Immobilization of a Fungal Fructosyltransferase onto Silica Gel and Glutaraldehyde-Functionalized Silica Gel for Biocatalytic Applications

The immobilization of fructosyltransferase enzymes has been identified as an essential strategy for the production of fructooligosaccharides (FOS) in heterogeneous reaction systems. This study investigated the applicability of silica gel and silica gel functionalized with glutaraldehyde as porous inorganic supports for the immobilization of the extracellular fructosyltransferase from <i>Aspergillus oryzae</i> IPT-301, aiming to obtain active and stable heterogeneous biocatalysts for FOS production. The silicas were characterized using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and N₂ physisorption. The thermal, operational, storage, and pH stability, as well as the kinetic profiles of the biocatalysts, were evaluated. The functionalized silica gel achieved higher immobilization yield but exhibited lower recovered activity values compared to the silica gel without glutaraldehyde. The enzyme immobilized on both supports showed higher activity at initial substrate concentrations between 400 g L^-1 and 600 g L^-1 with different kinetic behaviors. The functionalized silica gel showed greater capacity for reuse over eight consecutive reaction cycles, also exhibiting higher thermal, storage and pH stability compared to the biocatalyst adsorbed onto the pure support. The results suggest a high potential for the application of glutaraldehyde-functionalized silica gel as a support for FTase immobilization for FOS production.