LAUSR

Abstract We develop a new type of shallow porous microsphere carriers with core-shell structure by using glass beads as cores, chitosan as coating layer, glutaraldehyde as cross-linking agent and stearic acid powder as porogen. The characterization of FT-IR, SEM, XRD, TGA-DSC and XPS demonstrates that the modification in each step is feasible and chitosan forms a uniformly coated graft layer on the surface, accounting for 40 % of the total weight. Then, this study focuses on immobilization of inulinase on the shallow porous microsphere carriers. The optimal conditions for immobilization are: pH value is 5.0; cross-linking time is 2.5 h; the molar ratio of free enzyme, glutaraldehyde and carrier amino group is 5.0 × 10−3:0.3:1. Among them, pH value has the most significant influence on the reaction process. The prepared immobilized inulinase preserves 73 % activity of free inulinase, and the suitable ranges of pH and temperature widen. Thermal stability experiments are operated at 70 °C for 3 h, when immobilized inulinase still maintains 69.20 % of initial activities whereas free inulinase only maintains 33.79 %. The immobilized inulinase still maintains 77.93 % of initial activities after 10 reuses, and its calculated half-life is 22 times, demonstrating developmental potential in industrial application.