Characteristics of a Newly Isolated Bacterium for Decolorization of Textile Dyes

Abstract

In recent years, use of microbial biomass for decolorization of textile effluent is becoming a promising alternative for costlier treatment processes. In the present study, a newly isolated bacterial strain expressing azoreductase activity was utilized to remove the color of textile dyes (Red RR and Black GDN) which come under the group of reactive dyes. The effects of substrate concentrations, medium compositions, and operation parameters (e.g., pH and temperature) on decolorization of the dyes by the strain were systematically investigated to reveal the key factors that govern the performance of dye decolorization. The metabolites resulting from bacterial decolorization were analyzed by high-performance liquid chromatography (HPLC). Azoreductase activity in the crude cell extract was assayed by the method of Zimmermann et al. The results showed that maximum decolorization occurred at 37°C at pH 7–8. The optimum concentration of dye was found to be 20ppm. It was observed that there was an increase in the percentage of decolorization upon supplementation with yeast extract. Batch incubation studies revealed that maximum decolorization occurred within 72 h and it was found to be 98.25 and 78.47% for Red RR and Black GDN, respectively. Azoreductase activity in the crude extract was found to be 44% for Black GDN. We found in the present study that the isolated strain is very efficient in removing color of textile dyes and the key enzyme involved in the process is azoreductase.