Unlocking a Sustainable Future for Plastics: A Chemical‐Enzymatic Pathway for Efficient Conversion of Mixed Waste to MHET and Energy‐Saving PET Recycling

Abstract

The heterogeneous monomers obtained from plastic waste degradation are unfavorable for PET recondensation and high‐value derivative synthesis. Herein, we developed an efficient chemical‐enzymatic approach to convert mixed plastic wastes into homogeneous mono‐2‐hydroxyethyl terephthalate (MHET) without downstream purification, benefiting from three discovered BHETases (KbEst, KbHyd, and BrevEst) in nature. Towards the mixed plastic waste, integrating the chemical K2CO3‐driven glycolysis process with the BHETase depolymerization technique resulted in an MHET yield of up to 98.26% in 40 h. Remarkably, BrevEst accomplished the highest BHET hydrolysis (~87% efficiency in 12 h) for yielding analytical‐grade MHET compared to seven state‐of‐the‐art PET hydrolases (18%‐40%). In an investigation combining quantum theoretical computations and experimental validations, we established a MHET‐initiated PET repolymerization pathway. This shortcut approach with MHET promises to strengthen the valorization of mixed plastics, offering a substantially more efficient and energy‐saving route for PET recycling.