Abstract：GAL1 promoter is one of high-efficient inducible promoters of yeast (Saccharumyces cerevisiae), which is regulated by GAL4 and induced by galactose. GAL genotypes of yeast have significant effects on the expression levels of exogenous proteins controlled by GAL1 promoter, so the characteristics of recombinant GAL yeast strains need further study. In this study, the growth, fermentation performance and genetic stability of the recombinant GAL yeasts with different copies of GAL1 and GAL4 genes were evaluated. The results indicated that, the changed GAL genotypes were stable and recovery mutation didn't occurred during cultivation. The deficiency of GAL1 gene slightly affected the abilities of yeast to use glucose and the different cultivation modes had also impacts on galactose utilization for the recombinant yeasts. In yeast peptone galactose (YPG) and yeast peptone galactose glycerin (YPGL) medium, the depletion time of galactose was 20, 20, 20, 26, 20, 44, 44 and 68 h for MS-1, SG1, DG115 and DPG65, respectively. For GQ21, the galactose concentrations were always constant in medium, indicating that GAL1 genes' knockout. However, the heat-resistance temperature of yeast didn't change for the different GAL yeasts. This study will be helpful for large-scale and low-cost production of recombinant proteins using yeast expression system as bioreactor.
