Authors: Jiangfeng Ma Dongmei Gou Liya Liang Rongming Liu Xu Chen Changqing Zhang Jiuhua Zhang Kequan Chen Min Jiang
Publish Date: 2013/06/06
Volume: 97, Issue: 15, Pages: 6739-6747
Abstract
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 ratelimiting enzyme of NADH synthesis pathway resulted in a significant increase in cell mass and succinate production under anaerobic conditions However a high concentration of pyruvate accumulated Thus coexpression of NAPRTase and the heterologous pyruvate carboxylase PYC of Lactococcus lactis subsp cremoris NZ9000 in recombinant E coli BA016 was investigated The total concentration of NADH was 98fold higher in BA016 than in BA002 and the NADH/NAD+ ratio decreased from 060 to 004 Under anaerobic conditions BA016 consumed 1750 g l−1 glucose and produced 1408 g l−1 succinate with a small quantity of pyruvate Furthermore when the reducing agent dithiothreitol or reduced carbon source sorbitol was added the cell growth and carbon source consumption rate of BA016 was reasonably enhanced and succinate productivity increasedThis work was supported by the “973” Program of China Grant No2009CB724701 the “863” Program of China Grant No 2011AA02A203 National Natural Science Foundation of China Grant No 21106066 National Natural Science Foundation of China Grant No 21076105 a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions Program for Changjiang Scholars and Innovative Research Team in University Grant No IRT 10662 “Qinglan project” of Jiangsu province and “The six talent summit” of Jiangsu province and the PAPD Project of Jiangsu Province Natural Science Foundation of the Higher Education Institutions of Jiangsu Province China 11KJB530003
Keywords: