Abstract:

Lactase of Bifidobacterium have potential application value in lactose hydrolysis and galactooligosaccharides production, due to its advantages of safety and highly catalysis efficiency. In this study, four protein tag genes, cherry, cbd(cellulose-binding domains), gst(glutathione S-transferase) and mbp (maltose-binding protein), were fused with the gene bg42-106m in vector pPIC9 by genetic technology, respectively. The recombinant plasmids were transformed into Pichia pastoris GS115, respectively. As a result, a high yield strain coexpressed with cherry gene was obtained. The secretion level of bG42-106M in medium achieved 7.42 U/mL, which was 290% higher compared with the wide type strain. However, the CBD, GST and MBP tags had no effect on improvement of expression and secretion level of bG42-106M.

Key words: lactase, Bifidobacterium, Pichia pastoris, fusion expression

摘要：

双歧杆菌来源的乳糖酶具有催化效率高，安全性好等优点，在乳糖水解和低聚半乳糖生产等领域中应用潜力巨大。以来源于动物双岐杆菌（Bifidobacterium animalis B106）的乳糖酶基因bg42-106m为对象，将4种标签蛋白基因cherry、cbd(cellulose-binding domains)、gst(glutathione S-transferase)、mbp(maltose-binding protein)分别与bg42-106m基因连接，然后以pPIC9为载体构建融合蛋白重组表达载体，并在毕赤酵母GS115中进行诱导表达。结果表明,当融合Cherry标签蛋白基因后，可显著提高bG42-106M在毕赤酵母中的蛋白分泌表达量，培养基中乳糖酶活力可达到7.42 U/mL。与未融合标签的野生型菌株相比，乳糖酶bG42-106M的分泌表达量提高了290%。而其他3种标签蛋白没有提高bG42-106M的分泌表达量。

关键词: 乳糖酶;双歧杆菌;毕赤酵母;融合表达