Immobilization of fungal cells on positively charged cyclodextrin-based carriers: Enhanced PhAC degradation and...

The rational design of cellular interfaces is essential for advancing biocatalytic systems. White rot fungi are promising biodegraders of pharmaceutically active compounds (PhACs), but they are readily inactivated in wastewater treatment, while conventional carriers cannot simultaneously immobilize cells and retain extracellular enzymes. In this study, a stable fungus-enzyme synergistic interface was constructed by assembling Trametes versicolor with a positively charged porous thienyl cyclodextrin polymer (Th-CDP) to form Tv@Th-CDP. This design simultaneously immobilized fungal cells and retained their secreted laccases within the carrier, enhancing PhAC removal in continuous-flow reactors treating secondary municipal effluent to 93%. The system demonstrated sustained 30-d performance and reduced effluent toxicity by 58%. This performance was associated with the high positive charge density of Th-CDP, which enhanced mycelial attachment and laccase retention (48.2 U kg^-1). Furthermore, the hydrophobic cavities of cyclodextrin, coupled with electrostatic interactions, enhanced PhAC adsorption and enriched Trametes sp. (46%). This immobilization strategy improved the fungus-enzyme interactions, with enhanced laccase-related catalytic currents observed in electrochemical assays. Metaproteomics analysis and transformation pathway identification supported a degradation model mediated by electrostatic interactions between the fungus and the retained enzymes. A total of 305 proteins associated with oxidoreductase activity were enriched, while the key enzymes aldehyde dehydrogenase (ALDH) and epoxide hydrolase (EPHX2) were upregulated. These changes coincided with enhanced C-N bond cleavage, indicating activation of associated metabolic pathways. Overall, this study provides mechanistic understanding of immobilization mediated by electrostatic interactions and demonstrates its potential to improve the biodegradation of emerging contaminants in engineered biocatalytic systems.