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The Bacillus subtilis and Pseudomonas aeruginosa were isolated from disposal site of tannery effluent
and was tested for decolorization activity against commercially important dyes, acid red and acid blue in
nutrient agar medium and minimal salt broth. In agar medium, decolorization began with the formation of
zone of clearance around the colonies. Both bacteria are decolorized both the dyes to a great extent. In
liquid medium, the bacterial inoculums were inoculated into flasks containing acid red and acid blue (100
mg/l) with trace amounts of yeast extract and glucose and then sterilized and incubated for 72 hrs. Both
bacteria decolourized differently depending upon the strength of dyes present in the medium. Also, the
different parameters such as various carbon source, nitrogen source, time and inoculum size were
optimized for decolorization of both dyes by using bacterial isolates. Bacillus cereus and Pseudomonas
aeruginosa showed maximum dye decolorization of 90% at the end of 72h under all optimum conditions.
But the Pseudomonas aeruginosa was found to be more efficient in dye decolorization. High
decolorization extent and facile conditions shows the potential for this bacterial strain to be used in the
biological treatment of dyeing mill effluents.
Keywords: Tannery effluent, Acid Dyes, Decolourisation, Optimisation.