01863nas a2200157   4500008004100000245009900041210006900140260000800209300001400217490000800231520127100239100002101510700002301531700002401554856012701578       2018                        eng d00apH-dependent speciation and hydrogen (H-2) control U(VI) respiration by Desulfovibrio vulgaris0 apHdependent speciation and hydrogen H2 control UVI respiration b  cJUN  a1465-14740 v1153 aIn 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) (1mM) to form U(IV) solids that were characterized by X-ray diffraction and confirmed to be nano-crystalline uraninite with crystallite size 2.8 +/- 0.2nm. 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 H-2 transiently accumulated, but was ultimately oxidized via U(VI) respiration. Thus, D. vulgaris utilized H-2 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 H-2 and relieve thermodynamic inhibition of fermentation.1 aKushwaha, Shilpi1 aMarcus, Andrew, K.1 aRittmann, Bruce, E.  uhttps://library.ncl.res.in/content/ph-dependent-speciation-and-hydrogen-h-2-control-uvi-respiration-desulfovibrio-vulgaris