Decolourization and Biodegradation of Reactive Azo Dyes by Mixed Culture

Synthetic dyes, azo dye in particular, are widely found in the effluents from textile industries. The persistence and toxicity of these compounds cause adverse impact in the receiving streams. A mixture of isolated cultures, from domestic sewage treatment plant was found to decolourize reactive azo dyes, Red RB, Blue M2B and Yellow, efficiently in the absence of added external nitrogen source. After shaking incubation for 48 hrs, mixture of cultures removed these dyes and decolourization was 95% for Red RB and Blue M2B and 50% for Yellow. The mixed culture could degrade 500 mgll Red RB efficiently with the release of 84.9 mgll of ammonia. There was also degradation of 100 mgll of Blue M2B and 50 mgll of Yellow dyes but the release of ammonia was not observed in Blue M2B and Yellow. Decolourization was remarkably enhanced when peptone was used in the medium. Azoreductase activity was high in the presence of reactive azo dyes and the enzyme could decolourize the reactive dyes much faster when decolourization was studied as cell free extract in the presence of individual dyes.