Kinetic coefficients for simultaneous reduction of sulfate and uranium by Desulfovibrio desulfuricans

Abstract

Previously it was demonstrated that bacteria are capable of transforming soluble uranyl ion, U(VI), to insoluble uraninite, U(IV); however, the rate for this transformation has not been determined. We report the kinetic coefficients for Desulfovibrio desulfuricans DSM 1924 grown in a continuous-flow chemostat where pyruvate was the electron donor and sulfate was the electron acceptor. The medium was supplemented with 1 mM uranyl nitrate, and the chemostat flow rate ranged from 1.12 ml/h to 4.75 ml/h with incubation at 28°C. The maximum rate of pyruvate utilization (k) was determined to be 4.7 days-1, while the half-velocity constant (Ks) was 127 mg/l. The yield coefficient (Y) of cells per mole of pyruvate oxidized was calculated to be 0.021 g, while the endogenous decay coefficient (kd) was determined to be 0.072 days-1. More than 90% of U(VI) was transformed to U(VI) in the chemostat under the conditions employed.