Construction Of High Ethanol-yielding Yeast Strains And The Optimization Of Fermentation Process

Haploid strains C1-25, C1-88, C1-84, C1-14, C1-19, C1-74 C1-59 were obtained from Saccharomycss cerevisiae strain Cl by the optimum sporulation conditions, and fermentation activity of them was analyzed. After protoplast fusion and step by step screening process, seven diploid fusions strains were selected eventually. After fermentation activity of these fusions was analyzed, the result suggested that osmophilic traits and ethanol-producing capabilities of C7, C8 were better than Cl. After seventy-two hours fermentation in the saccharified wheat starch medium containing 24°Bx sugar at 33℃, the alcohol degree of the fermented mash reached 11.5%(v/v) and the conversion rate was 96%. Besides, we acquired the optimum conditions(20°Bx> 25°Bx sugar, PH6.0, 33℃) of continuous fermentation, which were performed by the L9(34) orthogonal design experiment. Continuous fermentation of Cl, C7, C8 was carried out by using cell recycle system in the optimum conditions. The result of continuous fermentation suggested that the ethanol-producing capabilities and the viability of cell was stabile.As far as the selected strains(C7, C8) were concerned, the traits of ethanol-tolerance, being osnophilic and producing ethanol were better than Cl, the analysis also showed that these abilities enhanced by the nuclear multiploidy increasing.