Decolourization of dyes by Alcaligenes faecalis and Bacillus flexus isolated from textile effluent

In textile industry, untreated effluents pollute aquatic systems, almost irreversibly. Synthetic dyes not only change the colour of water resources but also make them toxic. In this study, we evaluated decolourizing potential of microbial isolates so as to use them as bioremediation agents. Two bacterial isolates, Bacillus flexus and Alcaligenes faecalis were isolated from the textile effluent samples collected from Nahar textile industry, Lalru (Punjab). Both these isolates have high decolourization potential and take only 24 h for complete decolourization. Different parameters, such as carbon source, nitrogen source, temperature, pH, concentration of dyes and inoculum size were optimized for decolourization of remazol black, direct blue and acid orange which are azo dyes that are most widely used and are highly toxic. Bacillus flexus showed 100% decolourization after 20 h with acid orange and at 24 h for remazol black and direct blue. Alcaligenes faecalis showed the best incubation time for all the three dyes to be 24 h and the extent of decolourization was found to be 89, 98 and 100% for remazol black, direct blue and acid, respectively. Such decolourizing potential of the isolates is quite high as compared to the earlier reports and can be effectively used as a tool for bioremediation of various textile effluents.