Degradation and decolorization of Disperse red 167 dye with an in-situ isolated azo-reductase enzyme producing bacterium Paenochrobactrum glaciei

Present study establishes an eco-friendly and easy to scale up methodology for degrading Disperse Red 167 being discharged from textile industry effluents in India. In this study, monthly wastewater samples were collected and analysed for naturally occurring bacteria. Selected bacteria ( Bacillus subtilis, Paenochrobactrum glaciei, Brevibacillus panacihumi, Bacillus cereus, Bacillus sphaericus, Paenibacillus pocheonensis and Escherichia coli ) were isolated and selected to assess their biodegradation capability on Disperse Red 167 dye. Biodegradation study was conducted in the laboratory by preparing three different concentrations of Disperse Red 167 dye (50, 100 and 150 mg/l) and treating each of the seven bacteria in three replicates for a period of 24 h. Results of this study indicated that Paenochrobactrum glaciei showed the best biodegradation and decolourisation potential of 84% at a concentration of 50 mg/l (84.80 ± 0.34% within 24 h). Also, (GC–MS) analysis was conducted to delineate the biodegradation pathway of the dye and it was found that two intermediate metabolites, namely ‘2-chloro-4-nitro-phenylamine’ and ‘Acetic acid2-[(2-acetoxy-ethyl)-(4-amino-3-propionylamino-phenyl)-amino]-ethylester’, were formed as a result of asymmetric breakdown of the azo bond of Disperse Red 167 dye. These two metabolites were further tested for their phytotoxicity on ‘ Triticum aestivum ’ wheat seed germination, and it was confirmed that these two metabolites are of non-toxic nature. The results of study clearly indicate that naturally occurring bacteria in wastewater streams have the potential to treat textile industry wastewater containing ‘Disperse Red 167 dye’ and minimize the risk on the aquatic living environments in water bodies.