title: Regulation of NAD(H) pool and NADH/NAD(+) ratio by overexpression of nicotinic acid phosphoribosyltransferase for succinic acid production in Escherichia coli NZN111.
abstract: Succinic acid is not the dominant fermentation product from glucose in wild-type Escherichia coli W1485. To reduce byproduct formation and increase succinic acid accumulation, pyruvate formate-lyase and lactate dehydrogenase, encoded by pflB and ldhA genes, were inactivated. However, E. coli NZN111, the ldhA and pflB deletion strain, could not utilize glucose anaerobically due to the block of NAD(+) regeneration. To restore glucose utilization, overexpression of nicotinic acid phosphoribosyltransferase, a rate limiting enzyme of NAD(H) synthesis encoded by the pncB gene, resulted in a significant increase in cell mass and succinic acid production. Furthermore, the results indicated a significant increase in NAD(H) pool size, and decrease in the NADH/NAD(+) ratio from 0.64 to 0.13, in particular, the concentration of NAD(+) increased 6.2-fold during anaerobic fermentation. In other words, the supply of enough NAD(+) for NADH oxidation by regulation of NAD(H) salvage synthesis mechanism could improve the cell growth and glucose utilization anaerobically. In addition, the low NADH/NAD(+) ratio also change the metabolite distribution during the dual-phase fermentation. As a result, there was a significant increase in succinic acid production, and it is provided further evidence that regulation of NAD(H) pool and NADH/NAD(+) ratio was very important for succinic acid production.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 211816, People's Republic of China.
authors.forename: Liya
authors.initials: L
authors.lastname: Liang
authors.forename: Rongming
authors.initials: R
authors.lastname: Liu
authors.forename: Guangming
authors.initials: G
authors.lastname: Wang
authors.forename: Dongmei
authors.initials: D
authors.lastname: Gou
authors.forename: Jiangfeng
authors.initials: J
authors.lastname: Ma
authors.forename: Kequan
authors.initials: K
authors.lastname: Chen
authors.forename: Min
authors.initials: M
authors.lastname: Jiang
authors.forename: Ping
authors.initials: P
authors.lastname: Wei
authors.forename: Pingkai
authors.initials: P
authors.lastname: Ouyang
mesh_terms: D001709:Biotechnology / Q000379:methods*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005947:Glucose / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D010430:Pentosyltransferases / Q000235:genetics / Q000378:metabolism*; D015202:Protein Engineering / Q000379:methods; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D009243:NAD; D019802:Succinic Acid; D010430:Pentosyltransferases; C021864:nicotinate phosphoribosyltransferase; D005947:Glucose