Reduction of hexavalent chromium by Microbacterium paraoxydans isolated from tannery wastewater and characterization of its reduced products

The present study deals with a gram-positive and rod-shaped bacterium SCRB 19 isolated from chromium contaminated tannery wastewater of common effluent treatment plant (CETP), Kanpur (U.P), India. Based on 16S rRNA gene sequencing investigation, the bacterium was recognized as Microbacterium paraoxydans. This bacterium exhibits relatively elevated tolerance to Cr(VI) (≤1000 mg/L). The Cr(VI) reduction potential of isolated bacterium was studied at 100, 200 300 and 500 mg/L of Cr(VI) and the results revealed that bacterium reduced 93.45, 87.28, 72.01 and 39.24 % of Cr(VI) at their respective concentrations. The bacterial cell exterior showed the morphological changes and intracellular accumulation during the reduction of Cr(VI) was evidenced by SEM and EDX analysis. The Cr (VI) reduced product was bound with membrane functional groups such as amide and carboxyl group were determined through FTIR spectroscopy. The prominent peaks determined by XRD and XPS analysis corroborate the presence of possible reduced chromium species. The suspended culture of Microbacterium paraoxydans SCRB19 also showed chromate reductase enzyme activity of 1.603 ± 0.041 U/mL. Hence, this strain can be a promising bio-agent for ecofriendly clean up strategies of toxic Cr(VI) from polluted environments.