Volume No. 9 Issue No.: 3A Page No.: 840-848 January-March 2015




Biswas Gargi1, Das Ranjit and Kazy Sufia K.*2

1. Department of Chemical Engineering, National Institute of Technology Durgapur, West Bengal (INDIA) 2. Department of Biotechnology, National Institute of Technology Durgapur, West Bengal (INDIA)


Received on : October 10, 2014




Chromium (Cr) and its compounds are widely distributed in the environments by several industrial processes. Chromium is most important for environmental concern due to their toxicity, mutagenicity and carcinogenicity. High mobility of hexavalent chromium as compared to trivalent chromium has gained more importance for microbial reduction of chromium. In this study we used tannery effluent for the isolation of indigenous bioremediation relevant microorganisms. A new gram-negative Cr(VI) resistant bacteria strain designated as P-2 was isolated. Based on biochemical tests and 16S rRNA gene sequence analysis, the strain P-2 was identified as Alcaligenes faecalis (KF499017). It was grown in Minimal Salt Medium (MSM) containing Cr(VI) up to 750 mg L-1. Cr(VI) reducing capability of the bacterium was checked by estimating the amount of Cr(VI) in the growth medium at selected time intervals during the course of growth. The reduction of Cr(VI) was accompanied by an increase in the cell biomass under aerobic conditions. Initial pH value and glucose (0.1%) concentration were found to influence the reduction rate of Cr(VI) and the optimal pH was 8. At pH 8 and 37oC with 0.5% salinity more than 75% of initial Cr(VI) of 10 mg L-1 was reduced when 5% inoculum was used. Furthermore 95% Cr(VI) reduction was observed with cell free extract. Cr(VI) reductase activity enhanced (>1.1 fold) by NADH. The enzyme activity was enhanced by Cu2+, Zn2+, Ca2+ and Fe2+. Overall observation indicates the Cr(VI) reduction potential to the isolated A. faecalis strain P-2 indigenous to tannery waste


Keywords : Alcaligenes faecalis, Bioremediation, Cr(VI) reduction, 16S rRNA gene, Cr(VI) reductase