Reduction of Cr(VI) by a Bacillus sp. |
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Authors: | R Elangovan S Abhipsa B Rohit P Ligy K Chandraraj |
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Institution: | (1) Department of Civil Engineering, Indian Institute of Technology Madras, Chennai, 600 036, India;(2) Department of Biotechnology, Indian Institute of Technology Madras, Chennai, 600 036, India;(3) Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, 600 036, India |
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Abstract: | A Bacillus sp. RE was resistant to chromium and reduced Cr(VI) without accumulating chromium inside the cell. When Cr(VI) was 10 and
40 μg ml−1, >95% of the total Cr(VI) was reduced in 24 and 72 h of growth, respectively, whereas at 80 μg Cr(VI) ml−1 only 50% of Cr(VI) was reduced. However growth was not affected; the cell mass was 0.7–0.8 mg ml−1 in all cases. The cell-free extract showed Cr(VI) reducing enzyme activity which was enhanced (>5 fold) by NADH and NADPH.
Like whole cells the enzyme also reduced Cr(VI) with decreasing efficiency on increasing Cr(VI) concentration. The enzyme
activity was optimal at pH 6.0 and 30 °C. The enzyme was stable up to 30 °C and from pH 5.5 to 8, but from pH 4 to 5 the enzyme
was severely destabilized. Its Km and Vmax were 14 μm and 3.8 nmol min−1 mg−1 respectively. The enzyme activity was enhanced by Cu2+ and Ni2+ and inhibited by Hg2+.
Received 21 September 2005; Revisions requested 5 October 2005; Revisions received 16 November 2005; Accepted 16 November
2005 |
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Keywords: | Bacillus sp chromate reductase chromium tolerance Cr(VI) bioremediation |
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