In an attempt to obtain a microbial strain with higher yield of folate for industrial applications, we mutated the wild strain Candida utilis Y1.0 using a novel mutagenic process, i.e., irradiation by a helium-neon (He-Ne) laser with an output power of 20 mW and an exposure time of 20 min. The yield of folate in the mutated cells reached 1,102 ng/mL, which was 20.4-fold that of the wild strain. The mutant strain Y3.636 was relatively stable in terms of folate production through eight successive transfers of cultures and batch fermentation in a 3.7-L stirred-tank fermenter. Optimization further increased the yield of the mutant by 110 %, i.e., to 2,314 ± 13 ng/mL. The optimal culture conditions for folate production were: cultivation in fermentation culture medium composed of 62.5 g/L glucose, 15 g/L corn liquor, 3 g/L (NH 4)2SO4, 3 g/L MgSO4, and 1 g/L glutamic acid; inoculum size of 9 %; incubation at 28 C and 196 rpm for 36 h. A time-course study of cell growth and folate production by mutant strain Y3.636 strongly suggested that folate production in C. utilis is growth-associated.
- Candida utilis
- He-Ne laser
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology