Decolorization of the azo dye Acid Red 18 by crude manganese peroxidase: Effect of system parameters and kinetic study

To optimize operating conditions for the decolorization of the azo dye Acid Red 18 (AR18) by crude manganese peroxidase (MnP), some important factors affecting enzymatic decolorization were systematically investigated. Under the optimal enzyme reaction conditions, a decolorization efficiency of more than 82.3% was achieved after 60 min treatment. Furthermore, the manganese chelators, malate, tartrate, and lactate were found to be more favorable for the decolorization of AR18 than malonate, acetate, succinate, maleate, oxalate, and citrate. However, the presence of NaCl or Na2SO4 had a negative impact on the decolorization of AR18. The Km and Vmax values of MnP for AR18 were 169.66 μmol L− 1 and 20.63 μmol L− 1 min− 1, respectively. The decolorization of AR18 by MnP followed second-order reaction kinetics with respect to the dye concentration. The decolorization rate constant increased with increasing temperature from 20°C to 35°C, which indicated an activation energy (Ea) of 15.87 kcal mol− 1 and frequency factor (k0) of 1.36 × 108 mg− 1 L min− 1 according to the Arrhenius equation. The results obtained provide experimental data for the application of crude MnP for the decolorization of AR18, and help to elucidate the biochemical mechanism of dye decolorization by the enzyme.