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2 Environmental Biotechnology

2 2012

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The acute bacterial toxicity of the selenocyanate anion and the bioprocessing of selenium by bacterial cells

Montes R. A., Pradenas G. A., Pérez-Donoso J. M., Vásquez C. C., Chasteen T. G.

Environmental Biotechnology

2012

Vol. 8, No. 1

32-38

A water-soluble anion containing selenium, selenocyanate (SeCN-), is produced in various industrial settings including petrochemical refining and mining wastewaters and is difficult to remove using common chemical or physical processes. The work described was aimed at determining the relative acute toxicity of SeCNby evaluating its minimal inhibitory and minimal bactericidal concentrations for 1) a bacterium (LHVE) that produces volatile selenium-containing derivatives in cultures containing added SeCNand 2) for a sensitive E. coli wild-type strain. These measures of toxicity were compared to those of selenate and selenite, the oxyanions of selenium commonly found in the environment. Cultures of LHVE amended with SeCNon agar plates produced red, elemental selenium after three days. As far as we know this is the first evidence for the biological production of elemental Se by a metalloid-resistant bacterium exposed to selenocyanate. Bioprocessing of selenite and SeCNby both types of bacteria, as analyzed by inductively coupled plasma spectrometry, demonstrated that LHVE more successfully incorporates or precipitates Se compared to E. coli.

Determination of volatile organochalcogens using liquid phase microextraction and gas chromatography with fluorine-induced chemiluminescence detection

Hashemi M., Montes R. A., Chasteen T. G.

Environmental Biotechnology

2012

Vol. 8, No. 2

55--62

In this study, a simple and rapid liquid phase microextraction technique coupled with gas chromatography and fluorineinduced chemiluminescence detection has been developed for determination of volatile organochalcogens (dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide and dimethyl diselenide and dimethyl telluride). The effects of extraction parameters such as extracting solvent and its volume, stirring time extraction time and salt effect were optimized. Also, analytical figures of merit such as response linearity, repeatability and reproducibility, and limits of detection have been evaluated. The proposed method was found to be a simple and rapid analytical procedure for determination of volatile organochalcogens in real aqueous samples with detection limits of 5-620ng·l-1. The relative recoveries of these analytes for spiked bacterial cultures, tap water and lake water ranged from 95 to 105% with the relative standard deviations of 0.3-11.0%.