Divergent bioprocessing platforms for polyhydroxyalkanoate production from food and lipid-rich wastes

Polyhydroxyalkanoates (PHAs) are a promising class of bio-based, biodegradable polymers that offer a sustainable alternative to conventional fossil-based plastics. However, their commercialization is hindered by high production costs, primarily due to expensive feedstock and complex downstream processing. While valorizing organic waste is a clear path to economic viability, recent research has shown that the two primary feedstocks, food waste (FW) and lipid-rich waste (LRW), demand fundamentally divergent bioprocessing strategies rooted in their distinct biochemical composition and microbial utilization pathways. This review provides a critical, mechanism-based comparative analysis of these two waste-derived PHA platforms: the multi-stage FW-to-volatile fatty acids (VFA) and sugar platform, which is limited by costly pretreatment and mixed culture challenges, and the LRW-to-PHA platform, which offers a high-yield pathway constrained by mass transfer and the need for sterile fermentation. This review further examines advances in microbial metabolism and bioprocess design, highlighting how strain selection and fermentation strategies align with feedstock-specific challenges. It also evaluates modern downstream extraction and purification methods for their impact on polymer quality, cost, and scalability, demonstrating the potential of waste-derived PHAs for applications in packaging, biomedical devices, and agriculture. Finally, the review proposes an evidence-based, application-driven decision-support framework to guide platform selection based on feedstock composition and target polymer specifications.