S. Hapuarachchi and T. G. Chasteen

Department of Chemistry
Sam Houston State University
Huntsville, Texas 77341-2117

Presented at the 58^th ACS Southwest Regional Meeting in Austin, Texas USA November 3-6, 2002.

A great deal of attention has been focused towards the chemistry of toxic selenium in water and soils and detoxification of environmental selenium. Selenium is an animal nutrient and has been proposed as an anti-oxidant but it can be detrimental to living beings at only slightly higher amounts (5 to 10 times RDA of 55 micrograms/day for adults) and probably lethal to humans at only 5000 times the RDA. For an example, the accumulation of Se in the Kesterson Reservoir of California has been a serious threat to the animals around that area.

It is important to address environmental problems like this. Therefore, scientists have been trying to reduce the toxic nature of these selenium contaminated environmental sites by introducing detoxification methods. One of the detoxification techniques currently being practiced is bioremediation. The reducing power of bacteria such as Pseudomonas fluorescens has been used to chemically reduce the toxicity of soluble forms of selenium in laboratory studies.

Understanding of the parameters that effect the bioremediation process is key to the improvement of this technique. In the studies reported here the mass balance of selenium added to live bacterial cultures in the laboratory in a 2 L bioreactor was determined. The distribution of Se among solid, liquid, and gas phase in these cultures after 72 hours growth was examined using inductively coupled plasma spectrometry. New efforts to improve this method using alternating aerobic and anaerobic growth conditions were investigated.