8/13/2019 Contamination Inhibition Antibiotics as Inhibitors of Micr

1/5

(8) Fiske, C. H., and Subbarrow. Y..(9) Gilligan. G. M.: and Baker: G. L.,J . Biol Chem.. 66, 375 (1925).unpublished data, 1952.

(10) Green, J., Ind. Eng. Chem.?42, 1542(1950).(11) Hafford, B. C.. Leonard. F., andCummins? R. W., nd. En?.Chem., Anal. Ed.. 18 411 (1946).( 12 ) Hassid, \V. Z. , A Symposium ofPhosphorus Metabolism, X7o1.I. p. 14. Baltimore. Md.: Johns

Hopkins Press, 1951.(13) Henglein, F. A, , Krassig, H. andSteimmig, A , > Makromol . Chem..4 78 (1949).(14) hlaclav. W. D.. and Owens. H. S . .Chemurgic Digest. 6 ( 2 2 ) > 3 2 51 947).

(15) Natl. Bur. Standards: Letter Circ.993 (Aug. 10, 1950).(16) Pederson, K., U. S. Patent 2,540,-545 (Feb. 6, 1951).(17) Rudy, H., Angew. Chem., 54 447(1941).(18) Rud y, H ., Schloesser: H. : andWatzel, R. , Ibid ? 3, 525 (1940).(19) Sardik, Inc., French Patent 747:561

(Ju ne 20, 1933).( 2 0 ) Schneider, G.?and Bock, H., Chem.Ber., 71B, 1353 (1938).(21) Schultz, T. H.. Miers, J. C :Owens,H. S., and Maclay, W. .: J .PhTs. Colloid. Chem ., 53, 1320(1949).(22) Schultz. T. H.. Owens. H. S.. andMaclay, W. ., J . Colloid Sci., 353 (1348).( 2 3 ) \.an Wazer. J. R.. and Campanella,

D. A. , J . A m . Chem. SOL 2 , 655(1950).(24) Watzel, R.. Chemie. 55, 356 (1942).(25) Westman, A . E . R.. Scott. -4. E. .and Pedley, J. T.. Chem. in Can-ada, 4,35 (1952).(26) iVoodmansee. C. W.. nd Baker,G. L.. Calcium Pectinates,The ir Preparation an d Uses.Division of Agricul tural andFood Chemistry, 122nd Meeting,Atlantic City, 1952. MERICAN CHEMICAL SOCIETY

Receioed or reoiero J u b 76, 7953. AcceptedOctober 73, 7953. Part of a thesi s submztted tothe faculty of the Cnioersity of Delaware byG . R . T4aLler in partial fu(fi1lment of therequirementsfor the degree of master of science,September 7952.

Penicillin, Poly my xin, Thiolutin Control Infection in Beer Fermentatio n

CONT A M NAT10N NH B I T ONAntibiotics as Inhibitors of MicrobiologicalContamination in Beer

F B. STRANDSKOV and J. B BOCKELMANNThe F. 8 M. Schaefer Brewing Co., Brooklyn, N. Y.

The purpose of this investigation was to study the application o f antibiotics to the controlof bacterial and secondary yeast contamination in the brewery. Polymyxin was outstand-ing in its ability to control the Gram-negative bacterial infection of brewers yeast andbeer fermentation. The addition of bactericidal concentrations of polymyxin and othereffective antibiotics to the fermenting beer results in a stimulation of the fermentation.Of the antibiotics studied, penicillin is the most effective in the control of the Gram-positivelactic acid bacteria in finished beer. Used in combination with thiolutin for the control ofsecondary yeast growth, it gives complete protection against microbiological growth infinished beer.

.4NGER O F INFECTION with otherD microorganisms is one of the prob-lems that are common to all microbiolog-ical processes, in which pure cultures areused. Th e fermentation of beer in abrewery is no exception and at timesthe bacterial infection of the fermenta-tion presents a serious problem.

Breizers yeast infected with bacteriato a dangerous extent is often treatedM ith such weak bactericides as tartaricor phosphoric acid. This treatment.when carried out properly, kills a largepercentage of the contaminating bac-teria without affecting the yeast ad-versely. However, when such a treatedyeast is used in a subsequent fermenta-tion, the surviving bacteria again beginto multiply and the original level of in-fection is reached within a relativelyshort time.

The use of antibiotics in the control ofbacterial infections of brewers yeastwas reported on by Gray and Kazin asearly as 1946 7 ) . These investigatorsfound that the antibiotic tyrothricin com-pared favorably with the commonlyused bactericidal substances, but onlywhen its concentration \yas raised to500 p.p. m. Other investigators (2, 3have reported that the gro\vth of thelactic acid bacteria in finished beer canbe controlled by the addition of penicil-lin.

Strandskov, Brescia, and Bockelmann5) found that the antibiotic polymyxin

inhibits the groivth of the Gram-neg-ative rods, Gram-positive lactic acidcocci, and Gram-positive lactic acid rodsthat commonly contaminate brewersyeast and beer,, at concentration levelsmat are not inhibitory to brewery yeast.

These inhibitory studies ivere carried o uton a yeast extractdextrose medium.

These findings suggested that poly-myxin as well as other antibiotics shouldbe useful bacteriostatic and bactericidalagents in the brewery fermentation, dur-ing storage. and possibly in the finishedproduct.

The effect of polymyxin on the Gram-negative bacterial infection during fer-mentation was studied using as fermen-ters 3-liter glass cylinders, 3 inches indiameter and 36 inches tall. I t \vas dem-onstrated in a preliminary experimentthat fermentation in such a cylinderproceeds at the same rate as in a plantfermenter. T o test the effect on a fer-mentation, the desired quantity of anantibiotic, in 10 ml. of distilled water,was added to each cylinder except thecontrol , to which 10 ml. of distilled bvater

V O L . I , NO. 2 0 D E C E M B E R 23, 1 9 5 3 1219

8/13/2019 Contamination Inhibition Antibiotics as Inhibitors of Micr

2/5

I30

4.9 124.8 i I

io4.7e 9.0

8.04.6

f 4.5 v7.0a4.4 W 6.0

4.3 5.04.0.2

4.1 3.04 0 12 24 36 48 60 72 84 96 108 120 2 o Ih 24 /6 , 7 , 84 d6 Id8 120

HOURS AFTER PITCHING HOURS AFTER PITCHINGEffect of polymyxin on rate o f beer fermentationigure 1 Effect of polymyxin on pH of fermenting beer Figure 2.

were added. Thre e liters of fermentingbeer from a fermenter that had just beenfilled, which \vas contaminated withGram-negative bacterial rods of theFlavobacterium proteus type, were added toeach cylinder and the cylinders weresuspended in a temperature-controlled

Table 1 Mini mum Concentration ofAntibiotics Bactericidal to Gram-

Negative Rod Infection DuringNormal Fermentation

A n f i b i o f i c C o n c n . ,A n f i b i o f i c ?/MI.Streptomycin >125Bacitracin > 1 2 5Terram ycin 50Thiolutin >10Penicillin > 1 2 5Subtilin > 1 2 5Aureomycin 50Polymyxin B. 0 . 0 0 5

water bath. The temperature of thebath water was adjusted twice daily, sothat the fermentation temperature con-formed as nearly as possible to plant fer-mentation temperatures. Aliquots of thefermenting beer were drawn daily foranalysis. The bacterial plate countswere made on a dextrose-yeast extrac tmedium {vhich contained actidione as ayeast inhibitor 4) .

The data in Table I show the mini-mum concentrations of the antibioticsstudied that would completely eliminatethe Gram-negative bacterial rod infec-tion. This was the only type of infec-tion present. Thiolutin is not very sol-uble in water and could, therefore, notbe studied at a concentration level higherthan 10y per ml. of fermenting beer.

Terramycin, Aureomycin, and poly-myxin were found to be the only effec-tive antibiotics in the concentration levels

studied. The activity of polymyxinwas so superior relative to that of theother antibiotics that a rather detailedstudy of its effect on the fermentationwas made.

Selected data are presented in TableI1 to show the effect of a wide range ofpolymyxin concentrations on beer fer-mentation. Th e bacterial infection isnot affected by 0.001y per ml., but isalmost completely eliminated by 0.005 yper ml. 48 hours after the start of thefermentation. Higher concentrations ofthe antibiotic are completely bactericidalto the Gram-negative rod infection. The

fermentation is not adversely affected bypolymyxin at concentration levels below20y per ml. The data in Table Iindicate a possible stimulation of thefermentation by the antibiotic betweenthe concentrations of 0.005 and 20yper ml. as measured by the rate of reduc-tion of p H and gravity of the fermentingbeer. To verify this a number of fermen-tations were carried out in which therate of fermentation of fermenting beerscontaining 0.057 of polymyxin per ml.\vas compared with the fermentationrate of controls.

The data in Figures 1, 2, 3, and 4 are

Table II. Effect of Wide Range of Polymyxin Concentration on BeerFermentation

Hours A f fe r S for f o f Fermenta t ionPolymyx in ,Analysis ?/MI . 2 4 4 8 7 2 120Yeast count X 10-8

PH

Degrees Plato

Bacterial count, % of control

n o 1 8 . 8 2 6 .0 3 9 . 2 2 . 20 , 0 0 1 i S .O 2 9 . 3 3 7 . 3 2 . 60 . 0 0 5 1 6 . 7 3 0 . 8 4 0 . 2 1 . 90 . 0 5 2 0 . 2 30,5 4 4 . 9 2 . 41 0 . 0 1 8 . 8 3 0 . 0 4 6 . 0 2 . 120 0 1 9 5 29 7 39 3 4 35 0 . 0 1 7 2 24 4 26 2 22 8n n 4 -3 4 48 4 26 4 18

1 0 . 0 4 . 7 2 4 . 3 82 0 . 0 4 . 7 5 4 . 5 05 0 . 0 4 . 7 8 4 . 6 8 4 . 5 6 4 . 3 2n o i n 9 0 8 . 3 1 5 . 2 7 3 . 0 80 001 10 92 8 38 5 32 3 100 005 10 95 8 34 5 28 3 090 05 10 93 8 16 4 92 3 081 0 . 0 1 0 . 8 0 8 . 1 2 4 . 9 6 3 .102 0 . 0 10.95 8 . 4 4 5 . 4 9 3 . 2 150.0 1 1 . 1 0 9 . 9 6 8 . 7 9 5 , 5 80 . 00 : 0 0 10.0050 . 0 51 0 . 02 0 . 05 0 . 0

100100551 . 20 . 00 . 00 . 0

1001001 . 3n o0. 00 . 00 . 0

. . .

. . .

. . .. . .

1001000 90 . 00 .00 . 00 . 0

1220 A G R I C U L T U R A L A N D F O O D C H E M I S T R Y

8/13/2019 Contamination Inhibition Antibiotics as Inhibitors of Micr

3/5

Table 111 Effect of Polym yxi n and Tartaric Acid Wash on Bacterial Countof Yeast and Fermenting Beer 0 and 24 Hours After Pitching withWashed Yeast

Bacter ial Cou nt per MI.Ty p e o f W a s h Y ea s t a f t e r w a sh __ ermenting Beer

0 hour 24 hoursControl 9,700,000 52,000 316,000Tartaric acid 98,000 560 1 2 , 0 0 0Polymyxin 140,000 480 0

Table IV. Effect of Several Antibiotics on Microbiological Contaminationo f BeerCondi t i on o f Beer i n Bot t l e r

A f t e r 9 W e e k s a t 75 FHaze and heavy sediment

Ant ib io t i cs AddedNone (unpasteurized control)Thiolutin (5-,,'ml.)Thiolutin, bacitracin (5y/ml. Haze and light sedimentThiolutin, subtilin (5y/ml. Haze and light sedimentThiolutin, streptomycin (5 Haze and light sedimentThilut in, dihydrostreptomycinThiolutin, penicillin (5y lml . Clear and very lipht sedi-

Haze and light sediment

each)each)y/mL each)(5-,,/mI. each) Haze and light sediment

. .each) mentThiolutin, terramycin (5r/ml. Haze and lipht sedimenteach)each) ment

ment

Thiolutin, polymyxin (5y:ml.;\-one (pasteurized control)

Clear and very light sedi-Clear and very light sedi-

C o m p o s i t i o n o fHaze and Sed imenf

Secondary yeast + Gram-positive bacterial rods andcocciGram-positive bacterial rodsand cocciGram-positive bacterial rodsand cocciGram-positive bacterial rodsand cocciGram-positive bacterial rodsand cocciGram-positive bacterial rodsand cocciSormal sedimentGram-positive bacterial rodsSor mal sedimentNormal sediment

and cocci

average results of analyses of 12 compara-tive fermentations.

The data in Figure 1 show that thep H of the fermenting beer, which con-tains 0 05~f polymyxin per ml., de-creases from the very beginning morerapidly than the p H of the beer in thecontrol fermentation. The differencecontinues to increase until it reachesabout 0.15 pH unit at approximatelythe 80th hour of the fermentation.Although the difference becomes lesspronounced thereafter, the final p Hvalue of the polymyxin-containing beeris approximately 0.1 pH unit lower thanthat of the beer from the control fer-mentation.

The effect of polymyxin on the rate ofdecrease in gravity of the fermentingbeers is presented in Figure 2. Therate of fermentation. as measured inthis manner, is also stimulated by poly-myxin, but the final gravity of the beersis not affected.

In Figure 3 the pH of the fermentingbeer is platted against the fermentingextract. The dat a in this figure showtha t the rate of p H reduction of the fer-menting beer is affected to a greaterextent than is the rate of' extract fer-mented. At any selected degree offermented extract the p H is much lowerin the polymyxin-trrated fermentationthan in the control.

The data in Figure 4 show that 0.05y of polymyxin does not affect yeast mul-tiplication or the rate at which yeastsettles out of suspension.

In all of the 12 fermentations towhich 0.Ojy of polymyxin was added,the bacterial count of the fermentingbeers was reduced to zero during thefirst 48 hours of the fermentation.

The effectiveness of polymyxin as ayeast-washing agent was compared withthat of the commonly used tartaric acidXvash. A quanti ty of pitch ing yeastIvhich was highly contaminated LvithGram-negative rods of the Flac'obacteriumproteus type \vas divided into three batches.To one batch sufficient polymyxin\vas added to give a final concentrationof 107 of polymyxin per ml . of yeastslurry. Th e authors had found in thefermentation studies that this concentra-tion of the antibiotic was not injurious tothe yeast cells. To the second batchwere added 2.6 grams of tartaric acidper 1000 ml. of yeast slurry. This low-ered the p H of the yeast slurry to 2.9.This p H level has been found to give themaximum reduction of yeast bacterialcontaminan ts without affecting the yeastadversely. Th e third batch of yeastwas held as a control.

The three batches of yeast ivere thenheld at 45 F. for 4 hours before pitchingin small 3-liter fermenters. Plate countsof the bacterial contamination of the

Figure 3. Effect of polymyxin on relationship of pH to extract fermented5 0

4.94.0474.64.54.44.34.24.14.0

V O L . 1 NO. 20 , D E C E M B E R 2 3, 1 9 5 3 1221

8/13/2019 Contamination Inhibition Antibiotics as Inhibitors of Micr

4/5

Table V. Concentrations o f Poly my xin , Pencillin, and Thiolutin Requiredto Inhibit Growth o f Microbio logi cal Contaminants in Beer

Poly- Peni- Thio-myxin d i n , lutin, Condi f ion of Beer Composii ion o fy / M L ? / M I . y /M I A f i e r 9 Weeks ai 75 F. Har e and Sedimenf0 0 0 Haze and heavy sediment Gram-positive bacterial rodsand cocci + secondary yeast3 . 0 0 3 . 0 Clear and very light sediment Normal sediment1 . 0 0 3 . 0 Clear and very light sediment Normal sediment0 . 3 0 3.0 Clear and light sediment Gram-positive bacterial rods0 . 1 0 3 O Clear and light sediment Gram-positive bacterial rods0 . 0 3 0 3 . 0 Clear and light sediment0 0 . 1 3 . 0 Clear and very light sediment0 0 . 0 3 3 .0 Clear and very light sediment0 0.01 3 . 0 Clear and light sediment0 0 . 0 0 3 3 . 0 Hazy and light sediment0 0 . 0 0 1 3 . 0 Hazy and light sediment0 1 . 0 3 . 0 Clear and very light sediment0 1 o 1 O Clear and very light sediment0 1 . o 0 . 3 Haze and heavy sediment0 1 . o 0 , l Haze and heavy sedimentO b 0 0 Clear and very light sediment

a Unpasteurized control.Pasteurized control.

and cocciand cocciGram-positive bacterial rodsNormal sedimentNormal sedimentGram-positive bacterial rodsGram-positive bacterial rodsGram-positive bacterial rods

Normal sedimentNormal sedimentSecondary yeastSecondary yeastNormal sediment

and cocci

yeast lucre made on the original yeast,the three yeast batches at the end of the4-hour holding period, and the ferment-ing beer 24 hours after the start of fer-mentation.

The data in Table I11 show that tar-taric acid and polymyxin reduce theviable bacterial contaminants to approx-imately the same extent during the4-hour holding period. However, thesurviving bacteria in the fermenterpitched [cith the tartaric acid-washedyeast greic rapidly during the fermenta-tion, as evidenced by the 24-hour platecount. Th e polymyxin, on the otherhand, continued to exert a bactericidalaction in the fermenter and after 24hours the bacterial infection had beencompletely eliminated.

The effect of antibiotics onmicrobio-logical growth in finished beer was alsoinvestigated. To do this, the antibioticto be tested was added in 1 ml. of steriledistilled Tvater to clean empty 12-ouncebottles. The bottles were put on theregular production line, where theywere filled with beer and crowned. Th efilled bottles were incubated at 75 F.and were observed weekly for the de-velopment of sediment and turbidity.Pasteurized and unpasteurized bottles ofbeer were also incubated as controls.

In order to test the effectiveness ofantibiotics as inhibitors of bacterialgrowth in beer, it \cas necessary to findan agent that would inhibit the secondaryyeast groivth that is usually obtained.Four fungistatic antibiotics includingactidione. rimocidin, nystatin, and thio-lutin \

8/13/2019 Contamination Inhibition Antibiotics as Inhibitors of Micr

5/5

Although polymyxin was found to bethe most effective antibiotic, of thosestudied, for the control of the Gra m-negative bacteria that infect yeast andfermentations, it is entirely possible thatother antibiotics will be supe rior to poly-myxin in the control of the lactic acidrods and cocci that infect brewer's yeastand fermentations. For example peni-cillin is more active than polymyxinagainst the lactic acid bacteria in finishedunpasteurized beer and a combinationof antibiotics such as penicillin and poly-myxin may be required for the completecontrol of bacterial contaminants ofbrewer's yeast. It \vas, however, sur-prising to find that polymyxin is moreactive against the Gram-positive lacticacid bac teria in finished beer tha n any ofthe othe r antibiotics tested. with the ex-ception of penicillin. Polymyxin isgenerally considered as being specific forGram-negative bacteria. A more thor-ough study of its activity in beer m ay helpto elucidate its mode of action.

The stimulation of the fermentationby polymyxin is interesting. The sametype of sLimulation \vas observed \\.hena bactericidal concentration of terramy-cin a nd aureomycin \vas added to the fer-mentati on. It seems possible, therefore,that this stimulation is related to theelimination of bacterial action during thefermentation and may not be a directeffect of the an tibiotic on the yeast.

Acknowledgment

The authors acknoLvledge the techni-cal assistance of J.A Brescia. John Dlvyer,R. E. Miranda, and \tJilliam Tirado.They are also indebted to Chas. PfizerCo., Inc.. and Lederle Laboratories, Di-vision of American Cyanimid Co.. forthe antibio tics used in this investigation.

Literature Cited(1) Gray. P. P.? and Kazin: A . D.,TVullmtein Lab. Communs . , 9, 115( 1 9 4 6 ) .(2) Lund, A . . A m . B r e w e r 81, No. 2,4 2 (1948).(3) Shamis, D. L., and Boldyneva,

K . V., Imest. A k u d . S a u k Kurukh.S .S .R . , Sw .\iikrobiol.: No. 1,52 ( 1 9 4 9 ) .(4) Strandskov, F. B., and Bockelmann,J. B.? J . Inst. Brercing, 57 123(1951).(5) Strandskov, F. B., Brescia, J. A, ,

and Bockelmann, J . B., n'aller-stein Lab. Communs., 16, KO. 5 231 (1953).

Receiued for review September 16, 7953. A rcepted iVoouember 22, 19 53 . Presented beforethe Division of Agricuiturai and Food Chem-istry, Fermentation Subdioision, Symposiumon aVontherapeutic Uses for Antibiotics, at the724th .Meet ing O the t\MERICAN CHEMICALSOCIETY, Chicago, IN

NOTES AND COMMUNICATIONSWeeds Contain ValuableChemical Compounds

s A RESULT of our increasing popula-A ion and rising standard of livingit becGmes economically important toinvestigate the chemical possibilities ofsome noneconomic plants that can begrown readily and in good yield. Re-sults of analyses, by acceptable methods,of representative samples of several suchplants are listed in Ta ble I. These dataindicate that smartweed, poverty grass,sedge, and the stalk of the Jamestown

weed have industrial possibilitics on thebasis of their high content of furfural,cellulose, or a-cellulose. Purslane, forexample: is especially rich in pecticcompounds. Noneconomic plants mayhave an important role in meeting soiland economic conditions in the future.EMMETTENNETTAgricultural Experiment StationUniversity of Massachusetts,Amherst, Mass.Received for review Apr i i 30, 1953 AcceptedOctober I 1953. Contribution Vo. 893,Massachusetts Agricuiturai Experiment Station.

Table 1 A Partial Chemical Analysis o f Several Non econom ic PlantsOn n ash- and mois ture- f ree bas is )

Tofa l To ta lSoluble Pectic Tofal aSugars, Corn- Furfural, Cellulose CellulasePlant % pounds, % % %%

Smartweed, Po(ygonum hydropiper L.Nettle, Urtica dioica L.Jamestown weed (stalk), Datura stranmniumPoverty grass, Aristida dichotoma Michx.Milkweed, Asciepias syriaca L.LeavesStalkCurled dock, Rumex crispus L.\Vild lettuce. Lacttica scariola L.LeavesStalkSt. John's-wart, Hypericum perforatum L.Lambs quarter, Chenopodium album L.Butterweed, Erigeron canadensis L.LeavesStalkPurslane, Portulaca oleracea L.Couch grass, Agropyron repens ( L . ) Beau\-.Golden rod, Soiidugo rugosa .4it.Aster, Aster sps.Sedge, Scirpus atrovinens Willd.Catnip, epeta cataria L.Wild carrot, Daucus carota L.Flagroot, Acorus calamus L.Joe-pye weed, Eupatorium mnculatum L.Yarrow. Avhil lea mil i t fo i ium L.

5 . 3 24 . 3 3L. 7 . 2 82 . 8 64 . 6 01 1 . 6 26 . 9 04 401 4 6 57 6 00 . 8 52 . 7 44 . 9 02 . 9 18 . 7 52 . 6 24 . 1 71 0 . 7 56 178 57 325 6 23 59

6 . 3 3 8 . 1 8 4 2 1 12 98 7 23 25 427 99 11 55 4 6 1 3Trace 15 25 49 '61 27 5 54 30 261 79 6 85 31 -92 1 7 6 3 3 30 9 32 88 5 26 19 291 16 8 95 3 8 2 31 4 4 98 39 1 45 00 8 5 32 22 1 2 4 '4 16 883 43 11 32 49 099 1 4 6 6 3 2 5 010 55 11 95 42 344 65 8 49 3' 23 . 2 2 1 0 . 1 8 4 4 . 2 91 . 3 3 1 1 . 5 4 4 3 . 9 34 . 4 4 8 . 9 8 4 0 . 2 33 50 8 88 38 713 40 81 30 8'2 8 8 00 23 220 8' 9 '3 3 3 6 2

72, zo6 7 . 1 36 5 , 4 06 1 . 8 95 9 . 4 76 4 . 4 46 6 8 36 8 . 1 65 9 . 5 35 6 . 9 671 476 4 8 362 566 4 . 8 76 7 . 8 66 5 . 8 566 26 5 . 4 062 376 1 . 9 16 4 . 2 3Sumac,'Rhtrs typhina L.

Hardhack, Spiraea tomtntosa L. 3 . 0 2 2 . 0 0 6 29 5 4 , .Dock, Arctiurn minus (Hill.)Bernh.Leaves 3 . 9 0 1 , 6 9 5 .4 .5 2 1 . - 2 . ,Stalk 1 1 4 3 1 1 8 9 . 0 3 3 6 . - 4Ragweed, Ambrosia artemisilfoiia L. 2 . 8 0 3 . 9 5 6 . 4 6 2 3 61 6 5 ' 4 0

Leaves 7 . 5 0 2 . 3 5 4 10 2 0 2 3 5 2 . 6 9Blossom 5 . 6 2 2 . 2 1 9 7 9 31 03 62 0

Water Culture Crops Designed toStudy Deficiencies in Ani mals

SIR: A paper by McClendon andGershon-Cohen (2) appearing in a recentissue of this jou rna l conta ins a numberof statements that merit comment.

To the best of ou r knoLvledge. this isthe first attempt to produce feeds forspecial nutrition studies by means ofhydroponics. such, the paper is ofconsiderable interest to everyone workingin the field of mineral metabolism.

The authors implied that thev pro-duced a fluorine deficiency in rats fedplants grown according to their direc-tions. The "fluorine-free'' ration con-tained 30% yellow corn. 3 y sunflower

seed, 20% sunflower leaves: l@%yeast,and lOy0 sucrose. The corn and sun-flowers fed this group xvere raised inwater. The "control" animals receiveda similar diet, with the corn and sun-flowers grown in soil. The drinkingwater for the latter group contained 20p.p.m. of fluorine. A basic tenet of thescientific method requires that the con-trol rats be fed plant materials grownunder exactly the same conditions asthose used for the mineral-..free" groupplus the mineral being studied. If thathad been done, then any gro;vth stimu-lation resulting from the addition of purefluorides would have been good evidencethat the diet contained less of this ele-ment than tha t required by the rat .

VOL. 1 NO. 2 0 D E C E M B E R 2 3 1 9 5 3 1223