Optimization of medium for decolorization of Congo red by Enterobacter sp. SXCR using response surface methodology

Response surface methodology based central composite design (CCD) was employed to interpret the decolorization of sulfonated azo dye Congo red by newly isolated bacteria Enterobacter cloacae SXCR. The aim of this work was to evaluate the effect of various components of medium such as KH2PO4, Na2HPO4, NaCl, MgSO4, and trace elements on the dye decolorization. The effects of different sources of carbon and nitrogen sources were also considered for the better performance on the decolorization of Congo red. The influence of these factors on decolorization experiments were performed by newly isolated bacterial strain which was isolated from petroleum contaminates soil samples. However, the effects of salts, carbon, and nitrogen sources were investigated using classical methods while influence of interacting parameters like glucose, peptone, and beef extract on dye removal were examined using CCD. A second-order polynomial model successfully described the effect of independent variables on the dye removal. The value of the adjusted determinant coefficient (R-2 = 0.998) indicates a reasonably good model for practical implementation. Our results show the optimal concentration of KH2PO4 is 2.2 g/l, Na2HPO4 is 3.5 g/l, NaCl is 2 g/l, MgSO4 is 0.5 g/l, and trace elements is 0.01 g/l; glucose is 2 g/l, peptone is 3 g/l, and beef extract is 3 g/l were required for maximum decolorization (similar to 97%).