反復戻し交配による優良Killer清酒酵母の造成

概要

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Contamination by wild sake yeasts often occurs during fermentaion of sake mash, resulting in inferior products. An attempt was made, therefore, to breed useful killer yeasts which could produce sake of good quality while preventing contamination.Killer hybridds were bred by repeated crossing between a temporal parent KL88,a wild killer sake yeast, and a repetetive parent Kyokai no. 7 (K-7), sensitive and one of the best sake yeasts, in the f ollowing way; haploids of KL88 were crossed with haploids of K-7 to yield first generation-hybrids (1HY), killer haploids selected from 1HYs were back-crossed with haploids of K-7 to yield second generation-hybrids (2HY), and the same processes (selection of haploids and back-crossing with haploids K-7) were continued until sixth generation-hybrids were obtained. Several strains of killer hybrids were comparable to K-7 with regard to fermentation ability, flavor production, and acid production in a laboratory scale sake mash. Two choices of them, 3HY11 and 6HY48,were further confirmed to produce sake of as good quality as that of K-7 in sub-industrial scale fermentation. The hybrids could exclude sensitive contaminants of yeast from fermenting sake mash even if the level of the latter was more than ten times that of the hybrid at the beginning of fermentation.
1976-09-25