CAN POLLUTED URBAN WASTEWATER SLUDGES BE A SOURCE OF FUNGAL BIOCATALYSTS? INSIGHTS FROM THE SUSWATER PROJECT

The increasing presence of Contaminants of Emerging Concern (CECs) in urban wastewater poses serious environmental threats, particularly due to the inefficiency of conventional wastewater treatment plants (WWTPs) in removing these micropollutants. Within the European SusWater project, this study explored the biotechnological potential of fungal communities naturally inhabiting activated sludge from a WWTP in Turin (Italy). Using selective enrichment in the presence of four model CECs (carbamazepine, estriol, diclofenac, and ofloxacin), 104 fungal isolates were obtained and characterized morphologically and molecularly. The majority belonged to the Ascomycota phylum (78%), but Basidiomycota and Mucoromycota were also present, highlighting an unexpected fungal diversity. Thirty-four isolates were selected for biodegradation assays. Results showed marked variability in CEC degradation capacity, both between and within genera. Trichoderma, Mortierella, and Candida glaebosa were particularly promising, with Fonsecaea pedrosoi achieving 81.6% ofloxacin removal and Trichoderma virens reaching over 95% estriol degradation in 10 days. Conversely, carbamazepine remained the most recalcitrant compound. Surprisingly, laccase and peroxidase activity levels were negligible, suggesting alternative enzymatic pathways may be involved. The two best performing strains were selected for undergoing scale-up studies, due to their broad-spectrum degradation ability and robust growth under contaminant stress. These strains demonstrated high efficiency in reducing concentrations of multiple CECs—especially estriol, diclofenac, and ofloxacin—making them promising candidates for the development of sustainable, fungal-based wastewater treatment solutions. Future work will focus on optimizing culture conditions and reactor configurations to exploit their full biotechnological potential. These findings underline the potential of fungal consortia in the development of sustainable, bio-based strategies for advanced wastewater treatment.