基于连续发酵驯化的耐酸性酿酒酵母的育种

Breeding acid-tolerant Saccharomyces cerevisiae strain based on continuous ethanol fermentation under acid stressed condition

本研究以纯合二倍体工业酿酒酵母SC-iso-Kan作为出发菌株进行连续发酵,通过逐步降低发酵体系pH值,对酵母的耐酸性进行长期驯化.从pH 2.7发酵体系分离获得耐酸性突变菌株SCiK12,通过孢子形成、分离和培养,获得两株优秀的耐酸性单倍体菌株SCiK12-B3(MATa)和SCiK12-C(MATα),通过交配获得耐酸性二倍体菌株SCiK12-BC4.在35℃,pH 2.5条件下,利用15%YPD发酵48h,和原始出发菌株SC-iso-Kan相比,菌株SCiK12-BC4(MATa/α)和单倍体菌株SCiK12-B3(MATa)及SCiK12-C3(MATα)基于糖消耗的乙醇收率分别提高了12.5%,17.5%和17.2%.本研究结果表明,连续发酵驯化结合单倍体分离和交配是获得耐无机酸突变菌株的有效手段.

In this study, using diploid industrial Saccharomyces cerevisiae strain SC-iso-Kan as the original strain, acid tolerance of yeast was chronically acclimatized by gradually reducing the pH value of the continuous ethanol fermentation system. A mutant strain SCiK12 with improved acid tolerance was isolated from the fermentation system at pH 2.7. Two excellent acid-tolerant haploid strains SCiK12-B3 （MATa） and SCiK12-C3 （MATa） were derived from strain SCiK12 through sporulation. By mating these two haploids, diploid strain SCiK12-BC4 with improved acid tolerance was obtained. Compared to the original strain SC-iso-Kan, strains SCiK12-BC4 （MATa/α）, SCiK12-B3 （MATa） and SCiK12-B3 （MATα） produced 12.5%, 17.2% and 17.5% higher ethanol, respectively, when fermenting 15% YPD for 48 h under the condition of 35 ℃ and pH 2.5. The study revealed that continuous ethanol fermentation combined with haploidization and mating was an effective way to obtain mutant strains with inorganic acid tolerance.