Production of polyhydroxyalkanoate from acetate by metabolically engineered Aeromonas hydrophilia

Abstract

Aeromonas hydrophila 4AK4 normally produces the copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx) using lauric acid as the carbon source. In this study we reported the metabolic engineering of A.hydrophila 4AK4 for the production of polyhydroxyalkanoate (PHA) using acetate as a main carbon source. Recombinant A.hydrophila overexpressing β-ketothiolase and acetoacetyl-CoA reductase could accumulate poly-3-hydroxybutyrate (PHB) from acetate with a polymer content of 1.39wt%. Further overexpression of acetate kinase/phosphotransacetylase and acetyl-CoA synthetase improved PHB content to 8.75wt% and 19.82wt%, respectively. When acetate and propionate were simultaneously supplied as carbon sources, the engineered A.hydrophila overexpressing β-ketothiolase, acetoacetyl-CoA reductase, and acetyl-CoA synthetase was found able to produce the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV). The recombinant grew to 3.79g/L cell dry weight (CDW) containing 15.02wt% PHBV. Our proposed metabolic engineering strategies illustrate the feasibility for producing PHA from acetate by A.hydrophila.