【作者】 赵毅；

【导师】 李正强；

【作者基本信息】 吉林大学 ， 生物化学与分子生物学， 2007， 硕士

【摘要】 牛乳是一种营养丰富的天然饮品,但很多人在食用牛乳后会出现“乳糖不耐症”。目前,解决“乳糖不耐症”的最佳方法是通过乳糖酶催化反应制备出低乳糖牛乳,但现行生产工艺仍然存在着自由乳糖酶不能重复利用,生产成本高;高温杀菌时牛乳易发生“美拉德”褐变等问题。为此,我们拟用“Fish-In-Net”固定化乳糖酶的重复利用性和含Zn分子筛的抗菌性来同时解决生产成本高、高温杀菌影响产品品相等问题。在本论文中,我们对“Fish-In-Net”固定化乳糖酶的包埋效率,基本酶学性质,重复利用率,乳糖水解率及含Zn分子筛(Zn-SBA-15)的抗菌性能进行了初步研究,并尝试制备了含Zn“Fish-In-Net”固定化乳糖酶。实验结果表明,①“Fish-In-Net”固定化乳糖酶的包埋效率为10.8%;②与自由乳糖酶相比,“Fish-In-Net”固定化乳糖酶的最适反应温度、最适pH值没有明显地改变,热稳定性有显著地提高;③两者的乳糖水解率(5h)基本相同;④固定化乳糖酶重复利用六次活力均在80%以上;⑤Zn-SBA-15在LB液体培养基和脱脂牛乳中的抗菌率分别为90%和50%(培养体系Zn含量为85.5μg/ml)。综上所述,将“Fish-In-Net”固定化乳糖酶和含Zn分子筛抗菌联合使用有望解决目前低乳糖牛乳生产过程中的问题,具有良好的产业应用前景。更多还原

【Abstract】 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:①The immobilization efficiency of the‘Fish-in-net’immobilization method was 64%.②The 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.③After consecutive five reactions, the activity of immobilized enzyme remained 80%.④The 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.⑥The 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.更多还原