engleski

Changes of the Phospholipid Composition in Recycled Brewer’ s Yeast

Modern beer production is based on malt fermentation with chosen, aerobically grown culture of brewer's yeast, which is often recycled. The possibility of recycling is theoretically unlimited, but in practice it is reduced to few cycles only. Namely, during fermentation, yeast cells are continuously exposed to different stress factors that impair yeast growth and fermentative performance, because of changes provoked in the chemical composition of the cells. In order to determine changes in lipid composition we have analysed four generations of bottom fermenting brewer’ s yeast Saccharomyces cerevisiae, pitching yeast (zero generation) and three recycled generations (1st, 2nd and 3rd). Here we present the results of the phospholipid analysis of the whole cells and plasma membrane. The phospholipid content of the whole cells was the highest in zero generation (36% of total lipids) ; it decreased gradually to the second generation and increased again in the third generation. The same applies to total phospholipids of the plasma membrane. Main differences in phospholipid composition were significantly increased content of phosphatidylcholine and decreased content of phosphatidylethanolamine in all recycled generations compared to zero generation. The mass ratio phosphatidylcholine/phosphatidylethanolamine the lowest in zero generation, was the highest in the second generation (1.1 and 2.0, respectively).

Recycled Brewer’ s Yeast; Saccharomyces cerevisiae; Plasma membrane; Phospholipids

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