Enhanced formation of isoamyl alcohol in<i>Zygosaccharomyces rouxii</i>due to elimination of feedback inhibition of α-isopropylmalate synthase

Abstract

Mutants of the 'miso' yeast, Zygosaccharomyces rouxii, that produced a large amount of isoamyl alcohol, an important flavour in miso fermentation, were isolated from 5,5,5-trifluoro-DL-leucine-resistant mutants, an analogue of L-leucine. One of the mutants, M21-10, produced a three-fold higher level of isoamyl alcohol than the wild-type strain MY21 in miso fermentation. The activity of alpha-isopropylamalate synthase, one of the enzymes used for L-leucine synthesis, in the mutant M21-10 was not inhibited by the addition of L-leucine, a feedback inhibitor.