Reactive blue 19 decolouration by laccase immobilized on silica beads

Laccase (31.5 U of activity/g or 4.39 mu g of protein/m(2)) from Trametes versicolor was immobilized on controlled-porosity-carrier silica beads and evaluated for the decolouration of Reactive blue 19, an anthraquinone dye. Although there was an initial, rapid adsorption of the dye to the packed bed in a recirculating reactor, about 97.5% of Reactive blue 19 removal was due to enzymatic degradation. The free enzyme lost 52% of its activity in 48 h. However, the activity of the immobilized laccase was unchanged after 4 months of storage in phosphate buffer under ambient conditions followed by three successive decolourations over 120 h. Treating the laccase immobilized beads with ethanolamine reduced dye adsorption by 40%.