In this work a-amylase was immobilized on magnetic Fe3O4 nanoparticles with polyethylenimine (PEI)/ polydopamine (PDA) coating or 3-aminopropyl triethoxysilane (APTES) for the first time via adsorption-precipitation-cross-linking. Compared with the free a-amylase, the resultant magnetic cross-linked a-amylase aggregates (PEI/PDA-M-CLEAs and N-M-CLEAs) exhibited excellent thermal and storage stability as well as pH stability. After storage at 25 C-degrees for 60 days, free a-amylase only retained 60% of its initial activity, while PEI/PDA-M-CLEAs and N-M-CLEAs retained 80% and 78% of their initial activities, respectively. Furthermore, N-M-CLEAs and PEI/PDA-M-CLEAs showed good reusability. After 6 repeated uses, PEI/PDA-M-CLEAs and N-M-CLEAs still maintained 65% and 62% of their initial activities, respec-tively. Especially, PEI/PDA-M-CLEAs and N-M-CLEAs exhibited higher starch hydrolysis efficiency than free a-amylase. The maximum dextrose equivalent (DE) values of starch hydrolysis by PEI/PDA-M-CLEAs and N-M-CLEAs reached 29.24% and 28.79% within 90 min, respectively. However, the maximum DE values of starch hydrolysis by the free a-amylase was only 27.89% even in 150 min. The magnetic cross-linked a-amylase aggregates could be introduced as effective biocatalyst for industrial applications in production of maltose syrups. (c) 2023 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Recent years, biobased polymer packaging film in food packaging has witnessed great developments. However, it is still a challenge to develop biodegradable packaging films with antimicrobial property and mechanical strength. Herein, agar and polyvinyl alcohol (PVA)/Chitosan (CS) packaging films with e-polylysine/ZIF-L nanocomposites (epsilon-PL@ZIF-L) were developed for the first time. Due to the incorporation of the nanocomposite, UV/visible light barrier properties (the transmittance decreased by 10.9%) of the films were improved, and the elongation at break of the composite agar films were increased by 43.0%. In the antimicrobial assays, with 4% epsilon-PL@ZIF-L, the inhibition zone diameters against Bacillus subtilis were 10 times as compared with the pure PVA/ CS film. Furthermore, compared with commercial PE film, agar films and PVA/CS films with 4% epsilon-PL@ZIF-L nanocomposites could provide long-term protection for strawberry to avoid the microbial infection and prolong the shelf life of the fruit at 25 ?. The results suggested that the agar and PVA/CS packaging films with v-PL@ZIF-L nanocomposites could significantly behave as potent antibacterial material in food packaging and preservation systems.

金属有机骨架(MOFs)是由有机配体和金属离子或团簇通过配位键自组装形成的具有分子内孔隙的有机无机杂化材料,由于其比表面积大和化学稳定性、可调控的孔隙以及多样性被越来越多地用于生物分子的装载尤其是酶的固定化领域.本文综述了近年来国内外制备MOFs以及MOFs基的复合材料固定化酶的制备方法、改进策略和应用,并对MOFs基固定化酶的未来研究方向进行了展望,以期为其后续研究和应用提供参考.