Response Surface Methodology for Optimization of Enzyme-Catalyzed Azo Dye Decolorization

Abstract

Azo dyes are a water-pollution problem causing damage to ecosystems and human health. Soybean peroxidase–catalyzed reactions of azo dyes, Acid blue 113 (AB113) and Direct black 38 (DB38), were optimized for color removal using response surface methodology on a Box–Behnken design (BBD). Parameters optimized were H2O2 concentration (mM), pH, and enzyme concentration (U/mL; U is a standard unit of catalytic activity). Optimum conditions for AB113 were pH 4.49, 2.57 mM H2O2, and 1.52 U/mL of enzyme for a predicted 5.6% color remaining (experimental value of 8.1%) and R2 value of 99.68%; and for DB38 the conditions were pH 3.68, 2.92 mM H2O2, and 2.84 U/mL of enzyme for a predicted 3.6% color remaining (experimental value of 5.1%) and R2 value of 99.07%. In addition, the agreement with the one-factor-at-a-time approach was checked. The BBD is a less time-consuming approach that allows identification of interactions between parameters. Kinetic studies (Michaelis–Menten model) quantitatively confirmed the efficiency and effectiveness of enzymatic dye treatment.