Response surface methodology for decolorization of azo dye Methyl Orange by bacterial consortium: Produced enzymes and metabolites characterization

The use of chemometric methods such as response surface methodology (RSM) based on statistical design of experiments (DOEs) is becoming increasingly widespread in several sciences such as analytical chemistry, engineering and environmental chemistry. In the present study, the decolorization and the degradation efficiency of Methyl Orange (MO) was studied using a microbial consortium. The microbial growth of Sphingomonas paucimobilis, Bacillus cereus ATCC14579, Bacillus cereus ATCC11778 is well in the presence of MO (750 ppm) within 48 h at pH 7 and 30 °C. In fact, these microorganisms were able to decolorize and to degrade MO to 92%. The degradation pathway and the metabolic products formed during the degradation were also predicted using UV–vis, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy analysis. Under optimal conditions, the bacterial consortium was able to decolorize completely (>84%) the dye within 48 h. The color and COD removal were 84.83% and 92.22%, respectively. A significant increase in azoreductase, lignin peroxidase and laccase activities in the cells were obtained after complete decolorization. Phytotoxicity study using plants showed no toxicity of the produced products.