CONTROL OF VICINAL DIKETONE PRODUCTION BY BREWERS-YEAST .1. EFFECTS OF ILV5 AND ILV3 GENE AMPLIFICATION ON VICINAL DIKETONE PRODUCTION AND ILV ENZYME-ACTIVITY

The amount of vicinal diketone (VDK) precursors produced during the br ewery fermentation process was minimized by increasing the flux throug h the isoleucine-valine (ILV) biosynthetic pathway in brewer's yeast. Plasmid amplification of the gene products of ILV5, ILV3, or tandem IL V5+ILV3 in brewer's yeast resulted in VDK decreases of 70, 40, and 60% , respectively, when compared to that of normal brewer's yeast. No oth er flavor or attenuation profile differences were observed. Overall, I LV5 gene amplification was a very effective strategy for decreasing to tal VDK production.