Fundamental factors determining the molecular weight of polyhydroxyalkanoate during biosynthesis

This review focuses on the factors that determine the molecular weight of polyhydroxyalkanoate (PHA), an aliphatic polyester synthesized by bacteria for carbon and energy storage. PHA is a polymer with good thermoplastic, biodegradable, biocompatible and renewable properties. Therefore, it has attracted considerable attention as an environmentally friendly and biomedical material. Because the mechanical strength of PHA increases with its molecular weight, high-molecular-weight PHA polymers are preferred. The synthesis of high-molecular-weight PHA should consider the following factors: the concentration of PHA synthase, the occurrence of a chain transfer reaction, the catalytic activity of PHA synthase and the simultaneous degradation of PHA during biosynthesis. These factors have a direct impact on the molecular weight of PHA. Furthermore, the factors that affect the molecular weight of PHA during in vitro PHA polymerization and cultivation of PHA native and non-native bacteria are discussed. Polymer Journal (2016) 48, 1051–1057; doi:10.1038/pj.2016.78; published online 7 September 2016