title: Employment of stressful conditions during culture production to enhance subsequent cold- and acid-tolerance of bifidobacteria.
abstract: OBJECTIVE
  This study examined whether exposure of early stationary phase Bifidobacterium longum and B. lactis cells to various combinations of reduced temperature, reduced pH and starvation would enhance the cells' subsequent cold- and/or acid-tolerance.
  
  
  RESULTS
  Survival of B. longum in growth medium at 6 degrees C significantly (P < 0.05) increased as a result of starving cells for 30 or 60 min without any simultaneous decrease in temperature or pH. Acid-tolerance of B. lactis (at pH 3.5 in synthetic gastric fluid) increased significantly when the growth medium pH was decreased from 6.0 to 5.2 and cells experienced 30 or 60 min of starvation. Enhanced B. lactis acid-tolerance persisted through 8-11 weeks of -80 degrees C storage in the pH 5.2 growth medium. Upon addition to milk during yogurt manufacture, these cells initially had enhanced acid-tolerance relative to untreated cells but untreated cells became equally acid-tolerant during the first 2.5 h of yogurt manufacture.
  
  
  CONCLUSIONS
  The cold- and acid-tolerance of bifidobacteria vary widely, but may be significantly increased by application of sub-lethal stress to early stationary phase cells during culture production.
  
  
  CONCLUSIONS
  The enhancement of B. lactis acid-tolerance observed in this study may be of potential importance in the production of effective ready-to-consume probiotic dietary supplements.
authors.affiliation: Department of Food Science, University of Wisconsin-Madison, Madison, WI 53706-1565, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Maus
authors.forename: S C
authors.initials: SC
authors.lastname: Ingham
mesh_terms: D000222:Adaptation, Physiological; D001644:Bifidobacterium / Q000502:physiology*; D003080:Cold Temperature; D015169:Colony Count, Microbial; D003470:Culture Media; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D015014:Yogurt / Q000382:microbiology
chemical_list: D003470:Culture Media