Modeling reduction of uranium U(VI) under variable sulfate concentrations by sulfate-reducing bacteria

Area of Science:

• Environmental microbiology
• Bioremediation kinetics
• Geochemistry

Background:

• Sulfate-reducing bacteria (SRB) play a crucial role in biogeochemical cycles.
• Understanding the kinetics of SRB activity is vital for environmental applications.
• Uranium (U(VI)) contamination in aqueous sources poses significant environmental risks.

Purpose of the Study:

• To investigate the kinetics of sulfate reduction by SRB, both alone and concurrently with uranium (U(VI)) reduction.
• To compare the reduction kinetics between mixed and pure SRB cultures.
• To provide data for designing bioremediation strategies for U(VI) removal.

Main Methods:

• Studied sulfate reduction kinetics using mixed (Desulfovibrio vulgaris and Clostridium sp.) and pure (Desulfovibrio desulfuricans) SRB cultures at 21°C.
• Applied zero-order and first-order kinetic models to experimental data.
• Measured reaction rates under varying concentrations of sulfate and U(VI).

Main Results:

• Sulfate reduction followed zero-order kinetics for both cultures across tested concentrations (0.1-10 mM).
• Uranium (U(VI)) reduction was first-order when both electron acceptors were present.
• Both SRB cultures demonstrated accelerated U(VI) reduction rates in the presence of sulfate, with no lag phase observed.

Conclusions:

• The kinetics of sulfate reduction by SRB are well-described by a zero-order model.
• Concurrent sulfate and U(VI) reduction by SRB is kinetically favorable, with U(VI) reduction being faster in the presence of sulfate.
• This study provides essential kinetic data for developing effective SRB-based bioremediation technologies for U(VI) contaminated waters.