The production of esters and gene expression by saccharomyces cerevisiae during fermentation on agave tequilana juice in continuous cultures

Abstract

Volatile esters are formed during alcoholic fermentation, particularly performed by yeasts. These compounds confer “fruity" attributes to drinks. Fermented beverages contain namely two groups of esters: acetate esters formed by alcohol acetyltransferase enzymes (ATF1 and ATF2) and ethyl esters produced by the acyl-CoA ethanol O-acyltransferase enzymes (EHT1 and EEB1), encoded by the ATF1, ATF2, EHT1 and EEB1 genes. The purpose of this study was to evaluate the effect of nitrogen addition, aeration and low temperatures on ester production during fermentation on A gave tequilana juice in a continuous system. Low temperatures increased ethyl esters production (4.5-fold) and enhanced the expression of the involved genes (more than 3.5-fold). Conversely, when compared to aeration, the effect was negative as esters production decreased (75%) whereas the ATF1, ATF2 and EHT1 genes were repressed. On the other hand, the addition of nitrogen favored the production of ethyl acetate. The results obtained during continuous culture with Agave tequilana juice showed that an increase in gene expression favored mainly the production of ethyl esters and not so much the production of ethyl acetate. Therefore, the three genes evaluated do not seem to be the only ones involved in the production of ethyl acetate, they are more related to the production of ethyl esters. So, even though all these compounds belong to the same family, the regulation of their production, as well as their synthesis pathways, seem to be different.