Construction of enzyme immobilization system through metal-polyphenol assisted Fe3O4/chitosan hybrid microcapsules

Metal-polyphenol film consolidated Fe3O4/chitosan hybrid microcapsules (MPP–Fe3O4/CS) were developed based on Fe3O4/chitosan (Fe3O4/CS) aggregation and tannic acid–FeIII (TA–FeIII) coating. Specifically, citrate modified Fe3O4 nanoparticles were adsorbed onto enzyme-encapsulated chitosan–citrate (CS–citrate) microaggregates via ion exchange. After continuous stirring, the citrate moieties in the internal part of CS–citrate microaggregates were released to the bulk solutions and caused the disassembly of CS–citrate microaggregates, thus generating the enzyme-encapsulated capsule lumen. To further obtain an intact and robust structure, metal-polyphenol (TA–FeIII) was utilized to form adhesive coatings on the surface of Fe3O4/CS microcapsules. The microcapsule preparation process can be completed within 40 min. The candida rugosa lipase (CRL), was used as the target enzyme to be encapsulated in the microcapsules. After studying the properties of immobilized CRL such as activity, kinetic behaviors, stability and reusability, it was proved that TA–FeIII consolidated Fe3O4/CS microcapsules exhibited more excellent properties than Fe3O4/CS microcapsules only. Moreover, the magnetic microcapsules can be easily recycled by an extra magnetic field for the next use due to the high saturation magnetization values. The convenient operation process kept the enzyme activity as high as 70% and 77.8% for Fe3O4/CS and MPP–Fe3O4/CS after 12 times reuse respectively. Hopefully, the feasible, rapid and low cost assembly process may ensure the wide application in bio-catalysis of the hybrid microcapsules.