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ISRN Biotechnology
Volume 2013 (2013), Article ID 657160, 11 pages
http://dx.doi.org/10.5402/2013/657160
Research Article

Fermentation and Hydrogen Metabolism Affect Uranium Reduction by Clostridia

1Center for Biosignatures Discovery Automation, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
2Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
3Environmental Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA

Received 12 December 2012; Accepted 19 January 2013

Academic Editors: V. P. Bulgakov and M. Rossi

Copyright © 2013 Weimin Gao and Arokiasamy J. Francis. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Previously, it has been shown that not only is uranium reduction under fermentation condition common among clostridia species, but also the strains differed in the extent of their capability and the pH of the culture significantly affected uranium(VI) reduction. In this study, using HPLC and GC techniques, metabolic properties of those clostridial strains active in uranium reduction under fermentation conditions have been characterized and their effects on capability variance of uranium reduction discussed. Then, the relationship between hydrogen metabolism and uranium reduction has been further explored and the important role played by hydrogenase in uranium(VI) and iron(III) reduction by clostridia demonstrated. When hydrogen was provided as the headspace gas, uranium(VI) reduction occurred in the presence of whole cells of clostridia. This is in contrast to that of nitrogen as the headspace gas. Without clostridia cells, hydrogen alone could not result in uranium(VI) reduction. In alignment with this observation, it was also found that either copper(II) addition or iron depletion in the medium could compromise uranium reduction by clostridia. In the end, a comprehensive model was proposed to explain uranium reduction by clostridia and its relationship to the overall metabolism especially hydrogen (H2) production.