Enhanced decolourization of the azo dye Sirius rose BB by laccase–HBT system

Response surface methodology (RSM) was applied to optimize the decolourization of the diazo dye Sirius rose BB (SR) by crude laccase from the white-rot fungus Trametes sp. strain CLBE55. A Box–Behnken design using RSM with six variables, namely pH, incubation temperature, enzyme (laccase) concentration, 1-hydroxybenzotriazol (HBT) concentration, dye concentration and incubation time was used in this study to determine significant correlations between the effects of these variables on the decolourization of Sirius rose. The optimum concentrations of HBT, dye and laccase were 0.5 mM, 60 mg/L and 0.1 U/mL, respectively, to obtain maximum decolourization of Sirius rose (approx. 99.5% in 150 min at 45 °C, pH 3). A quadratic model was obtained for dye decolourization using this design. Experimental values were in good agreement with values predicted by the model, giving highly significant correlations.