Polyhydroxyalkanoate production from poly(ethylene furanoate) using a completely biotechnological approach

Plastics are indispensable in modern society, but their increasing production and disposal pose serious environmental challenges, including pollution and the depletion of non-renewable resources. Poly(ethylene furanoate) (PEF), a bio-based polyester composed of ethylene glycol and 2,5-furandicarboxylic acid (FDCA), is attracting attention as a sustainable alternative to poly(ethylene terephthalate) (PET). In this study, we developed a fully biotechnological upcycling system for PEF. Our approach involved enzymatic depolymerization of PEF to release FDCA, followed by microbial conversion of FDCA into polyhydroxyalkanoate (PHA), a biodegradable polyester. From soil samples enriched with FDCA as the sole carbon source, we isolated two bacterial strains: Pseudomonas sp. S8-1 and Caballeronia sp. S8-5. These strains produced medium-chain-length and short-chain-length PHAs, respectively, in defined medium containing FDCA. For enzymatic depolymerization, we employed the thermostable ICCG variant (F243I/D238C/S283C/Y127G) of leaf-branch compost cutinase, known for its high PET-degrading activity. The depolymerization of PET by this enzyme was enhanced by the addition of calcium carbonate (CaCO₃) powder to suppress acidification. Furthermore, the enzyme retained high activity even after partial purification by heat treatment at 60°C and efficiently depolymerized PEF as well. Finally, the PEF degradation solution was successfully utilized as a carbon source for PHA production by strain S8-5. These results demonstrate a proof-of-concept biorecycling system for PEF and represent a first step toward sustainable plastic management.