Production of Low Molecular Weight P(3HB-co-3HV) by Butyrate-acetoacetate CoA-transferase (cftAB) in Escherichia coli

Naturally degradable bioplastic polyhydroxyalkanoate (PHA) is a promising biopolymer and its physical properties could be changed by introducing of different monomers such as 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and 3-hydroxyhexanoate (3HHx). To produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(3HB-co-3HV)) including a high fraction of hydroxyvalerate, we introduced ctfAB into engineered Escherichia coli YJ200 possessing a pLW487 vector containing bktB, phaB, and phaC under control of the trc promoter. To enhance the HV fraction of P(3HB-co-3HV), the optimal concentrations of propionate, which acts as a precursor of 3HV and isopropyl β-D-1-thiogalactopyranoside, were determined and found to be 0.1 mM and 0.3%, respectively. Under the optimized conditions, E. coli, YJ201 produced P(3HB-co-3HV) containing a large amount of 3HV. Comparison with other CoA transferases showed that CtfAB produced relatively lower molecular weight copolymers. This demonstrates the necessity of identifying additional different CoA transferases, because CoA transferase can affect both the monomer fraction and molecular weight of polymers.