Production and Tolerance of Ethanol in Relation to Phospholipid Fatty-acyl Composition in Saccharomyces cerevisiae NCYC 431

Abstract

Accumulation of ethanol in supernatants from anaerobic cultures of Saccharomyces cerevisiae NCYC 431 closely paralleled growth during the early exponential phase of batch growth, and continued after growth had ceased. During the 8–64 h period of the fermentation, the intracellular ethanol concentration was greater than the extracellular concentration. Ethanol was very rapidly extracted from organisms by washing with water. During growth up to 32 h, there was a progressive decrease in fatty-acyl unsaturation in phospholipids, and a corresponding proportional increase in saturation. Thereafter, the trend was very slightly reversed. Supplementing cultures with ethanol (0·5 or 1·0 m) after 8h incubation retarded growth rate, while supplementation with 1·5 m-ethanol immediately stopped growth. In cultures supplemented with 0·5 or 1·0 m-ethanol, viability was not lowered, but supplementation with 1·5 m-ethanol caused a rapid decline in viability. Supplementation of cultures with ethanol at any of the three concentrations led to an increase in the proportion of mono-unsaturated fatty-acyl residues in cellular phospholipids, especially in C18 residues, which was accompanied by a decrease in the proportion of saturated residues.