Azo Dye Degradation by Chlorella vulgaris: Optimization and Kinetics

Abstract

Background and Objective: Azo dyes are most widely used in various industries due to their ease of synthesis and chemical stability. But many azo dyes and their breakdown derivatives have been suggested to be toxic to life. Biological treatments of dyes with microorganisms are relatively cost effective and eco-friendly due to lower sludge production. In this study, the microalgae Chlorella vulgaris was examined for its degrading ability of azo dyes viz., Reactive Black 5, Direct Blue 71 and Disperse Red 1. Materials and Methods: The experiments included dye decolorization experiments and factors affecting decolorization such as initial dye concentration, pH and temperature. Further, azoreductase enzyme specific activity and its kinetics were determined. Results: The results revealed that azo degradation based on the initial dye concentration varied among the dyes tested and the same was reflected for pH. In specific, 200 mg LG1 was found optimum for Reactive Black 71 and Direct Blue 71 whereas 300 mg LG1 was for Disperse Red 1. The optimum pH for decolorization of RB5, DB71 and DR1 was 5, 8 and 8, respectively. The optimum temperature for degradation of all the dyes was found as 40EC. Maximum azoreductase activity of 0.127 U mgG1 protein was observed for DR1 and the enzyme activity was not pH dependent but substrate specific. Conclusion: The results revealed the azo dye degrading potential of Chlorella vulgaris and the decolorizing conditions were optimized for the microalgae. Key