title: Heterologous expression of a recombinant lactobacillal β-galactosidase in Lactobacillus plantarum: effect of different parameters on the sakacin P-based expression system.
abstract: BACKGROUND
  Two overlapping genes lacL and lacM (lacLM) encoding for heterodimeric β-galactosidase from Lactobacillus reuteri were previously cloned and over-expressed in the food-grade host strain Lactobacillus plantarum WCFS1, using the inducible lactobacillal pSIP expression system. In this study, we analyzed different factors that affect the production of recombinant L. reuteri β-galactosidase.
  
  
  RESULTS
  Various factors related to the cultivation, i.e. culture pH, growth temperature, glucose concentration, as well as the induction conditions, including cell concentration at induction point and inducer concentration, were tested. Under optimal fermentation conditions, the maximum β-galactosidase levels obtained were 130 U/mg protein and 35-40 U/ml of fermentation broth corresponding to the formation of approximately 200 mg of recombinant protein per litre of fermentation medium. As calculated from the specific activity of the purified enzyme (190 U/mg), β-galactosidase yield amounted to roughly 70% of the total soluble intracellular protein of the host organism. It was observed that pH and substrate (glucose) concentration are the most prominent factors affecting the production of recombinant β-galactosidase.
  
  
  CONCLUSIONS
  The over-expression of recombinant L. reuteri β-galactosidase in a food-grade host strain was optimized, which is of interest for applications of this enzyme in the food industry. The results provide more detailed insight into these lactobacillal expression systems and confirm the potential of the pSIP system for efficient, tightly controlled expression of enzymes and proteins in lactobacilli.
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, A-1190, Vienna, Austria. nguyenthanh.ibft@gmail.com.|School of Biotechnology and Food Technology, Hanoi University of Science and Technology, 1 Dai Co Viet Street, Hanoi, Vietnam. nguyenthanh.ibft@gmail.com.
authors.forename: Tien-Thanh
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, A-1190, Vienna, Austria. hoang.nguyen@students.boku.ac.at.|Department of Biotechnology, Danang University of Technology, Nguyen Luong Bang 54, Danang, Vietnam. hoang.nguyen@students.boku.ac.at.
authors.forename: Hoang-Minh
authors.initials: HM
authors.lastname: Nguyen
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, A-1190, Vienna, Austria. barbara.geiger@boku.ac.at.
authors.forename: Barbara
authors.initials: B
authors.lastname: Geiger
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, , N-1432, Ǻs, Norway. geir.mathiesen@nmbu.no.
authors.forename: Geir
authors.initials: G
authors.lastname: Mathiesen
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, , N-1432, Ǻs, Norway. vincent.eijsink@umb.no.
authors.forename: Vincent G H
authors.initials: VG
authors.lastname: Eijsink
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, A-1190, Vienna, Austria. clemens.peterbauer@boku.ac.at.
authors.forename: Clemens K
authors.initials: CK
authors.lastname: Peterbauer
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, A-1190, Vienna, Austria. dietmar.haltrich@boku.ac.at.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Haltrich
authors.affiliation: Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, A-1190, Vienna, Austria. thu-ha.nguyen@boku.ac.at.
authors.forename: Thu-Ha
authors.initials: TH
authors.lastname: Nguyen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001430:Bacteriocins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D048191:Lactiplantibacillus plantarum / Q000254:growth & development / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013696:Temperature; D001616:beta-Galactosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001430:Bacteriocins; D011994:Recombinant Proteins; C087217:sakacin P protein, Lactobacillus; D001616:beta-Galactosidase; D005947:Glucose