Increased 3-Hydroxypropionic Acid Production from Glycerol Based on the Genome-Scale Metabolic Simulation in Escherichia coli

3-Hydroxypropionic acid (3HP) has been attracted attention because of its availability for precursor of various valuable chemicals such as acrylic acid and poly(3HP). Glycerol is one of the potential substrates for the bioproduction of 3HP since it is a surplus byproduct of growing biodiesel production and it can be converted to 3HP by only two reactions. For improvement of the target production, in silico simulation using a genome-scale metabolic model with flux balance analysis is a powerful tool to identify the candidate genes for metabolic engineering. In this study, we tried to increase 3HP production in Escherichia coli by modification of the central metabolism based on the genome-scale metabolic simulation.

For 3HP production from glycerol in E. coli, following genes were over-expressed in E. coli MG1655(DE3): dhaB and gdrAB encoding glycerol dehydratase and glycerol dehydratase reactivase derived from Klebsiella pnumoniae, respectively, and aldH encoding aldehyde dehydrogenase derived from E. coli (hereafter termed “3HP strain”). To identify the candidate genes whose deletion could improve 3HP production, in silico knockout simulation using genome-scale metabolic model of E. coli iAF1260 was performed. As the result, double knockout of tpiA-zwf was predicted to enhance the 3HP yield on glycerol. In consistent with the simulation result, the tpiA-zwf knockout strain constructed showed higher 3HP yield on the consumed glycerol (0.20 mol/mol) than that of the 3HP strain (0.046 mol/mol). However, the tpiA-zwf knockout strain produced high yield of 1,3-propanediol, thus, yqhD encoding an alcohol dehydrogenase related to the 1,3-propanediol biosynthesis was deleted in the tpiA-zwf knockout strain. The 3HP yield of the tpiA-zwf-yqhD knockout strain increased 7.4-fold of the 3HP strain (0.34 mol/mol).