Dissecting the mechanisms of copper-azole wood preservatives detoxification by ligninolytic fungi

Abstract

Copper-azole based formulations have been widely used to protect wood timbers against fungal decay. While these treatments are efficient for wood protection, leaching of both copper and azoles into the environment has deleterious impact on soils and surface waters. No bioremediation process is currently available for disposable of these wood wastes. Exploiting the natural ability of certain fungi to tolerate these active compounds, we propose that some ligninolytic fungi could serve as effective biocatalysts for detoxifying copper-azole formulations. Using the white-rot fungus Phanerochaete chrysosporium as a model, we demonstrated that these fungi engage multiple strategies to counteract the antifungal effect of azoles present in the preservatives. These include the modulation of the lipids and sterols content, the maintenance of DNA integrity, detoxification of azoles by extracellular degradation likely through the Fenton chemistry, biosorption at the cell wall, efflux, and intracellular detoxification by the three-step detoxification pathway. By using comparative transcriptomics between a copper-azole formulation and a copper-quaternary ammonium formulation, we identified genes specifically involved in azole resistance and detoxification within this complex system. This opens new perspectives for managing azoles residues through mycoremediation processes.