β半乳糖苷酶酶学性质及其在低聚半乳糖合成中的应用

摘要

The properties of β⁃galactosidase from Kluyveromyces lactis and the enzymatic synthesis of galactooligosaccharides ( GOS) were investigated. GOS ( degree of polymerization n>3) concentration was analyzed by high performance liquid chromatography ( HPLC ) and used as experimental index. The influences of temperature, pH, and the type and concentration of metal ions on β⁃galactosidase activity were evaluated. In addition,the effects of lactose concentration,reaction time and enzyme loading on the formed GOS concentration were optimized in the presence of K+. K+ and NH+4 could activate transglycosidase and β⁃galactosidase. However,Na+ could activate transglycosidase and inhibit hydrolase activity. Furthermore,the optimal conditions for enzymatic synthesis of GOS were determined as 37℃,pH 8,0�08 mol/L of K+,intial lactose concentration of 500 g/L,and the enzyme concentration of 10 μL/g lactose. Under these conditions,the maximum GOS concentration reached 94�74 g/L after 5 h.%研究乳酸克鲁维酵母所产β半乳糖苷酶的酶学性质及低聚半乳糖（ galactooligosaccharides，GOS）的酶法合成条件。利用高效液相色谱法进行检测，以GOS（聚合度n＞3）生成量为指标，考察温度、pH、金属离子种类和浓度对酶活性的影响，以及K＋存在时，底物浓度、反应时间、加酶量对乳糖转化率及GOS生成浓度的影响。结果表明：一价离子对β半乳糖苷酶转糖苷活性具有促进作用，其中K＋、NH＋4对水解活性同样起促进作用，而Na＋起抑制作用；制备低聚半乳糖的最佳工艺条件为37℃、pH 8�0、K＋0�08 mol／L、初始乳糖质量浓度500 g／L、反应时间5 h、加酶量10μL／g乳糖，此条件下低聚半乳糖的生成质量浓度达到94�74 g／L。