Bioleaching of uranium from ores and rocks using filamentous fungi

The purpose of this study is to review the role of filamentous fungi in the bioleaching of uranium from ores and rocks. Specifically, the paper evaluates how fungi produce short-chain fatty acids through fermentation and partial oxidation of organic compounds, which facilitate the dissolution and sequestration of uranium. This review highlights the efficacy of various ore types, including oxide, carbonate, and silicate ores containing hexavalent uranium, suitable for zinc leaching processes. Two primary methods of uranium leaching employing fungi are explored: the one-step process, where biomass is not separated prior to contacting the minerals, and the two-step method, which utilizes spent culture media after fungal biomass removal. The significance of carboxylic acid production, particularly by genera such as Aspergillus and Penicillium, in forming soluble U(VI)-carboxylate complexes is discussed. Key results indicate that maintaining a low pH level (between 1.5 and 3.5) in leach solutions enhances the leaching efficiency by promoting proton attack on minerals and minimizing metal precipitation. Notably, this article is the first comprehensive review of the application of filamentous fungi in uranium bioleaching from ores and rocks, identifying the gaps in process optimization efforts in existing literature.