title: An empirical model for describing the effects of nitrogen sources on nisin production.
abstract: OBJECTIVE
  A study on the effects of tryptone and yeast extract on nisin production by Lactococcus lactis was carried out using a second order rotatable factorial design.
  
  
  RESULTS
  The results show that both ingredients increased nisin production, although a small decrease in nisin levels was noted at high tryptone concentrations. In view of the low vitamin content of tryptone, the amino acids present in both tryptone and yeast extract may be responsible for these observations.
  
  
  CONCLUSIONS
  The observed response suggests that maintaining tryptone concentrations in the centre of the domain and increasing the concentration of yeast extract would be ideal conditions for nisin production. However, when the economic aspects are considered, it appears that low concentrations of yeast extract and reasonably high concentrations of tryptone are optimal.
authors.affiliation: Marine Research Institute (CSIC), C/Eduardo Cabello, 6. 36208 Vigo (Pontevedra), Spain. marta@iim.csic.es
authors.forename: M L
authors.initials: ML
authors.lastname: Cabo
authors.forename: M A
authors.initials: MA
authors.lastname: Murado
authors.forename: M P
authors.initials: MP
authors.lastname: Gonzalez
authors.forename: J A
authors.initials: JA
authors.lastname: Vazquez
authors.forename: L
authors.initials: L
authors.lastname: Pastoriza
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D003470:Culture Media; D005285:Fermentation; D005396:Fish Products / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013294:Lactococcus lactis / Q000254:growth & development / Q000378:metabolism*; D008954:Models, Biological; D009561:Nisin / Q000096:biosynthesis*; D010461:Peptones / Q000494:pharmacology*; D015003:Yeasts / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D010461:Peptones; D009561:Nisin; C001830:tryptones