title: Construction and secretory expression of beta-galactosidase gene from Lactobacillus bulgaricus in Lactococcus lactis.
abstract: OBJECTIVE
  This study is to examine the secretion effects of beta-galactosidase in Lactococcus lactis.
  
  
  METHODS
  The usp45 and beta-galactosidase genes were cloned and inserted into plasmid pMG36e to obtain the recombinant plasmid pMG36e-usp-lacZ. This recombinant plasmid was transformed into both Escherichia coli DH5alpha and L. lactis MG1363. The enzyme activity, gene sequencing, SDS-PAGE and hereditary stability were assessed and studied.
  
  
  RESULTS
  The lacZ gene inserted into plasmids pMG36e-usp-lacZ was 99.37% similar to the GenBank sequence, and SDS-PAGE revealed an evident idio-strap at 116 KDa between L. lactis MG1363/pMG36e-usp-lacZ in both supernatant and cell samples. Beta-Galactosidase activity measured 0.225 U/mL in L. lactis pMG36e-usp-lacZ transformants, and its secretion rate was 10%. The plasmid pMG36e-usp-lacZ appeared more stable in MG1363.
  
  
  CONCLUSIONS
  The authors concluded that these new recombinant bacteria well expressed and secreted beta-galactosidase, indicating that the beta-galactosidase expression system was successfully constructed, and this might provide a new solution for management of lactose intolerance specifically and promote the use of gene-modified organisms as part of the food-grade plasmid in general.
authors.affiliation: Department of Nutrition and Food Hygiene, West China School of Public Health, Sichuan University, Chengdu 610041, Sichuan, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Zhang
authors.forename: Chuan
authors.initials: C
authors.lastname: Wang
authors.forename: Cheng Yu
authors.initials: CY
authors.lastname: Huang
authors.forename: Qian
authors.initials: Q
authors.lastname: Yu
authors.forename: Heng Chuan
authors.initials: HC
authors.lastname: Liu
authors.forename: Chao Wu
authors.initials: CW
authors.lastname: Zhang
authors.forename: Xiao Fang
authors.initials: XF
authors.lastname: Pei
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D007778:Lactobacillus / Q000235:genetics*; D010957:Plasmids; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D017931:DNA Primers; D001616:beta-Galactosidase