Covalent immobilization of α-amylase on hollow metal organic framework coated magnetic phase-change microcapsules for the improvement of its thermostability

Exploring efficient immobilized carrier for α-Amylase (α-Amy) to enhance its thermostability has significant influence in starch related industry. Here, hollow ZIF-8 (HZIF-8) with amino groups coated magnetic phase change microcapsules (PCM) was designed for covalent immobilization of α-Amy. Magnetic PCM consisting n-docosane core and SiO₂/Fe₃O₄ hybrid shell were firstly synthesized. Then, HZIF-8 shell with amino groups was coated and α-Amy was subsequently immobilized through covalent cross-linking strategy. The morphology, chemical structure and magnetic property of PCM@HZIF-8@α-Amy (PCMHA) were comprehensively characterized. Moreover, heat control property of PCMHA was studied with encapsulation efficiency and thermal energy-storage efficiency of 50.55 % and 50.59 %, respectively. Catalytic activity of immobilized α-Amy was fully investigated with K_m and V_max of 2.773 mg/mL and 1.853 μmol/mL·min, respectively. From reusability and storage stability study, immobilized α-Amy not only maintained rather high activity after 9 cycles' reuse, but also exhibited good activity under high salt ion condition after 7 days.