Current trends in polyhydroxyalkanoates (PHAs) biosynthesis: insights from the recombinant Escherichia coli

Pursuing the current trend, the "green-polymers", polyhydroxyalkanoates (PHAs) which are degradable and made from renewable sources have been a potential substitute for synthetic plastics. Due to the increasing concern towards escalating crude oil price, depleting petroleum resource and environmental damages done by plastics, PHAs have gained more and more attractions, both from industry and research. From the view point of Escherichia coli, a microorganism that used in the biopolymer large scale production, this paper describes the backgrounds of PHA and summarizes the current advances in PHA developments. In the short-chain-length (scl) PHAs section, the study of poly[(R)-3-hydroxybutyrate] [P(3HB)] as model polymer, ultra-high-molecular-weight P(3HB) which rarely discussed, and P(3HB-co-3HV), another commercialized PHA polymer are included. Other than that, this review also shed some light on the new members of PHA family, lactate-based PHAs and P(3HP) with topics such as block copolymers and invention of novel biopolymers. Flexibility of microorganisms in utilizing different carbon sources to accumulate medium-chain-length (mcl) PHAs and lastly, the promising scl-mcl-PHAs with interesting properties are also discussed.