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.