Removal of Synthetic Dyes from Wastewaters Using Horseradish Peroxidase

Abstract

Horseradish peroxidase is a heme-containing plant enzyme (HRP; EC 1.11.1.7) with a wide range of biotechnological and medical applications. In combination with hydrogen peroxide (H2O2) as an oxidant HRP can be used in the oxidation of various substrates (e.g. considered as toxic, muthagenic, recalcitrant and carcinogenic compounds with harmful impact on human health and ecosystems and main textile industry problem when it comes to environment pollution with wastewaters. Traditional methods are inefficient, and in recent years, with a view to preserving the environment, the scientific community turns to the application of enzymes as the main catalysts in the removal of synthetic dyes. Based on the data available in the literature, HRP proved to be an enzyme with a high potential for the application of synthetic dyes removal by the mechanism of polymerization or ring opening. In this chapter well-studied enzyme is described with the focus on its promising use in colored wastewater treatment. C. I. Acid Violet 109 (AV 109) was used as a model dye in order to examine the feasibility of HRP application in removal of anthraquinone class of synthetic dyes. The reaction conditions were optimized in terms of dye, enzyme and H2O2 concentration as well as temperature and pH influence. It was established that the dye removal shows good agreement with two substrate ping-pong mechanism with substrate inhibition. The industrial application of this enzyme requires the economic feasibility. Accordingly, an expensive commercial preparation HRP was replaced with partially purified enzyme isolated from horseradish root which showed high efficiency in model dye removal. The next step towards the industrial application of this enzyme was the immobilization of various techniques (adsorption, covalent immobilization, cross-linked aggregates) to various carriers such as kaolin and the synthetic carrier Purolite® A109. Improvement in storage and operational stability after immobilization was confirmed and immobilized preparations were applied in different bioreactor configurations, batch and packed bed. HRP catalyzed removal of synthetic dyes appeared to be promising technique dye to high efficiency in dye removal and phytotoxicity and acute toxicity decrease, measured by Mung bean seeds and A. salina assays.