Improvement of l-lactic acid production by osmotic-tolerant mutant of Lactobacillus casei at high temperature |
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Authors: | Xiang-Yang Ge Jian Yuan Hao Qin Wei-Guo Zhang |
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Institution: | 1. The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, JiangNan University, #1800 Lihu Road, Wuxi, 214122, JiangSu Province, People??s Republic of China
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Abstract: | l-Lactic acid production by Lactobacillus casei was used as a model to study the mechanism of substrate inhibition and the strategy for enhancing l-lactic acid production. It was found that the concentration of cell growth and l-lactate decreased with the increase of glucose concentration and fermentation temperature. To enhance the osmotic stress resistance of the strain at high temperature, a mutant G-03 was screened and selected with 360?g/L glucose at 45°C as the selective criterion. To further increase the cell growth for lactic acid production, 3?g/L of biotin was supplemented to the medium. As a result, l-lactate concentration by the mutant G-03 reached 198.2?g/L (productivity of 5.5?g?L?1?h?1) at 41°C in a 7-L fermentor with 210?g/L glucose as carbon source. l-Lactate concentration and productivity of mutant G-03 were 115.2% and 97.8% higher than those of the parent strain, respectively. The strategy for enhancing l-lactic acid production by increasing osmotic stress resistance at high temperature may provide an alternative approach to enhance organic acid production with other strains. |
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