Inorganic Selenium and Tellurium Speciation in Aqueous Medium of Biological Samples

Basnayake, Rukma ST, Inorganic Selenium and Tellurium Speciation in Aqueous Medium of Biological Samples, Master of Science (Chemistry), December 2001, Sam Houston State University, Huntsville, Texas, 60 pp. Purpose The purpose of this research was to develop methods to study the ability of bacteria, Pseudomonas fluorescens K27 to detoxify tellurium and selenium salts by biotransformation processes under anaerobic conditions. Another purpose was to make an effort to separate biologically produced Se from cells. Methods Pseudomonas fluorescens K27 was grown in TSN3 medium (tryptic soy broth with 0.3% nitrate) under anaerobic conditions and the production of elemental tellurium and elemental selenium was observed when amended with inorganic tellurium salts and selenium salts, respectively. The amount of soluble tellurium species in the culture medium also was determined. Samples from a 2.75 L bioreactor were taken after cultures had reached the stationary growth phase and were centrifuged in order to separate insoluble species (elemental tellurium, elemental selenium) from soluble species (oxyanions of tellurium, oxyanions of selenium). In tellurium samples, supernatant consisting of soluble tellurium and the sediment consisting of insoluble tellurium were analyzed separately by oxidation and reduction procedures followed by using hydride generation atomic absorption spectroscopy (HGAAS). Sediment from selenium bioreactor samples was used to find free elemental selenium and elemental selenium inside and/or on K27 cells. A sucrose density gradient with overlaid precipitate was prepared, centrifuged, fractionated and analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) to find the concentration of Se and also analyzed by UV/Vis spectrometry to find the distribution of cells in the sucrose gradient.