Metabolic Engineering for the Production of Diverse Polyhydroxyalkanoates in Escherichia coli

We previously reported production of polylactate (PLA) by engineered Escherichia coli harboring an evolved polyhydroxyalkanoate (PHA) synthase and propionyl-CoA transferase. The evolved PHA synthase from Pseudomonas sp. MBEL 6-19 is able to accept broad range of substrates from short chain length (SCL) hydroxyacyl-CoA to medium chain length (MCL) hydroxyacyl-CoA, therefore the PLA producing E. coli was further engineered to expand monomer spectrum. Various hydroxy acids including 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) were copolymerized with lactate as novel biomaterials. First, for in vivo synthesis of 3HB-CoA, R. eutropha phaA and phaB genes encoding β-ketothiolase and acetoacetyl-CoA reductase were introduced. Second, to produce 4-hydroxybutyrate, the Clostridium kluyveri sucD and 4hbD genes encoding CoA-dependent succinate semialdehyde dehydrogenase and 4HB dehydrogenase were introduced. These copolymers showed enhanced polymer properties such as molecular weight, thermal properties as novel biopolymers for various applications. [This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries from the Ministry of Science, ICT and Future Planning (MSIP) through the National Research Foundation (NRF) of Korea (NRF-2012M1A2A2026556 and NRF-2012M1A2A2026557)].