Biotechnical applications of phasins: Small proteins with large potential

Phasins are a particularly fascinating class of small-molecular weight proteins that are the dominant proteins surrounding bioplastic granules produced by bacteria, called polyhydroxyalkanoates (PHAs). PHAs are biopolymers of interest since their thermomechanical properties are comparable to petroleum-based plastics, they are biodegradable, biocompatible, and can be produced from renewable bioresources. As the design and development of sustainable bioproducts from biomass and bioresources is becoming increasingly desirable, efforts to characterize and optimize PHA production have illuminated some exceptional functions of phasins. In addition to their surface performance in PHA granule formation, phasins have been shown to perform chaperone-like activities for bacterial stress mitigation, activate PHA depolymerization, contribute to PHA granule segregation, and boost the expression and activity of PHA synthases. Due to the newfound knowledge of the structures, functions, and strong amphiphilic tendencies of phasins, they have been applied in a wide variety of sustainable applications far beyond bioplastic production. Thus, phasins are emerging as a biotechnology platform for sustainable, next generation bioproduction from biomass. This review provides a synopsis of the biotechnical advances employing phasins, which include optimized bioplastic production, increased tolerance to growth inhibitors in biorefineries, “green” biocatalysis, environmental remediation, and an assortment of sustainable therapeutic bioproducts. Research gaps and suggested applications of phasins are also offered as a potential guide for future direction.