Complex formation of U(VI) with Bacillus-Isolates from a Uranium Mining Waste Pile


Complex formation of U(VI) with Bacillus-Isolates from a Uranium Mining Waste Pile

Panak, P.; Raff, J.; Selenska-Pobell, S.; Geipel, G.; Bernhard, G.; Nitsche, H.

The genus Bacillus consists of more than 70 species of Gram-positive, aerobic or facultatively anaerobic spore-forming rod-shaped bacteria. Because of the high resistance of their spores, Bacilli were found in a large variety of natural habitats. For our accumulation studies with U(VI), we used vegetative cells and spores of three Bacillus isolates (JG-A 30, JG-A 12, JG-A 22, classified as Bacillus cereus, Bacillus sphaericus, Bacillus megaterium) from a uranium mining waste pile (Johanngeorgenstadt, Saxony) and their corresponding reference strains. Sorption studies at pH 5.0 have shown that in the concentration range examined (11 – 214 mg/L) Bacilli accumulate high amounts of uranium. Information on the binding strength and the reversibility were obtained from extraction studies with different extractants. With 0.01 M EDTA solution the uranium bound to the biomass was released almost quantitatively. The characterization of the bacterial-UO22+-complexes by time-resolved laser fluorescence spectroscopy (TRLFS) has proved the formation of inner-sphere complexes with the biomass. At pH 5 a ternary complex of uranyl with the biomass and hydroxide in solution was detected. After cell fractionation, we examined the spectroscopic properties of the U(VI)-complexes with the isolated cell walls and the isolated surface-layer protein fraction of the bacteria. Spectroscopic studies of these complexes have shown that with intact cells (vegetative cells or spores) the complexation of U(VI) is stronger than with isolated cell wall components. Therefore, the good complexation properties, the easy release of the bound uranium by EDTA-extraction, and the high resistance against harsh environmental conditions makes these bacteria applicable for bioremediation purposes.

  • Radiochimica Acta 88, 71-76 (2000)

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Publ.-Id: 1430