title: Metabolic engineering of Corynebacterium glutamicum for methionine production by removing feedback inhibition and increasing NADPH level.
abstract: Relieving the feedback inhibition of key enzymes in a metabolic pathway is frequently the first step of producer-strain construction by genetic engineering. However, the strict feedback regulation exercised by microorganisms in methionine biosynthesis often makes it difficult to produce methionine at a high level. In this study, Corynebacterium glutamicum ATCC 13032 was metabolically engineered for methionine production. First, the metD gene encoding the methionine uptake system was deleted to achieve extracellular accumulation of methionine. Then, random mutagenesis was performed to remove feedback inhibition by metabolic end-products. The resulting strain C. glutamicum ENM-16 was further engineered to block or decrease competitive branch pathways by deleting the thrB gene and changing the start codon of the dapA gene, followed by point mutations of lysC (C932T) and pyc (G1A, C1372T) to increase methionine precursor supply. To enrich the NADPH pool, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the pentose phosphate pathway were mutated to reduce their sensitivity to inhibition by intracellular metabolites. The resultant strain C. glutamicum LY-5 produced 6.85 ± 0.23 g methionine l(-1) with substrate-specific yield (Y P/S) of 0.08 mol per mol of glucose after 72 h fed-batch fermentation. The strategies described here will be useful for construction of methionine engineering strains.
authors.affiliation: Laboratory of Microbiology, School of Life Science and Technology, Harbin Institute of Technology, Harbin, 150001, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: Laboratory of Microbiology, School of Life Science and Technology, Harbin Institute of Technology, Harbin, 150001, People's Republic of China.
authors.forename: Hua
authors.initials: H
authors.lastname: Cong
authors.affiliation: Liaoning Key Laboratory Food Biological Technology, Dalian Polytechnic University, Dalian, 116034, People's Republic of China.
authors.forename: Bingnan
authors.initials: B
authors.lastname: Liu
authors.affiliation: Laboratory of Microbiology, School of Life Science and Technology, Harbin Institute of Technology, Harbin, 150001, People's Republic of China.
authors.forename: Jinzhu
authors.initials: J
authors.lastname: Song
authors.affiliation: Laboratory of Microbiology, School of Life Science and Technology, Harbin Institute of Technology, Harbin, 150001, People's Republic of China.
authors.forename: Xueying
authors.initials: X
authors.lastname: Sun
authors.affiliation: School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, 150001, People's Republic of China.
authors.forename: Junzheng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Laboratory of Microbiology, School of Life Science and Technology, Harbin Institute of Technology, Harbin, 150001, People's Republic of China. microbio207@gmail.com.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D048230:Corynebacterium glutamicum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D060847:Metabolic Engineering / Q000379:methods; D053858:Metabolic Networks and Pathways; D008715:Methionine / Q000096:biosynthesis*; D016296:Mutagenesis; D009249:NADP / Q000378:metabolism*; D010734:Phosphogluconate Dehydrogenase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D009249:NADP; D008715:Methionine; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase
keywords: Corynebacterium glutamicum; Feedback inhibition; Fermentation; Metabolic flux; Methionine biosynthesis