Characterization Of "Fish-In-Net" Encapsulated Lactases In Macroporous Cages

Milk is a favorite natural drink, which contains various nutrient substances. But for 85% colored race, especially for Chinese,drinking milk and other milk products can cause dyspepsia, abdominal distention, borborygmus, diarrhea, emesis et al. It is called as'lactose intolerance'in medicine and caused by lack of quantity or activity of the human lactase.Currently,the best way to resolve'lactose intolerance'is to add some lactases during the milk production to provide a milk product of low lactose content, which is also called low-lactose milk. However, in production procedure there are still some problems to be solved as follows:(1) The enzyme in production can not be recycled, so the production cost is high.(2) Lactase is hard to separate from the reaction system, so it become a hybridprotein and influences the quality of the milk.(3) The optimum temperature of enzyme-catalyzed hydrolysis (35℃) can not be coincident with the production temperature (6℃) in which the activity of enzyme is only 10%. In order to keep equal activity, more enzyme or long reaction time should be employed.(4) The sterilization temperature is hard to control. Neither the higher nor lower temperature is good for quality of milk.In order to overcome the above disadvantages in enzyme-catalyzed reaction, the following strategies were designed in this paper: (1) Lactases from Aspergillus oryzae were immobilized by"Fish-In-Net"enzyme-immobilized method for recycle utilization to low the production cost.(2) Add Zn²⁺ to the molecular sieve skeletons of immobilized enzymes to improve the qualities of immobilized enzymes.In this paper, the basic characteristics were studied, such as immobilized efficiency,anti-bacterial effects, hydrolytic yield of lactose and recycle utilization effects. a Zn containing immobilized enzyme was attempted to synthesis by"Fish-in-Net"method, which is good at both anti-bacterial activity and recycle. The conclusions were drawn as follows:â‘ The immobilization efficiency of the'Fish-in-net'immobilization method was 64%.â‘¡The optimum reaction temperature of the immobilized enzyme was 55℃, and the optimum pH of it was 5.0～5.5, which was almost as the same as free enzyme.â‘¢After consecutive five reactions, the activity of immobilized enzyme remained 80%.â‘£The hydrolytic yield of five-hour reaction catalyzed by immobilized enzyme was as same as by free enzymes and is 80%, using lactose as substrate.⑤Using the milk as substrate, the hydrolytic yield of five-hour reaction catalyzed by immobilized enzyme was 50%, still as same as by free enzymes.â‘¥The anti-bacterial effect of Zn-containing immobilized-enzyme in milk was achieved to 90%.In all, Zn-containing immobilized-enzyme is good at both reaction activity and anti-bacterial, and can be used in recycle utilization for many times. The low lactose produced by this enzyme can significantly reduce the production cost and improve the production quality, and will be a break in low-lactose milk manufacture in future.