Immobilization of β-galactosidase within sponge: Hydrolysis of lactose in milk

Lactose can cause health problems in patients with lactose intolerance. β-Galactosidase is commonly used to catalyze the hydrolysis of lactose, thereby producing low-lactose or lactose-free products. However, most existing methods employ free enzymes, which significantly increases the economic cost. In this study, the polyurethane sponge (PUS) was selected as the carrier, and the cross-linked enzyme aggregates (CLEAs) were loaded onto the carrier after the sponge was modified. The reaction products were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier infrared transform spectroscopy, and simultaneous thermal analysis, respectively. The loading amount of β-galactosidase under the optimal conditions was 63 U/g support . The prepared PUS@β-galactosidase-CLEAs was successfully used for the hydrolysis of lactose in milk and could hydrolyze 228–304 μg of lactose in 30 min with good stability (RSD = 4.4%) and reusability. The method proposed in this study effectively combined the advantages of sponge and cross-linking enzyme aggregates, successfully achieving the decomposition of lactose in milk and rapid separation of the product. It is worth mentioning that this study provided a more effective and convenient industrial option for the production of lactose-free milk. • The developed feasibility of CLEAs modified permeable sponge was studied. • The prepared composite can be separated from the reaction system conveniently. • The prepared composite can be used to produce lactose-free milk efficiently.