Studies On Increasing The Plus-mutation Rate Of High Ethanol Production S. Cerevisiae Strains Through Interaction UV Irradiation With Temperature

To increase efficiency of selecting high-level S.cerevisiae strains conversing fermentable sugar into ethanol, 120 strains were obtained from Saccharomyces cerevisiae stain Hs25a and Hs27a. through UV irradiating at 15w for 40cm and then incubating at 25℃, 28℃, 31℃, 34℃, 37℃ and 40℃. Their capacity of conversion fermentable sugar to ethanol and the distribution of strains with different fermentation capacity were been analyzed, and a new strategy to select high ethanol production strains was set. The results are as follows:1. Strain Hs25a and Hs27a irradiated with the same dose of UV showed different destruction curve, the death percentages of strain Hs25a is higher than strain Hs27a. The strain Hs25a is haploid with agglomeration and its mating phenotype is a. The strain Hs27a is not euploid without agglomeration and Hs25a is more sensitive to ultraviolet radiation than Hs27a2. The ethanol production of S.cerevisiae stains which were not irradiated with UV and grew at different temperatures was not changed obviously. But the ethanol production of S.cerevisiae strains which were irradiated with UV and then grew at different temperatures has remarkable diversity.3. Results showed that when the irradiated strains were incubated at the temperature close to the inhibiting growth temperature (40℃) , the amount of plus mutants , which ethanol production were higher than parent strain, were more than that at other growth temperatures. The percentage of the plus mutants of strain HS25a was 7.03 % at 25℃ and 50.19% at 40℃ respectively. And the percentage of the plus mutants of strain HS27a was 19.0% at 25℃ and 47.67% at 40℃ respectively. The second higher points of the percentage of the plus mutants were 40.33%(HS25a) and42.15%(HS27a)at31°C.4. As far as the selected 5 strains were concerned, their ethanol productions are higher than parent strains.5. The optimum conditions of mutagenicity and screening were 70% of lethality rates and incubated at 40 °C or 31°C when strains were irradiated with UVThis study shows that high temperature can increase the amount of plus mutants and the work efficiency, the percentage of plus mutants can be controlled. It also set a new strategy to research mechanism of gene mutation caused by interaction UV irradiation with high culture temperature.