title: Increased 3-hydroxypropionic acid production from glycerol, by modification of central metabolism in Escherichia coli.
abstract: BACKGROUND
  3-hydroxypropionic acid (3HP) is an important chemical precursor for the production of bioplastics. Microbial production of 3HP from glycerol has previously been developed through the optimization of culture conditions and the 3HP biosynthesis pathway. In this study, a novel strategy for improving 3HP production in Escherichia coli was investigated by the modification of central metabolism based on a genome-scale metabolic model and experimental validation.
  
  
  RESULTS
  Metabolic simulation identified the double knockout of tpiA and zwf as a candidate for improving 3HP production. A 3HP-producing strain was constructed by the expression of glycerol dehydratase and aldehyde dehydrogenase. The double knockout of tpiA and zwf increased the percentage carbon-molar yield (C-mol%) of 3HP on consumed glycerol 4.4-fold (20.1 ± 9.2 C-mol%), compared to the parental strain. Increased extracellular methylglyoxal concentrations in the ΔtpiA Δzwf strain indicated that glycerol catabolism was occurring through the methylglyoxal pathway, which converts dihydroxyacetone phosphate to pyruvate, as predicted by the metabolic model. Since the ΔtpiA Δzwf strain produced abundant 1,3-propanediol as a major byproduct (37.7 ± 13.2 C-mol%), yqhD, which encodes an enzyme involved in the production of 1,3-propanediol, was disrupted in the ΔtpiA Δzwf strain. The 3HP yield of the ΔtpiA Δzwf ΔyqhD strain (33.9 ± 1.2 C-mol%) was increased 1.7-fold further compared to the ΔtpiA Δzwf strain and by 7.4-fold compared to the parental strain.
  
  
  CONCLUSIONS
  This study successfully increased 3HP production by 7.4-fold in the ΔtpiA Δzwf ΔyqhD E. coli strain by the modification of the central metabolism, based on metabolic simulation and experimental validation of engineered strains.
authors.forename: Kento
authors.initials: K
authors.lastname: Tokuyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ohno
authors.forename: Katsunori
authors.initials: K
authors.lastname: Yoshikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirasawa
authors.forename: Shotaro
authors.initials: S
authors.lastname: Tanaka
authors.forename: Chikara
authors.initials: C
authors.lastname: Furusawa
authors.affiliation: Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan. shimizu@ist.osaka-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimizu
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics; D055786:Gene Knockout Techniques; D005990:Glycerol / Q000378:metabolism*; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000201:enzymology; D019344:Lactic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D060847:Metabolic Engineering
chemical_list: D029968:Escherichia coli Proteins; D019344:Lactic Acid; C031601:hydracrylic acid; D000444:Aldehyde Dehydrogenase; D006836:Hydro-Lyases; C020671:glycerol dehydratase; D005990:Glycerol