Metabolic engineering ofCorynebacterium glutamicumstrain ATCC13032 to producel‐methionine

Abstract

L-Methionine-producing strain QW102/pJYW-4-hom(m) -lysC(m) -brnFE was developed from Corynebacterium glutamicum strain ATCC13032, using metabolic engineering strategies. These strategies involved (i) deletion of the gene thrB encoding homoserine kinase to increase the precursor supply, (ii) deletion of the gene mcbR encoding the regulator McbR to release the transcriptional repression to various genes in the l-methionine biosynthetic pathway, (iii) overexpression of the gene lysC(m) encoding feedback-resistant aspartate kinase and the gene hom(m) encoding feedback-resistant homoserine dehydrogenase to further increase the precursor supply, and (iv) overexpression of the gene cluster brnF and brnE encoding the export protein complex BrnFE to increase extracellular l-methionine concentration. QW102/pJYW-4-hom(m) -lysC(m) -brnFE produced 42.2 mM (6.3 g/L) l-methionine after 64-H fed-batch fermentation. These results suggest that l-methionine-producing strains can be developed from wild-type C. glutamicum strains by rationally metabolic engineering.

Rewiring the Central Metabolic Pathway for High‐Yield l‐Serine Production in Corynebacterium glutamicum by Using Glucose

“…Nowadays, great attention has been paid to l ‐serine production from cheap carbon sources through aerobic fermentation . Corynebacterium glutamicum ( C. glutamicum ) is widely used as a workhorse for producing amino acids, including l ‐glutamate, l ‐methionine, and l ‐lysine . Compared with the production of other amino acids, accumulation of l ‐serine is more challenging in C. glutamicum , because it is an intermediate metabolite that acts as an important building block for cellular physiology …”

Systems metabolic engineering strategies for the production of amino acids

“…The biosynthetic process of a certain amino acid usually comprises several enzymes that perform divided functions to fulfill the conversion of carbon source to the desired amino acid product. The most commonly used metabolic engineering strategy is to enhance the expression of the key enzymes to obtain the maximum precursor enrichment [20] , whilst, eliminate unnecessary byproduct formation by blocking or attenuating the competing pathways [21] , [22] , [23] , and cutting off the further degradation of the desired amino acid. Elimination of feedback inhibition of the key enzyme in a metabolic pathway is frequently the first and most important step for the development of a high-producing strain [24] , [25] .…”

“…The final titer of a desired amino acid product not only relies on its intracellular synthesis, but is also determined by the efficiency of the transporter system. With the discovery of various transporters for amino acids [28] , such as BrnFE for the export of branched chain amino acids and l -methionine [20] , ThrE for the export of l -threonine [29] , LysE for the export of l -lysine and l -arginine [30] etc., transporter engineering has been increasingly used to obtain higher titer, yield or productivity. Currently, transporter engineering is conducted mainly by enhancing the excretion of the desired amino acid, and simultaneously blocking the inverse import of the excreted product.…”

Modular systems metabolic engineering enables balancing of relevant pathways for l-histidine production with Corynebacterium glutamicum

“…Corynebacterium glutamicum is a Gram-positive, facultatively anaerobic bacterium which can grow on a wide range of sugars, alcohols, and organic acids [58, 65] and is known as a workhorse for the production of l -glutamate and l -lysine [8, 23, 83]. Moreover, metabolic engineering approaches expanded the product portfolio to other amino acids such as l -methionine, l -valine, l -arginine, and l -tryptophan [8, 42, 66, 68, 71], organic acids [17, 53, 94, 95], alcohols [13, 43, 46, 80], vitamins [40], carotenoids [35, 36], fatty acids [82], polymers [59], terpenes [26, 48], and others. Most relevant, C. glutamicum possesses an intrinsic histidine synthesis pathway but, in contrast to other industrially relevant bacteria such as Pseudomonas and several Bacillus genera, lacks a histidine utilization system (reviewed in [11]).…”