Decolorization of Reactive Blue-19 textile dye by Boletus edulis laccase immobilized onto rice husks

Reactive Blue-19 is one of the most important synthetic dyes, which is used in the different industrial processes, especially for textile industry. Due to its fused aromatic structure, it is regarded as a toxic organic pollutant in wastewater. In the present study, the decolorization activity of Boletus edulis laccase immobilized onto rice husks for Reactive Blue-19 was examined. Boletus edulis, an edible mushroom, was used as a laccase source for the first time. Laccase was immobilized onto the rice husks which are inexpensive support having lignocellulose structure by using a simple method. The operating conditions of immobilized laccase were optimized for dye decolorization, and the decolorization activity of immobilized laccase was determined to be 91% for Reactive Blue-19 with initial concentration of 100 mg/L kept in 0.1 M of citrate phosphate buffer solution (pH 3.5) for 1 h at 25 °C. The decolorization of Reactive Blue-19 catalyzed by immobilized laccase was monitored by ultraviolet–visible spectroscopy analysis. The results of reusing studies showed that immobilized laccase retains approximately 50% of its initial decolorization activity after 9 cycles. Also, the effects of some auxiliary chemicals and metal ions found in textile wastewaters were investigated for decolorization process. In the reaction medium, containing 10 mM Fe2+ and 10 mM Tween 80, the decolorization activity decreased to 76% and 80.8%, respectively. The remarkable decolorization activity of immobilized laccase showed that it has a high potential for the treatment of textile wastewaters.