Fungal diversity, a nature-based solution for rare elements recovery: investigation on interactions between fungal strains from culture collections and elements of strategic interest

Fungal biodiversity represents a promising bioresource for the sustainable recovery of critical elements essential to high-tech applications. Indeed, due to their ability to tolerate, bioaccumulate, and transform toxic elements, fungi are valuable agents in eco-friendly processes for electronic waste recovery. “FunMetals” project explores interactions between selected fungal strains and strategic elements, supporting the circular economy and the ecological transition through low-impact, biologically-driven recovery systems. This study focused on 24 fungal strains preserved in the culture collections of the Fungal Biodiversity Laboratory at Sapienza University of Rome and the National Research Council. Tolerance screenings were performed on solid medium in the presence of Gallium, Germanium, Indium and Yttrium oxides individually and evaluated by tolerance indexes based on mycelial weight and colony area. Medium’s pH variation and secondary biominerals precipitation were also assessed. To evaluate element bioaccumulation and assimilation, the biomass of fungi was analyzed using Energy-dispersive X-ray fluorescence (XRF). The fungi were then tested for siderophores and laccase production. Moreover, a modified microculture system that allows for a multimodal imaging approach and SEM-EDS analysis was employed to investigate fungal assimilation and transport of elements through hyphae, as well as biomineral precipitation. The Phenotype MicroArray™ was then used to gather information on the effects of single elements on fungal metabolism and the metabolic performance of selected strains with and without the elements. Information on the effects of different nutrients on fungal tolerance to metals and the effects of metals on the assimilation and use of carbon sources by fungi was obtained. The results highlighted that each strain had specific mechanisms of interaction with the elements and different degrees of tolerance, bioaccumulation, and biomineralization. ACKNOWLEDGMENTS PRIN 2022 PNRR Project funded by European Union -NextGenerationEU- Project Prot. P2022ENEWL - Title “Fungal interaction with metals (FUN METALS): transformation and mechanisms for biorecovery” CUP B53D23032130001.