Bioremediation of Hexavalent Chromium by Chromium Resistant Bacteria Isolated from a Polluted Soil

Abstract

Tannery effluents from the textile industry contain various organic chemicals used in manufacture, including dyes, chrome dyes, and other chemicals. These can result in large-scale liquid waste discharges that contain heavy metals, including hexavalent chromium. Chromium-resistant bacteria were isolated from polluted soil in order to address these heavy metals biologically as environmental contaminants. Using the atomic absorption spectrophotometer AAS, the concentration of chromium in the soil sample was determined to be 0.0863 mg/l. The effects of pH and different chromium concentrations on the bacterial tolerance to hexavalent chromium were also studied for a duration of 72–96 hours. Pseudomonas spp., a gram-negative rod-shaped bacterium, was isolated from the soil using a combination of microscopic identification (Gram staining) and other biochemical testing. The greatest biotransformation capability was found to be 90.65% and 90.99% at pH 6 and 7, respectively. The results of this study demonstrate that Pseudomonas species are capable of withstanding hexavalent chromium.