Propionyl-CoA dependent biosynthesis of 2-hydroxybutyrate containing polyhydroxyalkanoates in metabolically engineered Escherichia coli

•Escherichia coli strain was metabolically engineered to produce 2-hydroxybutyrate (2HB)-containing polyhydroxyalkanoate (PHA).•Propionyl-CoA was used as precursor for 2HB monomer for PHA synthesis.•PHA with modified monomer compositions could be synthesized by engineering precursor synthesis pathway for PHA monomers.

We have previously reported in vivo biosynthesis of 2-hydroxyacid containing polyesters including polylactic acid (PLA), poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)], and poly(3-hydroxybutyrate-co-2-hydroxybutyrate-co-lactate) [P(3HB-co-2HB-co-LA)] employing metabolically engineered Escherichia coli strains by the introduction of evolved Clostridium propionicum propionyl-CoA transferase (PctCp) and Pseudomonas sp. MBEL 6–19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1Ps6–19). In this study, we further engineered in vivo PLA biosynthesis system in E. coli to synthesize 2HB-containing PHA, in which propionyl-CoA was used as precursor for 2-ketobutyrate that was converted into 2HB-CoA by the sequential actions of Lactococcus lactis (d)-2-hydroxybutyrate dehydrogenase (PanE) and PctCp and then 2HB-CoA was polymerized by PhaC1Ps6–19. The recombinant E. coli XL1-blue expressing the phaC1437 gene, the pct540 gene, and the Ralstonia eutropha prpE gene together with the panE gene could be grown to 0.66 g/L and successfully produced P(70 mol%3HB-co-18 mol%2HB-co-12 mol%LA) up to the PHA content of 66 wt% from 20 g/L of glucose, 2 g/L of 3HB and 1 g/L of sodium propionate. Removal of the prpC gene in the chromosome of E. coli XL1-blue could increase the mole fraction of 2HB in copolymer, but the PHA content was decreased.The metabolic engineering strategy reported here suggests that propionyl-CoA can be successfully used as the precursor to provide PHA synthase with 2HB-CoA for the production of PHAs containing 2HB monomer.