This experiment was carried out to investigate the physiological characteristics of two orginal yeasts, 5-Y-5 and 6-Y-6, which selected from 24 Takju yeasts and three mutants, 30-24,30-81 and 40-27. induced from two original yeasts by the irradiation of UV light. The results were summarized as follows.
1) Alcohol tolerances of three mutants were decreased in some degree as compared with those of orginal yeasts.
2) Tolerances of lactic and citric acids of acid producing mutant 30-81, was increased than those of orginal yeasts.
3) In the case of using ammonium sulfate as a nitrogen source, two original yeasts and three mutants required Ca-pantothenate as a essential growth factor and four strains of yeasts except the mutant, 30-81, required biotin as a stimulated growth factor, When asparagine was used as a nitrogen source, two orginal yeasts and three mutants showed the same as above result but the stimulated effect of biotin was far less.
4) Propagation powers of the mutants were weaken than those of original yeasts, particular that of acid producing mutant, 30-81, was the weakest in the three mutants.
5) The optimum temperature for fermentation of original yeasts were 30℃ to 35℃ but three mutants were 25℃ to 30℃.
6) The optimum pH for fermentation of original yeasts were pH 5 to 6, and there is no appreciable difference between original yeasts and three mutants.
The fermentation power of mutant, 30-81, was decreased more rapidly than those of other mutants according to approach neutral.
Three mutants were more sensible to heat than original yeasts.
7) Two original yeasts and three mutants were inhibited more over 20 percent of sugar for fermentation and three mutants were more sensible to sugar concentration than original yeasts.
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