Increased 3-hydroxypropionic acid production from glycerol, by modification of central metabolism in Escherichia coli

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 Delta tpiA Delta zwf 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 Delta tpiA Delta zwf 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 Delta tpiA Delta zwf strain. The 3HP yield of the Delta tpiA Delta zwf Delta yqhD strain (33.9 +/- 1.2 C-mol%) was increased 1.7-fold further compared to the Delta tpiA Delta zwf strain and by 7.4-fold compared to the parental strain. Conclusion: This study successfully increased 3HP production by 7.4-fold in the Delta tpiA Delta zwf Delta yqhD E. coli strain by the modification of the central metabolism, based on metabolic simulation and experimental validation of engineered strains.