GENETIC PROPERTIES OF LOW-TEMPERATURE-GRO WING YEASTS

Yeast mutants capable of growing at a low temperature (5-degrees-C) we re isolated. Two dominant loci were assigned for the mutations, and te ntatively designated as LTG1 and LTG2 (low-temperature-growth). In gen eral, haploid strains having two LTG genes (LTG1-1 LTG2-1) and diploid strains having two (LTG1-1/LTG1-1, LTG1-1/+ LTG2-1/+, or LTG2-1/LTG2- 1) or three (LTG1-1/LTG1-1 LTG2-1/+ or LTG1-1/+ LTG2-1/LTG2-1) genes g rew faster at a low temperature. In particular, among the strains test ed, the LTG1-1/LTG1-1 diploid strains grew fastest at a low temperatur e. Low-temperature-growing mutant strains (LTG2-6 approximately 9) wer e also isolated from haploids of sake yeast strains (Nihon Jozo Kyokai No. 9). Fermentation at low temperatures (10-degrees-C or 15-degrees- C) in sake mash was improved in the mutant strains.