Microbiological assay for chemical species of selenium in foods utilizing Escherichia coli formate dehydrogenase

Tschursin, Elizabeth; Wolf, Wayne R.

doi:10.1007/bf00322602

Cited by 8 publications

(4 citation statements)

References 14 publications

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“…In the speciation studies of organometallic compounds, an increase in selectivity is frequently required and the field of organometallic speciation has paid special attention to the new possibilities of biological systems, above all including bacteria. 41,42 The Escherichia coli bacterium has been used, from an analytical point of view, for the speciation of inorganic and organoseleno compounds, by developing a bioassay method which takes advantage of the presence of the formate dehydrogenase enzyme that requires selenium for synthesis. 42 This enzyme catalyzes the formation of CO 2 from formic acid and the corresponding quantitation of selenium species [Se-Met, Se-Cyst, Se IV ] was indirectly carried out by IR measurements of CO 2 .…”

Section: Cellsmentioning

confidence: 99%

“…41,42 The Escherichia coli bacterium has been used, from an analytical point of view, for the speciation of inorganic and organoseleno compounds, by developing a bioassay method which takes advantage of the presence of the formate dehydrogenase enzyme that requires selenium for synthesis. 42 This enzyme catalyzes the formation of CO 2 from formic acid and the corresponding quantitation of selenium species [Se-Met, Se-Cyst, Se IV ] was indirectly carried out by IR measurements of CO 2 . Sensitivity of this assay is down to the ng ml 21 level of Se.…”

Section: Cellsmentioning

confidence: 99%

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Speciation of selenomethionine and selenourea using living bacterial cells†

Aller

1998

Analyst

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A novel and reliable method is proposed for speciation of selenomethionine (Se-Met) and selenourea (Se-U) combining a time-controlled solid phase extraction by using living bacterial cells and electrothermal atomic absorption spectrometry (ETAAS) for the determination of selenium. The extraction medium consists of a Pseudomonas putida strain cultivated in a culture medium based on glucose contaminated with an organoseleno compound. Firstly, equilibrium between the analyte in the solution and the retention medium is allowed to be established, and then the concentration of the organoseleno compound is determined directly in the biomass by slurry ETAAS. It is possible to discriminate between different chemical species of selenium by combining the optimization of both the growth conditions and the relative rates of their retention from the sample solution. A theoretical model of the retention process, based on a rate-determining step in reaching the adsorption equilibrium, is proposed to describe the experimental adsorption time profiles of the uptake process by the living bacterial cells. This relationship can also provide a feasible quantification of the extraction process before the adsorption equilibrium is reached, whenever the agitation conditions and the sampling time are under control. The experimental data agreed closely with the theoretical model. The study of the adsorption process was derived to develop an analytical procedure to determine Se-Met and Se-U in matrices containing other selenium species (Se-ethionine, Se-cystamine, Se-cystine and Se VI ). The best detection limits for the organoseleno compounds at their optimum extraction times are 1.5 ng ml 21 for Se-Met and 1.2 ng ml 21 for Se-U. The relative standard deviations of the retention/determination process are 2.2-5.6%.

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Section: Cellsmentioning

confidence: 99%

Section: Cellsmentioning

confidence: 99%

Speciation of selenomethionine and selenourea using living bacterial cells†

Aller

1998

Analyst

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“…In some applications, lyophilized bacterial cells were effectively adopted to preconcentrate metals (precious [9], alkaline-earth [10] and transition [11,12]) and metalloids [13] from aqueous solutions, with a particular emphasis on the ionic speciation. Nonetheless, speciation of organometals frequently required increased selectivity, paying special attention to the new possibilities of biological systems, and above all bacteria [14,15,16,17].…”

Section: Introductionmentioning

confidence: 99%

Fourier-transform infrared spectroscopic study of the interactions of selenium species with living bacterial cells

Feo

Castro

Robles

et al. 2004

Analytical and Bioanalytical Chemistry

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“…Selenomethionine as a source of selenium for incorporation into selenoenzymes is of particular importance because selenomethionine is reported to be the main selenium species present in grains (wheat, in particular), which are a major source of dietary selenium in the United States (16). The effect of methionine upon the metabolism of selenomethionine has been studied in whole animals and in tissue culture but not in bacteria prior to our initial study (24). Information on selenium metabolism in bacteria may provide information useful for animal studies regardless of possible potential differences in selenomethionine metabolism between bacteria and animals.…”

mentioning

confidence: 99%

Optimization of an Escherichia coli formate dehydrogenase assay for selenium compounds

Tschursin

Wolf

Lacroix

et al. 1994

Appl Environ Microbiol

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A microbiological assay to detect different chemical compounds of selenium for potential future use in the study of the distribution of these chemical forms in foods is being developed. This assay is based on the detection, by infrared analysis, of CO2 in a culture of Escherichia coli when the bacteria are grown in the presence of various selenium compounds. The CO2 production is the result of selenium-dependent formate dehydrogenase activity, which catalyzes oxidation of formic acid produced during glucose metabolism. Smooth response curves were generated over several orders of magnitude for selenocystine, selenite, and selenomethionine. The assay detects selenium concentrations (above background) as low as 1.5 nM for selenocystine and selenite and 4 nM for selenomethionine in minimal medium. Detection of selenomethionine was enhanced (to a sensitivity of 1.5 nM) by the addition of methionine to minimal medium and was enhanced even further (to a sensitivity of 0.8 nM) by the addition of a defined mixture of amino acids. Selenomethionine could be assayed in the presence of an amino acid concentration which is proportional to the amino acid/elemental selenium ratio found in a wheat gluten reference material (NIST SRM 8418). This implies that the assay can detect selenium compounds in a variety of foods at low concentrations, avoiding the background CO2 production caused by high concentrations of non-selenium-containing amino acids. The observation that methionine enhanced selenomethionine availability for formate dehydrogenase synthesis supports studies in animals demonstrating that methionine controls selenomethionine incorporation into selenoenzymes. Although determination of selenium by isotope dilution-mass spectrometry is more sensitive for detecting elemental selenium in biological materials, the microbiological assay detects metabolically utilized selenium, which is currently of interest in nutrition research.

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Microbiological assay for chemical species of selenium in foods utilizing Escherichia coli formate dehydrogenase

Cited by 8 publications

References 14 publications

Speciation of selenomethionine and selenourea using living bacterial cells†

Speciation of selenomethionine and selenourea using living bacterial cells†

Fourier-transform infrared spectroscopic study of the interactions of selenium species with living bacterial cells

Optimization of an Escherichia coli formate dehydrogenase assay for selenium compounds

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