Azo and anthraquinone dye decolorization in relation to its molecular structure using soluble Trichosanthes dioica peroxidase supplemented with redox mediator

Abstract

In this study we investigated the decolorizing ability of Trichosanthes dioica -derived soluble peroxidase on structurally complex azo and anthraquinone dyes in the presence of redox mediators. Our results show that riboflavin acted as a better redox mediator than antraquinone-2, 6-disulfonate (AQDS). Riboflavin served as an efficient electron transferor than AQDS in the reduction of azo dyes, by contrast with anthraquinone dyes. Although the extent of decolorization (expressed as percent dye decolorization) varied from one dye to the other, maximum decolorization was achieved for the case when suspensions containing 0.45 EU (Enzyme Units)/ml and 0.2 mM riboflavin at pH 5.0 were incubated for 2 h at 40 °C. Redox mediator supplementation remarkably improved the decolorizing potential of T. dioica peroxidase. Azo dyes exhibited higher decolorization as compared to anthraquinone dyes in the presence of riboflavin. On the contrary, percent decolorization in the absence of redox mediators was inadequate and slow. Redox mediators studied herein facilitated decolorization of stable anthraquinone dyes. Therefore, the effect of redox mediators on T. dioica peroxidase-dye decolorization is affected by stability, thus the molecular structure. ► Riboflavin enhances decolorization of azo and anthraquinone dyes more than AQDS. ► Anthraquinone dyes decolorized at higher concentrations of redox mediators. ► Cleavage of chromophore for azo dyes is favorable as compared to anthraquinone. ► Redox mediated dye decolorization is related to the dye molecular structure.