Investigation On Thermotolerance Of Baker’s Yeast With Site Directed Mutation Of Cyr1

As one of the four key elements in the process of making bread, baker’s yeast is a kind of microbial starter cultures, biological leavening agents, and especially a kind of biological nutrients. Good baker’s yeast is an important guarantee of the quality of bread. It was showed that the phenomenon of "solid" in the production of bread may be due to the lower thermotolerance of the ordinary baker’s yeast. In this study, we introduced a site directed mutagenesis of adenylate cyclase gene CYR1(Cyr1lys1682) into model yeast strain W303-1A and industrial strain BY14a in order to improve the high temperature tolerance of baker’s yeast and solve the problem of the phenomenon of "solid", looking forward to meet the need of industrial strains. The main research contents and results were as follows:Fragment PMs carrying site mutant (Cyr1lys1682) in C-terminal were amplified by PCR from the genomic DNA of fill, and were inserted into YIplac211to construct recombinant plasmid YIplac211-PM under the help of restriction enzymes and ligation enzymes.The plasmids YIplac211-PMs were transformed into haploid cells BY14α△URA3and W303-1A, both of which contained a ura3genes, to obtain mutant strains W303-PM and BY14aAURA3-PM.Taking thermotolerance as the main characterization of cell tolerance, the tolerance of mutant stains were analyzed, the results indicated that the introduction of the mutagenesis had little positive effect on the heat resistance of the strains, but displayed some growth disorder at a higher temperature.By transforming normal URA3into BY14α△URA3-PM, a back nutritional deficiencies strain was obtained, which was named BY14a-PM. The growth performance, the survival rate after heat shock, and biomass of the strain of BY14a-PM were investigated. These results showed that the mutant strain displayed a lower survival rate and decreased biomass compared with BY14α, which indicated a compromised growth performance under higher temperature.