Microbial conversion of waste-derived short-chain fatty acids into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV): A review

The escalating generation of organic waste and the environmental burden of petroleum-derived plastics have intensified the search for sustainable and circular material solutions. Among emerging alternatives, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable copolymer within the polyhydroxyalkanoate family, has attracted significant attention due to its tunable mechanical and thermal properties. However, large-scale commercialization of PHBV remains constrained by high production costs and reliance on refined carbon feedstocks. In this context, short-chain fatty acids (SCFAs) produced via anaerobic fermentation of organic wastes represent a promising and low-cost platform for PHBV biosynthesis. This review critically examines the integration of SCFAs generation and PHBV production, focusing on how substrate characteristics, pretreatment methods, and fermentation conditions govern SCFAs yield and composition. The influence of specific SCFAs on PHBV monomer distribution, polymer properties, and process performance is systematically analyzed, together with a comparative evaluation of pure cultures, engineered strains, and mixed microbial consortia. Key challenges related to feedstock variability, process scalability, and downstream recovery are discussed. Despite substantial progress, significant knowledge gaps remain in predictive mapping between waste-derived SCFAs profiles and PHBV monomer composition, in the standardization of pretreatment and fermentation strategies for heterogeneous substrates, and in the techno-economic validation of integrated SCFAs–PHBV platforms. Future research should prioritize development of hybrid pretreatment systems, real-time metabolic control of SCFAs production, continuous bioprocessing configurations, and comprehensive life cycle and economic assessments to enable industrial implementation within a circular bioeconomy framework.