Statistical analysis for enzymatic decolorization of acid orange 7 by Coprinus cinereus peroxidase

Enzymatic decolorization of the monoazo dye, acid orange 7 (AO7) by the fungal peroxidase from Coprinus cinereus NBRC 30628 is a complex system, which is greatly affected by temperature, pH, enzyme activity and the concentrations of H2O2 and dye concentration. The study of these factors and investigating the combined interactions between them by applying one-factor-at-a-time (OFAT) method and two other statistical methods including 2-factorial method and response surface methodology (RSM) were aimed in this work. Through OFAT analysis the optimized conditions were a temperature of 25 °C, pH 9.0 with H2O2 concentration of about 3.9 mM and AO7 concentration of 40 mg/l. A complete decolorization attained under such conditions in only 1 min. For statistical optimization, 2-factorial design method was applied first, and three factors of temperature, pH and initial dye concentration were recognized as significant factors. Then, response surface analysis was conducted through central composite design and a second-order polynomial model (R2 = 0.9718) was generated. ANOVA analysis of this model indicated that the temperature, pH and their interaction were the most significant in decolorization of AO7. The optimum condition through RSM was found to be the temperature of 25 °C, pH value of 9.0 and 50 mg/l of AO7 initial concentration, for the maximum decolorization of 100%.