Abstract
In the present study a moderately halophilic bacterium, Halomonas smyrnensis KS802 (GenBank Accession No. KU982965) was isolated from multi-pond solar salterns of Gujarat, India and evaluated for its potential to reduce hexavalent chromium during growth. Complete reduction of 2 mM Cr(VI) was achieved in 12 h when the strain was grown in medium for halophiles (MH medium) supplemented with 4% galactose and 5% NaCl at pH 7 and 32 °C. Presence of Mn, Cu and Pb in the culture media were non-toxic for growth and Cr(VI) reduction, while carbonyl cyanide-m-chlorophenyl hydrazone (CCC) inhibited both growth and Cr(VI) reduction. Hexavalent chromium of the untreated tannery effluent (100 µM) was completely reduced by the isolate in 6 h. The rate kinetics of reduction revealed a well fitted linearized exponential equation at a reduction rate of 5.9–1.8 × 10−2 h−1 in the range of 100–500 µM of Cr(VI) in the tannery effluent. Fourier transformed infrared (FTIR) spectroscopic analysis of chromate reducing cells showed characteristic shifting of functional group specific peaks possibly due to binding of reduced Cr-species. Scanning electron microscopy-energy dispersive X-ray (SEM–EDX) studies also supported deposition of Cr(III) on bacterial cells along with distinct changes in cellular morphology. Moreover, the powder X-ray diffraction (p XRD) pattern indicated the possible formation and complexation of chromium hydrogen phosphate and chromium hydroxide with cells of H. smyrnensis KS802.
Published Version
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