Cross-linked α-amylase aggregates on Fe3O4 magnetic nanoparticles modified with polydopamine/polyethyleneimine for efficient hydrolysis of starch

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.