Stability and catalytic kinetics of microencapsulated β-galactosidase in liposomes prepared by the dehydration-rehydration method

Lipid vesicles prepared by the dehydration-rehydration method were used as carrier for the microencapsulation of β-galactosidase in order to permit the hydrolysis of the milk lactose following the lysis of liposomes in the presence of gastric fluid. Some characteristics of the liposomal and free β-galactosidase were compared. The kinetic behaviour of the enzyme was altered substantially in presence of lipid vesicles. The kinetic study indicated an decrease in both substrate affinity and maximum velocity when β-galactosidase was associated with phospholipid vesicles. Differences in the activity of free and liposomal β-galactosidase as a function of pH and temperature were found, although the optimum incubation temperature of free and entrapped enzymes remained similar. However, the optimum pH for liposomal enzyme was more acid than that for free enzyme. First-order kinetic analysis of thermal inactivation of enzymes showed that the activation energy with free enzyme was smaller than that with liposomal enzyme. In relation to the ΔH* and ΔS*, their values were greater than that those with free enzymes. These results confirm that β-galactosidase entrapped in liposomes showed superior thermal stability at all temperatures evaluated. Moreover, the proteolytic stability of the β-galactosidase was enhanced by encapsulation in liposomes.