Reduction of Hexavalent Chromium by Viable Cells of Chromium Resistant Bacteria Isolated from Chromite Mining Environment

Abstract

Environmental contamination of hexavalent chromium [Cr(VI)] is of serious concern for its toxicity as well as mutagenic and carcinogenic effects. Bacterial chromate reduction is a cost-effective technology for detoxification as well as removal of Cr(VI) from polluted environment. Chromium resistant and reducing bacteria, belonging to Arthrobacter, Pseudomonas, and Corynebacterium isolated from chromite mine overburden and seepage samples of Orissa, India, were found to tolerate 12-18 mM Cr(VI) during growth. Viable cells of these isolates were also capable of growing and reducing 100 M Cr(VI) quite efficiently in Vogel Bonner (V.B.) broth under batch cultivation. Freshly grown cells of the most potent isolate, Arthrobacter SUK 1201, reduced 100 M Cr(VI) in 48 h. Reduction potential of SUK 1201 cells decreased with increase in Cr(VI) concentration but increased with increase in cell density and attained its maximum at 10 10 cells/mL. Chromate reducing efficiency of SUK 1201 was promoted in the presence of glucose and glycerol while the highest reduction was at pH 7.0 and 25 ∘ C. The reduction process was inhibited by divalent cations Ni, Co, and Cd, but not by Cu. Similarly, carbonyl cyanide m-chlorophenylhydrazone, N,N,-Di cyclohexyl carbodiimide, sodium azide, and sodium fluoride were inhibitory to chromate reduction, while 2,4 dinitrophenol promoted the process. Cells permeabilized by toluene increased the efficiency of Cr(VI) reduction and, thereby, indicate that Arthrobacter sp. SUK 1201, indigenous to chromite mining environment, could be used as an ideal tool for chromium bioremediation.

Electrogenic activity and hexavalent chromium reduction by Aeromonas hydrophila CrMFC5

“…It was possible to observe a decrease in the rate of reduction of chromium, although an increase in the number of microorganisms was presented (Figure 3). Similar results were observed in the work of Dey et al 30 who tested four different bacterial strains, showing that the highest rate of reduction was observed in the first hours of the assay. In contrast, in the assays performed with IW a significantly lower growth was showed than the one observed in LB.…”

Reduction of hexavalent chromium by Bacillus spp. isolated from heavy metals-polluted soil

“…The presented data shows that with an increase in the Cr(VI) content in the LB medium, decrease of the number of Cr(VI) [35] reported that only 12% of bacteria were capable of growth at 1000 ppm Cr(VI) were also detected at 500 ppm. However, Dey et al [36] found that the rate of bacterial growth reduction was about 50% at a Cr(VI) concentration of 2 mM compared to the control, which is in agreement with this study.…”

Effects of Incubation Conditions on Cr(VI) Reduction by c-type Cytochromes in Intact Shewanella oneidensis MR-1 Cells

“…Similar behaviors have been reported with Arthrobacter sp. SUK 1201 ( Dey et al, 2014 ), Pseudomonas CRB5 ( McLean et al, 2000 ), and Bacillus sphaericus AND 303 ( Pal and Paul, 2004 ). Simultaneously, the higher cell density induced faster Heme red recovery.…”

“…The microbial Cr(VI) reduction can be influenced by different environmental factors, such as Cr(VI) concentration, temperature, bacterial cell density, electron donor, pH, oxygen, and the presence of other metal ions ( Wang and Xiao, 1995 ; Dey et al, 2014 ). Past studies ( Wang and Xiao, 1995 ; Zakaria et al, 2007 ; Dey et al, 2014 ) mainly focused on effects of incubation factors on the apparent Cr(VI) reduction and rarely investigated the effects of incubation factors on the redox status of c -Cyts in the OM of DMRB, which play a key role in microbial Cr(VI) reduction. In situ spectral kinetics of Cr(VI) reduction by c -Cyts in live cells under different environmental conditions should provide a more fundamental understanding of the molecular-level mechanisms.…”