Polygenic analysis unveils a novel ethyl acetate biosynthesis enzyme, Eat1, in flavor production

Flavor compound production is an area in metabolism in which a lack of knowledge on enzymes in specific pathways still exists. Saccharomyces cerevisiae produces ethyl acetate, a compound with a solvent-like off-flavor, in levels that typically fringe the sensory threshold in beer. We have performed parallel polygenic analysis in a strain with low ethyl acetate production, either with or without additional deletion of ATF1, the major known gene in ethyl acetate biosynthesis. Surprisingly, this revealed no overlapping QTLs between WT and atf1?, and for mapping with atf1? only two mirrored and strong QTLs appeared in the pools for either high or low production of ethyl acetate, indicating a high level of epistasis in flavor production. We then identified two unique causative mutations, ygr015cK149fs and snf8E148*, responsible for most of the ethyl acetate produced without ATF1. YGR015C encodes a mitochondrial enzyme, that belongs to the recently described EAT1 (ethanol acetyltransferase 1) family. When overexpressed it strongly increases ethyl acetate levels without affecting other flavor compounds.