Rapid decolorization of methyl orange by a novel Aeromonas sp. strain DH-6

Azo dyes are extensively used, but are recalcitrant and refractory. In this study, an indigenous strain DH-6 was isolated and identified as Aeromonas sp. based on 16S rDNA analysis for its excellent methyl orange (MO) decolorizing capability. Plackett-Burman design and response surface methodology (RSM) were employed to investigate the effect of operational parameters on decolorization and to optimize the decolorization process. Based on the results the concentrations of glucose, Na2HPO4 and MO and temperature were selected as the four significant parameters of RSM. The optimal conditions for MO decolorization by the strain were as follows: 3.0 g/L glucose, 4.9 g/L Na2HPO4, 100 mg/L MO, and at 40 °C. The verification tests showed that 95.5% decolorization was observed after incubation for 2 h, which is within the confidence interval. Under the optimal conditions, the kinetics of the decolorization fitted the first-order model well (R(2) = 0.969). As the strain DH-6 still showed a good decolorizing capability at a relatively high temperature, it is considered a candidate for azo dye bioremediation in some tropical or subtropical regions.