米曲霉β-半乳糖苷酶催化合成低聚半乳糖

Synthesis of Galacto oligosaccharide by β-Galactosidase from Aspergillus oryzae

研究了温度、ｐＨ、酶量和起始乳糖浓度对低聚半乳糖合成的影响，发现乳糖水解为单糖和合成低聚糖所需的最佳条件并不相同；利用有机溶剂作反应介质有利于低聚糖合成。在疏水性环己烷／水（９５／５，Ｖ／Ｖ）反应体系中得到的低聚糖浓度为５２．６ｇ／Ｌ，占总产物的３９．１９％；在亲水性乙酸乙酯／水（８０／２０，Ｖ／Ｖ）体系中得到低聚糖的浓度为４０．０４ｇ／Ｌ，占总产物的３９．６２％。另外，疏水性有机溶剂抑制低聚糖水解的能力强于亲水性溶剂。

The effects of temperature, pH, enzyme amount and initial lactose concentration on the synthesis of galacto oligosaccharide from lactose using β-galactosidase were investigated. It was suggested that the best condition for lactose hydrolysis wasn't good for oligosaccharide synthesis. As the reaction bulk phase, hydrophobic and hydrophilic organic solvents were studied, in which ethyl acetate and cyclohexane proved to be good for oligosaccharide synthesis. A galacto oligosaccharide concentration of 52.6 g/L was obtained in a 95%( V/V ) cyclohexane/5% water mixture and 40.08g/L was acquired in a mixture composed of 80% ethyl acetate and 20% water. It was demonstrated that the use of hydrophobic organic solvent greatly decreased the rate of oligosaccharide hydrolysis while the use of hydrophilic solvent only insignificantly did.