Dual-Enzyme-Cascade Catalysis for PET Biodegradation Based on a Variable-Temperature Program

As an environmentally friendly technology, enzymatic degradation of waste polyethylene terephthalate (PET) has great application potential. Mono (hydroxyethyl) terephthalate (MHET), an intermediate product of PET degradation, accumulates during the degradation process. MHET reduces the activity of PETase and influences further enzymatic degradation. The combined catalysis of MHETase and PETase is an effective strategy to solve this problem. However, the difference in thermostability between MHETase and PETase limits their combination. In our previous study, a PETase of muEst1 exhibited acceptable PET-degradation ability, but the abundant MHET accumulation in its degradation products limited its further application. In this study, MHETases with good thermostability were screened for combination with muEst1 for the cascade reaction of PET degradation, and a two-stage variable-temperature program was developed. The results of this investigation show that this approach results in a PET-degradation rate of 92.71% with a terephthalic acid content above 85.9%. This investigation provides an alternative method for scaled-up enzymatic PET degradation.