研究室获得1株来源于Sulfolobus solfataricus P2的β-半乳糖苷酶突变体F441Y，该突变体具有转苷性高，热稳定性好的特点。研究中，成功将β-半乳糖苷酶突变体F441Y在枯草芽孢杆菌中进行重组表达，3 L发酵罐发酵80 h后胞内酶活达到76.5 U/mL。鉴于β-半乳糖苷酶为胞内表达，为提高酶的使用效率并降低酶的成本，以2%的海藻酸钠、1%的明胶混合作为固定化包埋载体，2%氯化钙为固化液，0.5%的戊二醛为交联剂对重组菌进行细胞的固定化，全细胞酶活回收率达到62%，将该固定化细胞进行乳糖的酶转化，优化酶转化条件后，低聚半乳糖的最高转化率高达55.1%。

A Sulfolobus solfataricus P2 β-galactosidase mutant F441Y was constructed, which has the characteristics of high trans-galactosyl activity and good thermostability. In this study, β-galactosidase mutant F441Y was successfully expressed in Bacillus subtilis and the fermentation process was optimized. After 80 h fermentation in 3 L fermentor, the intracellular enzyme activity reached 76.5 U/mL. Since β-galactosidase is expressed intracellularly, it was immobilized to increase the enzyme usage efficiency and reduce the cost. The immobilization of recombinant β-galactosidase cells was performed using 2% sodium alginate and 1% gelatin as carrier, 2% calcium chloride as curing solution, and 0.5% glutaraldehyde as cross-linking agent. The enzyme activity recovery rate of the cell immobilization reached 62%. Using the immobilized cells for lactose enzyme conversion, the highest conversion of galactooligosaccharides was up to 55.1% after optimizing the conversion conditions.