Coupled synthetic pathways improve the production of 3-hydroxypropionic acid in recombinant Escherichia coli strains

To improve the production of 3-HP with glucose as a substrate, the malonyl-CoA and propionyl-CoA pathways were coupled to regulate NADP⁺/NADPH regeneration in the recombinant E. coli. The strain Ec-AM that overexpressed the key enzymes of the malonyl-CoA pathway, acetyl CoA carboxylase (ACC) from Ustilago maydis and malonyl CoA reductase (MCR) from Chloroflexus aurantiacus, produced 0.26 g/L of 3-HP in 25-h shake flask cultivation. The strain Ec-P overexpressing the key enzyme of the propionyl-CoA pathway, propionyl-CoA dehydrogenase (PACD) from Candida rugosa, produced 0.11 g/L of 3-HP. However, 3-HP titer of the strain Ec-PAM overexpressing PACD along with ACC and MCR, via two pathways cooperation, was 1.29 g/L. The addition of biotin and bicarbonate improved the 3-HP production of the strain Ec-PAM. 3-HP titer of strain Ec-ΔY-ΔP-PAM with double deletion of ygfH (encoding propionyl-CoA: succinate-CoA transferase) and prpC (encoding methylcitrate synthase) genes reached 1.94 g/L, which was 1.5-fold higher than that of the strain Ec-PAM cultured under the same conditions.