缺失gpd2基因对工业酿酒酵母乙醇发酵的影响

Glycerol is the main by-product produced during anaerobic ethanol fermentation by Saccharomyces cerevisiae and consumes a considerable amount of substrate. The glycerol-3-phosphate dehydrogenase (GPD) is the vital rate-limiting enzyme in glycerol formation pathway of yeast. There are two GPD isoenzymes, encoded by gpd1 and gpd2. Through the method of sporulation, haploids of the two mating types, MATa and MATα, were obtained from the industrial S.cerevisiae AS2.489. Based on homologous recombination, a foreign gene targeting cassette consisted of the G418-resistance gene flanked with two short homology region of gpd2 gene was constructed by PCR. It was transformed into the haploids. The gpd2△ mutants were screened by G418 resistance. By mating the two haploids, a diploid mutant strain was generated and confirmed by the method of sporulation. All batch fermentation cultivations were carried out in a 250 ml flask with a working volume of 100 ml. The fermentation medium contains 20 g/L glucose. Compared to the wild type strain, the haploid gpd2△ mutant showed decrease of glycerol production by 29.4 %, while ethanol production rate increased by 2.8 %; the gpd2△/gpd2△ diploid strain showed 31.1 % decrease of glycerol production and the production of ethanol increased by 3.3 %.