Decolorization of Cibacron Blue 3G-A Dye by Agaricus bisporus CU13 Laccase - Mediator System: A Statistical Study for Optimization via Response Surface Methodology

Abstract

Aim: the present study aims to optimize Cibacron Blue 3G-A decolorization as a model dye through laccase ‎enzymatic biocatalysis presenting the role of HBT as a redox mediator via ‎RSM approach.‎ Study Design: RSM using Central Composite Design (CCD) was used in order to determine the most effective variables levels in Cibacron Blue 3G-A decolorization and to investigate their interactions. Place and Duration of Study: Department of Microbial Chemistry, Genetic Engineering and Biotechnology Research Division, National Research Centre (NRC), Cairo, Egypt, between August 2017 and January 2018. Methodology: The evaluation of Cibacron Blue 3G-A decolorization by A. bisporus CU13 crude laccase was conducted through different trials using a 1.5 mL reaction mixture containing different concentration of crude laccase, Cibacron Blue 3G-A, and HBT in 0.1 M sodium citrate buffer (pH 4.5) at room temperature for different incubation periods. Results: Hydroxybenzotriazole (HBT) as a mediator enhanced Cibacron Blue 3G-A decolorization levels significantly, where decolorization percentage caused by laccase enzyme alone were ‎11.92 and ‎23.78%, ‎whereas that caused by laccase HBT mediator system under the same conditions were 43.43 and ‎76.34% after 1 and 22 h of incubation, respectively. HBT concentration, dye concentration, enzyme activity, and incubation time were chosen as study variables to optimize Cibacron Blue 3G-A dye decolorization through RSM approach via central composite design (CCD). The optimum conditions for Cibacron Blue 3G-A decolorization were found to be under using 0.50 U/mL of Agaricus bisporus CU13 laccase, 92.19 ppm of Cibacron Blue 3G-A, and 1 mM of HBT in order to get decolorization percentage of 29.29% in 35 min. Conclusion: Agaricus bisporus CU13 crude laccase was used as a biocatalyst to decolorize Cibacron Blue 3G-A in presence of HBT as a mediator through utilizing the response surface methodology approach. HBT concentration, dye concentration, enzyme activity, ‎and incubation time affects the decolorization levels considerably.