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Applied and Environmental Microbiology, June 1999, p. 2691-2696, Vol. 65, No. 6
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Reduction of Technetium by Desulfovibrio desulfuricans: Biocatalyst Characterization and Use in a Flowthrough Bioreactor

J. R. Lloyd,1,* J. Ridley,1 T. Khizniak,2 N. N. Lyalikova,2 and L. E. Macaskie1

School of Biological Sciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom,1 and Institute of Microbiology, Russian Academy of Sciences, Moscow 117811, Russia2

Received 12 November 1998/Accepted 24 March 1999

Resting cells of Desulfovibrio desulfuricans coupled the oxidation of a range of electron donors to Tc(VII) reduction. The reduced technetium was precipitated as an insoluble low-valence oxide. The optimum electron donor for the biotransformation was hydrogen, although rapid rates of reduction were also supported when formate or pyruvate was supplied to the cells. Technetium reduction was less efficient when the growth substrates lactate and ethanol were supplied as electron donors, while glycerol, succinate, acetate, and methanol supported negligible reduction. Enzyme activity was stable for several weeks and was insensitive to oxygen. Transmission electron microscopy showed that the radionuclide was precipitated at the periphery of the cell. Cells poisoned with Cu(II), which is selective for periplasmic but not cytoplasmic hydrogenases, were unable to reduce Tc(VII), a result consistent with the involvement of a periplasmic hydrogenase in Tc(VII) reduction. Resting cells, immobilized in a flowthrough membrane bioreactor and supplied with Tc(VII)-supplemented solution, accumulated substantial quantities of the radionuclide when formate was supplied as the electron donor, indicating the potential of this organism as a biocatalyst to treat Tc-contaminated wastewaters.

* Corresponding author. Present address: Department of Microbiology, 203 Morrill Science Center IVN, University of Massachusetts, Amherst, MA 01003. Phone: (413) 545-9651. Fax: (413) 545-1578. E-mail: jrlloyd{at}microbio.umass.edu.

Applied and Environmental Microbiology, June 1999, p. 2691-2696, Vol. 65, No. 6
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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