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Yeast biomass for animal and pet nutrition

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Yeasts are unicellular microscopic fungi of typical size between 5 to 10 microns. The yeast cell transforms its food, namely simple sugars or starch, under anaerobic conditions into alcohol and carbon dioxide. Well known for their use in the production of beer, wines, bread and cheeses, these versatile microorganisms also have applications as direct-fed additives in human and animal health.

Remarkably, under aerobic conditions (opposite of fermentation) the yeast cells multiply rapidly and generate a high quality biomass containing up to 50 % protein on a dry basis. The various yeast species differ according to their cellular morphology, which substrates they can utilize, and the way they reproduce.

There are approximately 60 yeast genera, representing nearly 500 species. In terms of sugar metabolism, for example bread yeast (Saccharomyces cerevisiae) is produced industrially on cane or beet molasses, a concentrated source of sucrose. On the other hand, this yeast is unable to utilize lactose, the type of sugar found in milk.

The following table describes the types of sugars that can be metabolized by the main commercial yeasts.

Carbohydrate metabolism by the three main types of yeasts²

²Adapted from Reed & Nagodawithana, 1991, updated as per notes.
³dePaula F.C. et al. (2008). Sucrose hydrolysis (…) fixed Kluyveromyces marxianus. Food Chem. April 15 online edition
⁴Stambuk B.U. et al. (2003). D-Xylose Transport (…) and Kluyveromyces marxianus. Appl. Biochem. & Biotech. 106:255

The yeast strain chosen by GreenYeast is Kluyveromyces marxianus, a microorganism that can metabolize the main types of readily available carbohydrates.

Green Yeast is in the process of registering its Kluyveromyces marxianus strain with the Canadian Food Inspection Agency’s (CFIA) animal health division, in order to obtain the rights to market its products to the large animal feed manufacturers in the country.

Potential buyers such as feed manufacturers have a sound understanding of the various yeast advantages, for instance as a supply of key nutrients for animal nutrition : essential amino acids, nucleotides, cell wall components, vitamins and minerals. Moreover, a number of refereed scientific publications describe the benefits of yeasts on animal growth and on the immune status. In the EEC, ‘probiotic’ yeasts are being touted as alternatives to the use of antibiotic-type growth promoters in various animal species.

One can safely forecast an increase in demand for a ‘clean’ protein source - yeast - in animal health/nutrition. Factors behind this trend include the growing preoccupation of the average consumer towards publicized phenomena such as the overuse of antibiotics in food animal production and infectious outbreaks such as mad cow disease. Policy changes and progressive restrictions are likely to further help the introduction of new types of probiotic yeasts and their derivatives.

Up until now, the feed yeast market has been dominated by Saccharomyces cerevisiae, the yeast also known for breadmaking, wine and beer fermentations. Major players have focused their efforts towards the development of new products from that very Saccharomyces such as extracts and selenium- or chromium-enriched yeasts.