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KMID : 0545120100200010101
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Journal of Microbiology and Biotechnology
2010 Volume.20 No. 1 p.101 ~ p.109
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Enhancement of L-Lactic Acid Production in Lactobacillus casei from Jerusalem Artichoke Tubers by Kinetic Optimization and Citrate Metabolism
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Ge Xiang-Yang
Qian He
Zhang Wei-Guo
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Abstract
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Efficient L-lactic acid production from Jerusalem artichoke tubers by Lactobacillus casei G-02 using simultaneous saccharification and fermentation (SSF) in fed-batch culture is demonstrated. The kinetic analysis in the SSF signified that the inulinase activity was subjected to product inhibition, while the fermentation activity of G-02 was subjected to substrate inhibition. It was also found that the intracellularly NOX activity was enhanced by the citrate metabolism, which increased the carbon flux of Embden-Meyerhof-Parnas (EMP) pathway dramatically, and resulted more ATP production. As a result, when the SSF was carried out at 40°C after the initial hydrolysis of 1 h with supplemented sodium citrate of 10g/L, L-lactic acid concentration of 141.5 g/L was obtained in 30 h with a volumetric productivity of 4.7 g/L/h. The conversion efficiency and product yield were 93.6% of the theoretical lactic acid yield and 52.4 g lactic acid/100 g Jerusalem artichoke flour, respectively. Such a high concentration of lactic acid with high productivity from Jerusalem artichoke has not been reported previously, and hence G-02 could be a potential candidate for economical production of L-lactic acid from Jerusalem artichoke at a commercial scale.
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KEYWORD
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lactic acid, Lactobacillus casei, Jerusalem artichoke, kinetic optimization, citrate metabolism
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