Enzyme Storage and Recycling: Nanoassemblies of α-Amylase and Xylanase Immobilized on Biomimetic Magnetic Nanoparticles

Immobilization of enzymes has been extensively required in a wide variety of industrial applications, as a way to ensure functionality and the potential of enzyme recycling after used. In particular, enzyme immobilization on magnetic nanoparticles (MNPs) could offer reusability by means of magnetic recovery and concentration, along with increased stability and robust activity of enzyme at different physicochemical conditions. In the present work, microbial α-amylase (AmyKS) and xylanase (XAn11) were both immobilized on different types of magnetic nanoparticles [MamC mediated biomimetic magnetic nanoparticles (BMNPs) and inorganic magnetic nanoparticles (MNPs)] by using two different strategies (electrostatic interaction and covalent bond). AmyKS immobilization was successful using electrostatic interaction with BMNPs. Instead the best strategy to immobilize XAn11 was using MNPs through the hetero-crosslinker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The immobilization protocols were optimized by varying glutaraldehyde (GA) concentration, enzyme quantity and reaction time. Under optimal conditions, 92% of AmyKS and 87% of XAn11 were immobilized on BMNPs and MNPs-E/N respectively (here referred as AmyKS-BMNPs and XAn11-MNPs nanoassemblies). The results show that the immobilization of the enzymes did not extensively alter their functionality and that increased enzyme stability compared to that of the free enzyme following upon storage at 4 °C and 20 °C. Interestingly, the immobilized amylase and xylanase were reused for 15 and 8 cycles respectively without significant loss of activity upon magnetic recovering of the nanoassemblies. Results suggest the great potential of these nanoassemblies in bio-industry applications.