A novel approach to develop β-galactosidase entrapped in liposomes in order to prevent an immediate hydrolysis of lactose in milk

A fractional factorial screening design and a response surface methodology were applied to optimize the entrapment of β-galactosidase in liposomes by dehydration-rehydration vesicle method. The effect of lipid (phosphatidylcholine and cholesterol), enzyme concentration, buffer pH, type and time of sonication, and sucrose concentration were the parameters selected for this study. The cholesterol:phosphatidylcholine (Ch:PC) ratio was the most important factor followed by type of sonicator and enzyme:lipid (E:L) ratio. The buffer pH, sucrose concentration and sonication time did not play an important role in the response. Two of the factors (Ch:PC and E:L ratios) were further studied in a 32 central composite design. The optimized liposomal formulation with an entrapment efficiency of 28% was obtained with Ch:PC and E:L ratios of 0.53 and 13.76, respectively, at pH 6 and employing a probe type sonicator.