β-Cyclodextrin and APTES functionalized magnetic iron oxide nanoparticles for improved lipase immobilization, transesterification efficiency, and reusability

This study focuses on the immobilization of Rhizopus oryzae lipase (ROL) on magnetic iron oxide nanoparticles (MNPs) through physical adsorption, taking advantage of the magnetic properties of the nanoparticles for easy separation. Different types of nano-biocatalysts were prepared by immobilizing the lipase enzyme on bare iron nanoparticles (Fe3O4), APTES-functionalized iron nanoparticles (Fe3O4-APTES), and (3-cyclodextrin-functionalized iron nanoparticles (Fe3O4-APTES-GA-(3_CD). These nano-biocatalysts were employed in the transesterification process. The synthesis of Fe3O4 nanoparticles was achieved using the coprecipitation method, and the structural, magnetic, and morphological properties of the iron nanoparticles (MNPs) were characterized through FTIR, XRD, VSM, SEM, and TEM analyses. The presence of strong physical bonds, resulting from hydrophilic and hydrophobic adsorption between (3-cyclodextrin and the enzyme, led to an increased loading amount from 27.37% to 44.89%. The nano-biocatalysts exhibited enhanced thermal and storage stability compared to free lipase. In transesterification reactions, ROL/Fe3O4-APTES-GA-(3_CD exhibited the highest conversion percentage of 64.3% among the functionalized enzymes. Furthermore, the reusability study demonstrated that ROL/Fe3O4-APTES-GA-(3_CD retained 40.9% of the initial conversion percentage after five cycles, displaying the highest reusability among all nano-biocatalysts in this study.