Bioremoval of chemically different synthetic dyes by Aeromonas hydrophila in simulated wastewater containing dyeing auxiliaries

Aeromonas hydrophila, isolated from acclimated textile effluent after selective enrichment, was assessed for its dye biodegradability potential using chemically different dyes. The results revealed that the bacterium has a broad spectrum dye-degrading activity since it was able to efficiently decolorize the azo (Solophenyl red 3BL and Polar brilliant red B), triphenylmethane (Basic fuchsin and Crystal violet) and azine (Safranin and Nigrosine) dyes tested. Decolorization of azo dyes was more effective under microaerophilic conditions, whereas aerobic conditions were a prerequisite for the efficient decolorization of triphenylmethane and azine dyes by this isolate. UV/visible spectra of decolorized cultures indicated that color removal was the result of biodegradation rather than adsorption. Color reduction percentages obtained after 24 h of incubation at 30A degrees C were: 95 (Solophenyl red); 92 (Polar brilliant red B); 93 (Basic fuchsin); 75 (Crystal violet); 70 (Safranin) and 42 (Nigrosine). Optimal decolorization activity was obtained at an initial medium pH range of 6-9, and various concentrations of dyes (5-50 mg/L) and dyeing auxiliaries (sodium chloride, 0-20 g/L; SDS, 0-5 mg/L). The addition of carbon sources (especially glucose) significantly enhanced color reduction by this bacterium. A phytotoxicity bioassay using seeds of Phaseolus vulgaris confirmed the detoxification of dyes after treatment with A. hydrophila. The results indicate the potential of this isolate for use in biotechnological applications in the treatment of dye wastewater containing chemically different dyes.