title: Strategies for efficient repetitive production of succinate using metabolically engineered Escherichia coli.
abstract: Escherichia coli AFP111, a pflB, ldhA, ptsG triple mutant of E. coli W1485, can be recovered for additional succinate production in fresh medium after two-stage fermentation (an aerobic growth stage followed by an anaerobic production stage). However, the specific productivity is lower than that of two-stage fermentation. In this study, three strategies were compared for reusing the cells. It was found when cells were aerobically cultivated at the end of two-stage fermentation without supplementing any carbon source, metabolites (mainly succinate and acetate) could be consumed. As a result, enzyme activities involved in the reductive arm of tricarboxylic acid cycle and the glyoxylate shunt were enhanced, yielding a succinate specific productivity above g⁻¹(DCW)h⁻¹ and a mass yield above 0.90 g g⁻¹ in the subsequent anaerobic fermentation. In addition, the intracellular NADH of cells subjected to aerobic cultivation with metabolites increased by more than 3.6 times and the ratio of NADH to NAD+ increased from 0.4 to 1.3, which were both favorable for driving the TCA branch to succinate.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing, China.
authors.forename: Jiang-feng
authors.initials: JF
authors.lastname: Ma
authors.forename: Min
authors.initials: M
authors.lastname: Jiang
authors.forename: Ke-quan
authors.initials: KQ
authors.lastname: Chen
authors.forename: Bing
authors.initials: B
authors.lastname: Xu
authors.forename: Shu-wen
authors.initials: SW
authors.lastname: Liu
authors.forename: Ping
authors.initials: P
authors.lastname: Wei
authors.forename: Han-jie
authors.initials: HJ
authors.lastname: Ying
authors.forename: Ho-nam
authors.initials: HN
authors.lastname: Chang
authors.forename: Ping-kai
authors.initials: PK
authors.lastname: Ouyang
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001709:Biotechnology / Q000379:methods*; D002623:Chemistry Techniques, Analytical / Q000379:methods; D002952:Citric Acid Cycle; D003470:Culture Media; D004926:Escherichia coli / Q000378:metabolism*; D005285:Fermentation; D008956:Models, Chemical; D009243:NAD / Q000737:chemistry; D019802:Succinic Acid / Q000737:chemistry*; D013997:Time Factors
chemical_list: D003470:Culture Media; D009243:NAD; D019802:Succinic Acid