Enhancing the biodegradation of bis(2-hydroxyethyl) terephthalate by an IsPETasePA and MHETase dual-enzyme system

BACKGROUND

Environmental and ecological hazards caused by the accumulation of polyethylene terephthalate (PET) are becoming a global concern. The use of enzymes to address the plastic crisis has achieved many successes, but the difficulty in degrading high-crystallinity PET has limited its application. Numerous studies have investigated the degradation of PET with arbitrary crystallinity to bis-2-(2-hydroxyethyl) terephthalate (BHET) using chemical pre-treatment methods such as glycolysis, but few have tested its biocompatibility with enzymatic alliances.

RESULTS

Herein, we report the enzymatic characterization and subsequent engineering of the state-of-the-art IsPETase^PA and MHETase (where MHET is mono(2-hydroxyethyl) terephthalate), a dual-enzyme system which can be used for the degradation from BHET to a single-product terephthalate (TPA). Modulators, including surfactants, organic solvents and metal ions, enhanced the enzyme activity of IsPETase^PA and MHETase by up to 1.1-fold and 2.3-fold, respectively. 100% TPA yield (BHET of 25 g L⁻¹) was achieved within 5 h. We also analyzed the mechanism of optimal ion modulator modification by dynamics simulation, and it synergistically achieved enhancement of MHET degradation ability by improving stability and binding energy.

CONCLUSION

The introduction of modulators improves the efficiency of the dual-enzyme system in degrading BHET. This work provides a valuable strategy for the complete degradation of BHET to TPA, laying the groundwork for the realization of PET recycling. © 2024 Society of Chemical Industry (SCI).