title: Regulation of metabolic flux in Lactobacillus casei for lactic acid production by overexpressed ldhL gene with two-stage oxygen supply strategy.
abstract: 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.
authors.affiliation: The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, JiangNan University, Wuxi-214122, JiangSu Province, P.R. China.
authors.forename: Xiang-Yang
authors.initials: XY
authors.lastname: Ge
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
authors.forename: Xiang
authors.initials: X
authors.lastname: Chen
authors.forename: Long-Yun
authors.initials: LY
authors.lastname: Zhang
mesh_terms: D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D007770:L-Lactate Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D019344:Lactic Acid / Q000096:biosynthesis* / Q000302:isolation & purification; D007780:Lacticaseibacillus casei / Q000254:growth & development* / Q000378:metabolism*; D064688:Metabolic Flux Analysis; D010100:Oxygen / Q000378:metabolism
chemical_list: D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D010100:Oxygen