Talaromyces amestolkiae uses organic phosphate sources for the treatment of uranium-contaminated water.

Fungi have received particular attention in regards to alternatives for bioremediation of heavy metal contaminated locales. Enzymes produced by filamentous fungi, such as phosphatases, can precipitate heavy metal ions in contaminated environments, forming metal phosphates (insoluble). Thus, this research aimed to analyze fungi for uranium biomineralization capacity. For this, Gongronella butleri, Penicillium piscarium, Rhodotorula sinensis and Talaromyces amestolkiae were evaluated. Phytate and glycerol 2-phosphate were used as the phosphate sources in the culture media at pH 3.5 and 5.5, with and without uranium ions. After 4 weeks of fungal growth, evaluated fungi were able to produce high concentrations of phosphates in the media. T. amestolkiae was the best phosphate producer, using phytate as an organic source. During fungal growth, there was no change in pH level of the culture medium. After 3 weeks of T. amestolkiae growth in medium supplemented with phytate, there was a reduction between 20 and 30% of uranium concentrations, with high precipitation of uranium and phosphate on the fungal biomass. The fungi analyzed in this research can use the phytic acid present in the medium and produce high concentrations of phosphate; which, in the environment, can assist in the heavy metal biomineralization processes, even in acidic environments. Such metabolic capabilities of fungi can be useful in decontaminating uranium-contaminated environments.

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

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.