Abstract: The objective of the present study was to develop mutant strains of Candida versatilis for the production of soy sauce. A mutant library of spt15 encoding the TATA-binding protein of C. versatilis was constructed by error-prone PCR and it was recombined into the expression vector YEplac195 and then introduced into uracil auxotrophic strains W303 and WM2 for screening purpose. The results showed that the four best mutant strains A1, A2, A3, and A4 were obtained through screening in solid medium with different salt concentrations. Compared with the control group, their salt tolerance was improved and soy sauces fermented by these mutant strains contained higher contents of amino nitrogen. The sequence of the recombinant plasmid showed base insertion, deletion and substitution as indicated by the sequencing of PCR products.

Key words: error-prone PCR, spt15, gene mutation library, screening, soy sauce fermentation