Polyhydroxyalkanoates (PHAs) biological recovery approaches and protein-mediated secretion model hypothesis

Polyhydroxyalkanoates (PHAs) are a class of microbially synthesized polyesters with diverse structures with renewability, biodegradability, good biocompatibility, and broad application prospects. However, the level of commercialization of PHAs remains low. The high recovery cost is one of the main reasons preventing the widespread use of these "green polymers". For decades, efforts have been made to explore lower-cost, greener, and more economical PHAs recovery strategies, and significant progress has been made. This review presents cell lysis and yeast surface display (YSD)-based bio-recovery strategies for PHAs, and then proposes a model hypothesis for protein-mediated secretion of PHAs drawing on the lipid secretion model to provide essential information for further cost reduction and efficiency in the recovery of PHAs. In addition, this review also highlights the bio-recovery strategy of extracellular PHAs based on synthetic biology and exploring specific PHAs secretion mechanism is a promising strategy for reducing the cost of PHAs recovery in the future.