Electrospinning Enables Embedding of PET Hydrolases in High-Melting PET Microfibers

Polyethylene terephthalate (PET) is produced globally at 25.5 million metric tons annually, necessitating sustainable recycling and waste treatment strategies to address increasing plastic pollution. Embedding enzymes directly within polymers by extrusion is an emerging biological degradation approach. However, the high melting temperature (T_m) of PET (260 °C) has previously limited this strategy since no reported PET hydrolase can tolerate such conditions. Alternatively, electrospinning is based on polymer dissolution rather than melt processing and is a promising approach to embed solvent-tolerant enzymes into polymers with high T_m. Here, we embedded the PET hydrolase LCC-ICCG (ICCG) in PET microfibers via electrospinning. ICCG was distributed homogeneously along the two-dimensional plane (2D plane) of electrospun microfibers and was primarily localized in surface-associated fiber layers. Over 672 h, hydrolysis of PET microfibers catalyzed by embedded ICCG yielded 85.64 mM of mono-aromatic products (10.7 ± 0.3% mass loss), despite activity reduction by exposure of the biocatalyst to the solvent solution. Electrospinning increased the amorphous content of PET from 56.15% to 72.44%, while preserving microfiber elasticity. Mechanical strength decreased by 26.29% in ICCG-loaded PET microfibers, which confirmed effective fiber degradation.