ISOLATION OF SAKE YEAST MUTANTS RESISTANT TO ISOAMYL MONOFLUOROACETATE TO IMPROVE ISOAMYL ACETATE PRODUCTIVITY

The growth of sake yeast was significantly inhibited by isoamyl monofluoroacetate. This inhibition was caused by free monofluoroacetic acid, a highly toxic compound, formed from isoamyl monofluoroacetate by yeast esterase. Yeast mutants with low esterase activity were expected to become resistant to isoamyl monofluoroacetate. Fifty mutants resistant to this ester were isolated from haploid strains derived from sake yeast. Two strains which had less than 15% of the original activity of esterase were obtained. These 2 strains could be used for brewing sake like their parental strain, and produce sake which contained 1.5 to 2.0 times higher amounts of isoamyl acetate and isobutyl acetate and had an excellent fruity flavor.