Factors Affecting Microbial Uranium Reduction: Implications for Bioremediation
ChuanJun L. Zhang-Savannah River Ecology lab, Aiken, SC, USA
Scott Brooks and Philip M. Jardine-Oak Ridge National lab, Oak
Ridge, TN, USA
Hojatollah Vali-McGill University, Montreal, Canada
ABSTRACT: Batch experiments were conducted to evaluate
effects of environmental factors on U(VI) reduction by resting cells of
Shewanella algae strain BrY. Rates of U(VI) reduction were examined
at temperature 10-45°C, pH 4-8, and dissolved-oxygen 0.0-8.6 mg/L.
Rate of U(VI) reduction was fastest at 45D°C (rate constant = 0.2/hr)
and slowest at 10 D°C (rate constant = 0.02/hr). Holding temperature
constant (20D°C), rate of U(VI) reduction increased with increasing
pH; rate constant increased from < 0.01/hr at pH4 to 0.08/hr at pH
8. In abiotic controls, however, increases in pH had little effect on
U(VI) reduction, and the decrease in U(VI) was less than 15% of initial
concentration, compared with> 80% in cell suspensions at the same pH.
Oxygen content had little effect on U(VI) reduction when dissolved oxygen
was < 1.0 mg/L; at 8.6 mg/L concentration, how- ever, reduction of
U(VI) decreased by eight- to 10-fold. These results demonstrated that
reduction of U(VI) was enhanced at temperature, pH, and redox conditions
conducive to anaerobic growth or enzy- matic viability of the metal-reducing
bacterium. Transmission elec- tron microsGopy showed uranium mineral precipitation
on cell membrane, suggesting that BrY effectively immobilized soluble
uranium under the conditions examined.
SREL Reprint #2745
Zhang, C. L., S. Brooks, P. M. Jardine and H. Vali. 2002. Factors affecting microbial uranium reduction: Implications for bioremediation. p. 99-109. In Proceedings of the 2002 National Conference on Environmental Science and Technology, edited by G.A. Uzochukwu, K. Schimmel, G.B. Reddy, S. Chang, V. Kabadi, September 8-10, 2002. Greensboro, NC.
