Enzymatic degradation of PET using a novel thermophilic PETase

Single-use plastics, such as polyethylene terephthalate (PET), have become an overwhelming environmental issue due to their persistence and accumulation. The discovery of a class of biocatalysts (PETase) capable of breaking down PET into its monomeric components has opened new possibilities for sustainable PET recycling. In this study, we identified a novel thermophilic PETase, called Depolymerising Isolated Enzyme from Geothermal Origin (DIEGO), from geothermal metagenomic samples. DIEGO was produced in recombinant form and its ability to hydrolyse PET and its analogues, including bis(2-hydroxyethyl)-TPA (BHET) and nanoPET, as well as post-consumer PET (PcPET) food trays, was proved. We observed a synergistic effect of DIEGO and temperature at 60 °C: the enzyme converts PET into ethylene glycol (EG), terephthalic acid (TPA), along with the intermediates mono(2-hydroxyethyl)-TPA (MHET) and BHET; while temperature promotes auto-hydrolysis of MHET and BHET units. Therefore, this combined effect allowed the complete degradation of PET in TPA and EG within four days, by-passing the use of an additional enzyme for the degradation of intermediates. These findings highlight DIEGO as a promising candidate for industrial-scale enzymatic PET recycling and contribute to the development of sustainable plastic waste management strategies.