Biocatalytic Transformation of Industrial Polyurethane Waste Using Laccases: Toward Environmentally Sustainable Management Strategies for Plastic Pollution

Polyurethane foams (PUFs) account for approximately 5.3% of global plastic production and are highly persistent in the environment due to their resistance to degradation. Their progressive fragmentation into micro- and nanoplastics, together with the presence of hazardous additives and their ability to adsorb emerging contaminants, increases their environmental impact. This study evaluates the enzymatic degradation of rigid PUFs derived from industrial waste at the upper size limit of microplastics as a step toward developing environmentally sustainable strategies for mitigating plastic pollution across multiple scales. Rigid PUFs were treated using three laccase-based systems (purified, immobilized, and enzyme cocktail), and the transformation process was evaluated using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, Gas Chromatography–Mass Spectrometry (GC-MS), and Dynamic Light Scattering (DLS). SEM analysis revealed surface erosion, cracking, and pore wall thinning, particularly in cocktail-treated samples. FT-IR and Raman spectra revealed chemical transformations in the polyurethane matrix, while GC-MS detected compounds consistent with polyurethane degradation byproducts, including 1-methylcycloheptene, 2,5-furandione, and aromatic amines, suggesting oxidative transformation of the polyurethane matrix. DLS measurements detected particles within the nanoscale size range, with diameters as small as 262.58 ± 15.65 nm following enzyme cocktail treatment. The maximal weight loss (5.36% ± 0.01) was achieved using purified laccase over a 24-day period. This study demonstrates the biocatalytic potential of laccase enzymes for polyurethane transformation and highlights their promise for the development of sustainable remediation strategies. These findings provide a foundation for future biotechnological applications targeting plastic waste and support the development of environmentally sustainable polymer degradation technologies.