Production of Gos-Enriched Milk by Immobilization of Commercially Available Β-Galactosidase Enzymes on Chitosan Beads

Formation of galactooligosaccharides (GOS) was investigated in homogenized pasteurized milk using commercially available β-galactosidase enzymes (Saphera, Nola Fit) covalently immobilized on chitosan beads. The immobilization facilitated the improved thermal stability of the enzymes and enabled excellent operational stability. The immobilized enzymes were applied successfully to produce low-lactose or lactose-free milk even after 15 cycles of use. Moreover, the highest GOS content we reached by the enzymatic reactions was about 9% of total the sugar content of the milk, indicating the prebiotic effect of the treated milk having lactose concentration of 4.2 and 2.5 mg/ml for Nola Fit and Saphera, respectively. Nevertheless, the GOS concentration of milk was higher by using immobilized β-galactosidase during the whole hydrolysis process as compared to the free enzymes. These results revealed the implementation possibilities of GOS-enriched milk production in dairy industry with low lactose content by use of β-galactosidase immobilized on chitosan beads.