Abstract: Candida utilis CL1501 was mutagenized with a combination of UV irradiation and nitrosoguanidine treatment. An excellent mutant with high ability to produce nucleic acid, named as CL15013, was obtained. Its nucleic acid content was 16.8% on a dry cell weight basis, which was 47.8% higher than that of CL1501. The dry biomass yield of the mutant was 16.9 g/L in fed-batch culture, which was 94.3% higher than that from batch culture. Under optimized fed-batch culture conditions obtained by orthogonal array design, the biomass yield was up to 21.3 g/L, which was 144.8% higher than that from batch cultivation. These results indicated that mutant CL15013 has a great application potential in industrial production.

Key words: Candida utilis, combined mutation, nucleic acid, fed-batch culture