Electron reduction of chromium (VI) to chromium (III) by bacterial strains

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Steen, Noelle
Swindle, Andrew L.
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Chromium (Cr) is a heavy metal commonly used in industrial settings worldwide and is therefore a source of contamination in the environment due to leaks, spills, and releases. In the environment, chromium takes the highly toxic and soluble hexavalent chromium (Cr(VI)) form or the nontoxic, less soluble trivalent chromium (Cr(III)) form. Cr(VI) poses a risk to life and the environment, so its removal is vital. One method for this is the reduction of Cr(VI) to Cr(III), which will then precipitate and could be removed from the environment. This study seeks to determine if three different bacterial strains, Pseudomonas aeruginosa, Bacillus subtilis, and Micrococcus luteus can perform this reduction. The organisms used for this study are American Type Culture Collection (ATCC) strains, naïve to chromium in any valence state. They were grown on a blood agar plate for 24 hours, and then inoculated into a flask with 25 mL of Luria-Bertani (LB) broth. Each flask was then inoculated with a concentration of K2CrO4, either 1 μM, 50 μM, 100 μM, or 200 μM, and incubated for 24 hours at 35°C. The samples were filtered, and the Cr(VI) was measured using the 1,10-Diphenylcarbazide method on a UV-VIS spectrophotometer. All three organisms were able to reduce Cr(VI) to Cr(III) to some degree; Pseudomonas aeruginosa and Bacillus subtilis were able to reduce the Cr(VI) almost completely, while Micrococcus luteus was able to reduce most of it, but not all. These naïve organisms were all able to reduce Cr(VI) to Cr(III), which makes them candidates for Cr(VI) reduction strategies in the environment. Further studies must be done to determine whether they can be placed in an environment with other heavy metals, and if they could be used together for more robust remediation.

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Thesis (M.S.)-- Wichita State University, College of Liberal Arts and Sciences, Dept of Geology, Earth, Environmental and Physical Sciences Program
Wichita State University
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