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.
ABSTRACT
The present study is vital to the understanding of bioremediation of structurally different azo dyes by some unusual Brown-rot fungi. Bioremoval of each dye (20 mg l-1) was tested in two different culture media under static and shaking conditions by taking inocula from different fungi. Fungal strains showed varying dyes removal abilities, though considerable high in case of Acid Red (AR) 151(di-azo) as compared to Orange (Or) II (mono-azo). With an exception of Aspergillus tereus SA3, all the fungal isolates showed higher removal of dyes in SDB. Under static condition, the maximum decolorizing fungal strains were; Aspergillus flavus SA2 (67 percent) and Alternaria spp. SA4 (57 percent) in AR 151, while Penicillium spp. (34 and 33 percent) in Orange II, in SDB and STE, respectively. Bioremoval of dyes was considerably increased when experiments were shifted from static to shaking mode. It was specifically increased ( percent) in; AR 151 (255) with Penicillium spp., Or II with A. flavus SA2 (112) and Alternaria spp. (111). The primary mechanism of dyes removal proved to be fungal biosorption. However, reduction of dyes (onto fungal) with formation of their products (α. naphthol, sulphalinic acid and aniline) furthermore revealed that dyes (specifically azo) were actually biodegraded.