Determination of elemental selenium
production by a facultative anaerobic bacterium amended with selenite grown
under sequential anaerobic/aerobic conditions
S. Hapuarachchi and
T. G. Chasteen
Department of Chemistry
Sam Houston State University
Huntsville, Texas 77341-2117
Presented at the 225th ACS National Meeting
in New Orleans, Louisiana, USA, March 23-27, 2003.
Talk ENVR 112, presented in the second session
of "ACS Award for Creative Advances in Environmental Science and Technology,
Honoring Dr. John Birks"; T. G. Chasteen presiding.
This talk's PowerPoint presentation. (3.2 MB)
Experiments were carried out to determine the mass balance
of selenium biologically processed by an Se-resistant bacterium, Pseudomonas
fluorescens, isolated by Ray Fall, CU Boulder. The bioprocessing of
this toxicant in a growing liquid culture resulted in reduction and, in
some part, methylation that yielded Se distributed between the solid, liquid,
and gas phases. Initial anaerobic experiments with different amended selenium
concentrations were carried out and the Se mass balance determined using
inductively coupled plasma and fluorine-induced chemiluminescence-based
GC analysis. Finally, bioreactor experiments were carried out under sequential
anaerobic/aerobic culture growth conditions again the mass balance determined.
As a percentage of amended selenium, selenite was more effectively reduced
to metallic Se by P. fluorescens than selenate. When low amounts
of selenite were present in the solution, reducing efficiency as a percentage
of added Se was higher as measured by the production of Se zero. Sequential
anaerobic/aerobic growth conditions did not have a big effect in this detoxification
process as carried out under these conditions. A fast
motion movie of the bioremediation process will be used to visualize
the culture's action on added Se.
e-mail T.G. Chasteen