engleski

Ethanol-Induced Changes in the Lipid Composition of Brewer's Yeast Plasma Membrane

Fermenting yeast cells must maintain viability and methabolic activity in the presence of increasing levels of ethanol. Therefore, various physiological adaptations occur in the yeast cells. Although the influence of ethanol on yeast cells are complex, it appears that the plasma membrane structure is the main target of ethanol. It was established that unsaturated fatty acids and sterols in the yeast plasma membrane represent an important part of adaptive response. With the aim to study the influence of ethanol on yeast cells, the lipid composition of the plasma membrane in two generations of brewer's yeast Saccharomyces cerevisiae, pure culture (zero generation) and the second generation, was analysed. Highly purified plasma membranes were isolated from the cells after enzymatic disruption of the cell wall. Organelle quality was controlled by SDS-PAGE and Western blotting techniques. Fatty acids with chain lenght from 10 to 26 C-atoms were identified in plasma membrane total lipids in both generations. Fatty acids with 16 C-atoms were predominant, making more than 60% of total fatty acids in both generations. The level of unsaturated fatty acids, especially that of palmitoleic (C16:1) was significantly higher in the second generation. Among C18-acids, stearic acid, (C18:0) had the highest concentration in the zero generation, and oleic in the second generation. The content of plasma membrane phospholipids was more than two times higher in zero generation than in the second one (64 and 29 mg phospholipds/mg of proteins, respectively). Phosphatidylcholine and phosphatidic acid were the main phospholipid components. These data indicate that brewer's yesat in the presence of ethanol reduces the content of plasma membrane phospholipids and synthesizes lipids with a higher proportion of unsatureted fatty acids, thus increasing membrane fluidity as an adaptive response.

Brewer's yeast; ethanol; plasma membrane; lipid; Saccharomyces cerevisiae

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