Valorization of Textile Waste: Enzymatic Upcycling of Terephthalic Acid Toward a Sustainable PET Value Chain

The rapid expansion of the global textile industry, driven by the fast-fashion paradigm, which is characterized by low-cost, short-lived garments made from inexpensive synthetic fibers, has intensified environmental pressures through increased waste generation, resource depletion, microplastic pollution, and greenhouse gas emissions. Conventional polyethylene terephthalate (PET) recycling remains limited by high energy demands, harsh processing conditions, and the generation of low-value products. This review examines emerging upcycling strategies targeting PET-derived monomers, including terephthalic acid (TPA) and ethylene glycol, with particular emphasis on converting TPA into high-value chemicals, functional materials, and specialty polymers. By integrating biological and materials engineering approaches, these strategies offer a transformative pathway for converting textile waste into value-added products, thereby supporting the development of a circular and sustainable PET economy. Unlike previous surveys, this work focuses on the upcycling of TPA, providing a critical evaluation of how advanced protein engineering is driving improvements in enzymatic depolymerization and bioconversion pathways toward high-value products, thereby filling a key gap in existing research, which is predominantly centered on primary recycling approaches.