Biodegradation of Textile Azo Dyes by Bacteria Isolated from Dyeing Industry Effluent

Water pollution caused by industrial effluent discharges has become an alarming trend worldwide, while textile industries are considered as the most polluting among all others. In recent years, bio-treatment took attraction in removing the unwanted colour and toxicity of textile effluents than other conventional treatment processes. The present study concentrates in the isolation and identification of indigenous bacteria from textile dye effluent and evaluation of their ability to decolourize dyes. The decolourizing activity was measured spectrophotometrically after incubation of the isolates for 3, 5 and 7 days in mineral salt medium modified with 0.05% of respective Novacron dye, viz orange W3R, red FNR, yellow FN2R, blue FNR or navy WB. Three bacterial isolates exhibiting strong decolourizing activity were identified up to species as Micrococcus luteus, Listeria denitrificans and Nocardia atlantica. All the bacteria exhibited maximum decolourizing activity after 7 days of incubation with little deviation. The bacterium Micrococcus luteus caused 60% decolourization of yellow FN2R and navy WB, and 85-90% of orange W3R, red FNR and blue FNR. Likewise, Listeria denitrificans decolourized 70-80% of Blue FNR, Orange W3R, Red FNR and Navy WB. In contrast, the bacterium caused no significant decolourization of yellow FN2R. Notably, Nocardia atlantica caused almost complete decolourization of Blue FNR and Red FNR, while at least 80% of other dyes tested. This study thus reveals that some bacteria inhabit in textile effluent whereby utilize the dyes as their source of energy and nutrition, and imply their importance in treatment of industrial effluents. Keyword: Water pollution, industrial effluent, Azo dye, Bioremediation.