Synthesis of fibrous and non-fibrous mesoporous silica magnetic yolk–shell microspheres as recyclable supports for immobilization of Candida rugosa lipase

The mesoporous yolk–shell nanoparticles (MYSNs), with a movable Fe₃O₄ core inside the hollow capsules, with two different morphologies (1) Fe₃O₄@SiO₂@hollow@fibrous SiO₂ (Yolk Shell-1) (2) Fe₃O₄@SiO₂@hollow@mesoporousSiO₂ (Yolk Shell-2) were fabricated as carriers for Candida rugosa lipase (CRL) immobilization, through a template-assistant selectively etching method. Firstly the hydrophilic Fe₃O₄ nanoparticles were synthesized according to the solvothermal method. Then, SiO₂ shell was coated on the Fe₃O₄ nanoparticle surface by a sol–gel reaction. Subsequently, the resorcinol farmaldehyde (RF) shell was covered on the surface of as-prepared Fe₃O₄@SiO₂ composites and sandwiched Fe₃O₄@SiO₂@RF composites were formed, which were finally provided with mesoporous fibrous (KCC) in the Yolk Shell-1 and mesoporous Silica in the Yolk Shell-2(Non fibrous). After selectively etching CTAB and the middle RF layer, the two kinds of yolk/shells composites were obtained. By utilization of their large and open mesopores (20–50 nm) with good surface area (457.78–625.54 m²/g,) CRL was immobilized after amino functionalization using glutaraldehyde as a linker. The ICRL on Y.S-1, Y.S-2 showed good loading (797–501 mg/g) and enzyme activity of (1503–837 U/g) respectively. Thermal stability, resistance to pH, recycling and storage capacity were improved as compare to free lipase.