Peroxidases as a potential tool for the decolorization and removal of synthetic dyes from polluted water

Abstract

Environmental pollution by discharge of dye-containing effluents represents a serious ecological problem all over the world. Public demands for colour-free discharges to receiving waters have made decoloration of a variety of industrial wastewater a top priority. The current existing chemical, physical and biological techniques used for the removal of colored pollutants have several drawbacks such as high cost, low efficiency, use of large amounts of chemicals and formation of side toxic products. It has necessitated for the search of alternative procedures such as those based on oxidative enzymes. This approach is believed to be a promising technology since it is cost-effective, environmentally friendly, highly specific and does not produce sludge. Enzymatic transformation of synthetic dyes can be described as the conversion of dye molecules by enzymes into simpler and generally colorless products. Peroxidases have attracted much attention from researchers in last decades due to their ability to oxidize both phenolic and nonphenolic compounds as well as highly recalcitrant environmental pollutants, which makes them a very useful tool for the removal of colored pollutants from industrial effluents. Detailed characterization of the metabolites produced during enzymatic transformation of synthetic dyes as well as ecotoxicity studies is of great significance to examine the effectiveness of the biodegradation processes. However, most reports on the bio-treatment of dyes mainly deal with decoloration and there are few reports on the reduction in toxicity or on the identification of the biodegradation products. In this work an effort has been made to review the literature based on the applications of peroxidases for the removal of colored compounds from wastewater. Peroxidases immobilized on numerous supports have been used to treat dyes in batch as well as in continuous processes. The role of various redox mediators in peroxidase catalyzed dye decolorization has also been discussed in this chapter.