Immobilization Of β-galactosidase And Study Of Producing Low-lactose Sheep's Milk By It

The purpose of this study was to prepare low-lactose milk by hydrolysis of lactose in sheep's milk withβ-galactosidase to solve the problem of lactose intolerant people who have difficulty in consuming milk and dairy products.Immobilization is a new technology developed in the sixties of the 20th century, it means that the enzyme is difficult to flow in water (That is to say the movement is limited) and can give play the role of catalysis, after dealt with by physics or chemical method. It provides easy recovery and reuse of enzyme and many other advantages, including ease in product separation and continuous operation. Another name is infusible enzyme. The most commonly used methods include covalent attachment, crosslinking, and adsorption. It has more technological advantage than dissociate enzyme. It is accepted by the people and applied for national economic construction of our country.There are many people in our country who are unable to completely digest lactose, due to the decreasing in intestinal lactase activity. To promote the production and consumption of milk, it is necessary to produce and popularize low lactose milk. The nutrition of sheep's milk is better than milk. Hydrolyzing lactose of sheep's milk with the lactase can solve the problem of lactose intolerance. At the same time, hydrolyzed sheep's milk has more advantages than common one, like tasted well and nutrition improved. So, hydrolyzing lactose of sheep's milk has great significance. The low-lactose sheep's milk has larger market.In this study, The enzyme was entrapped by align calcium alginate(sodium alginate 2%,CACl₂ 2%) , the chitosan(1%) could avoid leakage of immobilized enzyme, the operation is simple and the recovery of enzyme activity is high. For free enzyme, the optimal pH was 6.8, the optimal temperature was 39℃; For immobilized enzyme, the optimal pH was remain, the optimal temperature was increased 6℃. pH stability and thermostability improved greatly, the stock and operational stability was better。Both enzyme hydrolyzed lactose in sheep's milk, hydrolyzation rate of free enzyme was 74.5 % after one and half hour; hydrolyzation rate of immobilized one was 71.5 % after three hour. Since the immobilized enzyme was used twenty times, enzyme activity of it was only decreased 20%.