Polyurethane depolymerization by the white-rot basidiomycete Cyclocybe aegerita

Plastics are widely used due to their durability and chemical resistance. Ηowever, these same properties contribute to their long-term environmental persistence and accumulation. Polyurethane (PUR) is particularly recalcitrant due to its ester and urethane bonds. Conventional disposal methods often rely on landfilling or processes that generate secondary environmental impacts. Consequently, biodegradation is a promising alternative for the removal of persistent plastic materials. Although fungal degradation of PUR has been mainly studied in ascomycetes, basidiomycetes remain underexplored. White-rot basidiomycetes produce extracellular oxidative and hydrolytic enzymes capable of transforming diverse natural and xenobiotic compounds. This study investigates Cyclocybe sp. strains for degradation of Impranil® DLN-SD, a model substrate for polyurethane. Cyclocybe sp. isolates (Basidiomycota), identified by ITS rRNA sequencing, were screened for growth on Impranil® DLN-SD as the sole carbon source under solid and submerged cultures. The most efficient strain was further investigated through extracellular enzymatic assays. Polymer modifications were assessed using ATR-FTIR spectroscopy, while degradation of polyurethane powder by cell-free supernatants was quantified via gravimetric analysis. LC–MS/MS proteomics was applied to identify extracellular enzymes involved in polymer transformation. Phylogenetic analysis revealed two species, Cyclocybe cylindracea sensu Vizzini and C. aegerita sensu Frings. Strong strain-dependent variability was observed, with strain LGAM 960 completely clearing Impranil® within 6 days. Enzymatic profiling showed early secretion of laccases and peroxidases followed by esterases, indicating a sequential mechanism. ATR-FTIR confirmed cleavage of ester and urethane bonds, while gravimetric analysis showed up to 11.5% weight loss after 96 h. Proteomics identified 22 upregulated extracellular proteins, including CE16 esterases, AA1 multicopper oxidases, aromatic peroxygenases, peptidases and accessory proteins, supporting a synergistic degradation system. These findings highlight white-rot basidiomycetes as promising biocatalysts for polyurethane bioremediation and emphasize the need to screen multiple strains to identify those with enhanced biodegradation capabilities.