engleski

Ethanol-induced changes in the fatty acid composition of brewer's yeast

The most important chemical stress for brewer's yeast is the toxic effect of ethanol, which accumulates during fermentation. Yeasts respond to stress by evoking an adaptive stress response. Cell lipids make a part of an effective adaptation mechanism. In this work lipid fraction of pure culture (zero generation) of brewer's yeast, Saccharomyces cerevisiae and the second generation of the same yeast, which was used twice in beer production, was analysed. The content of total cell lipids was almost equal in both generations (3, 1 % and 3, 4 %, of dry biomass, respectively). Nonpolar lipids were the major part of total lipids in both generations. FAs with chain length from 10 to 26 C-atoms were identified in total lipids and main lipid fractions in both generations. Fatty acids with 16 C-atoms were predominant, making more than a half of total fatty acids in all lipid samples. In addition, chain-elongation was observed in the second generation. The level of unsaturated FAs, especially that of linoleic acid (18:2), was significantly higher in total lipids and in both lipid fractions of the second generation. These data indicate that brewer's yeast in the presence of ethanol synthesize lipids with longer chain and with higher proportion of unsaturated FAs thus increasing membrane fluidity as a protective response.

brewer's yeast, ethanol, Saccharomyces cerevisiae, fatty acid composition

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