Microbial Decolorization of Reactive Black by Pseudomonas stutzeri ETL-79

Abstract

Azo reductase are often associated with decolorization of non-degradation of non-degradable azo dyes via cleavage azo bonds. In this study, Pseudomonas stutzeri ETL-79 bacterium was used for the decolorization of Reactive Black dye. The highest activity of azoreductase was obtained during the end of log phase. Azoreductase produced intracellularly had the highest specific activity of 0.0334 U/mg compared to the culture supernatant (Extracellular), resting cell and cell debris with low enzyme activity of 0.034 U/mg, 0.010 U/mg and 0.200 U/mg respectively. The optimum assay condition for the maximum azoreductase activity were at 37°C, pH 7, Reactive Black dye concentration of 100 mg/L and NADH concentration of 0.2 Mm by using phosphate buffer as a medium for the enzyme reaction. Alternatively the azoreductase assay was also carried out using ionic liquid that may function to enhance the activity and stability of azoreductase. Results using phosphate buffer (pH-7) showed higher enzyme activity twice that of the ionic liquid besides enhancing the stability of enzyme. Under the optimum assay condition upto 93% of decolorization was achieved after 8h of incubation. In addition, growth of bacteria was also concurrently observed during decolorization of Reactive Black.