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Biotechnol Bioeng. 2018 Jun;115(6):1465-1474. doi: 10.1002/bit.26579. Epub 2018 Mar 24.

pH-dependent speciation and hydrogen (H2 ) control U(VI) respiration by Desulfovibrio vulgaris.

Author information

1
Biodesign Swette Center of Environmental Biotechnology, Arizona State University, Tempe, Arizon.

Abstract

In situ bioreduction of soluble hexavalent uranium U(VI) to insoluble U(IV) (as UO2 ) has been proposed as a means of preventing U migration in the groundwater. This work focuses on the bioreduction of U(VI) and precipitation of U(IV). It uses anaerobic batch reactors with Desulfovibrio vulgaris, a well-known sulfate, iron, and U(VI) reducer, growing on lactate as the electron donor, in the absence of sulfate, and with a 30-mM bicarbonate buffering. In the absence of sulfate, D. vulgaris reduced  >90% of the total soluble U(VI) (1 mM) to form U(IV) solids that were characterized by X-ray diffraction and confirmed to be nano-crystalline uraninite with crystallite size 2.8 ± 0.2 nm. pH values between 6 and 10 had minimal impact on bacterial growth and end-product distribution, supporting that the mono-nuclear, and poly-nuclear forms of U(VI) were equally bioavailable as electron acceptors. Electron balances support that H2 transiently accumulated, but was ultimately oxidized via U(VI) respiration. Thus, D. vulgaris utilized H2 as the electron carrier to drive respiration of U(VI). Rapid lactate utilization and biomass growth occurred only when U(VI) respiration began to draw down the sink of H2 and relieve thermodynamic inhibition of fermentation.

KEYWORDS:

Desulfovibrio vulgaris; U(VI) reduction; UO2 nanoparticles; bioavailable U(VI) species; hydrogen gas

PMID:
29476629
DOI:
10.1002/bit.26579
[Indexed for MEDLINE]

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