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KMID : 0545120150250010081
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Journal of Microbiology and Biotechnology
2015 Volume.25 No. 1 p.81 ~ p.88
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Regulation of Metabolic Flux in Lactobacillus casei for Lactic Acid Production by Overexpressed ldhL Gene with Two-Stage Oxygen Supply Strategy
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Xiang-Yang Ge
Yan Xu
Xiang Chen
Long-Yun Zhang
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Abstract
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This study describes a novel strategy to regulate the metabolic flux for lactic acid production in Lactobacillus casei. The ldhL gene encoding L-lactate dehydrogenase (L-LDH) was overexpressed in L. casei, and a two-stage oxygen supply strategy (TOS) that maintained a medium oxygen supply level during the early fermentation phase, and a low oxygen supply level in the later phase was carried out. As a consequence, a maximum L-LDH activity of 95.6 U/ml was obtained in the recombinant strain, which was over 4-fold higher than that of the initial strain. Under the TOS for L. casei (pMG-ldhL), the maximum lactic acid concentration of 159.6 g/l was obtained in 36 h, corresponding to a 62.8% increase. The results presented here provide a novel way to regulate the metabolic flux of L. casei for lactic acid production in different fermentation stages, which is available to enhance organic acid production in other strains.
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KEYWORD
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Lactobacillus casei, lactic acid, oxygen supply, L-Lactate dehydrogenase
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