Breeding of Sake Yeasts f or Making Sake with Low Alcohol Content

Abstract

The protoplast fusion between sake yeast Kyokai No.7 strain (K-7) and adenineless strain of sake yeast Kyokai No.10 was carried out to breed sake yeasts for making sake with low alcohol content. Four nuclear fusant strains were obtained as judged from cell size, nuclear DNA content and chromosomal band patterns in pulse field gel electrophoresis. The specific growth rate of these strains in yeast extract-polypeptone-glucose (YEPD) medium at 1° was intermediate between those of parent strains. But alcohol acetyl transferase activities (estimated from the formation of iso-amyl acetate/108cells) of these strains were 2-3 times those of parent strains. The time course of fermentation during small-scale low alcohol sake making using fusant strains showed slower rate than that of the parent K-7 strain. The resulted sake by fusant strains contained more amino aids and reducing sugar than that made by K-7 strain, and the former had better sensory peculiarity than the latter.