Recent advances in the synthesis, production, processing, and applications of polyhydroxyalkanoates and polyhydroxyalkanoate‐based composites

This review provides a structured, filler-class-organized analysis of recent advances in polyhydroxyalkanoate (PHA)-based composite materials, spanning synthesis, processing, properties, and applications. Unlike prior reviews focusing primarily on biosynthesis or individual filler types in isolation, this work offers a comparative framework across five reinforcement classes, namely inorganic fillers, cellulosic reinforcements, synthetic polymer blends, carbon nanostructures, and multi-component hybrid systems. This approach enables the extraction of cross-filler design guidelines from aggregated data. Synthesis coverage encompasses both microbial fermentation and recent advances in stereoselective chemical synthesis via ring-opening polymerization. Property improvements are attributed to mechanistically distinct processes—nucleating and barrier effects for inorganic fillers, interfacial load transfer for cellulosic reinforcements, and synergistic multifunctional coupling in carbon-based and multi-component formulations—alongside characteristic trade-offs such as reduced ductility at higher filler loadings. Finally, these property profiles are mapped onto specific application domains, such as food packaging, biomedical scaffolds, and specialty functional materials, providing a performance-based framework for material selection.