Abstract

Bacterial species capable of decolorizing textile and laboratory dyes were isolated from textile effluent treatment plant. Two bacterial strains (one Gram negative and another Gram positive bacterial strain) were screened for their ability to decolorize Red H₅BL (reactive dye), Thymol blue (acid dye), Malachite green, Crystal violet (Triphenyl dye) and Congo red (azo dye). The highest decolorization was achieved for Red H₅BL (90%) and lowest for Thymol blue (26%) in 24 h incubation. The effect of different carbon sources and nitrogen sources were studied. The presence of dextrose in the culture medium suppresses the decolorization ability of Gram negative bacterial strain. In case of Gram positive strain, decolorization of Red H₅BL was achieved in the range of 75 to 86% for all the tested carbon sources. During the experiments of checking the effect of carbon sources it was found that shaking culture condition offers high biomass and less color removal of the dye. Decolorization of dyes was effective only under static culture condition. Inorganic or organic nitrogen source has no remarkable effect of decolorization process. Increased dye concentration and salt concentration has negative effect on the process of dye decolorization and biomass synthesis.

Key words: Biodegradation, decolorization, textile dyes, bioremediation.