Isolation, Characterization and Growth Optimization of a Chromate-reducing Bacterium

Abstract

The application of chromium in industries has introduced anthropogenic release of chromatewhich is very toxic and a soluble environmental contaminant. The contaminated sites andindustrial wastewater containing chromate are treated based on reduction of Cr(VI) to Cr(III)which is insoluble and less toxic to environment. This can be achieved through utilization ofCr(VI)-reducing bacteria which serves more economical and environmental-friendly treatmentas compared to conventional chemical treatment method. To fulfill this, a new chromatereducing bacterium was isolated from an agricultural site. This bacterium was identified asAeromonas encheleia using Biolog analysis with 0.603 similarity index. Chromate reductioncapability of the bacterium was optimized using Response Surface Methodology with optimumconditions occurring at 250 μM Cr(VI), temperature 34 °C and pH 7.5 with 99% reduction wasachieved. The bacterium showed high tolerance in LB media containing 3.0 mM of K2Cr2O7,but only reduce 1.5 mM Cr(VI) within 24 hours. The presence of metals and metabolicinhibitors in the media did not give significant inhibitory effect on Cr(VI) removal except Hg,NaCN and Co with percentage inhibition 6.7, 80.5 and 90.8 respectively. Based on this study,Aeromonas encheleia could be a good candidate in bioremediation of contaminated site orindustrial wastewater containing Cr(VI).