Correlation between ethanol stress and cellular fatty acid composition of alcohol producing non-Saccharomyces in comparison with Saccharomyces cerevisiae by multivariate techniques.

Wine production is a complex process both from biochemical and microbiological point of view in which yeast plays a central role. The use of the wine yeast Saccharomyces cerevisiae and non- Saccharomyces yeasts as mixed starter cultures for wine fermentations is of increasing interest to enhance the quality of wine.The most common stress, yeast cells encounter during wine fermentation is the increase in ethanol concentration.To enhance ethanol tolerance, alteration in the cellular lipid composition is one of its defence mechanism. Ethanol tolerance and cellular fatty acid composition of alcohol producing non Saccharomyces forms were compared with enological strains of Sacccharomyces cerevisiae. Saccharomyces cerevisiae used for the study, tolerated 15 % of ethanol and the non Saccharomyces strains such as, Issatchenkia occidentalis and Issatchenkia orientalis tolerated 10 % of ethanol. On exposure of Saccharomyces cerevisiae to ethanol stress, the proportion of monounsaturated fatty acids increased with concomitant decrease in saturated fatty acids. Decrease in monounsaturated fatty acids, exhibited by non-Saccharomyces yeasts when exposed to ethanol stress, could be one of the reasons for their inability to withstand more than 10 % of alcohol. Multivariate techniques of data analysis - principal component analysis and linear discriminant analysis were employed in order to establish differentiation criteria as function of yeast strains, alcohol stress and their fatty acid profile. Based on the data, Chemometrics, such as principal component analysis and discriminant function analysis, can be successfully applied to fatty acid data to categorize the yeast.