Paenibacillus sp.K1 乳糖酶基因bga在乳酸乳球菌中的表达

为了提高乳酸乳球菌利用乳糖的能力，缓解乳糖不耐症，以实验室构建的含有乳糖酶基因的质粒pUC-bga为模板，通过PCR扩增得到乳糖酶基因bga，将其分别与载体pSEC和pMG36e连接，获得重组质粒pSEC-bga和pMG36e-bga，重组质粒分别电转Lactococcus lactis NZ9000和Lactococcus lactis MG1614，并在乳酸乳球菌细胞内实现了活性表达。高压液相色谱（HPLC）分析其对培养基中乳糖的利用能力，结果重组菌L.lactis NZ9000-Bga对乳糖的利用能力比对照菌株高一倍，为生产低乳糖的发酵乳制品奠定了基础。

Expression of lactase gene bga from Paenibacillus sp. K1 in Lactococcus lactis

To increase the ability of hydrolyzing lactose of lactococci, the recombinants with overproduction of lactase from Paenibacillus sp. K1 in 　Lactococcus lactis were constructed. The bga gene was amplified by PCR using the plasmid pUC-bga as templates. PCR products were ligated with L.lactis/E.coli shuttle vector pSEC and pMG36e, which resulted in the formation of plasmids pSEC-bga and pMG36e-bga, respectively. The plasmids pSEC-bga and pMG36e-bga were respectively electroporated into Lactococcus lactis NZ9000 and Lactococcus lactis MG1614. The expression of Lactase in L. lactis NZ9000-Bga and L. lactis MG1614-Bga were carried out in the cytoplasm under the nisin inducible promoter or without induction. Analysis of the residual lactose in the medium by high performance liquid chromatography (HPLC) showed that the ability of utilizing the lactose by constructs L. lactis NZ9000-Bga was significantly higher than that of the control strain, which suggests potential application in dairy fermentation with low lactose.