Abstract: Candida versatilis (called T yeast) and Zygosaccharomyces rouxii (called S yeast) are often used as starter cultures to enhance the flavor quality of high-salt liquid-state soy sauce. However, there are currently no auxotrophic strains available for the genetic manipulation of S yeast and T yeast. Therefore, ethylmethane sulfonate (EMS) and ultraviolet (UV) irradiation were used to mutagenize the yeasts obtain uracil auxotrophic strains. On the basis of mortality rate, the optimal concentration of EMS, EMS treatment time, UV irradiation distance, UV irradiation time, and yeast concentration were determined. In the end, the uracil auxotrophic strains were screened out and identified by gene sequencing, which will lay the foundation for molecular biology studies of salt tolerant yeast.

Key words: Candida versatilis, Zygosaccharomyces rouxii, ethylmethane sulfonate (EMS), ultraviolet mutagenesis, uracil auxotrophic