title: Collaborative regulation of CO2 transport and fixation during succinate production in Escherichia coli.
abstract: In Escherichia coli, succinic acid is synthesized by CO2 fixation-based carboxylation of C3 metabolites. A two-step process is involved in CO2 integration: CO2 uptake into the cell and CO2 fixation by carboxylation enzymes. The phosphoenolpyruvate (PEP) carboxylase (PPC) and carboxykinase (PCK) are two important carboxylation enzymes within the succinate synthetic pathway, while SbtA and BicA are two important bicarbonate transporters. In this study, we employed a dual expression system, in which genes regulating both CO2 uptake and fixation were co-overexpressed, or overexpressed individually to improve succinate biosynthesis. Active CO2 uptake was observed by the expression of SbtA or/and BicA, but the succinate biosynthesis was decreased. The succinate production was significantly increased only when a CO2 fixation gene (ppc or pck) and a CO2 transport gene (sbtA or bicA) were co-expressed. Co-expression of pck and sbtA provided the best succinate production among all the strains. The highest succinate production of 73.4 g L(-1) was 13.3%, 66.4% or 15.0% higher than that obtained with the expression of PCK, SbtA alone, or with empty plasmids, respectively. We believe that combined regulation of CO2 transport and fixation is critical for succinate production. Imbalanced gene expression may disturb the cellular metabolism and succinate production.
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education) and Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068 China.
authors.forename: Li-Wen
authors.initials: LW
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education) and Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068 China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education) and Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068 China.
authors.forename: Li-Na
authors.initials: LN
authors.lastname: Wei
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education) and Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068 China.
authors.forename: Hong-Mei
authors.initials: HM
authors.lastname: Li
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education) and Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068 China.
authors.forename: Zhan-Peng
authors.initials: ZP
authors.lastname: Yuan
authors.affiliation: Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 China.
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 China.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 China.
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: Liang
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education) and Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan 430068 China.
authors.forename: Ya-Jie
authors.initials: YJ
authors.lastname: Tang
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000235:genetics / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D002245:Carbon Dioxide; D019802:Succinic Acid; D010730:Phosphoenolpyruvate Carboxylase