Not Every Yeast Cell Wall Is Equal
The yeast cell wall, commonly referred to as MOS, is widely used by the feed industry as a natural antibiotic substitute. They are enriched in two functional polysaccharides with known health improving properties: mannooligosaccharides (MOS) and beta-glucans.
About 1,000 scientific papers demonstrate the benefits of yeast cell walls in animal husbandry and aquaculture and demonstrate that dietary supplements improve animal health and performance. However, despite the widely accepted benefits of yeast cell walls and all relevant scientific evidence, farmers are reporting more and more, and their performance under agricultural conditions is not consistent. This is because the composition of yeast cell walls from different sources is highly different.
To ensure a strong improvement in animal health and performance in the yeast cell wall, Ohly has now introduced two yeast cell wall products with high product consistency. Photo: Shutterstock
What is the yeast cell wall?
Traditionally, yeast cell walls are a by-product of the yeast extract production industry. The intact yeast cells are lysed and then the soluble intracellular fraction (yeast extract) and the insoluble yeast cell wall fraction are isolated (Fig. 1).
Figure 1 - Production of yeast cell walls.
The liquid yeast cell wall is sold to farmers close to the manufacturing plant. As the demand for yeast cell walls has increased, companies have emerged that collect liquid yeast cell wall byproduct streams from different producers. They dry the yeast cell wall and greatly extend their shelf life, allowing them to be distributed globally. As demand grows further and/or due to cost reasons, recently used brewer's yeast or biofuel yeast collected from different breweries or bioethanol production plants is used as a feedstock for yeast cell wall production.
Effect of process on product composition
The yeast cell wall production process has a great influence on the composition of the yeast cell wall. Although it is generally believed that all yeast cell walls are produced by autolysis (the yeast self-enzymatically lyses intact cells), in fact more and more yeast cell walls are produced by hydrolysis. During the hydrolysis process, the addition of exogenous proteases not only leads to the cleavage of the yeast, but also to the hydrolysis of mannoproteins present outside the yeast cells (Fig. 2). Since the hydrolyzed mannoproteins are soluble, they do not eventually enter the insoluble yeast cell wall fraction after centrifugation. Therefore, the MOS content of the hydrolyzed yeast cell wall is about 50% lower than the MOS content of the autolyzed yeast cell wall.
Figure 2 - Difference between autolysis yeast cell wall and hydrolyzed yeast cell wall.
(Source: EM image: SGS Institute Fresenius).
In addition, the yeast cell wall is a sphere, so functional carbohydrates present outside it determine its functionality. The autolyzed yeast cell wall contains MOS on the outside, while the hydrolyzed yeast cell wall contains a mixture of MOS and β-glucan on the outside.
Mode of action
MOS and β-glucan have different modes of action, which affect their health benefits. MOS binds to intestinal pathogens, thereby limiting their colonization of the gut. In contrast, beta-glucan is a regulator of the innate immune response, activates phagocytic cells, and subsequently enhances its ability to resist pathogens. In addition, yeast β-glucan binds to mycotoxins.
To ensure stable animal health and performance through yeast cell walls, Ohly now introduces two yeast cell wall products with high product identity to the market based on primary cultured baker's yeast (Saccharomyces cerevisiae). Ohly-GO MOS is a yeast cell wall product produced by autolysis and contains MOS outside the yeast cell wall. Ohly-GO Wall is a yeast cell wall product produced by hydrolysis, which contains a mixture of MOS and β-glucan on the outside.