engleski

Characterization of lipid components in the whole cells and plasma membranes of baker^, s yeast

The viability and functionality of the yeast cells is largely determined by their lipid composition. The aim of this study was to determine the content and composition of phospholipids (PL) and neutral lipids, as well as the fatty acid (FA) composition of the whole cells and plasma membranes of the industrial strain of the baker^, s yeast. Highly purified plasma membranes were isolated after mechanical disruption of the cell wall. The quality of the membrane preparations was tested by Western blotting. Lipids from the whole cells and plasma membranes were extracted by Folch method and analysed by standard methods. Total lipids accounted for 6.7% of the dry biomass. Phosphatidylcholine was by far the most abundant phospholipid of the whole cells and plasma membrane making up 47 and 36% of total PL, respectively. In the neutral lipid composition of the whole cells steryl esters were present in the highest concentration (19% of total lipids), which corresponds to the stationary growth phase. The content of ergosterol for the whole cells (4.6% of total lipids) and plasma membrane (0.117 mg/mg proteins) was few times lower than for the laboratory grown strains. Unsaturated acids, namely palmitoleic (C16:1) and oleic acid (C18:1), prevailed significantly in the FA composition of the whole cells, making 81 % of total identified FAs. The same acids were also principle ones in the composition of the plasma membrane. Interesting feature both of the FA acid composition of the whole cells and plasma membrane was surprisingly high concentration of very long chain FA C26:0, which accounted for 6% and 12% of total FAs, respectively. Low molar ratio of ergosterol to proteins is the characteristics of the yeasts resistant to freezing, which makes the yeast analysed in this study suitable for the frozen dough. Further more, it has been proven that aerobic cells with membranes enriched in C 16:1 and C 18:1 acids showed the highest resistance to stress under all conditions.

lipids; plasma membrane; baker^; s yeast

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