in1999 and 2006 on the addition of hop acids to control infectionduring the production of baker’s yeast, although the use of hopshas been patented as early as 1890 (Gelinas 2010a). To a lesserextent than for antimicrobials, some interest was given on thedesign of easy-to-clean equipment providing sterile conditions,including air.

Historical contextFor the baker’s yeast industry, infection control during fermen-

tation is a major subject because patenting activity showed a lastinginterest in these technologies. This is confirmed by the specifica-tion of a patent filed in 1926 by Distillers Co. Ltd. and Meyer(Table 10): « . . . it has been found impossible to prevent, at someperiod or other, the invasion of the fermenting liquid by un-desirable organisms. The gradual accumulation of these organisms



Table 10–Patents published between 1900 and 2009 on infection control during the manufacturing of baker’s yeast.

Inventor (publication year);priority datea Country Patent nr. Details

Verein der Spiritus-Fabrikanten inDeutschland (1901, 1902a, 1902b,1902c); February 16, 1900

DE DE 127355 (AT8977); DE 129577;DE 129302; DE127810

Cereal-based media acidified with butyric acid or lactic acid(instead of lactic acid bacteria starter)

Jacquemin (1901); February 7, 1901 FR FR 307950 Antiseptics (copper salts of acids; hydrofluorosilicic acid withformic acid) added to nonsterile distillery mash

Kusserow (1904); September 27, 1902 DE DE 152136 Hyposulfites; no discoloringLapp (1903); November 15, 1902 (DK)a DE DK 5719 Large storage tank (500 to 1000 hL) made from steel

instead of wood and with double walls to improve coolingand control infection

Somlo (1905); April 13, 1904 HU AT 19616 Oxalic acid; for distilleriesFritsche (1907); Jacquemin and Fritsche

(1906); November 9, 1904 (DE)AT-HU DE 179915; AT

27341 (GB190624093); FR361643

Formaldehyde in milk solution; reduced acidity; for distilleries

Forster and Finitzer (1910); April 10, 1909(DE)

AT-HU(HU)

US 978282 (GB191008652)

Acidified with sulfuric acid and fermented with lactic acidbacteria

Cohendy (1911); November 22, 1909 (FR) FR GB 191026773 (AT54818)

Apparatus for pure yeast production, with an inner and anouter vessel (with a single cover)

Pechstein (1912); assigned to GebruderJacob; February 3, 1910

DE US 1023032 Flexible easy-to-clean metallic hose pipe

d’Herelle (1912); October 22, 1910 (MX) FR FR 435373 Apparatus for pure yeast production; sterilizer andfermentation vat connected in closed circuit

Hess (1922); June 4, 1914 AT-HU(AT)

AT 88349 Molasses-based medium acidified with alum (aluminiumsulfate) instead of sulfuric acid, without harming yeast

Hayduck (1923); Verein derSpiritus-Fabrikanten in Deutschland(1919); licensed to The Fleischmann Co.(US and CA); May 8, 1915 (DE)

DE DE 303253 (US1449112; GB155288; CA238176)

Antiseptics (formaldehyde; formic acid) added to dilutedgrowth media

Donham (1917); assigned to SprayEngineering Co.; December 6, 1915

US US 1222541 Air purifying device installed between the air compressorand the fermentation tank

Magne (1917); June 19, 1916 FR; MX US 1212656 (GB124237)

Apparatus for the production of pure yeast, including airsterilizing mechanism

Etablissements Poulenc Freres, and Vigreux(1924); Vigreux (1927); March 17, 1923(FR)

FR FR 575518 (US1623896)

Large-scale apparatus for pure yeast production withautomatic controls (media sterilization, temperature, andso on)

Pollak (1927); September 29, 1923 CS; AT CS 23232 Lactic acid bacteriaKlein (1926); December 30, 1924 (US) US AT 103908 Lactic acid (high levels)Meyer (1933); The Distillers Co. Limited and

Meyer (1927; 1930); licensed to StandardBrands Inc. (US only); May 4, 1926 andMay 1, 1929 (GB)

DK; GB GB 275329; GB334502 (FR689238; DK43822; CH149387; US1938081)

Halogen (saturated chlorine water); for continuous cultures

Reinisch (1931); September 28, 1929 AT AT 121078 Surface of growth medium is treated with ultravioletradiation

Magne (1938); assigned to AmericanBiochemical Products Co., Inc.; January 22,1934

FR US 2111102 Apparatus for the production of pure yeast, including airfilter

Schwarz and Erda (1939); assigned toSchwarz Laboratories, Inc.; July 16, 1937

US US 2147271 Large-scale apparatus for the production of pure yeast withindependent chambers and easy to sterilize transfer lines

Steinhart (1958); assigned to Sinner A.G.;March 31, 1955

DE DE 1033618 Water ozonation of media prior to yeast seeding

Gray and others (1958); assigned toWallerstein Co.; priority date unknown

US CA 555770 Antibiotics effective against Gram-negative bacteria(coliforms)

Wolnak and Barrington (1962); Armour andCo. (1961); January 11, 1957 (US)

US GB 861784 (US3041250)

Hydrogen peroxide; also added incrementally with catalaseto form oxygen

Hill (1978); assigned to Henkel KGaA;October 8, 1976

DE DE 2645386 At various steps, cream yeast is acidified (pH 2 to 6) withmonopersulfuric acid

Fukuda and others (1981a, 1981b, 1981c);assigned to Kanegafuchi Chem. Ind. Co.,Ltd; August 23, 1979

JP JP 56032987; JP56032988; JP56032989

Part of the growth medium is recovered, pasteurized withchemicals, and returned to the main fermentation vat

Knackmuss and others (1985); assigned toAkademie der Wissenschaften der DDR;June 28, 1984

DD DD 225436 Treated with acid for 0.5 to 3 h (pH 1.5 to 2.0) withoutaeration; continuous culture

Pilepp and others (1987); assigned to Fried.Krupp GmbH; November 29, 1985

DE DE 3542246 Continuously sterilized with a specific homogenizer

Maye and Beddie (2000); Maye (2004);assigned to Haas Hop Products Inc. (John I.Haas Inc.); March 5, 1999 (DE)

US WO 0052212; WO2004072291

Hop acids

Baczynski and others (2007); assigned toBetatec Hopfenprodukte GmbH; May 12,2006 (DE)

DE WO 2007131669 Hop acids, colophonium, or myristic acid

aBreakthrough.



Table 11–Patents published between 1900 and 2009 on the control of temperature during the manufacturing of baker’s yeast.

Inventor (publication year);priority date Country (city) Patent nr. Details

Braasch (1909, 1910a, 1910b); May5, 1908 (DE)a

DE FR 404183 (GB190910458; DK13175; CH 45910);GB 190927360(DK 14492); GB190929114 (DK13821)

Growth at 13 to 15 °C for 16 to 19 h, then at 25 to 30 °C for 4 to 7h, under aeration and with high level (8%) of seed yeast in abudding state; yield (oxygen transfer is higher at lowtemperature)

Kierulff (1911); October 5, 1910a DK DK 15072 Yeast is activated at 24 °C, then growth is performed at 15 °C withaeration for 4 h in dilute medium, and fermentation ends at 28 to30 °C for 4 to 6 h; yield

Wahl (1921); July 26, 1919a US US 1373468 Yeast propagator is equipped with cooling system (inner wall) tocool rapidly growth media (20 to 25 °C); infection control

Lavedan (1929); July 1, 1925 US US 1718910 Injection of carbon dioxide during yeast growth to control acidityand temperature; yield and keeping properties

Buhrig (1931); assigned to StandardBrands Inc.; January 22, 1926

US US 1817232 The outer surface of the tank is subdivided into several independentzones containing cooling liquid

Horch (1931); February 20, June 4,October 4, and October 14, 1930(DE)

DE FR 705807 (DE543775; DE587638; CH151946; US1937226; AT127776; AT134864)

Cool air is circulated in a jacket in contact with the liquid in thefermentation vat; improved temperature control compared tocooling units placed inside or rolled around the vats

Strauch & Schmidt (1932); January15, 1931

DE DE 543549 Heat insulating cooling jacket is provided for yeast storagecontainer; more efficient than refrigeration chambers

Knappe (1937); licensed to LarsBrandstrup (DK); March 10, 1933(DE)

DE DE 641753; DK51473

Low-temperature (16 °C) growth in media with plant proteinhydrolyzed with phosphoric acid

Meyer and Chaffe (1942); TheInternational Yeast Co. Limitedand others (1940); licensed toStandard Brands Inc. (US only);December 22, 1938

GB GB 523019 (US2304471)

Growth at a lower temperature than optimum (30 ºC for 4 h, 24 ºCfor 6 h and, facultative, 30 ºC for 2 h); yield

Griesbach (1955); May 8, 1951 US US 2705215 Controlled heating (43 to 63 °C) of small portions of growth mediawhile the main culture is at a normal temperature (21 to 32 °C);yield and infection control

Suzuki and others(1989); assigned toKirin Beer Kabushiki Kaisha;January 8, 1988

JP EP 0325907 (US4906578)

Internal cooling jacket secured concentrically to the inner wallsurface and with close contact with the fermentation tank; highheat transmission and easy-to-wash; probably for small-scale only

aBreakthrough.

always produces a degeneration in the quality of the yeast obtained,so that it is necessary to stop the process and restart the operation.It is of course the usual procedure in discontinuous methods ofyeast manufacture to add sufficient quantity of either a mineralacid to inhibit the growth of foreign organisms, but it has beenfound that when this acidity has to be maintained throughout along period the yeast after a time becomes sluggish in growth and,moreover, tends to deteriorate in quality. »

According to a patent by Valentin Lapp cited in Table 10, inthe early years of yeast manufacturing, yeast storage tanks weremade of wood. These vats were difficult to clean and refrigerate,which suggests that this was a major source of infection of seedyeast and any yeast stored in the liquid state. Filed in 1902, thispatent that recommended the use of steel tanks so this inventorappears to have been the first to propose a long-term solution toyeast infection.

Even nowadays, fermentation conditions associated with thegrowth of baker’s yeast are not performed under absolutely sterileconditions. To reduce bacteria and wild yeast contamination to aminimum, growth medium is now sterilized, air is filtered, andequipment is thoroughly cleaned. The number of patented in-ventions (30 between 1900 and 2009) on the control of infectionduring baker’s yeast manufacturing is probably not very indicativeof the economical importance of this matter. Thanks to numer-ous nonpatented technologies such as easier-to-clean equipmentsand the strict application of hygienic procedures, much of theseproblems were solved. This improved yeast yields, gassing power,

and keeping properties due to the elimination of excessive levelsof wild yeast and bacterial contaminants.

Temperature ControlMuch heat is produced during yeast growth. This has encour-

aged the filing of a few patent applications on the temperature con-trol of fermentation media for baker’s yeast (Table 11). Inventorswere mainly interested in designing cooling systems for fermenta-tion and storage vats (6 patents) or to specify temperature that weresaid to improve yeast properties (5 patents). Specifically for thebaker’s yeast industry, the interest for temperature control droppedin the early 1950s. However, it is likely that much more patentedinventions were later issued on miscellaneous fermentation vats.

Historical contextNowadays, baker’s yeast is generally grown at 27 to 30 °C.

Around 1900, it was already known that 28 to 38 °C was themost favorable for yeast cell multiplication. According to a patentspecification filed in 1908 by Braasch (Table 11), it was customaryto begin the fermentation at about 22 to 23 °C so most of thefermentation would occur at 25 to 30 °C due to the heat formedduring cell growth. However, according to a patent specificationfiled in 1926 by Buhrig, cooling systems were not very efficientbecause they were based on the temperature of water. For exam-ple, seasonal variations were seen and this might partly explainwhy yeast propagation was mainly practiced in Nordic countries.According to this author, it was a common practice to conduct



Table 12–Patents published between 1900 and 2009 on the concentration and rate of addition of sugar-based ingredients during the manufacturingof baker’s yeast.

Inventor (publication year);priority datea Country Patent nr. Principleb Details

Vignier (1905); February 9, 1904 FR GB 190403196 R Wort is supplied at regularly occurring periods;distillers’ yeast combined with wine or beerproduction

Verein der Spiritus-Fabrikanten in Deutschland(1919); Hayduck (1923); licensed to TheFleischmann Co. (US and CA); March 17, 1915a

DE DE 300662 (US1449105,invalid; GB155284; CA238172)

R In highly diluted media (1°B), a wort of higher sugarconcentration (12 °B) is added at a minimal rate,with aeration, to allow minimal alcohol formation;yield

Schwarz (1921); with depending patents by Klein(1923; liquid media), MellemeuropaeiskPatent-Financieringsselskag (1927; seed growth),and Jacobsen (1929; continuous culture); April 8,1915

AT AT 83559 (AT103075; AT109526; AT130435)

R; Q Nutrient medium is added progressively, based onanalyses (sugar, acidity, nitrogen, phosphoric acid,alcohol, and yeast), with little sugar excess; yieldand gassing power

Kraus Moskovits EgyesultIpartelepekReszvenytarsasag (1923); November 24, 1915(HU)

HU HU 70215 (GB174628)

R In diluted media, concentrated and acid-controlledmedia is added gradually, avoiding alcoholformation; yield

Dupire (1920); April 23, 1919 FR FR 498590 (GB149438)

C Growth medium is diluted with water (final density is1030 g/L) in such a proportion that yeast findsonly the quantity of sugar that is necessary for itsfull development

Aktieselskabet Dansk Gaerings-Industri (1920); Sak(1924); licensed to Vereinigte Mautner’schePresshefe-Fabriken Gesellschaft m.b.H., andEugene Fould-Springer (AT only); licensed to TheFleischmann Co. (US and CA only); July 5, 1919(DK)

DK DK 28507 (GB153667; FR515704; CH90954; FI 8842;AT 102274; AT105785; US1566431; CA215671; CA237963)

R To compensate for nutrients assimilation duringgrowth, highly concentrated growth medium isadded to a less concentrated medium at suchspecific rate that much alcohol (20%) is formedand later assimilated during the latter part of thepropagation; to allow joint manufacturing ofalcohol and yeast; yield

Sak (1919); Aktieselskabet Dansk Gaerings-Industri(1919); licensed to Vereinigte Mautner’schePresshefe-Fabriken Gesellschaft m.b.H., andEugene Fould-Springer (AT only); licensed to TheFleischmann Co. (CA only); July 5, 1919 (DK) andJuly 15, 1919 (NO)a

DK NO 39412 (SE56428; FI 9712;FR 503808; CH94210; NL8737;GB146947, notaccepted; AT105784; CA209947; CA237961); FR503810 (CA209948; CA237962)

R To compensate for nutrients assimilation duringyeast growth, specific amounts of growth mediaconstituents (one or several) are addedincrementally, according to specific curves;without joint alcohol manufacturing; yield

Allen and Timmer (1930); Vitamin Food Co., Inc.(1931); December 14, 1925

US US 1775800 (GB361026)

R Use of highly diluted media and excess aeration toprevent media acidification; yield

Bratton (1930); assigned to Anheuser-Busch, Inc.;March 6, 1926a

US US 1767646 C; R Nitrogen-rich yeast is first obtained by feeding withsugar-deficient medium (rich in protein andnutrient salts) and, later, it is slowly fed withsugar-rich medium (deficient in protein andnutrient salts)

Knappe (1933); March 21, 1926 DE DE 570932 R Yeast is fed stepwise with just enough growthmedium to double cell concentration, until it ismature (burgeoning is completed), and newmedium is added in concentration sufficient todouble again the yeast cell concentration; yieldand gassing power

M. Fisch’s Sohne and Rosenberg (1930); Braun andothers (1931); December 18, 1928 (AT)a

AT; CS AT 119946 (DK47188; FR686784; GB346361)

R Divided into several phases of short duration,feeding rates increase according to calculatedmaximum cell growth (logarithmic) and fullconsumption of sugars, using a series of containers

Moskovits (1934); Kraus-Moskovits VereinigteIndustrie-Anlagen Aktiengesellschaft (1930);Moskovits and Kraus-MoskovitsEgyesultIpartelepek Reszvenytarsasag (1931);March 22, 1929 (HU)a

HU FR 692546 (DK44716; DE568756; AT125192; GB349201; CH154496; US1962831)

R; C Near the end of fermentation, yeast is grown innitrogen-rich media (sugar-limited), acidified, thenswitched to glucose-rich media (nitrogen-limited);yield and gassing power

Jellinek (1931); assigned to VereinigteMautner-Markhof’sche Presshefe Fabriken undAktien-Gesellschaft Ignaz Kuffner & Jacob Kuffnerfur Bauerei, Spiritus- und PresshefefabrikationOttakring-Dobling (AT only); licensed toHefefabriken A.-G. (CH only); licensed to ArthurKoenig (DK only); October 22, 1929 (AT)

AT AT 130438 (GB354118; FR704113; US1920395; BE374358; BE374996; CH153184; DK46078)

R; C Highly active yeast (protein-rich) is fed with highlyconcentrated sugar-based medium to allow muchethanol production; after separation, yeast isslowly fed for 6 to 8 h with the previous mediumcontaining ethanol; yield and keeping properties(lower protein content)

(Continued)



Table 12–Continued.


Wroten (1933); March 19, 1930 US US 1917283 R; Q Weight of added sugar is constantly lower than theweight of yeast, using a large proportion ofinorganic nitrogen salts and without acidneutralization; when sugar has been assimilated,this process is repeated; to obviate the necessity ofconstant supervision, the acidity or gravityreadings are determined throughout the run andthe handling of large volumes of liquid

Stich (1934); licensed to Standard Brands Inc. (CAonly); March 3, 1933 (GB)

DE GB 411611 (CA371677)

R At hourly intervals, the amounts of air and molassesincrease according to exponential yeast growthcurve; yield

Lutz and Irvin (1937); assigned to National GrainYeast Corp.; July 1, 1933a

US US 2084736 C; R Yeast is seeded in a small quantity of growthmedium and fed with a larger volume of medium(2 to 10 times that of the initial wort compared to0.25 times, normally); less media and improvedaeration; yield and cost

Norddeutsche Hefeindustrie Aktiengesellschaft(1935); September 26, 1933

DE GB 431129 (notaccepted)

C; R Seed yeast is mixed with sugar-free media containingphosphoric acid (avoiding alcohol formation), andfed incrementally with sugar-containing media

Kitzmeyer (1937); October 14, 1933a US US 2097292 (CA352872)

R Yeast is fed with a sugar solution at an increasingrate and using a specific time schedule (19 steps),providing brief periods where no sugar is available(to limit pH fluctuations); alternative tocontinuous sugar feed; no hard lumps incompressed yeast; for high-sugar dough; gassingpower and keeping properties

Hilbers (1938); January 7, 1936 DE AT 154818 (US2162217)

R; Q Acid is controlled by stopping feeding andcontinuing aeration; yield and keeping properties

Irvin and Mead (1939); July 28, 1937 US US 2183570 C; R Yeast is first grown under batch conditions (7% to10% seed instead of 15% to 25%, much sugar,and low aeration; 6 h); after water addition,aeration is increased and growth medium is addedfor 8 h; less seed and air; yield and cost

de Becze (1939); January 26, 1938 (DE) US FR 849426 (US2199722; GB524312)

C; R Yeast is grown in very dilute media (80% to 90% ofthe final volume) and fed stepwise by appropriateadjustment of seed yeast, aeration, and nutrients(15% to 25% sugar); yield and gassing power

Berkel (1952); licensed to AktiengesellschaftJungbunzlauer Spiritus- und Chemische Fabrik(1949; AT only); February 5, 1943 (DE)

DE DE 767347 (AT164248)

C Yeast is fed with easy-to-ferment media and,progressively, with difficult-to-ferment media(concentrated molasses by-products); cost

Aktieselskabet Dansk Gaerings-Industri (1949);February 20, 1946 (DK)

DK DK 68667 (FR941938; CH276131)

C Growth in concentrated media and reduced aeration,followed by dilution and fermentation undernormal aeration; reduced air consumption; cost

Aktieselskabet Dansk Gaerings-Industri (1968);August 28, 1954

DK DK 108781 R Constant addition of concentrated medium withoutalcohol production, using a specific yeast strain;higher gassing power in lean dough

Pyke and others (1958); assigned to The DistillersCo. Limited; November 17, 1954

GB GB 800030 (FR1137889)

R An excess of molasses is added exponentially for 2 to3 consecutive stages followed by optimizedfeeding; to increase maltase activity (non-sugareddough); gassing power

Patentauswertung Vogelbusch Gesellschaft m.b.H.(1960); Rungaldier and Braun (1961); MautnerMarkhof (1961); all assigned to PatentauswertungVogelbusch Gesellschaft m.b.H.; November 14,1958 and December 14, 1959a

AT AT 208802 (CH379444; DK91861; DE1080048; FR1236196; GB882476; US3002894); AT214392 (DK96261; CH394090; DE1152984; GB897166; US3010881)

Q A portion of alcohol in outlet of aeration system iscontinuously measured (by colorimetry orcalorimetry) and signal is transformed into electriccurrent, which controls nutrients and aeration;yield

Svenska Jastfabriks Aktiebolaget (1964; 1965);February 5, 1963 (SE)a

SE FR 1379225 (GB1035552); FR1390262 (GB1035551)

Q Using an apparatus for analyzing alcohol anddissolved oxygen (electrode), feedback control ofthe oxygen transfer is performed by varying therate of rotation of the agitator and/or the surfacetension of the medium with antifoam

Ceskoslovenska Akademie Ved (1965); Caslavskyand Hospodka (1968); October 11, 1963 (CS)

CS FR 1418296 (GB1045930; US3384553)

Q Dissolved oxygen content is determined with apolarographic electrode equipped with anoxygen-permeable membrane and connected witha regulating device for metering nutrient feed

Oriental Yeast Co., Ltd. (1971); March 29, 1967 JP GB 1220101 R Based on a 2-stage process, sugar feed rate isswitched from high to low, providing alternatingfeed and non-feed periods; sweet dough (15% to25% sugar); gassing power and keepingproperties

(Continued)



Table 12–Continued.


Aiba and others (1977); assigned to Oriental YeastCo., Ltd., and Marubishi Rika Sochi Kenkyusho;April 12, 1976

JP JP 52125686 Q Respiratory quotient and feed rate are maintained ina specific range

Dairaku and Kuki (1979); assigned to KanegafuchiKagaku Kogyo Kabushiki Kaisha; March 13, 1978

JP JP 54121196 (US4257257)

Q Ethanol is detected by flame ionization; automaticcontrol of sugar feed

Nagai and Nanba (1982); assigned to Oriental YeastCo., Ltd.; August 15, 1980

JP JP 57036983 Q Ethanol concentration is determined constantly;automatic control of sugar feed

Shimizu and others (1983); assigned to Hitachi, Ltd.;November 4, 1981

JP EP 0078500 Q Oxygen and carbon dioxide are determined with gasanalyzers; automatic control of sugar feed; yield

Fukuda and others (1983); assigned to KanegafuchiKagaku Kogyo KK; March 16, 1982 (JP)

JP GB 2118722 (US4474051)

Q Ethanol concentration is determined with a detectorhaving a semiconductor gas sensor to control feedrate

Sakado (1985); assigned to Kyowa Hakko Kogyo KK;August 3, 1983

JP JP 60034180 Q Ethanol concentration is determined electrically tocontrol feed rate

Murayama and Takemoto (1985); assigned to ToyoSoda Kogyo KK; December 28, 1983

JP JP 60141283 Q Respiratory quotient (molar ratio the carbon dioxideformed to the oxygen consumed) is determinedonline and controls feed rate

Knackmuss and Asperger (1986); assigned toAkademie der Wissenschaften der DDR; August 9,1984

DD DD 231803 R Glucose concentration is set (0.1 to 0.3 g/L) andcontrols molasses feed or air incorporation;gassing power

Albrecht and others (1985); Chalupka and others(1986); assigned to Akademie der Wissenschaftender DDR; May 24 and June 21, 1985

DD DD 225437; DD238627

Q; R Feeding rate for molasses is controlled by theethanol concentration in the fermentor,programmed to increase according to yeastconcentration; to reduce molasses consumptionand to slowly progress from an anaerobic stage toan aerobic stage; cost

Kell and Todd (1988); September 22, 1986 GB WO 8802115 (US4810650)

Q Yeast concentration is determined by an apparatusmeasuring differences of capacitance; to controlfermentation parameters

Nakamura and others (1992); assigned to AjinomotoCo., Inc.; November 30, 1990 (JP)

JP FR 2669935 (US5912113)

Q Sugar feeding rate is controlled by carbonconcentration, obtained by monitoring pH ordissolved oxygen; preferable to ethanoldetermination; yield

Tuljakova and others (1994); assigned toAssotsiatsijaproizvoditelejoborudovanijaikhle-bopekarnykhdrozhzhej; January 28,1992

RU RU 2016896 C Specific nitrogen–carbon ratio (1:8) for 2generations

Ono and Tashimo (1994); assigned to KanegafuchiChem. Ind.; October 7, 1992

JP JP 61113822 R Feed rate is reduced in the 2nd half of thefermentation; yield

Bishop and others (1997); assigned to G.D. Searle &Co.; August 12, 1994

US US 5595905 Q In real time, a computer calculates nutrientsconsumption and feed rates by comparing thenutrients concentrations of samples

Ishii and others (1997); assigned to Oriental YeastCo., Ltd.; August 31, 1995

JP JP 9065873 Q Model is based on integrated value of the differencebetween sugar flow acceleration value andtheoretical sugar flow not producing ethanol; yield

Mead and Van Urk (1997); assigned to DeltaBiotechnology Limited; March 13, 1996

GB WO 9733973 (US6150133)

Q Electrical conductance of the fermentation mediumis determined at intervals; algorithm compareschanges with predetermined value; acetic acid(toxic) is determined

Plomp (1998); assigned to Gist-brocades; July 26,1997a

NL EP 0821057 (US5916609)

C; R Slow fed-batch growth (more than 20 h) in anon-molasses carbon source, without washing andconcentrating, and to get a yeast concentrate(10% to 22% solids); to reduce waste water andgive cheaper yeast with improved taste and aroma

Lendl and Schuster (2002); assigned toInnovationsagentur Gesellschaft m.b.H.; April 5,2001a

AT WO 02082061(US20040096930)

Q Rapid (5 min intervals) and on-line measurements onmedia and microorganisms which are directlyspectroscoped (infrared) to determine yeast cellscomposition (glycogen, trehalose, mannan,protein structure, and so on)

Wagner (2003); May 16, 2002 DE DE 20207697U Q Alcohol is continuously measured; to control nutrientfeed

Korneev (2004); December 15, 2002 RU RU 2230111 Q Portions of yeast biomass are removed, based oncells growth stage

Kimura and others(2006); assigned to AsahiBreweries Ltd; April 4, 2005

JP JP 2006288201 Q Respiratory quotient (inflow and exhaust gas) ismeasured by mass spectrometry, to controlfeeding

aBreakthrough.bC, concentration (sugar); Q, quality control; R, rate of addition.



yeast propagation in large tanks often formed of copper over theouter surface of which a cooling liquid, usually water, was allowedto flow at suitable temperature for preventing undue rise of thetemperature of the material within the tank during yeast growth.In such prior processes in which the cooling liquid was allowed toflow over a unitary zone comprising substantially the entire heightof a usual fermenting tank, the cooling was not effected in themost efficient manner, one reason for this being that unless thecooling liquid was supplied in unduly large and wasteful quanti-ties its temperature approximated that of the contents of the tankadjacent its inner surface after the cooling liquid has descendedover a fraction only of the total height of the surface over which itflowed. After this approximate equalization of temperature, it nolonger exerted any cooling effect while passing over the remainingsurface of the tank.

According to a patent filed in 1938 by Meyer and Chaffe, «It is known to carry out a fermentation for the production ofyeast by operating for the entire fermentation period at the op-timum temperature known for any given organism and it is alsoknown to work at that temperature until shortly before the endof the entire working period and then to raise the temperaturesomewhat to improve the quality. It is also known to initiate fer-mentation at a temperature below the optimum temperature andthereafter raise the temperature during the course of the fermen-tation.» In several of the patents cited in Table 11, the use oftemperatures much lower than standard (27 to 30 °C), even as lowas 13 to 15 °C, was recommended to improve yeast yields. How-ever, such low growth temperatures were proposed until the 1930swhen yeast yields and cooling requirements were lower than in thefollowing years. Using such low temperature was also beneficialto yeast growth because of improved oxygen transfer. In somepatents, low fermentation temperatures were also said to controlinfection. However, in modern yeast production, it might not beeconomically feasible to use temperatures lower than 27 to 30 °Cbecause yeast yields would be too low.

Sugar Concentration and Rate of AdditionThe following section presents patented inventions on the con-

trol of sugar in yeast fermentation media, which is one of the mostimportant issues in baker’s yeast production. Table 12 applies tothe development of fed-batch conditions in which basic growthmedium is regularly supplemented with nitrogen-rich molassessolution. Table 13 describes inventions where portions of growthmedia were regularly removed during the course of the fermen-tation, to control the sugar concentration in fermentation media.Generally called the addition-withdrawing method, the latter issomewhat related to the concept of continuous culture. Althoughnot considered in this review and in the list of patents counted (Ta-ble 1), Table 14 presents a short list of patents on ethanol recoveryas part of baker’s yeast production. Mainly filed around 1910, suchpatented inventions suggest that early control of sugar feeding wasnot very thorough and allowed substantial alcohol formation atthe expense of yeast yield.

Historical contextAcceptable baker’s yeast was available around 1905 to 1915

in some European countries (Gelinas 2012). Control of sugarconcentration in fermentation media was applied as part ofthe “aeration process” giving high biomass yields because largequantities of air were blown in fermentation tanks. This processwas introduced around 1890 and by-passed the so-called Viennaprocess where no aeration was provided and yeast was allowed to

freely float to the surface due to natural gas production during itsgrowth (Gelinas 2010a).

During that period, the idea of adding nutrients gradually to themain fermentation medium was not new because this had beenpatent-protected in 1879 by Rainer (Gelinas 2010a). According tothe latter literature review, applications of this idea were later de-veloped by Levy, Jacquemin, and, in 1904, by Vignier (Table 12)who added fractions of growth medium to stimulate alcoholicyeast growth. Although granted only in 1919 due to World WarI, an important series of 13 German patents were filed within 18mo from February 1915 to August 1916 by Friedrich Hayduckwho assigned the inventions to Verein der Spiritus-Fabrikantenin Deutschland. This series of patents addressed most aspects ofmodern baker’s yeast production, including the control of sugarconcentration in growth media. In essence, baker’s yeast was fedat a minimal rate to avoid alcohol production, by adding concen-trated sugar-based media to diluted media in the vat. Such an ideawas very close in nature with the concept proposed by JacquesRainer in 1879. However, this inventor added dilute media tothe fermentation vat which required vats of increased volumes, sothis was a major problem for the large-scale production of baker’syeast.

Shortly after Hayduck filed his 1st patent specification onthe controlled addition of nutrients in baker’s yeast produc-tion (February 24, 1915), other patents with closely relatedspecifications were also filed: on April 8, 1915, in Austria bySchwarz and on November 24, 1915, in Hungary by KrausMoskovits. On April 23, 1919, Dupire also adapted this con-cept and filed a closely related patent specification in France. In1919, Søren Sak (1883 to 1950), technical director at Aktieselska-bet Dansk Gaerings-Industri (Copenhagen, Denmark), improvedthe original idea by increasing substrate concentration or rate ofaddition, to compensate for yeast growth. In 1928, Braun and oth-ers recommended short feeding curves for optimal yeast growth,to get about 3% to 5% yeast cells (dry matter basis) at the end of thefermentation. However, these patented inventions were backed bylittle scientific knowledge on baker’s yeast physiology. It was notuntil 1929, or several years after the baker’s yeast industry hadapplied these concepts, when it was scientifically recognized thatyeast growth was inhibited by large amounts of sugar, a conceptcalled the Crabtree Effect (Barnett and Entian 2005).

According to Table 1, 12, and 13, the interest for inventionson the control of sugar concentration peaked around 1915 to1935, although the number of patents was low with about 1 peryear. At the end of the 1950s, much more interest was put onquality control tools when devices for measuring ethanol weredeveloped to confirm that sugar concentration in the growthmedium did not inhibit cell growth, so high yields of yeast couldbe obtained. Interest for such technologies lasted until the recentyears. In the scientific literature, much effort was put on the opti-mization of feeding control for sugar and other nutrients throughmathematical models. Respiratory quotients were determined aspart of various fed-batch fermentation processes, including baker’syeast and antibiotics manufacturing (Johnson 1987; Reyman 1992;Beuermann and others 2012). In addition to the control of sugar,aeration was a very important limiting factor leading to reducedbiomass yields through the production of excessive amounts ofethanol, which may have negative impact on the yeast resistanceto stresses during bread manufacturing, including frozen dough(Gelinas and others 1989; Viera and others 2013). As recalled byRolf and Lim (1985), a small amount of ethanol production dur-ing yeast growth is beneficial for acceptable baker’s yeast showing



Tabl

e13

–Pat

ents

publ

ishe

dbe

twee

n19

00an

d20

09on

the

cont

inuo

uscu

ltur

epr

oces

s(a

ddit

ion-

wit

hdra

wal

)dur

ing

the

man

ufac

turi

ngof

bake

r’sye

ast.

Inve

ntor

(pub

licat

ion

year

);pr

iori

tyda

tea

Coun

try

Pate

ntnr

.Pr

inci

pleb

Det

ails

Mey

er(1

912)

;Aug

ust2

,191

1D

KD

K16

250

WIn

dual

yeas

tand

alco

holp

rodu

ctio

n,ye

astp

ortio

nsar

egr

adua

llyre

mov

ed,c

entr

ifuge

d,an

dco

nditi

oned

;yie

ldV

erei

nde

rSpi

ritus

-Fab

rikan

ten

inD

euts

chla

nd(1

919a

,19

19b)

;Hay

duck

(192

3);l

icen

sed

toTh

eFl

eisc

hman

nCo

.(U

San

dCA

);A

pril

1an

d13

,191

5

DE

DE

3032

21(U

S14

4910

7;CA

2381

73);D

E30

4241

(US

1449

108;

CA23

8174

;GB

1552

92)

WIn

ade

epva

t,m

ediu

mis

cont

inuo

usly

with

draw

nat

the

sam

era

teat

whi

chnu

trie

ntsa

read

ded

Lave

dan

(191

6);F

ebru

ary

12,1

916

US

US

1201

062

W;R

Pure

yeas

tisc

ontin

uous

lysk

imm

edan

dse

para

ted,

liqui

dis

retu

rned

toth

efe

rmen

tatio

nva

t,an

dsu

ffici

ents

ugar

isad

ded

toto

keep

itco

nsta

nt;y

ield

Corb

yan

dBu

hrig

(192

8);B

uhrig

(192

9);T

heIn

tern

atio

nal

Yeas

tCo.

Lim

ited

(192

6);a

ssig

ned

toTh

eFl

eisc

hman

nCo

.;lic

ense

dto

The

Inte

rnat

iona

lYea

stCo

.Lim

ited

(GB,

FR,a

ndD

E);A

ugus

t16,

1924

,and

May

14,1

925

US

US

1673

735,

inva

lid(G

B23

8554

;FR

6039

56;D

E58

3760

);U

S17

3087

6(G

B25

2193

;FR

6277

01;D

E49

9506

)

W;R

Port

ions

ofth

egr

owth

med

ium

(3ºB

)are

perio

dica

llyw

ithdr

awn,

tran

sfer

red

into

anau

xilia

ryfe

rmen

ter,

and

dilu

ted

(2ºB

)whi

lene

wgr

owth

med

ium

isad

ded

inth

em

ain

vat;

tem

pera

ture

is30

to35ºC

inth

efir

stst

ages

Has

ling

(192

9);a

ssig

ned

toTh

eFl

eish

man

nCo

.;Th

eFl

eisc

hman

nCo

.(19

27);

Dec

embe

r30,

1924

US

US

1722

746

(GB

2774

76)

WO

ne-t

hird

ofm

ediu

mis

repl

aced

whe

nse

edye

astc

onte

ntha

sin

crea

sed

by50

%H

arris

on(1

930)

;ass

igne

dto

Stan

dard

Bran

dsIn

c.;H

arris

on(1

927)

;lic

ense

dto

The

Inte

rnat

iona

lYea

stCo

.Lim

ited

(GB

only

);O

ctob

er6,

1925

US

US

1761

789

(GB

2595

72)

EG

row

nin

3co

mpa

rtm

ents

inst

ead

ofa

sing

lefe

rmen

ter

Har

rison

(192

8);a

ssig

ned

toTh

eFl

eisc

hman

nCo

.;O

ctob

er19

,192

5U

SU

S16

7643

7W

Med

ium

isw

ithdr

awn

whe

nsu

garc

once

ntra

tion

hasd

ropp

edto

0.6

to1ºB

The

Dis

tille

rsCo

.Lim

ited

and

Mey

er(1

927)

;Mey

er(1

929)

;lic

ense

dto

The

Flei

schm

ann

Co.(

US

only

);M

ay4,

1926

(GB)

DK;

GB

GB

2753

28(U

S17

2495

2)W

Med

ium

(mol

asse

s)is

switc

hed

tosa

ccha

rified

cere

alm

ater

ial;

topr

even

tyea

stde

gene

ratio

n

Buch

er(1

928)

;Jun

e19

and

Oct

ober

7,19

26(D

E)D

EG

B29

1146

(FR

6328

48)

EU

sing

asp

ecifi

cap

para

tus,

med

ium

flow

sin

the

form

ofa

stre

amto

cont

rols

ugar

conc

entr

atio

n,an

dpo

rtio

nsof

the

yeas

tare

cont

inuo

usly

harv

este

d;yi

eld

Boye

(192

8);O

ctob

er26

,192

6(S

E)SE

FR64

2019

(US

1818

530;

DE

5341

08)

EYe

asti

smai

ntai

ned

atdi

ffer

ents

tage

sofg

row

than

dco

ntin

uous

lypa

sses

thro

ugh

ase

rieso

fcha

mbe

rsor

vats

supp

lyin

gth

ere

ques

ted

nutr

ient

sSa

k(1

930a

,193

0b,1

930c

;193

1;19

32a,

1932

b,19

32c,

1932

d,19

32e,

1932

f,19

32g)

;Jan

uary

8,19

27(N

O)a

ndA

ugus

t30,

1927

(NO

)

DK

DK

4146

3(G

B29

4123

;GB

2941

31;G

B29

4132

;GB

2941

33;G

B29

4134

;FR

6708

00;F

R67

3283

;DE

6072

34;C

A30

8828

;US

1884

272;

US

1891

841)

;D

K41

765;

DK

4176

6;D

K44

492

(FI1

3752

);D

K45

542;

DK

4554

3;D

K45

544;

DK

4554

5;D

K45

546;

DK

4554

7;D

K45

887

(GB

3083

24;D

E62

0995

)

W;R

;EIn

cont

inuo

us(s

ever

alda

ys),

whe

nsu

gari

ngr

owth

med

ium

has

been

cons

umed

,spe

ntm

ediu

mis

cent

rifug

ed;t

hera

teof

yeas

tw

ithdr

awal

may

beba

sed,

fore

xam

ple,

onth

eye

ast–

suga

rrat

io;

unde

rcon

trol

led

cond

ition

s,a

spec

ific

amou

ntof

yeas

tfro

mva

rious

sour

cesi

sret

urne

dw

ithor

with

outf

resh

orsp

entw

ort

(fre

efr

omal

coho

land

preh

eate

dat

70°C

)to

1or

seve

ral

ferm

enta

tion

vats

Jaco

bsen

(192

9);l

icen

sed

toSt

anda

rdBr

ands

Inc.

(US

only

);Ju

ne8,

1927

(DK)

DK

DK

4280

8(G

B29

1770

;FR

6601

95;U

S17

5200

3;A

T13

0435

,dep

ende

nton

AT

8355

9)

R;W

;QSu

pply

ofnu

trie

ntis

adap

ted

tobu

ddin

gan

drip

enin

gpe

riods

ofye

astc

ells

;to

keep

cells

inth

ebu

ddin

gst

age

Har

rison

(193

0);a

ssig

ned

toSt

anda

rdBr

ands

Inc.

;Jun

e9,

1927

US

US

1750

267

EA

serie

sof3

to8

ferm

ento

rsar

rang

edat

diff

eren

tand

prog

ress

ivel

ylo

wer

leve

ls;t

oal

low

bett

erpr

oces

scon

trol

and

occa

sion

alcl

eans

ing

Ols

enan

dTh

eIn

tern

atio

nalY

east

Co.L

imite

d(1

928)

;Jun

e21

,192

7G

BG

B29

9336

(DK

4676

1;FR

6768

35;D

E60

7712

)E

Med

ium

(fed

orde

plet

ed)i

stra

velle

din

ase

rieso

ffer

men

ters

prov

idin

gva

riabl

enu

trie

ntsa

dditi

onW

irtsc

haft

liche

Ver

eini

gung

derD

euts

chen

Hef

eind

ustr

ie(1

935)

;Jan

uary

31,1

930

DE

DE

6195

55E

Gro

wn

ina

serie

sofc

ham

bers

ofin

crea

sing

size

Jans

enan

dJa

nsen

(193

1);J

une

19,1

930

NL

GB

3575

41W

;RYe

astc

once

ntra

tion

ism

aint

aine

dat

10to

25g/

Lth

roug

hin

term

itten

torc

ontin

uous

with

draw

alof

med

ium

;fer

men

tatio

nliq

uori

sret

urne

din

tova

t;yi

eld

and

gass

ing

pow

er

(Con

tinu

ed)



Tabl

e13

–Con

tinu

ed.

Inve

ntor

(pub

licat

ion

year

);pr

iori

tyda

tea

Coun

try

Pate

ntnr

.Pr

inci

pleb

Det

ails

Hum

mer

(193

3);F

ebru

ary

4,19

31A

TA

T13

5538

(DE

6550

34)

W;R

Perio

dica

llyse

para

ted

from

the

grow

thm

ediu

m,a

ndfe

dw

ithnu

triti

veso

lutio

nsof

vary

ing

com

posi

tion

and

conc

entr

atio

nD

aran

yi(1

936)

;Inv

entio

nG

esel

lsch

aftf

urV

erw

altu

ngun

dV

erw

ertu

ngCh

emis

chte

chni

sche

rPat

ente

G.m

.b.H

.and

Dar

anyi

(193

2);l

icen

sed

toM

osko

vits

(193

8;D

Eon

ly);

inA

T,jo

intly

licen

sed

to:(

1)V

erei

nigt

eM

autn

erM

arkh

of’sc

hePr

essh

efe

Fabr

iken

und

Akt

ien-

Ges

ells

chaf

tIg

naz

Kuff

ner&

Jaco

bKu

ffne

rfur

Brau

erei

,Spi

ritus

-und

Pres

shef

efab

rikat

ion

Ott

akrin

g-D

oblin

g(V

ienn

a),(

2)Er

ste

Obe

r-Ost

erre

ichi

sche

Spiri

tus-

&Pr

essh

efef

abrik

Jose

fKirc

hmei

r&So

hn(U

rfah

r-Lin

z),a

nd(3

)Bru

der

Rein

ingh

ausA

ktie

n-G

esel

lsch

aftf

urBr

auer

eiun

dSp

iritu

s-In

dust

rie(G

raz-

Stei

nfel

d);A

pril

23,a

ndJu

ly28

,19

31a

DE

GB

3760

38(D

K49

362;

FR74

0817

;US

2035

048;

DE

6599

51;A

T14

5684

;CH

1707

54)

EG

row

nin

ase

rieso

fcon

nect

edfe

rmen

tatio

nve

ssel

s,st

artin

gw

ithhi

ghse

edco

ncen

trat

ion

(8%

byvo

lum

e);m

ediu

mis

regu

larly

with

draw

nto

perm

itco

ntro

lofh

igh

yeas

tcon

cent

ratio

nan

dco

mpe

nsat

efo

rmed

iaad

ditio

n;fin

alm

atur

atio

nfo

r2h

with

out

aera

tion;

toge

thig

hye

astc

once

ntra

tion

(8%

)in

med

iaco

mpa

red

tost

anda

rd(3

.2%

to3.

8%)

Wirt

scha

ftlic

heV

erei

nigu

ngde

rDeu

tsch

enH

efei

ndus

trie

(193

7);J

anua

ry26

,193

2D

ED

E64

1025

EG

row

nin

ase

rieso

fcha

mbe

rsof

incr

easi

ngsi

ze,w

ithau

tom

atic

tem

pera

ture

and

aera

tion

cont

rols

Wirt

scha

ftlic

heV

erei

nigu

ngde

rDeu

tsch

enH

efei

ndus

trie

(193

5);i

nA

T,jo

intly

licen

sed

to:(

1)A

ktie

nGes

ells

chaf

tIg

naz

Kuff

ner&

Jaco

bKu

ffne

rfur

Brau

erei

,Spi

ritus

-und

Pres

shef

efab

rikat

ion

Ott

akrin

g-D

oblin

g,(2

)A

ktie

n-G

esel

lsch

aftf

urSp

iritu

s-un

dPr

essh

efe-

Indu

strie

Wol

frum

,(3)

M.F

isch

l’sSo

hne,

and

(4)V

erei

nigt

eM

autn

erM

arkh

of’sc

hePr

essh

efe

Fabr

iken

(193

5);M

arch

11,1

932

DE

DE

6180

21(A

T14

1399

)E;

RG

row

nin

ase

rieso

fcha

mbe

rsof

incr

easi

ngsi

zein

whi

chm

ash

flow

sat

incr

easi

ngsp

eeds

toav

oid

yeas

tdep

osits

Akt

iese

lska

betD

ansk

Gae

rings

-Indu

stri

(193

7);H

anse

n(1

938;

US)

;Feb

ruar

y26

,193

6(D

K)D

KD

K53

883

(AT

1570

92;F

R81

8300

;GB

4810

45;U

S21

2293

9;FI

1814

7)

W;E

Gro

wn

and

tran

sfer

red

betw

een

2va

ts,l

eavi

ngbe

hind

the

resp

ectiv

ew

orts

;1fe

rmen

tatio

nis

aero

bic

(for

yeas

tpro

duct

ion)

and

the

othe

risa

naer

obic

(for

etha

nolp

rodu

ctio

n);s

imul

tane

ous

prod

uctio

nof

yeas

tand

etha

nol

Scho

llera

ndSe

idel

(194

0);M

ay4,

1936

(DE)

DE

US

2188

192

EU

sing

asp

ecifi

cve

ssel

with

apl

ural

ityof

cham

bers

,yea

stis

fed

with

fres

hnu

trie

ntso

lutio

nan

dfe

rmen

ted

liqui

dis

with

draw

n;yi

eld

Boin

otan

dBo

ige

(194

9);a

ssig

ned

toLe

sUsi

nesd

eM

elle

;Se

ptem

ber1

7,19

43(F

R)FR

FR94

2099

(CH

2425

90;D

K71

046;

US

2446

737;

GB

6006

24)

W;R

Und

erba

tch

cond

ition

s,ye

asti

shar

vest

edw

hen

cells

conc

entr

atio

nis

600

mill

ions

perc

m3

and

asm

allp

ropo

rtio

nof

the

yeas

tis

retu

rned

toth

eva

t;pr

oces

sisr

epea

ted

until

suga

rsar

eas

sim

ilate

d;no

spec

ific

bake

r’sye

asta

pplic

atio

n;yi

eld

Scho

llera

ndSe

idel

(195

8);M

ay3,

1944

DE

DE

9687

21(C

H25

3466

)E

Gro

wn

unde

r2in

depe

nden

tsys

tem

s,pr

ovid

ing

cont

inuo

usfe

edin

gan

dye

astr

emov

alA

ktie

sels

kabe

tde

Dan

ske

Sprit

fabr

ikke

r(19

51);

Oct

ober

31,

1947

DK

DK

7270

1E

Inco

ntin

uous

,con

cent

rate

dgr

owth

med

ium

isad

ded

whi

lea

port

ion

ofth

esp

entg

row

thm

ediu

mis

tran

sfer

red

toa

2nd

vat

Stic

h(1

951,

1957

);Ju

ne17

,194

9(C

H),

Dec

embe

r22,

1949

(DE)

,and

Mar

ch7,

1950

(DE)

DE

CH27

6707

(US

2657

174;

FR10

0043

5;D

E81

4134

);D

E16

0950

4U;D

E93

9023

(CH

2898

81;G

B68

3501

;N

L79

006)

EM

ediu

mci

rcul

ates

coun

terfl

ow(f

rom

the

top)

toth

eae

ratio

nsy

stem

,allo

win

gco

ntro

lled

with

draw

alof

port

ions

;opt

imiz

edae

ratio

n,lo

wfo

amin

g,an

dsm

alle

rvat

s(lo

wer

cost

s)

Mon

od(1

953)

;ass

igne

dto

LeBa

ctog

ene;

Dec

embe

r21,

1949

,Jul

y13

,195

0,an

dN

ovem

ber9

,195

0(F

R)FR

GB

7048

72(C

H28

9373

;US

2686

754;

CA52

0643

)E

Gro

wn

ina

spec

ific

appa

ratu

stha

tallo

wsm

axim

alut

iliza

tion

capa

city

and

abso

lute

hom

ogen

eity

ofth

ecu

lture

;for

yeas

tand

othe

rmic

roor

gani

sms

(Con

tinu

ed)



Tabl

e13

–Con

tinu

ed.

Inve

ntor

(pub

licat

ion

year

);pr

iori

tyda

tea

Coun

try

Pate

ntnr

.Pr

inci

pleb

Det

ails

Rost

(195

2,19

58);

Apr

il19

,195

1D

DD

D52

6;D

D14

136

EIn

cont

inuo

us,g

row

th(f

ed-b

atch

)in

seve

ralv

atsw

hich

are

succ

essi

vely

empt

ied

and

ster

ilize

dM

onod

(195

8);A

ugus

t17,

1954

FRU

S28

2231

9E

Stea

dy-s

tate

syst

emin

whi

chth

egr

owth

rate

ofth

eor

gani

smis

dete

rmin

edan

dpe

rman

ently

mai

ntai

ned;

fory

east

and

othe

rm

icro

orga

nism

sO

lsen

(196

0);a

ssig

ned

toTh

eD

istil

lers

Co.L

imite

d;M

ay10

,19

57G

BG

B82

7404

(US

3057

785;

DK

9945

1)E

Ferm

enta

tion

vess

eldi

vide

din

tose

ctio

nsof

incr

easi

ngvo

lum

es,

with

devi

cesf

orw

ithdr

awin

gga

sbet

wee

nzo

nes;

yiel

dSh

er(1

960)

;ass

igne

dto

The

Dis

tille

rsCo

.Lim

ited;

Aug

ust3

,19

57G

BG

B84

5315

(FR

1209

378;

US

3032

476)

ESe

vera

lcon

nect

edfe

rmen

tatio

nve

ssel

spro

vide

dw

ithco

ntro

loft

hera

teof

tran

sfer

Ebbu

tt(1

960)

;ass

igne

dto

The

Dis

tille

rsCo

.Lim

ited;

Oct

ober

25,1

957

GB

GB

8475

38E

Two

inte

rcon

nect

edfe

rmen

tatio

nve

ssel

s,ea

chw

ithsp

ecifi

cgr

owth

cond

ition

sW

estf

alia

Sepa

rato

rAG

(196

8);N

ovem

ber5

,196

5D

ED

E14

4217

9W

;RYe

asti

sper

iodi

cally

rem

oved

from

the

ferm

enta

tion

tank

and

subm

itted

tose

lect

ive

sepa

ratio

nth

atel

imin

ates

bact

eria

infe

ctio

nin

the

grow

thm

ediu

mw

hich

isre

cycl

ed;y

ield

Schr

oede

rand

othe

rs(1

970)

;ass

igne

dto

Fors

chun

gsin

stitu

tfu

rdie

Gar

ungs

indu

strie

,Enz

ymol

ogie

und

tech

nisc

heM

ikro

biol

ogie

;Nov

embe

r15,

1967

DD

DD

7054

1E

Gro

wn

ina

serie

soft

anks

with

inde

pend

entc

ontr

olpr

ovid

ing

rapi

dgr

owth

rate

and

low

aera

tion

inth

efir

stta

nksa

ndth

ere

vers

ein

the

last

tank

sEh

nstr

om(1

975)

;ass

igne

dto

Alfa

-Lav

alA

B;Ju

ly9,

1973

(SE)

SESE

7309

617

(DE

2426

120;

US

3940

492;

15ot

hers

)E

Feed

ing

inan

elon

gate

dcl

osed

chan

nel;

wor

tisc

ontin

uous

lyce

ntrif

uged

todi

scha

rge

exce

ssof

yeas

tcel

lsfr

omth

eci

rcui

tto

avoi

din

terr

uptio

nof

oper

atio

nsFu

kuda

and

othe

rs(1

978a

,197

8b,1

978c

,197

8d,1

979)

;as

sign

edto

Kane

gafu

chiK

agak

u;A

ugus

t27,

1976

JPJP

5302

9985

;JP

5304

7583

;JP

5311

8584

;JP

5312

4677

;JP

5403

2687

(GB

2003

177;

FR24

0006

1;U

S42

8472

4)

W;R

Brot

hco

ntai

ning

yeas

tisp

erio

dica

llyre

mov

ed,a

ndye

asti

sse

para

ted

and

retu

rned

toth

efe

rmen

tort

oge

thig

hye

astc

ell

conc

entr

atio

n(6

%to

20%

)and

supp

ress

the

grow

thof

cont

amin

ants

;yie

ld

Knac

kmus

sand

othe

rs(1

985a

,198

5b);

assi

gned

toA

kade

mie

derW

isse

nsch

afte

nde

rDD

R;D

ecem

ber1

5,19

83

DD

DD

2200

45;D

D22

5438

QFe

edra

tean

dai

ram

ount

are

dete

rmin

edby

yeas

tand

etha

nol

leve

ls;g

assi

ngpo

wer

Ripk

a(1

985)

;ass

igne

dto

Nab

isco

Bran

ds,I

nc.;

Janu

ary

4,19

84U

SEP

0148

764

(US

4764

471)

ECo

ntin

uous

feed

ing

thro

ugh

atu

bula

rmem

bran

em

ater

ial

prov

idin

ghi

ghly

aero

bic

cond

ition

s(ox

ygen

-rich

gass

trea

m)

aBr

eakt

hrou

gh.

bE,

equi

pmen

t;R,

recy

cled

med

ia;W

,with

draw

nm

edia

.



Table 14–Patents published between 1900 and 2009 on alcohol recovery during the manufacturing of baker’s yeast.a

Inventor (publication year)priority date Country Patent nr. Details

Maschinenbau-AktiengesellschaftGolzern-Grimma, and Zeckendorf (1911);November 5, 1910 (DE)

DE; US DE 240473 (AT55758; GB191122411; FR434949)

At the outlet of the aeration system, alcohol is recovered bymixing air with steam and condensed

Maschinenbau-AktiengesellschaftGolzern-Grimma (1913); November 8,1911 (DE)

DE DE 255300 At the outlet of the aeration system, alcohol is recoveredwith solvent-impregnated fabrics which is regularlysqueezed

Fischl and Schick (1913); February 5, 1912 HU AT 57434 Vessel is covered with wire netting to condense alcoholPfalzische Presshefen- und Spritfabrik

(1924); March 9, 1923DE DE 399894 Vessel is covered with a pipe system with showers

aNot included in the list of patents on baker’s yeast production (Table 1).

high gassing power. This was confirmed by Zamani and others(2008) who showed that slightly higher sugar concentration in thegrowth medium had a slight depressing effect on yield, althoughit improved nitrogen assimilation, which resulted in higher doughleavening ability and improved shelf-life.

Continuous withdrawal-addition process. A more sophisticatedway to control sugar concentration in the growth medium wasthe “continuous withdrawal-addition process” that consisted inpumping out growth medium at a specific rate to recover yeastand replace spent growth medium. Again, such a process had beenpatent-protected in 1879 by Rainer who proposed “the successiveadditions of peptones and hydro-carbons to the propagating liquidtogether with the successive removals of the yeast produced.” Inthe 1920s, as shown in Table 13, this became a very popular con-cept that was likely to eliminate frequent stop of yeast productionto recover biomass and clean fermentation tanks.

In the early years, inventors simply recommended withdrawal ofportions of growth media so yeast could be harvested continuously.To a lesser extent, some inventors also saw some opportunities forrecycling spent growth media. From 1925 to the 1980s, most of thepatented inventions on this process described very specific equip-ment for controlling fermentation, including feed and withdrawalrates of the growth medium. According to patent activity, interestin technologies related to continuous culture lasted longer thanfor the improvement of fed-batch processes. According to a patentby Knappe (1933) cited in Table 11, infection problems with so-called addition-withdrawal continuous processes were more im-portant than true economical benefits, so this process did not findwidespread application. Hence, about 1 century after the imple-mentation of modern production practices, baker’s yeast is stillproduced with a discontinuous or fed-batch process.

Nitrogen Concentration and Rate of AdditionTable 15 presents a list of patented inventions on nitrogen con-

trol during baker’s yeast manufacturing. In the early days of thistechnology, this aspect was a critical issue, although not as much asthe control of sugar concentration in growth media. Most of thepatented inventions in 1900 to about 1950 proposed the best com-binations of organic and inorganic nitrogen sources, with thoroughcontrol of acidification. Several attempts were made to use inor-ganic nitrogen salts instead of miscellaneous nitrogen-rich plantextracts. To control pH, inventors also recognized that slightlyacidic conditions were essential for controlling yeast infection, butthe addition of inorganic nitrogen-based compounds caused pHfluctuations, which had a negative effect on yeast growth and over-all quality. This is why some authors proposed to indirectly controlpH with specific nitrogen-based ingredients.

Historical contextIn the early days of baker’s yeast production, cereal-based me-

dia were the main growth medium and little interest was givento alternative sources of inorganic nitrogen sources. Malt sproutswere generally used in addition to malt as a source of nitrogenousfood. Besides ammonia, interest in organic sources of nitrogen forgrowing yeast lasted until the 1930s (Gelinas 2012). During thatperiod, it was already known that yeast could be nourished withorganic or inorganic nitrogen, the latter being much cheaper thanmalt sprouts. In growth media, yeast cells first take up the ammo-nium salts, as ammonia, because of its simple composition, insteadof organically combined nitrogen. However, it was not possible togrow yeast solely with inorganic salts of ammonia because yeastyield and gassing power dropped markedly.

According to Hamburger and others in a German patent filedin 1924, when mineral salts are used as the sole or main sourceof nitrogen in growing yeast, the acidity of the fermenting massincreased at the rate at which the ammonia was consumed by theyeast. For this reason, the mineral acids liberated by the action ofthe growing yeast were usually rendered innocuous by neutraliza-tion. This measure did not remove the anions of the mineral acids,which adversely affect the growth and the quality of the yeast. Ithas therefore been the practice to employ free ammonia which wasconsiderably more expensive than, for instance, ammonium sulfateand moreover necessitates a most careful control of the fermenta-tion process. For example, ammonium salts are added to substitutefor organic nitrogen sources because they are cheaper and stimu-late yeast reproduction. Yeast manufacturers preferred the organicsource of nitrogen because it produced yeast with greater gassingpower and keeping properties. On the contrary, yeast preparedwith inorganic nitrogen has the disadvantage that, while it is veryrich in protein, it is not durable and its fermenting power, whichis very good at first, decreases in a very short time. As cited inGelinas (2012), to obtain the best color of the finished product,it is necessary to closely regulate the degree of acidity producedduring the period of yeast propagation (King 1935).

Compared to sugar concentration, few quality control toolsappeared to have been patent-protected for the surveillance of therate of addition of nitrogen in yeast growth media. It seems thatpH determination was the main quality control tool. In 1953,Olsen proposed to determine excess nitrogen in growth media,using the well-known “formol degree” test which was adopted bythe yeast industry.

ConditioningWhen the feeding period is over, yeast may be ripened or treated

to improve its properties, as shown by 15 patents described inTable 16. Most of these efforts have been made to stimulate yeastgassing power and keeping properties, for example, with intense



Tabl

e15

–Pat

ents

publ

ishe

dbe

twee

n19

00an

d20

10on

the

conc

entr

atio

nan

dra

teof

addi

tion

ofni

trog

en-b

ased

ingr

edie

nts

duri

ngth

em

anuf

actu

ring

ofba

ker’s

yeas

t,in

clud

ing

acid

ity

cont

rol.

Inve

ntor

(pub

licat

ion

year

);pr

iori

tyda

teCo

untr

yPa

tent

nr.

Prin

cipl

eD

etai

ls

Will

cox

(191

2);A

pril

29,1

912a

US

US

1044

615

R;O

;AG

radu

alad

ditio

nof

wat

eram

mon

iato

neut

raliz

eth

eac

idity

ofw

aste

sulfi

teliq

uor(

pape

rman

ufac

turin

gby

-pro

duct

);w

itham

mon

ium

salts

and

phos

phor

icac

id;a

erat

edPo

llak

(191

3);A

ugus

t9,1

912

(DE)

DE;

FRD

E26

6396

(CH

6553

9;G

B19

1313

193;

US

1123

920;

AT

6402

2)

R;O

Gra

dual

addi

tion

ofw

ater

amm

onia

tofo

rmla

ctic

acid

acid

deriv

ativ

es(y

east

nutr

ient

s);f

orce

real

-bas

edm

edia

Mos

kovi

ts(1

923a

,b,c

);D

ecem

ber5

,19

13(H

U)

ROH

U77

361;

GB

1746

25;

GB

1746

26;G

B17

4627

R;I;

AG

radu

alad

ditio

nof

amm

oniu

msa

lts(la

ctat

e)or

amin

oco

mpo

unds

,pre

fera

bly

with

am

ixtu

reof

dist

iller

yye

ast(

mai

nly)

and

Toru

la,a

ndw

ithox

idas

e;un

der

aera

tion

and

toco

ntro

linf

ectio

n,ac

idity

isco

ntro

lled

with

caus

ticso

da;s

ubst

itute

tom

alte

xtra

ctW

ohla

ndSc

herd

el(1

919)

;Woh

l(19

23);

licen

sed

toTh

eFl

eisc

hman

nCo

.(U

Son

ly);

Janu

ary

16,1

915

DE

DE

3105

80(F

R51

7038

;D

K30

865;

GB

1456

23;

CH95

835;

AT

9483

6;U

S14

7521

5)

R;I;

AG

radu

alad

ditio

nof

10%

to50

%am

mon

ium

salts

(sul

fate

,pho

spha

te,o

rnitr

ate)

aspa

rtia

lsub

stitu

teto

mal

tspr

outs

(mor

eex

pens

ive)

;aci

dity

isco

ntro

lled

byca

rbon

ates

;cer

eal-o

rsug

ar-b

ased

med

ia;a

erat

ed;

cost

,com

pres

sibi

lity,

and

keep

ing

prop

ertie

sH

aydu

ck(1

923)

;Ver

ein

der

Spiri

tus-

Fabr

ikan

ten

inD

euts

chla

nd(1

919)

;lic

ense

dto

The

Flei

schm

ann

Co.(

US

and

CA);

Febr

uary

25,M

arch

16,M

arch

20,A

pril

16,a

ndA

pril

24,

1915

a

DE

DE

3006

63(D

K29

326;

FR52

0523

;GB

1552

81;U

S14

4910

2;CA

2217

56);

DE

3032

51(F

R52

0523

;G

B15

5286

;US

1449

103,

inva

lid;C

A23

8175

);D

E30

3222

(GB

1552

85;U

S14

4910

6,in

valid

;CA

2381

78);

DE

3042

42(G

B15

5287

;US

1449

110;

CA23

8179

);D

E30

4243

(GB

1552

89;U

S14

4910

9,in

valid

;CA

2381

80)

R;I;

AG

radu

alad

ditio

nof

high

leve

lsof

amm

oniu

msa

ltsin

high

lydi

lute

dm

olas

ses(

abou

t7×)

;aci

dity

isco

ntro

lled

byth

epr

ogre

ssiv

ead

ditio

nof

amm

onia

wat

eror

amm

oniu

mca

rbon

ate;

aera

ted;

yiel

dan

dga

ssin

gpo

wer

;firs

tto

avoi

dor

gani

cni

trog

en

Har

rison

(192

0);N

ilsso

nan

dH

arris

on(1

922)

;The

Flei

schm

ann

Co.(

1921

);Ja

nuar

y7,

1919

(US)

US;

GB

CA20

6753

;CA

2425

40(F

R51

9798

;GB

1483

73;U

S14

4912

7)

OPh

osph

orus

(pho

spho

ricac

id,a

mm

oniu

mph

osph

ate)

tosu

pple

men

tbee

tmol

asse

sund

erne

utra

lcon

ditio

nsan

dw

ithgr

adua

ladd

ition

ofaq

uaam

mon

ia;c

ost,

yiel

d,co

lor,

and

keep

ing

prop

ertie

sKo

hman

and

othe

rs(1

923)

;ass

igne

dto

The

Flei

schm

ann

Co.;

Janu

ary

20,

1919

a

US

US

1475

494

AIn

crea

sed

acid

ityis

stric

tlyco

ntro

lled

bygr

adua

lad

ditio

nof

carb

onat

es;c

ost,

yiel

d,an

dga

ssin

gpo

wer

Hix

son

and

Hug

oson

(193

0);a

ssig

ned

toSt

anda

rdBr

ands

Inc.

;Jan

uary

14,

1921

US

US

1745

693

O;A

pHco

ntro

l(6)

with

abu

ffer

(chl

orid

eof

lime

and

salts

ofph

osph

oric

acid

)and

urea

(sol

eni

trog

enso

urce

;doe

sno

tfor

mac

idor

base

subs

tanc

es);

with

amm

oniu

msu

lfate

(to

prev

entc

ells

aggr

egat

ion)

;yie

ldPo

llak

(192

7);S

epte

mbe

r29,

1923

(CS)

CS;A

TU

S16

2467

4I;

AA

mm

oniu

mla

ctat

e(f

rom

ferm

ente

dla

ctic

acid

neut

raliz

edw

ithni

trog

en-c

onta

inin

gal

kalis

)is

cont

inuo

usly

form

edin

mol

asse

s-ba

sed

med

ia;y

ield

Barr

ingt

on(1

930)

;ass

igne

dto

Stan

dard

Bran

dsIn

c.;N

ovem

ber1

6,19

23U

SU

S17

8461

8O

;I;A

pHco

ntro

lwith

aqua

amm

onia

(1st

stag

es)a

ndam

mon

ium

sulfa

te(la

ters

tage

s);y

ield

(Con

tinu

ed)



Tabl

e15

–Con

tinu

ed.

Inve

ntor

(pub

licat

ion

year

);pr

iori

tyda

teCo

untr

yPa

tent

nr.

Prin

cipl

eD

etai

ls

Web

er(1

925)

,ass

igne

dto

Rhei

nisc

her

Act

ien-

Ver

einf

urZu

cker

fabr

ikat

ion

(DE

only

);Cl

aass

en(1

927)

,ass

igne

dto

Web

er(G

Bon

ly)a

ndPf

eife

r&La

ngen

Akt

.-Ges

.(D

Eon

ly);

Mar

ch2,

1924

and

Janu

ary

22,1

926

(DE)

DE

GB

2300

98(D

E53

6989

);G

B26

4795

(DE

5887

38)

IA

mm

oniu

msa

ltsar

ead

ded

only

atth

ebe

ginn

ing

orth

e1s

tsta

geof

the

ferm

enta

tion

(low

tem

pera

ture

);to

stim

ulat

eye

astg

row

th;g

assi

ngpo

wer

and

keep

ing

prop

ertie

s

How

ells

(192

5);M

arch

3,19

24(A

U)a

AU

FR59

3402

(GB

2301

10;

US

1725

583;

CH12

0505

)

RRa

teof

addi

tion

ofsu

gars

toni

trog

enis

base

don

ara

tio(1

7.5

to1)

,acc

ordi

ngto

aye

asth

ourly

grow

thra

teof

1.26

;yie

ldH

ambu

rger

and

othe

rs(1

925)

;ass

igne

dto

Mel

lem

euro

paei

skPa

tent

-Fin

anci

erin

gs-S

elsk

abA

ktie

sels

kab;

licen

sed

toSt

anda

rdBr

ands

Inc.

(US

only

);M

arch

3,19

24(D

E)

CSG

B23

0051

(DK

3555

0;FR

5931

28;U

S17

3396

2;CA

2584

56)

AA

mm

oniu

mla

ctat

eis

cont

inuo

usly

form

edby

inte

ract

ion

ofla

ctat

eof

lime

(fro

mfe

rmen

ted

lact

icac

id)a

ndam

mon

ium

sulfa

te;t

oel

imin

ate

SO4

anio

nsth

atin

hibi

tsgr

owth

;yie

ldan

dco

lor

Effr

ont(

1926

);A

pril

18,1

925

FRFR

6014

84R;

OG

radu

alad

ditio

nof

liqui

dam

mon

iaw

ithsm

alla

mou

nts

ofhy

drol

yzed

prot

ein

(to

get3

0to

150

mg

nitr

ogen

perl

iter)

,with

nitr

icni

trog

en;w

ithm

olas

ses-

base

dm

edia

(car

bona

te-t

reat

ed);

yiel

dBa

lls(1

930)

;par

tlyas

sign

edto

Nils

son

and

Hix

son;

Dec

embe

r24,

1925

US

US

1759

536

A;I

pHco

ntro

lwith

perio

dica

ladd

ition

ofca

lciu

mla

ctat

e;w

ithur

eaas

the

sole

nitr

ogen

sour

ce(d

oesn

otfo

rmac

idor

base

subs

tanc

es);

yiel

dBu

cher

(192

8);F

ebru

ary

19,1

927

DE

GB

2922

02A

;O;I

Carb

amid

e(u

rea)

topr

even

tmed

iaov

er-a

cidi

ficat

ion

and

the

use

ofaq

uaam

mon

iato

neut

raliz

eit,

and

allo

win

gm

edia

reus

e;ad

ded

with

amm

oniu

msa

ltsin

aera

ted

mol

asse

s-ba

sed

med

ia;c

ost

Brat

ton

(192

9);a

ssig

ned

toA

nheu

ser-B

usch

,Inc

.;A

pril

15,1

927

US

US

1732

922

A;O

Glu

co-u

reid

es(u

rea

with

redu

cing

suga

rs)t

hatd

ono

tac

idify

mol

asse

s-ba

sed

med

iaan

dsh

owco

mpl

ete

assi

mila

tion

cont

rary

tour

ea;y

ield

Frey

and

othe

rs(1

931)

;ass

igne

dto

Stan

dard

Bran

dsIn

c.;J

une

30,1

927

US

US

1814

210

(CA

3006

18)

R;O

;AG

radu

alad

ditio

nof

urea

and

urea

seun

derp

Hco

ntro

l(4

.2to

4.5)

;to

optim

ize

nitr

ogen

avai

labi

lity

from

urea

and

avoi

dac

idifi

catio

n;yi

eld

Ferm

enta

(192

9);J

anua

ry18

,192

8YU

YU57

99R;

O;I

Add

edgr

adua

lly,a

smal

lpor

tion

ofor

gani

cni

trog

enis

repl

aced

byin

orga

nic

nitr

ogen

(am

mon

ium

chlo

ride

orca

rbon

ate)

Schu

ltz(1

936)

;ass

igne

dto

Stan

dard

Bran

dsIn

c.;D

ecem

ber2

9,19

31U

SU

S20

2959

2R

Seed

yeas

t(w

ithhi

ghpr

otei

nle

vel)

isgr

own

unde

rco

ntro

lled

phos

phor

usan

dni

trog

enad

ditio

n;yi

eld,

gass

ing

pow

er,a

ndke

epin

gpr

oper

ties

Pfei

feru

ndLa

ngen

A.G

.(19

33);

Febr

uary

23,1

933

DE

FR75

1268

OEa

sy-a

ssim

ilate

dni

trog

enfr

omor

gani

cso

urce

sisa

dded

first

,the

nha

rd-t

o-as

sim

ilate

amin

oac

idsi

sadd

edpr

ogre

ssiv

ely

for5

to6

h,an

dfe

rmen

tatio

nen

dsw

itham

mon

iaso

lutio

n;yi

eld

and

gass

ing

pow

erSc

hultz

and

othe

rs(1

936)

;ass

igne

dto

Stan

dard

Bran

dsIn

c.;S

epte

mbe

r26,

1934

US

US

2032

443

I;O

;AA

mm

oniu

mla

ctat

eis

prog

ress

ivel

yfo

rmed

byfe

rmen

ted

lact

icac

idne

utra

lized

byam

mon

ia(f

orm

edby

urea

and

urea

se);

yiel

dBr

owne

(193

9);F

ebru

ary

23,1

937

US

US

2166

339

I;A

Gra

dual

addi

tion

ofam

idin

es(g

uani

dine

and

guan

ylgu

anid

ine)

with

phos

phor

icac

id;t

oav

oid

prod

uctio

nof

dele

terio

usac

idity

;yie

ldTh

eIn

tern

atio

nalY

east

Co.L

imite

dan

dM

eyer

(193

9);M

eyer

(194

0);l

icen

sed

toSt

anda

rdBr

ands

Inc.

(US

only

);Fe

brua

ry9,

1938

GB

GB

5027

62(U

S22

1402

8)I;

AG

radu

alfo

rmat

ion

ofam

mon

ium

acet

ate

byth

ere

actio

nof

acet

icac

idw

itham

mon

ium

hydr

oxid

e;to

avoi

dac

idifi

catio

n;yi

eld

Seid

el(1

951)

;Dec

embe

r14,

1940

DE

DE

7598

41(F

R87

8985

)I;

AA

dditi

onof

inor

gani

cni

trog

enis

stric

tlyco

ntro

lled

(not

dete

ctab

le);

FRpa

tent

also

cove

rsan

ti-fo

am;y

ield

Ols

en(1

956)

;Dec

embe

r18,

1953

aG

BG

B76

2655

QA

utom

atic

dete

rmin

atio

nof

form

olde

gree

,an

indi

catio

nof

the

nitr

ogen

cont

enti

ngr

owth

med

iaa

Brea

kthr

ough

.b

A,a

cidi

tyco

ntro

l;I,

inor

gani

cni

trog

en;O

,org

anic

nitr

ogen

;Q,q

ualit

yco

ntro

l;R,

rate

ofad

ditio

n.



Tabl

e16

–Pat

ents

publ

ishe

dbe

twee

n19

00an

d20

09on

the

final

ferm

enta

tion

step

san

dco

ndit

ioni

ng(r

ipen

ing)

duri

ngth

em

anuf

actu

ring

ofba

ker’s

yeas

t.

Inve

ntor

(pub

licat

ion

year

);pr

iori

tyda

tea

Coun

try

Pate

ntnr

.D

etai

ls

Braa

sch

(191

0);S

epte

mbe

r12,

1909

(DE)

aD

ED

E22

7777

Whe

nm

osto

fthe

suga

rhas

been

assi

mila

ted

(1.5ºB

),ae

ratio

nis

cont

inue

dw

ithre

cycl

edai

rins

tead

offr

esh

air;

yiel

dBr

aasc

h(1

911)

;Oct

ober

16,1

909

(DE)

DE

FR43

2860

(GB

1910

2366

2,no

tac

cept

ed)

Yeas

tofi

nfer

iorq

ualit

yis

re-fe

rmen

ted

indi

lute

dm

edia

and

ripen

edat

alo

wte

mpe

ratu

re;g

assi

ngpo

wer

Reik

and

Roth

(191

4);J

uly

10,1

913

AT-

HU

(AT)

AT

6545

9In

non-

aera

ted

med

ia(V

ienn

apr

oces

s),y

east

isha

rves

ted

befo

reits

full

mat

urat

ion,

clea

ned,

and

grow

nun

deri

nten

seae

ratio

nin

dilu

ted

med

ia;y

ield

Ham

burg

eran

dot

hers

(192

6);

Mel

lem

euro

paei

skPa

tent

-Fin

anci

erin

gs-S

elsk

abA

ktie

sels

kab

(192

5);D

ecem

ber3

1,19

23(D

E)a

CS;C

S;A

TFR

5906

85(A

T10

8897

;GB

2271

19)

Aft

erse

para

tion

and

unde

rslig

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aeration for several hours. A few patents described treatments forreducing off-flavors in baker’s yeast, in the fermentation vat andprior to harvesting.

Historical contextIn the early days of baker’s yeast technology, contamination

(infection) of baker’s yeast was of major concern as this reducedits gassing power and keeping properties (Gelinas 2010a). Whenfeeding was completed, a ripening period was proposed by Braaschin 1909, allowing continued aeration. This step appeared to havebeen readily adopted because it was mentioned in most of thepatents issued later. In some cases, prior to harvesting, yeast wasfed with specific nutritive solutions to suppress cell budding andimprove its keeping properties.

Major BreakthroughsImportant breakthroughs have been obtained from patents on

the control of fermentation during the production of baker’s yeast.

A. Fed-batch process: Gradual addition of nutrients is the heart ofbaker’s yeast production. Such an inventive idea was developedin 1879 by Rainer (Gelinas 2010a) so, contrary to commonknowledge, patents filed between 1915 and 1935 were adapta-tions of this concept. Addition of concentrated growth mediato a diluted solution (and not the contrary) was the most use-ful improvement by Hayduck in 1915. Rates of addition wereprecised by Sak in 1919. Compared to the batch process whereall ingredients are added simultaneously, the fed-batch processgreatly improved yeast yield, gassing power, and keeping prop-erties.

B. Infection control: As reported in Gelinas (2010a), pure seedyeast and sterile growth conditions were already applied inthe 19th century for the production of miscellaneous foods,including baker’s yeast, beer, and so on. In the early daysof bakers’ yeast manufacturing, hygienic conditions of large-scale fermentation vats needed much improvement. One goodexample was the abandonment of wood fermentation tanks,an innovative idea proposed by Lapp in 1902. Much later, in1934, Kitzmeyer stressed the importance of repeated transferof yeast starters from growth media, to avoid its degradation.

C. Temperature: The importance of temperature control has longbeen dismissed in large-scale fermentation. However, effectivecooling units did not appear to have been proposed for suchapplications until Wahl filed his patent specification in 1919.

D. Acidity control, nitrogen feeding: The optimal combinationsof nitrogen sources (organic or inorganic) were difficult todetermine. Thanks to a series of patent applications filed byHayduck in 1915, the importance of gradual feeding of ni-trogen sources was made popular in the industry. However,the main contribution of these patents may be the use of in-organic nitrogen. This has led to the development of severalpatented solutions for finding the right combinations of nitro-gen sources, to avoid overacidification of the growth medium.

E. Ripening: The importance of the final steps of yeast growthwas recognized very early as shown by the patent specificationsby Braasch in 1909, allowing a short period of starving to allowcells to complete their growth cycle and form some reservematerial. This simple idea had a major impact on yeast keepingproperties and was widely adopted by the yeast industry.

F. Quality control: Thorough control of the fed-batch processwas not available until the 1950s when Olsen, in 1953, andVogelbusch, in 1958, respectively, proposed to measure ni-trogen in the growth medium and ethanol in the outlet of

aeration units. This has led to a series of patents describingimproved units for the optimization of feeding curves.

Technological Lessons from Patents on FermentationControl

This review of the patent literature on fermentation control forbaker’s yeast production shows that, contrary to common belief,many of the innovative ideas in this sector were developed in the19th century, not in the 20th century. Nowadays, several of thepatented inventions developed after 1900 may be regarded as im-provements on former innovative ideas. This may explain whyessential patents for the yeast industry, such as those developed byHayduck in 1915, were later invalidated in courts. This strange sit-uation indicates that it may be very difficult to claim inventorshipon processes. It is likely that many inventors and companies de-cided not to patent their innovative ideas, preferring trade secrecyto keep technological advantages without disclosing their claimsto competitors.

Fermentation control of baker’s yeast production has been atthe forefront of the development of several industrial fermentationtechnologies. Since the 1950s, thorough quality control tools wereproposed and this certainly helped much to assure the productionof baker’s yeast with constant quality.

Impact on the Baking IndustryIn 1900, the cost of baker’s yeast was a serious obstacle to its

widespread use by bakers. Reduction of yeast quantities in doughwas a major concern for bakers, and this led to the development ofseveral additives for stimulating yeast activity or improving doughgas retention, including potassium bromate. Getting yeast withhigh gassing power and good durability was also a concern. Yeastwith a pale color was important; crumbling qualities and absenceof off-flavor were also mentioned in several patent specificationson yeast fermentation control.

Along with the optimization of growth media (Gelinas 2012),improvement of fermentation control during baker’s yeast produc-tion greatly reduced its cost due to increased yields and reducedcontamination. Modern baker’s yeast with uniform gassing powercould be shipped to bakers and kept for longer periods.

ConclusionsThis literature review on fermentation control indicates that

baker’s yeast technology developed as a large-scale industry withinabout 30 y, between 1910 and 1939, in parallel to the optimizationof growth media (Gelinas 2012). Nowadays, online processingcontrol tools are still searched for to further optimize the qualityof baker’s yeast. Surprisingly, several of the early key inventionsdisclosed in patents on the control of sugar concentration ingrowth media were later invalidated for want of novelty. After1940, this situation dismissed the true value of patents describingprocesses and probably encouraged trade secrets in the yeast sectorand other industries. Between 1900 and 2009, the main incentivesin the yeast industry were clearly to simplify the manufacturingprocess, to get the highest yields possible, to reduce costs, and toimprove gassing power of baker’s yeast. More effort was neededto improve yeast keeping properties and that essentially camethrough the development of active dry yeast.

Conflict of interestThere is no conflict of interest.



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Fermentation control in baker’s yeast production

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