Synthesis and Characterization of 3-Hydroxybutyrate and 3-Hydroxy-9-octadecenoate Copolymer from Engineered Halomonas

Abstract

Polyhydroxyalkanoate (PHA) is a family of biodegradable polyesters accumulated by various microorganisms. Halophilic microorganism Halomonas bluephagenesis has been developed as a production platform strain for various PHA, chemicals and proteins under open unsterile and continuous condition. For the first time, H. bluephagenesis was engineered to synthesize copolymers of short chain length PHA (SCL-PHA) and long chain length PHA (LCL-PHA) called SCL-co-LCL PHA. This study engineered H. bluephagenesis for synthesizing SCL-co-LCL PHA via β-oxidation inhibition and expression of heterologous PHA synthase (PhaC). Oleate was utilized as structural related carbon source due to its low cost, long carbon chain length, unsaturated bonds and sustainability. The engineered H. bluephagenesis successfully synthesized copolymers of 3-hydroxybutyrate (3HB) and 3-hydroxy-9-octadecenoate (3H9Od) on oleate. It could grow to 8 g/L of cell dry weight (CDW) containing 51wt% P(3HB-co-12mol% 3H9Od) in shake flasks, and 28 g/L of cell dry weight (CDW) containing 53wt% P(3HB-co-6mol% 3H9Od) in 7-L fermenters. The thermal properties of this new PHA were characterized, and chemical click reactions were applied to modify P3HB3H9Od.