Analysis of the azoreductase gene harbored by Alcaligenes sp. YB4 capable of concurrent removal of sulphonated azo dye and hexavalent chromium

Abstract

Continuous discharge of textile wastewater consisting of variety of pollutants is a serious threat to ecosystems. Microbial bioremediation might serve as an effective approach for treating these unwanted contaminants. In this study, several bacteria isolated from textile wastewater were studied for decolorization of Congo red (CR) dye. The strain Alcaligenes sp. YB4 showed the most efficient potential to decolorize CR dye. Moreover, this strain efficiently decolorized CR while concurrently removing hexavalent chromium [Cr(VI)] in the same medium with maximum removal (> 90 %) of both pollutants at pH 7 and pH 8. The potential of YB4 for concurrent removal of both pollutants was observed to decrease with increasing concentration of NaCl. Similarly, Alcaligenes sp. YB4 efficiently removed the 91.6 % of CR and 95.7 % of Cr(VI) simultaneously, under static condition as compared to the shaking condition. While MS media amended with yeast extract showed about 92.2 % and 90.1 % removal of CR and Cr (VI) within 48 hours of incubation, respectively. Moreover, it was also noticed that presence of heavy metals effected the concurrent removal of both pollutants. The in-silico analysis of the azoreductase amplified from the strain YB4 identified the binding of CR with azoreductase and proposed the hypothesis that their association may be the primary cause of CR degradation. This study indicated that Alcaligenes sp. YB4, having azoreductase gene, is a potential resource to treat textile wastewater.