Potential of immobilized bitter gourd ( Momordica charantia) peroxidases in the decolorization and removal of textile dyes from polluted wastewater and dyeing effluent

Abstract

Immobilized peroxidases from Momordica charantia were highly effective in decolorizing reactive textile dyes compared to its soluble counterpart. Dye solutions, 50–200 mg/l, were treated with soluble and immobilized bitter gourd peroxidases (specific activity of 99.0 EU per mg protein). The decolorization of dyes with soluble and immobilized enzyme was maximum in the range of pH 3.0–4.0. The effect of different temperatures on the dye decolorization was monitored and it was observed that all the dyes were maximally decolorized at 40 °C. In order to examine the operational stability of the immobilized preparation, the enzyme was repeatedly exploited for the decolorization of the dyes from fresh batch of dye solutions. Even after 10 cycles in each case the immobilized preparation retained nearly 50% of the initial enzyme activity. The immobilized enzyme exhibited more than 90% of the original activity while the soluble enzyme lost 33% of the initial activity when stored for 40 d at room temperature. Mixtures of three, four and eight dyes were prepared and treated with soluble and immobilized bitter gourd peroxidase. Each mixture was decolorized by more than 80% when treated with immobilized enzyme. Dyeing effluent collected from local dyers was treated with both types of enzyme preparations. Immobilized enzyme was capable of removing remarkably high concentration of color from the effluent. TOC content of soluble and immobilized enzyme treated individual dyes, mixture of dyes and dyeing effluent was determined and it was observed that higher TOC was removed after treatment with immobilized enzyme.