Microaerophilic decolorization of a textile dye C.I. Reactive Red 31 by indigenous bacterial consortium: Process optimization and enzymatic mechanism

摘要

Dyestuff compounds released by textile and dye manufacturing units pose a great threat to the quality of soil-water ecosystems. The present study investigates the ability of bacterial consortium isolated from dye contaminated sites to decolorize a sulfonated azo dye Reactive Red 31. Dye decolorization results, indicated that consortium RV2 under microaerophilic condition decolorized (87.05% of 100 mg/L) dye within 12 h in MSM medium at 37 degrees C. Under oxygen-rich conditions (at 120 rpm), consortium RV2 was incapable for metabolizing dye and only 39.74% (of 100 mg/L) dye was decolorized in the similar time period. The optimum pH and temperature for the dye decolorization were 8 and 37 degrees C, respectively using consortium RV2. A significant increase in azoreductase (14 folds) and tyrosinase (10 folds) activities in the culture broth were obtained after complete decolorization as compared to the initial stage. Initial screening by Plackett-Burman design was performed to select major variables out of eleven media and culture conditions, among which peptone, meat extract, pH and dye concentration were found to have significant effects on decolorization. pH with Prob F-value of 0.0032 was found to be the most influencing factor followed by concentrations of Peptone (0.0066), Meat Extract (0.0098) and Dye concentration (0.0127) in the medium. The comparison of the response surfaces obtained suggests that peptone and pH along with meat extract plays an important role in dye decolorization, azoreductase and tyrosinase activity. The consortium RV2 possesses the ability to decolorize (99.88%) dye within 12 h under optimum conditions.