BALANCE OF ACTIVITIES OF ALCOHOL ACETYLTRANSFERASE AND ESTERASE IN SACCHAROMYCES-CEREVISIAE IS IMPORTANT FOR PRODUCTION OF ISOAMYL ACETATE

Isoamyl acetate is synthesized from isoamyl alcohol and acetyl coenzym e A by alcohol acetyltransferase (AATFase) in Saccharomyces cerevisiae and is hydrolyzed by esterases at the same time. We hypothesized that the balance of both enzyme activities was important for optimum produ ction of isoamyl acetate in sake brewing. To test this hypothesis, we constructed yeast strains with different numbers of copies of the AATF ase gene (ATF1) and the isoamyl acetate-hydrolyzing esterase gene (IAH 1) and used these strains in small-scale sake brewing. Fermentation pr ofiles as well as components of the resulting sake were largely alike; however, the amount of isoamyl acetate in the sake increased with an increasing ratio of AATFase/Iah1p esterase activity. Therefore, we con clude that the balance of these mo enzyme activities is important for isoamyl acetate accumulation in sake mash.