Cao Weijia, Gou Dongmei, Liang Liya, Liu Rongming, Chen Kequan, Ma Jiangfeng, Jiang Min
Sheng Wu Gong Cheng Xue Bao. 2013 Dec;29(12):1855-9.
Escherichia coli BA002, in which the ldhA and pflB genes are deleted, cannot utilize glucose anaerobically due to the inability to regenerate NAD+. To restore glucose utilization, overexpression of nicotinic acid phosphoribosyltransferase (NAPRTase) encoded by the pncB gene, a rate-limiting enzyme of NAD(H) synthesis pathway, resulted in a significant increase in cell mass and succinate production under anaerobic conditions. However, a high concentration of pyruvate was accumulated. Thus, co-expression of NAPRTase and the heterologous pyruvate carboxylase (PYC) of Lactococcus lactis subsp. cremoris NZ9000 in recombinant E. coli BA016 was investigated. Results in 3 L fermentor showed that OD600 is 4.64 and BA016 consumed 35.00 g/L glucose and produced 25.09 g/L succinate after 112 h under anaerobic conditions. Overexpression of pncB and pyc in BA016, the accumulation of pyruvic acid was further decreased, and the formation of succinic acid was further increased.
大肠杆菌BA002缺失ldhA和pflB基因，由于无法再生NAD⁺，因而不能在厌氧条件下利用葡萄糖。为恢复葡萄糖利用能力，由pncB基因编码的烟酰胺磷酸核糖转移酶（NAPRTase）作为NAD（H）合成途径的限速酶，其过表达导致在厌氧条件下细胞量和琥珀酸产量显著增加。然而，丙酮酸积累到了很高的浓度。因此，研究了在重组大肠杆菌BA016中共表达NAPRTase和乳酸乳球菌乳脂亚种NZ9000的异源丙酮酸羧化酶（PYC）。3 L发酵罐中的结果表明，在厌氧条件下培养112 h后，BA016的OD600为4.64，消耗了35.00 g/L葡萄糖，产生了25.09 g/L琥珀酸。在BA016中过表达pncB和pyc，丙酮酸的积累进一步减少，琥珀酸的生成进一步增加。
