Abstract
Lipase A from Candida antarctica (CalA) and β-glucosidase from Thermotoga maritima (bgl) were covalently co-immobilized onto the surface of chitosan-coated magnetic nanoparticles (CS-MNPs). Several parameters regarding the co-immobilization procedure (glutaraldehyde concentration, incubation time, CS-MNPs to enzyme mass ratio and bgl to CalA mass ratio) were evaluated and optimized. The developed nanobiocatalyst was characterized by various spectroscopic techniques. Biochemical parameters such as kinetic constants and thermal stability were also evaluated. The nanobiocatalytic system revealed an increase in the Km constant followed by a decrease in Vmax value compared with the native enzymes, while a significant increase (>5-fold higher) of the thermal stability of the immobilized CalA, both in individual and in co-immobilized form, was observed after 24 h incubation at 60 °C. Finally, the nanobiocatalyst was efficiently applied for the bioconversion of oleuropein to hydroxytyrosol, one of the most powerful naturally derived antioxidants, and it could be recycled for up to 10 reaction cycles (240 h of constant operation) at 60 °C, retaining more than 50% of its initial activity.
Highlights
Various methods were applied for the characterization of the chitosan-coated magnetic nanoparticles, such as X-ray diffraction (XRD) and atomic force microscopy (AFM)
The successful preparation of the CS-MNPs was evidenced with XRD, while their structural and morphological characterization was revealed by Atomic force microscopy (AFM)
The structure and the morphology of the prepared Fe3 O4 chitosan nanoparticles was revealed by atomic force microscopy (AFM)
Summary
Its chemical structure consists of an ester bond between a molecule of elenolic acid (EA) and. OLE is characterized by various biological activities, such as antimicrobial, antioxidant, anti-inflammatory and anticancer. It is a well-known compound for its cardioprotective, neuroprotective and hypolipidemic activities, which establish OLE a potentially natural additive for cosmetics and medicine [3]. HT, the main degradation product of OLE, is considered one of the most powerful naturally derived antioxidants, exhibiting a plethora of biological activities, usually superior to OLE [4]. Oleuropein aglycone has been reported to exhibit many activities similar to those of oleuropein [5], while the secoiridoid, elenolic acid, has been recognized as an antiviral agent [6,7]. Contents of HT are low in natural sources, and many challenges are revealed in its chemical synthesis, including the low final yield and the large number of toxic reagents and expensive catalysts required
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