Progress in the biosynthesis of bio-based PET and PEF polyester monomers

With the rapid development of modern industry and the increasing scarcity of petroleum resources, bio-based polymeric materials using biomass resources as the primary raw material, with dual roles in resource conservation and low carbon, are promising alternatives to traditional petrochemicals. The efficient and low-cost preparation of terephthalic acid (TPA), 2,5-furandicarboxylic acid (FDCA) and ethylene glycol (EG), the monomers of the bio-based polyesters polyethylene terephthalate (PET) and polyethylene 2,5-furandicarboxylic acid (PEF), has attracted substantial attention. Both chemical and biocatalysis can oxidize biomass to produce bio-based monomers; however, chemical catalytic methods often require high temperatures, high pressure, and precious metal catalysts, resulting in high production costs. Compared with chemical conversion, bioconversion, with its mild reaction conditions and high selectivity, is an important development for the efficient use of biomass resources, but currently has a lower yield. In this review, we discuss and summarize strategies for the preparation of TPA, FDCA and EG and their applications, focusing mainly on biocatalytic approaches. Next, we illustrate the need to optimise the generation of efficient biocatalysts using strategies such as protein, enzyme, and metabolic engineering. Finally, the challenges and recommendations that must be addressed for each monomer's biosynthesis pathway are discussed, and an outlook for future directions and prospects is provided. This review provides theoretical guidance for developing efficient and cost-effective green manufacturing technologies for TPA, FDCA, and EG.