title: Osmotic stress affects the stability of freeze-dried Lactobacillus buchneri R1102 as a result of intracellular betaine accumulation and membrane characteristics.
abstract: OBJECTIVE
  To help cells to better resist the stressful conditions associated with the freeze-drying process during starter production, we investigated the effect of various osmotic conditions on growth, survival and acidification activity of Lactobacillus buchneri R1102, after freeze-drying and during storage for 3 months at 25°C.
  
  
  RESULTS
  High survival rates during freeze-drying, but not during storage, were obtained when 0·1 mol l(-1) KCl was added at the beginning of fermentation, without any change in membrane properties and betaine accumulation. This condition made it possible to maintain a high acidification rate throughout the process. In contrast, the addition of 0·6 mol l(-1) KCl concentrations at the beginning of fermentation led to a high survival rate during storage that was related to high intracellular betaine levels, low membrane fluidity and high cycC19:0 concentrations. However, these modifications induced the degradation of acidification activity during storage. When a moderate stress was applied by combining 0·1 mol l(-1) KCl at the beginning and 0·6 mol l(-1) KCl at the end of fermentation, betaine accumulated in the cells without any membrane alteration, allowing them to maintain high acidification activity and survival rate during storage.
  
  
  CONCLUSIONS
  Specific osmotic conditions during fermentation induced intracellular betaine accumulation and modifications of membrane character-istics, thus affecting stress resistance of Lact. buchneri R1102. A slight osmotic stress made it possible to maintain a high acidification activity, whereas a high osmotic stress at the end of fermentation led to the preservation of cell survival during freeze-dried storage.
  
  
  CONCLUSIONS
  This study revealed that the survival and preservation of acidification activity of freeze-dried Lact. buchneri R1102 during starter production can be improved by using appropriate osmotic conditions.
authors.affiliation: UMR 782 Génie et Microbiology des Procédés Alimentaires, AgroParisTech - INRA, Thiverval-Grignon, France; Laboratoire Procédés Bactéries, Lallemand SAS, Blagnac Cedex, France.
authors.forename: S
authors.initials: S
authors.lastname: Louesdon
authors.forename: S
authors.initials: S
authors.lastname: Charlot-Rougé
authors.forename: V
authors.initials: V
authors.lastname: Juillard
authors.forename: R
authors.initials: R
authors.lastname: Tourdot-Maréchal
authors.forename: C
authors.initials: C
authors.lastname: Béal
mesh_terms: D001622:Betaine / Q000378:metabolism*; D005285:Fermentation; D005612:Freeze Drying; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000187:drug effects* / Q000502:physiology; D008560:Membrane Fluidity / Q000187:drug effects*; D050296:Microbial Viability / Q000187:drug effects; D009997:Osmotic Pressure; D011189:Potassium Chloride / Q000494:pharmacology*; D011309:Preservation, Biological / Q000379:methods*
chemical_list: D001622:Betaine; D011189:Potassium Chloride
keywords: Lactobacillus buchneri; acidification activity; membrane; osmotic stress; survival