Degradation of pharmaceuticals and personal care products (PPCPs) in municipal wastewater by white rot fungi: Neutral environment exploitation and degradation mechanisms

Abstract

Refractory pharmaceuticals and personal care products (PPCPs) represented by diclofenac, ibuprofen, sulfamethoxazole, and carbamazepine have become risk compounds in municipal wastewater, and they possessed generalized antimicrobial properties along with numerous electron-withdrawing groups, difficult to biodegrade through bacterial-based systems. In contrast, fungi could thrive even in environments contaminated by antibiotics, among which the white rot fungus Trametes versicolor (T. versicolor) possessed enzymatic degradation systems represented by laccase, capable of degrading complex chemical bonds. However, almost all white rot fungi reactors were conducted at pH 4.5, which limited their application. In this study, the neutral degradation environment was developed for T. versicolor, and the pH-dominated laccase degradation mechanism was clarified. It was found that T. versicolor could possess both laccase activity and production at pH 6.5, with better application potential compared to acidic conditions. Accordingly, fluidized bed T. versicolor reactors were developed, and their application potential under neutral pH was validated for the first time in municipal wastewater. Compared with reactors without any adjustment, the four refractory PPCPs removal by T. versicolor reactors was increased from 26% to 72%, and T. versicolor abundance was increased from almost zero to 27% by adding carbon and nitrogen sources and adjusting pH to 6.5. Metabolic pathway analysis revealed the cytochrome P450 and amide hydrolase functional genes of T. versicolor, which were critical for PPCPs degradation. Nine transformation products of PPCPs were identified, further validating the multiple capabilities of T. versicolor for both hydroxylation and complex chemical structures (carbon–nitrogen bonds, epoxides, carbon–sulfur bonds) degradation. Furthermore, these findings also provided new ideas for the degradation of more complex aminobenzene or chlorinated aniline wastewater.