The optimization of reactive black 5 dye removal using Coprinus cinereus peroxidase (CIP)

Coprinus cinereus (NBRC 30628) peroxidase was implemented to eliminate the diazo dye of reactive black 5 (RB5). The optimization was conducted in batch mode using three approaches, i.e., the one-factor-at-a-time (OFAT), factorial design, and response surface methodology (RSM). Based on the results of the OFAT method, the optimum conditions for decolorization of RB5 dye were at a temperature of 30oC, a pH of 9-10, an H2O2 concentration of 3.9 mM, and an RB5 concentration of 40 mg/L. In the first stage of statistical optimization, these factors plus enzyme activity were screened by the 2-factorial design, wherein enzyme activity, temperature, and hydrogen peroxide concentration were distinguished as the most significant parameters in the enzymatic decolorization of RB5. In the second stage, RSM was applied over three adopted factors through the central composite design (CCD), and a reduced cubic polynomial model was generated, which indicated an accurate regression (R2 = 0.997, Adj.R2 = 0.994) and no significant lack of fit (p-value 0.05). The contour and surface plots suggested that the removal efficiency was enhanced by increased enzyme activity and decreased H2O2 concentration and temperature. The optimum condition was obtained at 1.0 mM H2O2, 6 U/mL enzyme activity, and 35°C for a maximum decolorization efficiency of 96.046%.