[Effect of overexpression of malate dehydrogenase on succinic acid production in Escherichia coli NZN111].
Escherichia coli NZN111 is a double mutant with lactate dehydrogenase (ldhA) and pyruvate formate-lyase (pflB) inactivated. Under anaerobic conditions, disequilibrium of coenzyme NADH and NAD+ causes Escherichia coli NZN111 losing the glucose utilizing capability. In this study, we constructed a recombinant strain E. coli NZN111/pTrc99a-mdh and overexpressed the mdh gene with 0.3 mmol/L of IPTG under anaerobic fermentation condition in sealed bottles. The specific malate dehydrogenase (MDH) activity in the recombinant strain was 14.8-fold higher than that in E. coli NZN111. The NADH/ NAD+ ratio decreased from 0.64 to 0.26 and the concentration of NAD+ and NADH increased 1.5-fold and 0.2-fold respectively. Under anaerobic conditions, the recombinant strain possessed the capability of growth and glucose absorption. We took dual-phase fermentation for succinate production. After the dry cell weight (DCW) reached 6.4 g/L under aerobic conditions, the cell culture was changed to anaerobic conditions. After 15 h, 14.75 g/L glucose was consumed and succinic acid reached 15.18 g/L. The yield of succinic acid was 1.03 g/g Glu and the productivity of succinic acid was 1.012 g/(L x h).
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 210009, China.
Liya
L
Liang
Jiangfeng
J
Ma
Rongming
R
Liu
Guangming
G
Wang
Bing
B
Xu
Min
M
Zhang
Min
M
Jiang
D000123:Acetyltransferases / Q000235:genetics; D000693:Anaerobiosis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D055786:Gene Knockout Techniques; D005947:Glucose / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D011995:Recombination, Genetic; D019802:Succinic Acid / Q000378:metabolism*
D011994:Recombinant Proteins; D019802:Succinic Acid; D007770:L-Lactate Dehydrogenase; D008291:Malate Dehydrogenase; D000123:Acetyltransferases; C022560:formate C-acetyltransferase; D005947:Glucose