Fabrication of a core-shell-shell magnetic polymeric microsphere with excellent performance for separation and purification of bromelain

Bromelain is an important industrial proteolytic enzyme which has great commercial value and is of wide application in food, beverage, tenderization, cosmetic, textile and pharmaceutical industries. In this work, the core-shell- shell magnetic polymeric microspheres (Fe3O4@SiO2@P(NIPAM-co-AIM)/Ni2+) composed of an SiO2-coated Fe3O4 magnetite core and a Ni2+-immobilized cross-linked poly (N-isopropyl acrylamide-co-propylimidazole) (NIPAM-co-AIM) shell were synthesized via distillation-precipitation polymerization. The Ni2+ cations in the magnetic polymeric microspheres shell provided docking sites for histidine and the microspheres exhibited excellent performance in the separation of bromelain with a binding capacity as high as 198 mg/g, and the recovery of enzyme activity could achieve 80%. It was found that the microspheres showed excellent performance for separation and purification of bromelain from the crude extract of pineapple peel, moreover the enzyme structure remained unchanged before and after elution process.