Abstract: Lactobacillus pentosus is a potential strain which can make use of the lignocellulose hydrolysate fermentation to produce lactic acid, optimization of fermentation conditions and the breeding of high yield strain are the important means to improve lactic acid production. Fermentation medium and fermentation conditions were optimized for strain Lactobacillus pentosus ATCC 8041, through single factor experiment, Plackett-Burman design and response surface experiment. The results showed that the best combination of fermentation medium is 93.11 g/L glucose, 5.19 g/L yeast powder, 29.43 g/L calcium carbonate, 10.00 g/L peptone, 5.00 g/L Na₂HPO₄?12H₂O, 0.20 g/L MgSO₄, 50 mg/L MnSO₄. The best fermentation conditions is temperature 37℃, pH6.5, quantity of 6%, and fluid amount 80%. The lactic acid production is 54.12 g/L under the optimized fermentation medium and fermentation conditions. And then, Lactobacillus pentosus ATCC 8041 was taken as the original strain, treated with UV mutation ATCC 8041 protoplast, after through multiple screening, finally we have got a mutant which has high lactic acid production, named Lactobacillus pentosus lactic UVC-02 which conserved in China Center for Type Culture Collection, registration number for CCTCC M 2013209. The results for glucose fermentation showed that lactic UVC-02 produced 64.17 g/L lactic acid, which was 18.6% higher than the original strain.

Key words: Lactobacillus pentosus , Lactic acid fermentation, UV mutation, Response surface experiment