Improved biodegradation of synthetic azo dye by horseradish peroxidase cross-linked on nano-composite support

•A novel ZnO nanowires/macroporous SiO2 composite support was used to immobilize horseradish peroxidase through in-situ cross-linking method using long-spaced epoxy cross-linker.•The formed nanobiocatalyst can provide many block-free channels for mass transfer and allow the cross-linked HRP to take a proper orientation for exposing of active site.•The positive-charged ZnO nanowires played an important role in promoting both the immobilization of HRP and the reaction between HRP and dyes.•Immobilized HRP exhibited satisfied efficiency in the decolorization of azo dyes.•The storage stability and reusability of HRP were greatly improved through the immobilization. A ZnO nanowires/macroporous SiO2 composite was used as support to immobilize horseradish peroxidase (HRP) by in-situ cross-linking method. Using diethylene glycol diglycidyl ether (DDE) as a long-chained cross-linker, it was adsorbed on the surface of ZnO nanowires before reaction with HRPs, the resulted composite was quite different from the traditional cross-linking enzyme aggregates (CLEAs) on both structure and catalytic performance. The immobilized HRP showed high activity in the decolorization of azo dyes. The effect of various conditions such as the loading amount of HRP, solution pH, temperature, contact time and concentration of dye were optimized on the decolorization. The decolorization percentage of Acid Blue 113 and Acid black 10 BX reached as high as 95.4% and 90.3%, respectively. The immobilized HRP gave the highest decolorization rate under dye concentration as 50mg/L and reaction time of 35min. The immobilized HRP exhibited much better resistance to temperature and pH inactivation than free HRP. The storage stability and reusability were greatly improved through the immobilization, from the decolorization of Acid blue 113 it was found that 80.4% of initial efficiency retained after incubation at 4°C for 60 days, and that 79.4% of decolorization efficiency retained after 12 cycles reuse.