Nearly complete depolymerization of untreated post-consumer plastic with an immobilized and reusable PET hydrolase

The accumulation of plastics in the environment has become a serious concern for the entire society. In recent years, enzyme-based biodegradation has emerged as a promising and sustainable strategy for the recycling of polyethylene terephthalate (PET), one of the most widely used polyester plastics. However, the translation of these technologies to the industrial field faces several underexplored challenges, including the immobilization and reusability of the biocatalysts. Here, we present the use of IC-Tagging as a novel one-step methodology for the "in cellulo" self-immobilization of the benchmark PET-degrading enzyme LCC^ICCG in protein nanospheres. The immobilized enzyme showed to be active against soluble substrates and exhibited improved thermal resistance and long-term storage stability, retaining 58 % of relative activity after 3 months at room temperature. Immobilized LCC^ICCG also demonstrates remarkable reusability, with minor activity loss up to 10 reuse cycles. Most importantly, nearly complete depolymerization (>90 %) of various untreated amorphous post-consumer PET materials was achieved at a wide range of temperatures (50-70 °C) by removing the products and reusing the enzyme repeatedly. Furthermore, reutilization led to almost full degradation of two consecutive batches of post-consumer PET in 6 days, outperforming all immobilized biocatalysts reported at laboratory scale. Overall, IC-Tagging emerges as a promising and versatile platform for the production, immobilization and reutilization of top-performing PET hydrolases, contributing to sustainable management of plastic waste.