Metabolic engineering of Corynebacterium glutamicum for methionine production by removing feedback inhibition and increasing NADPH level
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- 作者：Ying Li ; Hua Cong ; Bingnan Liu ; Jinzhu Song ; Xueying Sun…
- 刊名：Antonie van Leeuwenhoek
- 出版年：2016
- 出版时间：September 2016
- 年：2016
- 卷：109
- 期：9
- 页码：1185-1197
- 全文大小：840 KB
- 刊物类别：Biomedical and Life Sciences
- 刊物主题：Life Sciences
Microbiology
Medical Microbiology
Plant Sciences
Soil Science and Conservation - 出版者：Springer Netherlands
- ISSN：1572-9699
- 卷排序：109
文摘
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 (YP/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.KeywordsCorynebacterium glutamicumFeedback inhibitionFermentationMetabolic fluxMethionine biosynthesis