Reduction of Hexavalent Chromium by a Potent Novel Haloalkaliphilic Nesterenkonia sp strain NRC-Y Isolated from Hypersaline Soda Lakes

We reported a novel haloalkaliphilic bacterial strain NRC-Y with remarkable hexavalent chromium reduction efficiency and studied its detoxification mechanism. Strain NRC-Y was identified based on 16S-rDNA sequence analysis as Nesterenkonia sp. Strain NRC-Y exhibited high Cr6+ reduction efficiency under a wide range of sodium chloride concentration, pH, shaking velocity, and temperature, showing maximum Cr6+ reduction at 6% NaCl, pH 9, 150 rpm and 40oC, respectively. In addition, strain NRC-Y could grow and reduce Cr6+ effectively in the presence of a variety of heavy metals and oxyanions. The co-existence of Cd2+ and Zn2+ caused a slight decrease in the Cr6+reduction, while Fe3+ and Cu2+ ions significantly increased the Cr6+ reduction by 1.7-and 1.8-fold, respectively. Among the tested electron donors, maximum Cr6+ reduction was observed using glycerol. Cell fractionation experiments proved that Cr6+ bioremoval occurred because of chromate enzyme activity, which was detected mainly in the bacterial cell membranes (73.2%) and cytoplasm (22.6%). SEM-EDX analyses confirmed the biosorption of chromium species into the cells. Strain NRC-Y exhibited a potent Cr6+ bioreduction efficiency, which could reduce up to 800 mgL-1 within 24 h. Therefore, strain NRC-Y is a promising candidate in the bioremediation of Cr6+ contaminated sites, particularly under harsh conditions. Further investigation using chromium containing industrial waste is recommended

Automated summary

We reported a novel haloalkaliphilic bacterial strain NRC-Y with remarkable hexavalent chromium reduction efficiency and studied its detoxification mechanism.