Fungi’s got talent: a study on fungal interactions with Gallium, Germanium, Indium and Yttrium for bio-recovery applications

Veronica Spinelli ¹, Flavia Pinzari ², Valerio Giorgio Muzzini ³, Enrica Donati ², Valentina Iori ⁴, Maria Luisa Astolfi ⁵, Anna Maria Persiani ¹, Marco Mazzonna ², Andrea Ceci ¹

Department of Environmental Biology, Sapienza University of Rome ¹, Institute for Biological Systems - National Research Council (CNR-ISB) ², Research Institute On Terrestrial Ecosystems - National Research Council (CNR-IRET) ³, Institute of Agricultural Biology and Biotechnology - National Research Council (CNR-IBBA) ⁴, Department of Chemistry, Sapienza University of Rome ⁵

Strategically critical elements play important roles in modern and future technologies and are indispensable in high-tech products. Due to surging global demand, their sustainable supply is a major issue, given the environmental negative impact often associated to their extraction. Fungi in nature play crucial roles in geology and ecology, and represent valuable bioresources for sustainable recovery processes [1]. Fungi can tolerate, bioaccumulate, and transform toxic compounds and several strategic elements. Fungal-mediated bio-recovery of critical elements from electronic wastes offers an eco-friendly solution to mitigate environmental impacts, and support sustainable resource management [2]. In this study, 24 strains, isolated in previous studies and currently preserved in the culture collections of the Fungal Biodiversity Laboratory of Sapienza University of Rome and of the National Research Council, were investigated for their interactions with Gallium, Germanium, Indium and Yttrium. Tolerance screenings for these elements were performed on solid Raper Hoffman medium for 14 days at 25°C in the presence of 1.5 mM Ga as Ga2O3, 5 mM Ge as GeO2, 2.4 mM In as In2O3, 2.25 mM Y as Y2O3. Fungal tolerance was assessed by Rt:Rc (%) index, based on colony areas, and T.I. (%) index, based on dry weights [3]. The medium’s pH variation and the presence of secondary biogenic minerals were also assessed. The selected fungi were then tested for siderophores production using the Chrome-Azurol-S (CAS) assay [3]. Siderophores are crucial in metal-fungi interactions and there is increasing interest in their potential for biomining. Finally, considering the relevance of laccase in bioleaching processes and the fact that these elements share chemical features with those playing primary roles in fungal biology, a screening to evaluate the production and release of laccase was carried out using the Guaiacol assay [4]. One-third of the tested strains had already released siderophores after 48 h; after 7 days, 21 strains produced siderophores, 7 of which showed high Fe-chelation activity. Laccase release was detected in only 8 strains, all basidiomycetes. Finally, all fungi could grow in all tested conditions, even though several evident effects of these elements on biomass production and morphological modification were observed. Most of the tested species resulted tolerant to Ga, Ge and In, showing indexes values higher than 70%. Interestingly, several strains showed indexes values higher than 100%, pointing out a growth stimulation due to the metal(loid) exposure. Y resulted in being more toxic, indeed only 9 species showed T.I. higher than 70%, even if most of the strains were tolerant according to Rt:Rc, suggesting an explorative mycelial growth pattern. REFERENCES 1. Gadd G.M., et al. (2012) Environ. Microbiol. Rep. 4:270–296. 2. Liang X., Gadd G.M. (2017) Microb. Biotechnol. 10:1199–1205. 3. Ceci A., et al. (2020) Appl. Sci. 10:3218. 4. Mehnert M., et al. (2017) Sol. St. Phen. 262:509–512. 5. Senthivelan T., et al. (2019) Biotechnol. Rep. 23:e00344. 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.

Main author career stage: Postdoc / Fellow

Contribution type: Talk

First choice session: 6. Plants, Fungi and Society

Second choice session: 4. Structure, physiology, and development