High-value poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from kitchen waste via mixed anaerobic-aerobic consortia: fermentation performance, metabolic networks, and carbon footprint

Despite serving as an abundant carbon source for traditional biogas and fertilizer production, kitchen waste remains underexploited for high-value poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) biosynthesis due to unresolved feasibility and efficiency challenges. This study developed an integrated process (thermal-alkaline pretreatment with anaerobic-aerobic mixed microbial fermentation) for PHBV biosynthesis with kitchen waste as feed. The results showed that thermal-alkaline pretreatment could significantly enhance organic solubilization, resulting in the highest volatile fatty acids (VFAs) yield (28,949.5 mg-COD·L −1 ) at the anaerobic condition. Butyric acid emerged as the predominant VFA component, facilitating efficient PHA biosynthesis (1.25 g·L −1 ). Clostridium and Lactiplantibacillus were key VFAs producers, and Azoarcus communis and Pseudomonas spp. were the dominant PHBV-accumulating organisms. Functional gene analysis confirmed the metabolic pathways converting VFAs into PHBV monomers, involving polymerization mediated by acyl-CoA or via the β-oxidation pathway. This integrated approach reveals the feasibility, efficiency, and green footprint potentials of PHBV biosynthesis from kitchen waste, offering a great potential alternative to traditional treatment technologies while supporting circular economies and improving the cost-competitiveness of waste valorization. • An integrated approach for PHBV biosynthesis via kitchen waste was developed. • VFAs dominated by butyric acid promoted efficient PHBV synthesis (1.25 g·L −1 ). • Clostridium , Azoarcus , and Pseudomonas primarily act on the VFA-PHBV conversion. • The β-oxidation and CoA-mediated pathways facilitated the PHBV conversion. • The PHBV biosynthesis route has the lowest carbon footprint (105.143 kg CO₂-eq/t).