Size-Tailored Nanospaces in Hierarchical Magnetic Core-Shell Microspheres for Lipase Immobilization and Phytosterol Ester Synthesis.

A size-matched magnetic core-shell platform (Fe3O4@MnO2@mSiO2) was constructed for immobilizing Candida rugosa lipase (CRL). The flower-like MnO2 interlayer provides chemical shielding, while mesoporous channels were expanded to 6.45 nm to geometrically match CRL (approximately 5 nm). Driven by interfacial activation, the support exhibited a selective purification effect, achieving a high activity-based immobilization yield (85.2%) and protein loading (143.1 mg g-1). The immobilized specific activity reached 31.4 U mg-1 (1.57-fold higher than the free enzyme) with 88.2% recovered activity. Crucially, in the sterically demanding esterification of phytosterols, the biocatalyst achieved 84.33% maximum conversion at 50 °C within 40 h. Furthermore, the rigid silica walls exerted a spatial "cage effect" that locked the enzyme active conformation, conferring exceptional thermal stability and reusability. This hierarchical support design offers a robust solution for macromolecular industrial biocatalysis.