Factors Affecting Detoxification of Hexavalent Chromium into Trivalent in Industrial Effluents by Indigenous Bacteria

Abstract

Potassium chromate (K₂CrO₄) is a natural source of Cr(VI) and its reduction by Bacillus pumilus-CrK08, Exigubacterium sp-CrKS1 and Cellulosimicrobium cellulans-CrK16 bacterial strains (reportedly chromium resistant) using varied potassium chromate concentrations (500 and 1000 μg ml^-1) at different temperature (28^oC, 37^oC and 45^oC) and pH (5, 7 and 9) in the presence of antibiotics (ampicillline and chloramphenicol), heavy metals (Mn, Cu, Zn, As and Ni) and industrial effluents for different time intervals (24, 48 and 72 hours). Crude extract of CrK08 and CrK16 strains were also evaluated to determine the effects of K₂CrO₄, temperature, pH and industrial effluent. Highest reduction potential was observed at 500 μg ml^-1 of K₂CrO₄ whereas ideal pH and temperature were 37^oC and pH7, respectively. Increased reduction was observed in the presence of heavy metals especially CuSO₄. However, ampicillline suppressed reduction rate by all the strains. All three strains showed better reduction potential in the presence of wastewater after 24 hours of incubation. In addition, CrK16 extract showed comparatively better potential under these parameters.

Keywords: chromium, bioremediation, pollution, bacteria, heavy metals