Decolorisation and detoxification of Direct Blue-15 by a bacterial consortium

Studies were carried out on decolorisation and biotransformation of the dye Direct Blue-15 into 3,3′-dimethoxybenzidine (O′-dianisidine) and a sulphonated derivative by a five-member bacterial consortium. Chromatographic studies revealed further complete biodegradation of 3,3′-dimethoxybenzidine coupled with release of ammonia, but the recalcitrant sulphonated derivative persisted. The microorganisms identified in the mixed consortium by 16S rDNA sequence analysis were Alcaligenes faecalis, Sphingomonas sp. EBD, Bacillus subtilis, Bacillus thuringiensis and Enterobacter cancerogenus. The cytotoxicity data showed a significant reduction in the toxicity (P < 0.001) of the degraded dye as evidenced from the number of viable human polymorphonuclear leukocyte cells present.