INVESTIGATING ESTER METABOLISM - CHARACTERIZATION OF THE ATF1 GENE INSACCHAROMYCES-CEREVISIAE

Esters, which are produced during fermentation, are important contribu tors to the flavor of beer and whisky. Many different esters are forme d during wort fermentations, however, most research has centered on th e production of acetate esters. The mechanisms that regulate ester met abolism are not well characterized but it has been known for many year s that ester levels produced during fermentation are influenced by a v ariety of factors. Nevertheless, it is unclear how these environmental factors influence yeast metabolism and, accordingly, ester synthesis. The enzyme alcohol acetyltransferase has been implicated in the forma tion of acetate esters and, as a result, most work has concentrated on the role of this enzyme. However, alcohol acetyltransferase is an ext remely unstable protein when it has been purified; consequently, it is difficult to study. In this work, we have developed an in vivo system to study the expression of the gene encoding alcohol acetyltransferas e, ATF1. A 3.3 kb BamHI/XbaI fragment of ATF1, containing 1.9 kb of na tive promoter sequence, was fused to the Escherichia coli lacZ gene, a nd expression of ATF1 was measured under different conditions. Express ion of ATF1 correlated with the production of ethyl acetate during fer mentation. There was no clear relationship between ATF1 expression and isoamyl acetate production.