Glutaraldehyde-crosslinked cells from Aspergillus oryzae IPT-301 for high transfructosylation activity: optimization of the immobilization variables, characterization and operational stability

Abstract

Cells of Aspergillus oryzae IPT-301 rich in fructosyltransferase (FTase) were successfully immobilized by crosslinking with glutaraldehyde and used for the transfructosylation reaction of sucrose. The glutaraldehyde concentration and pH used in the immobilization process were optimized for maximizing the transfructosylation activity (AT) and minimizing the hydrolytic activity (AH). Also, the operational stability and the influence of temperature, pH and sucrose concentration on the enzymatic activities of the free and crosslinked cells were evaluated. Both the maximum AT and minimum AH were obtained for cells immobilized with glutaraldehyde concentration of 2.1% (v/v) and pH 7.9. Crosslinked cells showed considerably higher AT/AH ratio than free cells at several temperatures, pH and sucrose concentrations in the reaction media. Kinetics data suggested that crosslinked cells present higher substrate-enzyme affinity and transfructosylation rate than free cells. Furthermore, after 12 batch reaction cycles the FTase present in the immobilized cell kept 88.9% of its initial AT, demonstrating a considerably higher operational stability than the FTase present in the free cell, which showed 50.3% of its initial AT. These results suggest the potential use of crosslinked cells of Aspergillus oryzae IPT-301 for the large-scale production of fructooligosaccharides (FOS).