Co-immobilization of laccase and ABTS onto novel dual-functionalized cellulose beads for highly improved biodegradation of indole.

The method developed in this work, for the first time, for the co-immobilization of mediator 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and laccase, in which the dual-functionalized cellulose beads with network pore structure were constructed by polydopamine (PD) and polymeric glycidyl methacrylate (GMA) to obtain the biocatalyst co-immobilizing ABTS and laccase. ABTS molecules were encapsulated into the dual-functionalized cellulose beads to obtain an efficient carrier (PD-GMA-Ce/ABTS) on which the laccase could be covalently immobilized by means of the coupling between the amino groups of the enzyme and the epoxy groups and ortho-dihydroxyphenyl groups existing on the beads. The as-prepared PD-GMA-Ce/ABTS with network pore structure were characterized by SEM, XRD, FT-IR and EPR. The resultant beaded biocatalyst (PD-GMA-Ce/ABTS@Lac) co-immobilizing laccase and ABTS were used in the biodegradation of indole and the degradation rate was up to 99.7%, while indole is difficult to be degraded by free laccase. The PD-GMA-Ce/ABTS@Lac beads displayed considerably reusability and storage stability for indole degradation after cycling of 10 runs or storage of 100 days benefited from the mediation effect of the immobilized ABTS. The effective recovery of both expensive laccase and hazardous ABTS by using PD-GMA-Ce/ABTS@Lac is promising to reduce the cost for the laccase application in wastewater treatment and might be helpful to eliminate the secondary pollution from the free mediator.