ENHANCED FORMATION OF 3-(METHYLTHIO)-1-PROPANOL IN A SALT-TOLERANT YEAST, ZYGOSACCHAROMYCES-ROUXII, DUE TO DEFICIENCY OF S-ADENOSYLMETHIONINE-SYNTHASE

Mutants resistant to L-ethionine, an analogue of methionine, were derived from Zygosaccharomyces rouxii MA(r)1. Some of them produced large amounts of 3-(methylthio)-1-propanol (methionol): an important flavor component of soy sauce. One of these mutants, M33, produced 60-fold as much methionol as the parental strain MA(r)1 in a minimum medium without methionine. The intracellular methionine pool of this mutant was increased 5-fold. S-Adenosylmethionine (SAM) synthase (EC 2.5,1.6) in the mutant was reduced to 45% of that in the parent and a decrease in intracellular SAM level was also confirmed. The reduction of the SAM level due to the deficiency of SAM synthase, accompanied by derepression of enzymes of the methionine synthetic pathway, was considered to be responsible for the hyper-production of methionol in the mutant.