Machine learning-guided discovery of poly(ethylene terephthalate)-binding modules to enhance durable whole-cell degradation.

The enzymatic degradation of poly(ethylene terephthalate) (PET) offers a sustainable route for plastic recycling but is often hindered by limited enzyme adsorption on hydrophobic surfaces. Inspired by carbohydrate-binding modules (CBMs), which enhance enzyme performance on insoluble substrates, we developed a machine-learning-assisted pipeline to discover PET-binding modules from natural protein architectures. Integration of profile hidden Markov model-based homology searching with a supervised PET hydrolase machine-learning model (PETML) revealed that CBMs belonging to family 13, typically known for glycan recognition, were the most abundant CBMs associated with putative PET hydrolase homologs in the screened dataset. From 197 non-redundant candidates, high-throughput docking and molecular dynamics simulations prioritized tCBM13-1 (WP_357125140.1), which exhibited stable interfacial binding via cooperative aromatic and polar interactions. When fused to sfGFP, tCBM13-1 demonstrated superior adsorption (∼70%) and surface retention (∼90%) on PET powder at 37 °C and 45 °C, outperforming a benchmark CBM2. Co-displayed with FAST-PETase on the Escherichia coli (E. coli) surface using a dual-anchor system (OmpA and EhaA), tCBM13-1 enhanced PET film depolymerization by ∼ 43%, achieving a rate of 2793  μg/(d·cm2). The whole-cell catalyst retained > 64% of its initial activity after 10 cycles, indicating robust recyclability. This work integrates machine-learning-guided module mining with synthetic biology to engineer efficient, reusable biocatalysts for PET degradation, offering a scalable strategy for polymer biorecycling.