**1. Introduction**

The history of dyes began over 4000 years ago, and for many years, dyes were extracted from natural sources, such as flowers, vegetables, wood, insects, and roots, among others [1]. The synthetic dye industry began with the synthesis of mauveine, by researcher William Henry Perkin, in 1865. This dye, which until then was extracted from coal tar, was synthesized by Perkin while the researcher was looking for a new synthetic route for quinine, a drug used to treat malaria [2]. Perkin's discovery marked the creation of a new generation of dyes [3].

Synthetic dyes are organic compounds that are produced from raw materials of petrochemical origin. Such compounds may or may not be soluble in water, are generally easily absorbed, and quickly impart color to substrates [1]. Structurally, dyes

contain three essential groups: the chromophore, which is the active site of dyes where atoms interacting with visible electromagnetic radiation are located [2]; auxochrome, which has functional groups that introduce the chromophore, increase the fiber's affinity to color, and decrease its solubility in water [4] and conjugated aromatic structures, such as benzene, anthracene and perylene rings [2]. Dyes are classified according to their chemical structure and application mode. Thus, according to the chemical structure of the dye, this is classified into azo, anthraquinone, sulfur, phthalocyanine, and triarylmethane [2]. Depending on its method of application, the dye is classified as reactive, direct, dispersed, basic, and by vat dyeing [5].

The chemical composition of the dye reflects in its pigmentation (formation of its color), being also responsible for the lighter or darker tone of each dye. The coloring is due to the absorption of light of a certain wavelength in the visible range of the electromagnetic spectrum, that is, the dye is a molecule capable of absorbing certain light radiations and then reflecting the complementary colors [6]. **Table 1** brings together the main classes of dyes used in the textile industry, the types of fiber or substrates to which the dyes of each class are applied, the types of interaction between dye and fiber or substrate, and the methods of application or dyeing.

Dyes are materials of great importance in different industrial sectors, such as fabric production, papermaking, plastics, cosmetics, as well as in medicine and biology [8]. Currently, the world production of dyes is about 800 tons a year and most of the dyes produced, about 70 million tons a year, are used in the textile industry [1].

With high world production, the textile industry occupies the second place among the industrial sectors that most pollute since during the dyeing stage a large amount


#### **Table 1.**

*Main classes of dyes used in the textile industry, types of fiber to which the dyes of each class are applied, types of interaction between dye and fiber, and methods of application or dyeing [7].*

#### *Enzymatic Bioremediation of Dyes from Textile Industry Effluents DOI: http://dx.doi.org/10.5772/intechopen.103064*

of dyes is released into the environment due to the nonadhesion of the dye to the substrate to be dyed [2]. Therefore, the search for economically viable and ecologically sustainable alternatives for the treatment of effluents containing textile dyes is of extreme importance and interest, whereupon bioremediation is a process that can help to solve this industrial problem.

This chapter brings together the main and most recent information reported in the scientific literature on the enzymatic bioremediation of dyes from textile industry effluents. In this context, the negative impacts of dyes used in this industrial segment on human and animal health are discussed, as well as methods conventionally used for the treatment of industrial effluents containing dyes, the principles of enzymatic bioremediation, the enzymes used in this process, and their by-products.
