Optimization of internal conditions for biocatalytic dye color removal and a comparison of redox mediator's efficiency on partially purified Trichosanthes dioica peroxidase

The decolorization proficiency of partially purified Trichosanthes dioica peroxidase was examined for the degradation/decolorization of textile, non-textile dyes and dye mixtures. Internal conditions of pH, temperature, time intervals and enzyme concentration with selected redox mediator was optimized to obtain a cost effective decolorization setup for recalcitrant dyes.Among the tested redox mediators, 1-hydroxybenzotriazole (HOBT) acted as a better electron transfer agent by contrast to vanillin for both textile and non-textile dyes. Maximum decolorization for reactive and disperse dyes was achieved with optimum conditions of 0.45 EU/ml, 1.0 mM HOBT, pH 5.0, 50 °C, 2 h and 0.20 EU/ml, 0.2 mM HOBT, pH 4.0, 40 °C, 1 h, respectively. The dye color change was related to its structure and consequently reduction/oxidation mediated by HOBT. To study the performance of biocatalysis in a redox mediated heterogeneous system, dye mixtures simulating industrial effluents were used which exhibited more than 82% decolorization with 1-hydroxybenzotriazole.Result indicates the use of inexpensive peroxidase from easily available natural resources in overcoming the limitations in current wastewater treatment strategies. Such heterogeneous biocatalytic system can be extended on to large-scale treatment of wide spectrum of structurally complicated dyes by using immobilized peroxidases along with relatively cheaper redox mediators. A comparison of the efficiency with other redox mediators has also been discussed.

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► 1-Hydroxybenzotriazole (HOBT) acted as a better electron transferor than vanillin for both textile and non-textile dyes.
► Optimum parameter for reactive dyes was 0.45 EU/ml, 1.0 mM HOBT, pH 5.0, 50 °C, 2 h.
► Disperse dyes decolorized maximally at 0.20 EU/ml, 0.2 mM HOBT, pH 4.0, 40 °C, 1 h.
► Synthetic dye mixtures decolorized up to 82%.
► Redox mediated dye decolorization is related to the dye molecular structure.