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.