Biodegradation of Synthetic Dyes—A Review

Abstract

The contamination of soils and waters by dye-containing effluents is of environmental concern. Due to the increasing awareness and concern of the global community over the discharge of synthetic dyes into the environment and their persistence there, much attention has been focused on the remediation of these pollutants. Among the current pollution control technologies, biodegradation of synthetic dyes by different microbes is emerging as an effective and promising approach. The bioremediation potentials of many microbes for synthetic dyes have been demonstrated and those of others to be explored in future. The biodegradation of synthetic dyes is an economic, effective, biofriendly, and environmentally benign process. Bioremediation of xenobiotics including synthetic dyes by different microbes will hopefully prove a green solution to the problem of environmental soil and water pollution in future. This review paper discusses comprehensively the science and arts of biodegradation of synthetic dyes.

Destruction of azo dyes by anaerobic–aerobic sequential biological treatment: a review

“…High dye concentration may adversely affect the microbial growth and decrease the efficiency of microbial dye degradation process. Increasing dye concentration gradually decreases the decolourization rate, probably due to the toxic effects of dyes with regard to the individual bacteria and/or inadequate biomass concentration, as well as the blockage of active sites of azoreductase by dye molecules (Ali 2010). Similar results are also reported for a mixture of azo dyes (Talarposhti et al 2001).…”

“…Table 3 lists several reactor studies providing evidence for the formation of aromatic amines under anaerobic condition, the method of detection, and the fate of aromatic amines during aerobic biodegradation. Aromatic amines formed from azo dye reduction have been reported to be resistant to anaerobic biodegradation and partially or completely biodegradable under aerobic conditions (Libra et al 2004;Sponza and Isik 2005;Koupaie et al 2011;Supaka et al 2004;Ali 2010;Shaw et al 2002). The decrease or disappearance of the peaks or shifting towards the lower retention time in the HPLC chromatograms, the decrease or disappearance of aromatic amines as detected by diazotization method, as well as the decrease in UV absorbance; all indicate removal of aromatic amines (Solis et al 2012).…”

“…Biodegradation is a preferred process in which the azo dye structure is destroyed resulting in generation of aromatic amines and sometimes achieves complete mineralization, i.e. conversion into CO 2 , H 2 O, and some inorganic salts (Ali 2010). A huge variety of micro-organisms, such as, bacteria, fungi, yeasts, and algae, are capable of decolourizing different dyes.…”

“…Azo dyes are characterized by the presence of one or more azo bonds (R1-N=N-R2) connecting aromatic rings. Different substitutions on aromatic nucleus give structurally diverse and most versatile group of compounds which makes them recalcitrant and xenobiotic (Ali 2010). These complex aromatic substituted structures make conjugated system and are responsible for intense colour, high water solubility, and resistance to degradation of azo dyes under natural conditions (Khan et al 2013;Senthikumar et al 2012).…”

Microbial Decolorization of an Azo Dye Reactive Black 5 Using White-Rot Fungus Pleurotus eryngii F032

“…removal of synthetic dye containing wastewater (Ali 2010). There are two important mechanisms for treatment of dye by white-rot fungi which are by biosorption of dye to the fungal biomass and biodegradation of dye into another compound by extracellular enzyme (Banat et al 1996).…”