title: Modeling reduction of uranium U(VI) under variable sulfate concentrations by sulfate-reducing bacteria.
abstract: The kinetics for the reduction of sulfate alone and for concurrent uranium [U(VI)] and sulfate reduction, by mixed and pure cultures of sulfate-reducing bacteria (SRB) at 21 +/- 3 degrees C were studied. The mixed culture contained the SRB Desulfovibrio vulgaris along with a Clostridium sp. determined via 16S ribosomal DNA analysis. The pure culture was Desulfovibrio desulfuricans (ATCC 7757). A zero-order model best fit the data for the reduction of sulfate from 0.1 to 10 mM. A lag time occurred below cell concentrations of 0.1 mg (dry weight) of cells/ml. For the mixed culture, average values for the maximum specific reaction rate, V(max), ranged from 2.4 +/- 0.2 micromol of sulfate/mg (dry weight) of SRB. h(-1)) at 0.25 mM sulfate to 5.0 +/- 1.1 micromol of sulfate/mg (dry weight) of SRB. h(-1) at 10 mM sulfate (average cell concentration, 0.52 mg [dry weight]/ml). For the pure culture, V(max) was 1.6 +/- 0.2 micromol of sulfate/mg (dry weight) of SRB. h(-1) at 1 mM sulfate (0.29 mg [dry weight] of cells/ml). When both electron acceptors were present, sulfate reduction remained zero order for both cultures, while uranium reduction was first order, with rate constants of 0.071 +/- 0.003 mg (dry weight) of cells/ml. min(-1) for the mixed culture and 0.137 +/- 0.016 mg (dry weight) of cells/ml. min(-1) (U(0) = 1 mM) for the D. desulfuricans culture. Both cultures exhibited a faster rate of uranium reduction in the presence of sulfate and no lag time until the onset of U reduction in contrast to U alone. This kinetics information can be used to design an SRB-dominated biotreatment scheme for the removal of U(VI) from an aqueous source.
authors.affiliation: Division of Environmental Science and Engineering, Colorado School of Mines, Golden, Colorado 80401, USA. spearj@colorado.edu
authors.forename: J R
authors.initials: JR
authors.lastname: Spear
authors.forename: L A
authors.initials: LA
authors.lastname: Figueroa
authors.forename: B D
authors.initials: BD
authors.lastname: Honeyman
mesh_terms: D003013:Clostridium / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D003470:Culture Media; D003901:Desulfovibrio / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D016969:Desulfovibrio vulgaris / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D020459:Genes, rRNA; D007700:Kinetics; D008954:Models, Biological; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D021521:Ribotyping; D013431:Sulfates / Q000378:metabolism*; D014501:Uranium / Q000378:metabolism*
chemical_list: D003470:Culture Media; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D014501:Uranium