8/16/2019 Brewers’ yeast products

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BREWERS’ YEASTPRODUCTS

B

rewers’ yeast and derived products

have been successfully used in animal

nutrition, including aquafeeds, for

several decades now. Leiber GmbH,

with two production sites in Germany

and further facilities in Poland and

Russia, have manufactured brewers’

yeast products for more than 60 years.The following article will shed more

light on production background, well-known properties as well

as new insights into by-products of beer production and their

efcient use in aquaculture.

Reinheitsgebot: German Purity Laws

Beer brewing has a centuries-long tradition, and especially the

famous Reinheitsgebot, sometimes called the “German Purity

Law” of beer brewing. From the year 1516, this regulation has

enormously contributed to the great acceptance of beer as a high-

quality, food-grade product.

In fact, the Reinheitsgebot is a collective name for a series of

regulations limiting the ingredients for beer brewing to water,

barley (in specic cases wheat), hops and yeast.

Consequently, processing this yeast to a rened quality by

Leiber GmbH after the brewing process results in a premium,

standardised, quality consistent, guaranteed non-GMO raw

material free from other contaminants or additives (e.g. additional

avor components, enzymes or even antibiotics and heavy

metals).

The yeast used during beer brewing is Saccharomyces

cerevisiae. The average cell size ranges between 5 – 13 µm with

the yeast cell wall being approximately 200 nm thick (which

constitutes 25 – 40 percent of the total dry mass of the cell).

For animal nutrition and dietetic purposes, brewers’ yeast canbe used as the whole, inactivated yeast cell (either drum-dried

or spray-dried). Furthermore, several products derived from the

yeast cell can be produced depending on the production process,

e.g. autolysed yeast, yeast cell walls, yeast extracts and highly

puried ß-glucans.

Inactivated, unextracted brewer’s yeast

Inactivated brewers’ yeast is characterised by a moderate to

high protein content of approximately 46 percent. Furthermore,

high levels of minerals and trace elements, amino acids, vitamins

and enzymes as well as many micro-nutrients are accumulated by

the fermentation process. All components are organically bound

and therefore highly bioavailable. Brewers’ yeast is especially

well-known for its high levels of B vitamins (with the exceptionof vitamin B12), selenium and chromium.

Table 1 compares B vitamin contents and important trace

element levels of Leiber brewers’ yeast, soybean meal and sh

meal.

Autolyzed brewers’ yeast

Vertebrate as well as invertebrate organisms do not possess

the enzymes necessary for the breakdown of the yeast cell wall.

When the whole, inactivated yeast is administered through the

diet this can only be achieved through bacterial fermentation by

the gut microbiota.

Alternatively, the yeast collected from the breweries however

may be subjected to a gentle autolysis process, instead of direct

drying to produce inactivated, unextracted yeast.

This action is achieved by the yeast’s own enzymes, which

then leads to a break-up or perforation of the yeast cell wall. As

a result, the highly valuable cell contents including amino acids,

nucleotides and nucleosides, vitamins and trace elements, etc.

are released, and are therefore considerably easier and earlier

available to the organism during intestinal passage. This is

especially benecial for organisms with a short digestive tract

like in shrimp.

Another characteristic of autolysed brewers’ yeasts are high

native levels of natural DNA and RNA components, named

nucleotides, nucleosides and pyrimidine and purine bases. Theyare the building blocks for the synthesis of bases and nucleotides

for doubling of the DNA (cell division). During periods of

high requirements and physiological stress e.g. reproduction,

high growth and immunological stress; there is a clearly higher

demand for those components.

- excellen fo us i aquafeed

by Dr. Holger Kühlwein, Leiber GmbH, Germany

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The organism can build up DNA and RNA by itself but only

with great energy expenditure and over a long period of time.

Thus, nucleotides are considered to be semi-essential; in order

to support and accelerate cell division, cell regeneration and cell

repair they need to be supplemented in sufcient amounts.

Brewers’ yeast cell walls

The production process may not stop after autolysis of

the yeast cells. High power centrifuges are used in order to

separate soluble and insoluble components; such as the yeast

cell walls. The soluble cell contents are then predominantly

processed into various products for the food industry. The

insoluble yeast cell walls are used for dietetic purposes and in

animal nutrition. Yeast cell walls are naturally rich in β-glucans

and mannanoligosaccharides (MOS), e. g. Leiber’s yeast cell

wall product Biolex® MB40 contains approx. 25 – 30 percent

ß-glucans and 20 – 25 percent mannans.

Yeast cell wall supplementation leads to various effects in the

gastro-intestinal tract of the animal including a prebiotic effect

on benecial gut microbiota, binding and deactivation of certain

mycotoxins and agglutination of a range of pathogens and

their toxins. Further direct and subsequent effects include theformation of a biolm on the gut mucosa (additional protective

layer against infections), the improvements in immunity as well

as increased growth performance and feed conversion.

The overall aim of using yeast cell wall products is the

improvement of gut health, which is considered highly important

in animal husbandry. The gut is in many cases the main port of

entry for pathogens; a breaking of these pathogens through the

intestinal barrier often leads to disease outbreaks.

Brewers’ yeast products however have an additional major

advantage over yeast products sourced from other industries

(e.g. yeasts from bioethanol production, baker’s yeast):they contain bioactive hop substances which remain from

the beer brewing process. Hops have not only been used in

beer brewing for centuries to give the typical bitter taste, but

also to preserve the beer. Important hop constituents include

humolones (α acids) and lupulones (β acids) plus xanthohumol,

as well as signicant amounts of polyphenols (> 10 percent).

While xanthohumol is attributed with having cancer-inhibiting

properties, alpha and beta acids help defend the hop plant

against predation and pathogens.

Turning ideas into opportunities.

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Table 1: Vitamin and trace element levels (mg/kg dry matter; DM) of

various aquafeed ingredients.

Vitamins and trace

elements (mg/kg DM)

Leiber

Brewers’

yeast,

unextracted

Soybean meal

extracted

Fish meal

B1 133 5 2

B2 48 3 9

B6 48 6 6Niacin 425 34 59

Biotin 0.9 0.3 0.1

Folic acid 19 1 0,4

Pantothenic acid 106 16 10

Copper 64 20 6

Selenium 1.1 0.3 1.6

Zinc 106 50 90

(Data for soybean meal and sh meal according to NRC, 1998)

International Aquafeed - March | April 2016  | 17 

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The bioactive hop components have calming, antioxidative, and

most importantly bacteriostatic effects. This bacteriostatic effect

has been proven in a range of inhibition tests against a pathogenic

Staphylococcus aureus strain with Leiber brewers’ yeast products,

and due to the high concentration of hop constituents on the yeast

cell wall, Biolex® MB40 showed the strongest inhibiting effect on

Staphylococcus aureus and seems to be particularly effective in

this respect.

Highly purifed ß-glucans

Saccharomyces cerevisiae ß-glucans are considered highly

effective immunomodulators. They are located in the middle of

the three layers of the yeast cell wall, and their actual function in

yeasts is to provide strength and rigidity against environmental

inuences. By a particularly gentle process, developed by Leiber

GmbH, the (1,3)-(1,6)-ß-D-glucan molecules are isolated fromthe brewers’ yeast cell wall. However, the original structure of

the glucan molecules is retained. As a result, their full biological

activity is guaranteed and Leiber® Beta-S exerts an active

immune-modulating effect during intestinal passage. Due to

high levels (> 80 percent) of ß-glucans Leiber® Beta-S is able to

effectively support the animals’ metabolism and immune system

in a long lasting manner.

ß-glucans are administered through feed to prophylactically

support and augment the competence of the immune systems

of aquatic species. The reason is that under today’s intensive

rearing conditions, a variety of stressors including pathogens,

high stocking densities, handling and transport and suboptimal/poor water quality may occur and negatively affect the

animal’s immune status. These factors compromise the immune

competence of sh, subsequently promoting outbreaks of

infectious diseases. Immune modulators like ß-glucans which

activate the immune system can contribute to improve immune

status and animal performance.

Leiber® Beta-S was shown to have a signicant inuence in

improving health and immunological status in sh when fedto rainbow trout and carp in a dose-response trial for 4 weeks

supplemented to the feed at dosages of 0 g (control), 100 g, 200

g, 500 g and 1000 g per ton of feed. Analysis of various immune

parameters in blood serum after 4 weeks of feeding conrmed a

signicant increase of the immune status.

Subsequently, trout were challenged with Aeromonas

salmonicida and carp with Aeromonas hydrophila to determine

if the increase in the immune status also translates into a higher

disease resistance. Indeed, compared to the control the survival

rates were signicantly higher in both species with Leiber® 

Beta-S supplementation after the challenges. It should also be

noted however that with the highest supplementation (1000 g/to)

the increase was less pronounced emphasising the importance of

meeting the optimal dosage.

In conclusion, an optimum dosage of 200 g Leiber® Beta-S per

ton of feed is recommended for both species.

Conclusions

Brewers’ yeast is a high quality by-product of the beer brewing

industry and offers great opportunities to be rened into a whole

set of different products with specic properties in a sustainable

way. Depending on the aquaculture industry’s needs these

properties range from nutrient-rich and dietetic unextracted

brewers’ yeast to very sophisticated, highly puried ß-glucans

augmenting the immunocompetence of aquatic species in order toaid in the reduction of disease outbreaks and mortalities.

Future investigations will further explore antimicrobial

properties of brewer’s yeast products which enable to formulate

feeds with functional benets to face a new and sustainable future

in aquaculture.

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