Enzymatic decolorization and degradation of azo dyes – A review

The control of water pollution has become of increasing importance in recent years. The release of dyes into the environment constitutes only a small proportion of water pollution, but dyes are visible in small quantities due to their brilliance. Tightening government legislation is forcing textile industries to treat their waste effluent to an increasingly high standard. Currently, removal of dyes from effluents is by physio-chemical means. Such methods are often very costly and although the dyes are removed, accumulation of concentrated sludge creates a disposal problem. There is a need to find alternative treatments that are effective in removing dyes from large volumes of effluents and are low in cost, such as biological or combination systems. This article reviews the current available technologies and suggests an effective, cheaper alternative for dye removal and decolourisation applicable on large scale.

Laccases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) are blue multicopper oxidases that catalyze the oxidation of an array of aromatic substrates concomitantly with the reduction of molecular oxygen to water. In fungi, laccases carry out a variety of physiological roles during their life cycle. These enzymes are being increasingly evaluated for a variety of biotechnological applications due to their broad substrate range. In this review, the most recent studies on laccase structural features and catalytic mechanisms along with analyses of their expression are reported and examined with the aim of contributing to the discussion on their structure-function relationships. Attention has also been paid to the properties of enzymes endowed with unique characteristics and to fungal laccase multigene families and their organization.