Waste treating waste: Organic micropollutant removal from water by Agaricus bisporus spent mushroom substrate

The continual increase in domestic and industrial wastewater poses a significant challenge, as conventional wastewater treatment methods struggle to effectively remove persistent organic micropollutants (OMPs). OMPs, including pharmaceuticals, personal care products (PPCPs), and pesticides, persist in treated water, posing risks to human health and ecosystems. Current water quality in Europe is compromised by the prevalence of OMPs. While various technologies exist for OMP removal, they often entail high costs and carbon footprints. This study explores the potential of bioremediation, particularly using wood and litter-degrading fungi (WLDF), such as Agaricus bisporus, as a sustainable and cost-effective solution. A. bisporus, commonly known as the champignon mushroom, is a prolific WLDF. The mushroom's substrate, a waste product after harvest, is rich in lignin-modifying enzymes (LMEs) that have demonstrated OMP removal capabilities. LMEs, including lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), and laccase (Lcc), are essential in mineralizing lignin. This study investigates whether A. bisporus spent mushroom substrate (SMS) can be utilized for OMP removal from water and aims to elucidate the underlying mechanisms. Research indicates that A. bisporus SMS and its tea exhibit substantial OMP removal capabilities. They effectively remove a variety of dyes, PPCPs, pesticides, and even industrial compounds like per- and polyfluoroalkyl substances (PFAS). This study reports, for the first time, the removal of PFAS using SMS and its tea. Furthermore, other WLDF, such as Pleurotus ostreatus and Trametes versicolor, also show potential for OMP removal. Mechanisms of OMP removal by A. bisporus involve both enzymatic and non-enzymatic processes. LMEs play a crucial role, but non-enzymatic activities, such as the Fenton reaction, also contribute to OMP removal. The study suggests that a combination of these mechanisms is responsible for the observed effectiveness in OMP removal. Interestingly, SMS outperforms its tea in OMP removal, indicating the importance of solid particles and potential stabilization of enzymes on these particles. Heat treatment of SMS and its tea highlights both enzymatic (heat-dependent) and non-enzymatic (heat-independent) activities contributing to OMP removal. The presence of metal ions and hydrogen peroxide supports the hypothesis that the Fenton reaction is involved in the process. Individual LMEs, when overexpressed in Schizophyllum commune, exhibit enhanced removal of specific OMPs. However, the study suggests that multiple enzymes and non-enzymatic activities collectively contribute to OMP removal, emphasizing the need for further research into enzyme combinations and interactions. In conclusion, A. bisporus SMS emerges as a sustainable and effective solution for OMP removal from water. The study lays the foundation for developing eco-friendly water purification technologies that mitigate the environmental impact of OMPs and contribute to improved water quality.