Immobilization of laccase on organic-inorganic nanocomposites and its application in the removal of phenolic pollutants

Polydopamine-functionalized nanosilica was synthesized using an inexpensive and easily obtainable raw material, mild reaction conditions, and simple operation. Subsequently, a flexible spacer arm was introduced by using dialdehyde starch as a cross-linking agent to bind with laccase. A high loading amount (77.8 mg·g⁻¹) and activity retention (75.5%) could be achieved under the optimum immobilization conditions. Thermodynamic parameters showed that the immobilized laccase had a lower thermal deactivation rate constant and longer half-life. The enhancement of thermodynamic parameters indicated that the immobilized laccase had better thermal stability than free laccase. The residual activity of immobilized laccase remained at about 50.0% after 30 days, which was 4.0 times that of free laccase. Immobilized laccase demonstrated excellent removal of phenolic pollutants (2,4-dichlorophenol, bisphenol A, phenol, and 4-chlorophenol) and perfect reusability with 70% removal efficiency retention for 2,4-dichlorophenol after seven cycles. These results suggested that immobilized laccase possessed great reusability, improved thermal stability, and excellent storage stability. Organic-inorganic nanomaterials have a good application prospect for laccase immobilization, and the immobilized laccase of this work may provide a practical application for the removal of phenolic pollutants. [Figure not available: see fulltext.].