Immobilization of fungal laccase on glutaraldehyde cross-linked chitosan beads and its bio-catalytic potential to degrade bisphenol A

Bisphenol A is an endocrine disrupting compound that is continuously released into the environment. In this study, a laccase from Trametes versicolor was covalently immobilized onto high quality chitosan beads as carrier support chemically cross-linked with glutaraldehyde. Chitosan beads (average 2.0 mm diameter) developed using 2.5% (w/v) chitosan and functionalized with 2.0% (v/v) glutaraldehyde for 3 h yielded maximum immobilization efficiency (similar to 84.7%). The surface topology of laccase-attached chitosan support was envisaged and compared with control beads by scanning electron microscope (SEM). The immobilized biocatalyst showed good operational stability, retaining 71.24% of its original activity after 10 repeated catalytic cycles with reference to its native form. Storage stability profile exhibited the superiority of the laccase-immobilized chitosan beads presenting over 90% of activity after preserving for 28 days at 4 degrees C, whereas free enzyme showed only 47.3% activity under the same conditions. In addition, the chitosan-based biocatalytic system achieved almost complete removal of bisphenol A from the aqueous solution after 150 min of the transformation process. Conclusively, these results proposed the use of the chitosan hydrogel beads immobilized laccase as a promising and environmentally friendly biocatalyst for the degradation of environmental pollutants, particularly the removal of phenolic compounds in wastewater.