Discovery and mechanism-guided engineering of BHET hydrolases for improved PET recycling and upcycling

Although considerable research achievements have been made to address the plastic crisis using enzymes, their applications are limited due to incomplete degradation and low efficiency. Herein, we report the identification and subsequent engineering of BHETases, which have the potential to improve the efficiency of PET recycling and upcycling. Two BHETases (ChryBHETase and BsEst) are identified from the environment via enzyme mining. Subsequently, mechanism-guided barrier engineering is employed to yield two robust and thermostable & UDelta;BHETases with up to 3.5-fold enhanced k(cat)/K-M than wild-type, followed by atomic resolution understanding. Coupling & UDelta;BHETase into a two-enzyme system overcomes the challenge of heterogeneous product formation and results in up to 7.0-fold improved TPA production than seven state-of-the-art PET hydrolases, under the conditions used here. Finally, we employ a & UDelta;BHETase-joined tandem chemical-enzymatic approach to valorize 21 commercial post-consumed plastics into virgin PET and an example chemical (p-phthaloyl chloride) for achieving the closed-loop PET recycling and open-loop PET upcycling. The degradation of PET using PETase enzymes has great potential but can face problems with incomplete degradation. Here, the authors identified two BHETases from the environment and engineered them to improve their hydrolysis efficiency for applications in dual-enzyme PET recycling and tandem chemical-enzymatic PET upcycling systems.

Automated summary

The authors identified and engineered two BHETases to improve PET recycling and upcycling efficiency. By coupling BHETase into a dual-enzyme system, the challenge of heterogeneous product formation was overcome, resulting in an improved TPA production compared to other PET hydrolases. Furthermore, a tandem chemical-enzymatic approach was used to convert commercial post-consumed plastics into virgin PET and an example chemical, achieving closed-loop PET recycling and open-loop PET upcycling.