Abstract

Background: The separation of enzymes from the bio-product medium constitutes a significant part of total process cost. Therefore, it is of crucial importance that the separation processes for enzymes be specially developed. In this study, the advantages of cross-linked enzyme aggregates (CLEAs) and magnetic iron oxide nanoparticles (MIONPs) have been combined in magnetic CLEAs matrix.

Methods: MIONPs were produced by co-precipitation methods. The synthesized MIONPs and CLEAs were characterized by scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), dynamic light scattering (DLS), phase analysis light scattering (PALS), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) analyses.

Results: Optimal pH and temperature values of magnetic and non-magnetic CLEAs have been determined to be pH=7.5 and T=45oC. It has been observed that there are differences in apparent KM and Vmax values of magnetic and non-magnetic biocatalysts. Moreover, the high activity of nonmagnetic CLEAs is a result of low α -helix and β -sheet contents. Compared with non-magnetic CLEAs, magnetic CLEAs showed high storage stability and good reusability. Due to the different the protein content, the weight loss of the non-magnetic and magnetic CLEAs determined by TGA was about 65% and 53%, respectively. From DSC analysis, the denaturation temperatures of nonmagnetic and magnetic CLEAs were 97±0.8oC and 108±0.8oC, respectively.

Conclusion: The present work provided important information on production, comparison and characterization of non-magnetic and magnetic CLEAs from Candida rugosa lipase (CRL) enzyme. The magnetic CLEAs had significant enhancement on the storage stability, thermal stability, reusability comparing with that of non-magnetic CLEAs. These improved properties of magnetic CLEAs could be an attractive feature towards more stable CLEAs preparation. The high cost of complex separation processes could be eliminated with magnetic CLEAs.

Keywords: Cross-linked enzyme aggregates, iron nanoparticles, magnetic biocatalyst, Candida rugosa lipase, secondary structure analysis.

Graphical Abstract