Decolorization of reactive dyes by laccase immobilized in alginate/gelatin blent with PEG.

To achieve effective decolorization of reactive dyes, laccase immobilization was investigated. Laccase 0.2% (m/V) (Denilite IIS) was trapped in beads of alginate/gelatin blent with polyethylene glycol (PEG), and then the supporters were activated by cross-linking with glutaraldehyde. The results of repeated batch decolorization showed that gelatin and appropriate concentration of glutaraldehyde accelerated the decolorization of Reactive Red B-3BF (RRB); PEG had a positive effect on enzyme stability and led to an increase of color removal. While the beads contained 0.2%, 2.0%, 2.0%, and 0.5% (m/V) of laccase, alginate, gelatin, and PEG, respectively. The dye of 50 mg/L initial concentration of RRB was decolorized down to 50% during the tenth repeated batch. As far as the decolorization mechanism was concerned, the thermal and pH stabilities of the immobilized laccase were also investigated and were both appreciably improved. The study indicates that the immobilized laccase can be potential candidate for utilization in biodecolorization processes.