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Preparation of the Immobilized Lactase and Its Application

Author: YuHongFeng
Tutor: SunZhiHao
School: Jiangnan University
Course: Fermentation Engineering
Keywords: Lactase Immobilized Low-lactose milk Galactooligosaccharide Packed bed reactor
CLC: TS241
Type: Master's thesis
Year: 2006
Downloads: 476
Quote: 3
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Abstract


Lactose lactase can catalyze the hydrolysis reaction and the transglycosylation reaction. Low concentration, hydrolysis of lactose to glucose and galactose; high concentration occurs transglycosylation reaction galactooligosaccharides. In Therefore, lactase can be used for the preparation of low-lactose milk and galactooligosaccharide. Low-lactose milk, meet lactose intolerant dairy consumer demand, and promote the development of China's dairy industry is significant the; galactooligosaccharide is a new food additive, has good physical health functions, a vast market. Compared to the free enzyme, immobilized enzyme the enzyme is enclosed within a certain space, to achieve a catalyst recovery and repeated use. The immobilized enzyme is very beneficial in many aspects of the conservation of energy resources, reduce costs, protect the environment, production automation, continuous. This paper focuses on a microbial extracellular lactase immobilized. Recombinant Pichia pastoris fermentation with the Chinese Academy of Agricultural Sciences microbial extracellular lactase the adsorption - embedding - a combination of cross-linking methods immobilized, repeated use of lactase, and the immobilization process optimization. Found that after the comparison the properties of the immobilized enzyme and free enzyme after immobilization, lactase nature occurs a large variation: immobilized lactase optimum temperature significantly lower than that of free lactase, the free lactase optimum temperature 65 ℃, while immobilized later reduced to 35 ° C; immobilized optimum pH change is small, compared to the slightly acidic optimum pH 2.5 (free lactase optimum pH 3.5), maintained in the range of pH 2.5-6 more than 80% of the relative activity (free enzyme within the range of pH 3-6 to maintain more than 80% relative activity); compared with the free enzyme after the immobilization, there are significant changes in the kinetic constants, and Vmax the unique KM were 0.714 mol / L, 626.56μmol / min · mL and 0.267 mol / L, 666.67μmol / min · mL. Also studied the the immobilized lactase hydrolysis of 5% lactose solution, the operational stability of the preparation of low-lactose milk and galactooligosaccharides. 5% lactose solution as the substrate, the batch reaction, the immobilized enzyme reaction 52 consecutive batches, the lactose hydrolysis ratio is maintained at 75%; packed bed reactor, in 0.5 h -1 dilution rate, the immobilized enzyme continuous reaction of 62 days, the rate of hydrolysis of lactose maintained at 80%, operating a half-life of 136 days. Immobilized lactase hydrolyzed milk lactose preparation of low-lactose milk, the dilution rate control in 0.67 h -1 , lactose hydrolysis rate of 70%. Reaction for 30 consecutive days, the remaining lactose content is always lower than 15 g / L, a dilution rate of 0.67 h -1 . Galactooligosaccharide prepared with immobilized lactase hydrolysis of lactose solution. Batch reactor conditions to optimize the best conditions for the temperature of 35 ° C, pH 6.5-7.0, lactose concentration of 40%. Galactooligosaccharides maximum concentration reached 160 g / L. The immobilized enzyme reaction 7 consecutive batch still has good stability. The packed bed reactor, the dilution rate of the formation of galactooligosaccharides. Dilution rate of 0.5 h -1 , galactooligosaccharide generation of 148 g / L; dilution rate 0.78 -1 , galactooligosaccharide production strength reached a maximum of 87.11 g / L · h. Dilution rate of 0.5 h -1 to react for 20 consecutive days, the yield of galactooligosaccharide an average of 32.20%. The use of activated carbon adsorption - ethanol eluted method to extract galactooligosaccharide. The resulting sample, the content of more than 90% of the galactooligosaccharide. The entire extraction process, galactooligosaccharides almost no loss.

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