title: Optimization of fermentation conditions for the expression of sweet-tasting protein brazzein in Lactococcus lactis.
abstract: OBJECTIVE
  To improve the production of sweet-tasting protein brazzein in Lactococcus lactis using controlled fermentation conditions.
  
  
  RESULTS
  The nisin-controlled expression system was used for brazzein expression. The concentration of nisin for induction and the optical density (OD) at induction were therefore optimized, together with growth conditions (medium composition, pH, aerobic growth in the presence of hemin). Brazzein was assayed with ELISA on Ni-NTA plates and Western blot. Use of the M-17 medium, containing 2.5% glucose, anaerobic growth at pH 5.9 and induction with 40 ng ml(-1) nisin at OD 3.0 led to an approx. 17-fold increase in brazzein per cell production compared to non-optimized starting conditions. Aerobic growth in the presence of hemin did not increase the production.
  
  
  CONCLUSIONS
  Considerable increase in brazzein per cell production was obtained at optimized fermentation conditions.
  
  
  CONCLUSIONS
  Optimized growth conditions could be used in application of brazzein expression in L. lactis. The importance of pH and OD at induction contributes to the body of knowledge of optimal recombinant protein expression in L. lactis. The new assay for brazzein quantification was introduced.
authors.affiliation: Department of Biotechnology, JoZef Stefan Institute, Ljubljana, Slovenia. ales.berlec@ijs.si
authors.forename: A
authors.initials: A
authors.lastname: Berlec
authors.forename: G
authors.initials: G
authors.lastname: Tompa
authors.forename: N
authors.initials: N
authors.lastname: Slapar
authors.forename: U P
authors.initials: UP
authors.lastname: Fonović
authors.forename: I
authors.initials: I
authors.lastname: Rogelj
authors.forename: B
authors.initials: B
authors.lastname: Strukelj
mesh_terms: D015153:Blotting, Western; D005285:Fermentation; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D013294:Lactococcus lactis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009561:Nisin / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics / Q000378:metabolism*; D013549:Sweetening Agents / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D013549:Sweetening Agents; C090521:brazzein protein, Pentadiplandra brazzeana; D009561:Nisin; D005947:Glucose