Acetate ester production by Saccharomyces cerevisiae lacking the ATF1 gene encoding the alcohol acetyltransferase

Alcohol acetyltransferase (AATase) was believed to be the only enzyme responsible for acetate ester production of Saccharomyces cerevisiae. However, recent studies have shown that S. cerevisiae has several types of AATase. In order to determine the precise role of each AATase in ester production, the A TF1 gene encoding one type of AATase, was disrupted and the ability of the atf1 null mutant to form isoamyl acetate and ethyl acetate was studied. The results of AATase assays using isoamyl alcohol as a substrate revealed that although the AATase activity of the null mutant was dramatically reduced, 20% activity was retained. However, when ethanol was used as a substrate, more than 80% activity was retained. The production of isoamyl acetate and ethyl acetate during fermentation was also compared and it was shown that, compared to the control, the null mutant produced less than 20% isoamyl acetate but produced more than 60% ethyl acetate. These results suggest that the yeast cell has several different types of AATase, and that the Atf1 protein plays a major role in isoamyl acetate production but has a relatively minor role in acetate ester production during fermentation.