β-半乳糖苷酶催化乳糖合成低聚半乳糖

Synthesis of Galactooligosaccharides from Lactose by β-Galactosidase

摘要:

通过对环状芽孢杆菌B. circulans SK28.003的发酵获得β-半乳糖苷酶酶液，经过浓缩、盐析沉淀和低温冷冻干燥，制备酶粉。利用β-半乳糖苷酶的转糖苷功能催化乳糖合成低聚半乳糖（Galactooligosaccharides，GOS），采用单因素和正交试验优化，通过高效液相色谱法检测，以GOS产率为评价指标，确定最佳合成条件为：乳糖起始质量浓度为50 g/dL，加酶量为6 U/g，反应温度为60 ℃，pH 7.5。在此条件下反应12 h，GOS产率可达45.5%。

Abstract:

Beta-galactosidase solution was obtained through the fermentation of Bacillus circulans SK28.003，and its powder was prepared from the concentration of its solution，salting and precipitation，and freeze drying. To increase the efficiency of transgalatosylation and GOS yields，the optimal reaction conditions，such as initial lactose concentrations，loading amount of the enzyme，temperatures and pH values of the buffer，were determined through single factor and orthogonal experiments. Using the yields of GOS as the evaluation index，the maximum GOS yield was achieved up to 45.5% after 12 h synthesis when the reaction conditions were at 60 ℃，50 g/dL initial lactose concentration，6 U/g lactose in 0.1 M，and sodium phosphate buffer at pH 7.5. Keywords：