Costly effective bioleaching of valuable metals from low grade ore using Aspergillus nidulans

Abstract

This research investigated the feasibility of employing organic acids, like citric acid, produced by Aspergillus nidulans MT355567 in a bioleaching process to recover uranium (U) from a low-grade rock sample. The optimal conditions for fungal growth and maximum citric acid (CA) synthesis across three distinct media were determined. The maximum citric acid concentration was produced on medium made from wheat bran (83%) and tea waste (77%). An investigation was carried out to see how citric acid and, by consequence, uranium bioleaching affinity, were affected by varying carbon sources, nitrogen sources, pH, temperature, incubation period, ore particle size, and the solid–liquid ratio. At 25 °C and a pH of 5.0, media containing 100 g/L of sucrose as a carbon source and peptone as a nitrogen source made the highest yield of citric acid and U bioleaching. Higher U bioleaching was achieved with ore particles 0.075 mm at a ratio of 2 g/L after only 30 min of contact with the fungal filtrate. Iron interference has a negative impact on uranium extraction. Interestingly, none of the conditions applied to enhance CA synthesis and U-bioleaching caused iron (Fe) dissolution. Based on these findings, it appears that bioleaching using A. nidulans MT355567 metabolic products is a promising economic and ecofriendly technology for extracting uranium from low-grade ore that might be adopted on a pilot scale.Graphical abstractsummarizing the experimental workflow for bioleaching of uranium from low-grade ore using citric acid produced by Aspergillus nidulans. The process involved optimizing A. nidulans growth and citric acid biosynthesis, evaluating factors influencing bioleaching activity of the acid metabolite solutions, and finally applying the optimized conditions to bioleach uranium from the ore sample. The schematic illustrates the key steps and the optimal condition for Aspergillus nidulans growth medium preparation using agricultural wastes, downstream application of metabolite synthesized for uranium bioleaching