Abstract
Purpose: Evaluation of Cr (VI) removal by indigenous chromium resistant bacterial strains alone and in combination with Eichornia sp.Methods: Three chromium resistant bacterial strains S-4 Ochrobactrum grignonense, SF-5 Bacillus sp. and S-6 Ochrobactrum pseudogrignonenses were isolated from industrial effluent. The isolated chromium-resistant bacterial strains were subjected to heavy-metal resistance profiling. Cr (VI) reduction was evaluated in mobilized as well as immobilized forms. The phytoremediation potential of Eichornia sp. in conjunction with chromium resistant bacterial isolates was also determined. Fourier transform infra-red (FTIR) spectroscopy was performed to rule out the involvement of various functional groups in the binding activity of Cr (VI).Results: Three bacterial strains resisted up to 1000 μg/mL of potassium dichromate (K2CrO4). Bacterial strains S-4, SF-5 and S-6 showed significant Cr (VI) removal in mobilized state (84.93, 85.85 and 83.97% respectively) compared with immobilized state (41.27, 37.99, 37.96 %) at an initial concentration of 500 μg/mL of chromate. Bacterial strains caused reduction in chromate uptake in inoculated plants relative to control plants. FTIR spectra revealed significant changes in the absorption peaks, reflecting the binding of Cr (VI) ions with bacterial cell surface under stress conditions.Conclusion: The selected isolates tested possess the ability to remove Cr (VI) synergistically with Eichornia sp.Keywords: Phytoremediation, Heavy-metal, Pollution, Chromium-resistant bacteria
Highlights
Chromium (Cr) is one of the toxic heavy metals often found in the environment due to industrial and man-made activities
All selected bacterial strains were able to resist the concentration of 1000 μg/mL of potassium chromate (K2CrO4), which is the maximum tolerable range
Mercuric chloride (HgCl2) proved to be toxic as all bacterial strains were sensitive to this heavy metal
Summary
Chromium (Cr) is one of the toxic heavy metals often found in the environment due to industrial and man-made activities. The physicchemical methods include precipitation of chemicals through evaporation, filtration through membranes, ion exchange resins and reverse osmosis [3] These expensive methodologies generate toxic by-products, so ecologically cost effective methods are required to remediate hexavalent chromium pollution. Different heavy-metals like Copper sulphate (CuSO4), potassium chromate (K2CrO4), mercuric chloride (HgCl2), cadmium chloride (CdCl2) were selected to check the multiple resistances of the isolates to other heavy-metals For this purpose, 10 % stock solutions were prepared. Reduction of Cr (VI) by mobilized and immobilized bacterial strains was monitored by using the diphenyl carbazide method [10]. For the estimation of chromium uptake, the Eichornia plants were grown in natural environment.
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