Bioremediation of Cr(VI) using novel thermophilic bacteria Brevibacillus borstelensis SSAU-3 T: optimization, mechanism and phytotoxicity study

Abstract

Rapid industrialization and advancement of chemical fertilizers in agriculture get infused with water causing heavy pollution of inorganic pollutants has become a serious problem. This research focuses on the utilization of a thermophilic bacteria Brevibacillus borstelensis, SSAU-3 T in the bioremediation of hexavalent chromium (Cr (VI)). The strain has capability in > 99% removal of 40 ppm Cr (VI). Further optimization was studied by varying parameters (pH, Inoculum size, salinity, volume and temperature) based on Cr(VI) removal capabilities. Removal mechanism was determined by studying thermodynamic, kinetic, and isotherm under optimized parameters: pH 7, salinity 5 g/L, inoculum size 2%, medium volume 20 mL, temperature 55 °C which resulted that Redlich-Peterson isotherm model is a best fit for this study. Characterization of functional groups and bonds present on bacterial cell surface before and after treatment with chromium were optimized by Fourier Transform Infrared Spectroscopy and surface morphology changes were also observed by Scanning Electron Microscopy. A phytotoxicity study was conducted on wheat, which showed that bacterial secondary metabolites were not toxic. The study highlights an eco-friendly and cost-effective approach to mitigate Cr(VI) toxicity using thermophilic microbes from hot springs.