engleski

Lipid composition of the brewer's yeast plasma membrane

Plasma membrane, as the site of the primary contact of the cell with its environment, largely determines the survival ability of the cell. It is well known that membrane lipids make a part of an effective adaptation mechanism reflecting the changes in the extracellular space. Investigations have been focused mainly on the lipid composition of the plasma membrane of the yeasts grown in well defined laboratory conditions. We have analyzed the lipid composition of the plasma membrane of brewer's yeast Saccharomyces uvarum, obtained as by-product of malt fermentation during the anaerobic process of beer production. Plasma membranes were isolated after mechanical disruption of the cell wall using glass beads and cell homogenizer. Lipids were analyzed by chromatographic and spectrophotometric methods. Total phospholipids of the plasma membrane accounted for 0.08 mg / mg proteins. The major one was phosphatidylinositol, making up 37% of total phospholipids, followed by phosphatidylcholine (19%) and phosphatidylethanolamine (17%). The content of phosphatidic acid was unusually high (13%). The composition of neutral lipids was characterized by extremely low content of ergosterol and high content of squalene (0.012 mg vs. 0.025 mg / mg proteins) as the consequence of strongly anaerobic conditions. In the composition of fatty acids saturated acids prevailed significantly, unsaturation index being only 0.25. Palmitic and stearic acids were the main ones accounting for 41 and 20% of total fatty acids, respectively. Such high content of saturated fatty acids was in agreement with low content of ergosterol, since the essential step in the biosynthesis of unsaturated fatty acids and ergosterol as well, is oxygen-requiring.

Saccharomyces uvarum; plasma membrane; lipid composition

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