title: Escherichia coli W as a new platform strain for the enhanced production of L-valine by systems metabolic engineering.
abstract: A less frequently employed Escherichia coli strain W, yet possessing useful metabolic characteristics such as less acetic acid production and high L-valine tolerance, was metabolically engineered for the production of L-valine. The ilvA gene was deleted to make more pyruvate, a key precursor for L-valine, available for enhanced L-valine biosynthesis. The lacI gene was deleted to allow constitutive expression of genes under the tac or trc promoter. The ilvBN(mut) genes encoding feedback-resistant acetohydroxy acid synthase (AHAS) I and the L-valine biosynthetic ilvCED genes encoding acetohydroxy acid isomeroreductase, dihydroxy acid dehydratase, and branched chain amino acid aminotransferase, respectively, were amplified by plasmid-based overexpression. The global regulator Lrp and L-valine exporter YgaZH were also amplified by plasmid-based overexpression. The engineered E. coli W (ΔlacI ΔilvA) strain overexpressing the ilvBN(mut) , ilvCED, ygaZH, and lrp genes was able to produce an impressively high concentration of 60.7 g/L L-valine by fed-batch culture in 29.5 h, resulting in a high volumetric productivity of 2.06 g/L/h. The most notable finding is that there was no other byproduct produced during L-valine production. The results obtained in this study suggest that E. coli W can be a good alternative to Corynebacterium glutamicum and E. coli K-12, which have so far been the most efficient L-valine producer. Furthermore, it is expected that various bioproducts including other amino acids might be more efficiently produced by this revisited platform strain of E. coli.
authors.affiliation: Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 Program), KAIST, Daejeon, Republic of Korea. jinhwan@kaist.ac.kr
authors.forename: Jin Hwan
authors.initials: JH
authors.lastname: Park
authors.forename: Yu-Sin
authors.initials: YS
authors.lastname: Jang
authors.forename: Jeong Wook
authors.initials: JW
authors.lastname: Lee
authors.forename: Sang Yup
authors.initials: SY
authors.lastname: Lee
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics*; D005818:Genetic Engineering; D011401:Promoter Regions, Genetic; D014633:Valine / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D017931:DNA Primers; D014633:Valine