Metabolic Engineering of for Production of Polyhydroxyalkanoates with Hydroxyvaleric Acid Derived from Levulinic Acid.

Polyhydroxyalkanoates (PHAs) are emerging as alternatives to plastics by replacing fossil fuels with renewable raw substrates. Herein, we present the construction of engineered strains to produce short-chain-length PHAs (scl-PHAs), including the monomers 4-hydroxyvalerate (4HV) and 3-hydroxyvalerate (3HV) produced from levulinic acid (LA). First, an strain expressing genes () from the LA metabolic pathway of KT2440 was constructed to generate 4HV-CoA and 3HV-CoA. Second, both PhaAB enzymes from H16 were expressed to supply 3-hydroxybutyrate (3HB)-CoA from acetyl-CoA. Finally, PHA synthase (PhaC) from was introduced for the subsequent polymerization of these three monomers. The resulting strains produced four PHAs (w/w% of dry cell weight): 9.1 wt% P(4HV), 1.7 wt% P(3HV--4HV), 24.2 wt% P(3HB--4HV), and 35.6 wt% P(3HB--3HV--4HV).