Jr. Lloyd et al., Reduction of technetium by Desulfovibrio desulfuricans: Biocatalyst characterization and use in a flowthrough bioreactor, APPL ENVIR, 65(6), 1999, pp. 2691-2696
Resting cells of Desulfovibrio desulfuricans coupled the oxidation of a ran
ge of electron donors to Tc(VII) reduction. The reduced technetium was prec
ipitated 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. Techneti
um reduction was less efficient when the growth substrates lactate and etha
nol were supplied as electron donors, while glycerol, succinate, acetate, a
nd methanol supported negligible reduction. Enzyme activity was stable for
several weeks and was insensitive to oxygen. Transmission electron microsco
py showed that the radionuclide was precipitated at the periphery of the ce
ll. Cells poisoned with Cu(II), which is selective for periplasmic but not
cytoplasmic hydrogenases, were unable to reduce Tc(VII), a result consisten
t with the involvement of a periplasmic hydrogenase in Tc(VII) reduction. R
esting 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, indicatin
g the potential of this organism as a biocatalyst to treat Tc-contaminated
wastewater.