Abstract: The experimental conditions to obtain a genetically stable haploid strain from the Saccharomyces cerevisiae diploid strain W5 were optimized in this study. Seven haploid strains were isolated and identified by random spore analysis and MAT-PCR. Then, the stability of the haploid strains was evaluated by continuous passage culture. Ultimately, the fermentation performance of two selected haploid strains was analyzed. The results showed that the highest sporulation rate of the strain W5 of (35.57 ± 0.82)% was acquired when it was cultured on a modified SPM medium at 30 ℃ for 8 days. Spore release rate was (47.06 ± 0.23)% after 2 h treatment of the suspension with 3% snailase. S. cerevisiae H14 (MAT-a) was the most genetically stable among seven haploid strains. Strain H14 gave the highest ethanol production of (40.46 ± 1.06) g/L when cultured at 30 ℃ with glucose as a substrate for 30 h with agitation at 150 r/min, which was 21.67% lower than that of W5 at 24 h, whereas the yields of acetic acid and acetoin were increased by 12.7% and 57.14%, respectively. This research can provide useful information for researchers to prepare haploid S. cerevisiae and also enrich the fundamental theory of yeast genetics.

Key words: Saccharomyces cerevisiae, haploid, preparation, identification, metabolism analysis