Resistant fungi isolated from contaminated uranium mine in Brazil shows a high capacity to uptake uranium from water

Abstract

The Osamu Utsumi uranium mine occupies a 20 km2 area in the city of Caldas, which is located in the state of Minas Gerais, Brazil. Since mining activities ended at Osamu Utsumi 24 years ago, the surrounding area has become contaminated by acid effluents containing high concentrations of uranium. Thus, the aim of this study was to assess the uranium bioremediation capacity of 57 fungi isolated from the mine area. In tolerance tests, 38% (22) of the fungal isolates were considered tolerant to uranium, including 10 Penicillium species. At a uranium concentration of 2000 mg L−1 48 fungi did not exhibit mycelial growth index inhibition. Minimal inhibitory concentration (MIC) analysis showed growth of 25 fungi above a uranium concentration of 8000 mg L−1. At high uranium concentrations, some fungi (i.e., Talaromyces amestolkiae and Penicillium citrinum) showed morphological changes and pigment (melanin) production. Among the fungal isolates, those considered to be more tolerant to uranium were isolated from soil and sediment samples containing higher concentrations of heavy metal. When comparing the results of resistance/tolerance tests with those for uranium biosorption capacity, we concluded that the fungi isolated from the Osamu Utsumi mine with the best potential for uranium bioremediation were Gongronella butleri, Penicillium piscarium, Penicillium citrinum, Penicillium ludwigii, and Talaromyces amestolkiae. Biosorption tests with live fungal biomass showed that 11 species had a high potential for uranium uptake from contaminated water.