Abstract: In order to obtain an excellent strain with multi traits for ethanol production,using flocculating strain RHZ-1 and acid-tolerant strain SEB2 as the parents,auxotrophic strains were obtained by UV mutagenesis induction. Saccharomyces cerevisiae strain RS-1 with excellent acid-tolerant and flocculating ability was selected by screening fusants with the technology of protoplast fusion. When fermenting 15% YPD at 30℃ and pH2.2 for 24 h,the ethanol yield was 47.87 g/L,the glucose consumption rate and ethanol yield of strain RS-1 was greatly improved compared to the original strain RHZ-1,increased 19.5% and 9.8%,respectively. When fermenting 15% YPD at 35℃ and pH2.2 for 48 h,the ethanol yield was 38 g/L,the glucose consumption rate and ethanol yield of strain RS-1 increased 46.8% and 21.6%,respectively compared to the original strain RHZ-1. The results suggest that the strain obtained in this study could be a potential microorganism for ethanol industry.

Key words: Saccharomyces cerevisiae, UV mutagenesis, protoplast fusion, acid tolerance, ethanol fermentation