High fungal-mediated leaching efficiency of valuable metals from deep-sea polymetallic nodules

Polymetallic nodules on abyssal seafloor represent a major reservoir of valuable metals. Here we analysed fungal-mediated leaching of metals from nodules collected at ca. 5000 m depth in the Clarion-Clipperton Fracture Zone of the Pacific Ocean. The bioleaching efficiency of Aspergillus and a mixed cultures of A. niger and Trichoderma sp., at different growing conditions, were investigated and compared to chemical treatments using citric acid. 11 days of treatment with A. niger growing in optimal medium conditions, produced the best result with the extraction of more than 80% of Mn, Cu, Ni, and 70% and 30% of Co and Fe, respectively. Our findings suggest that biotechnological processes can be a sustainable approach in terms of carbon footprint reduction compared to chemical strategies. Results presented here provide the potential of fungal-mediated leaching and pave the way for the development of effective and eco-sustainable biotechnologies for the metal recovery from deep-sea nodules