The use of chemometnc 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 48h at pH 7 and 30 degrees 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 8483% 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 (C) 2010 Elsevier B V All rights reserved