title: Effects of protective agents on membrane fluidity of freeze-dried Lactobacillus delbrueckii ssp. bulgaricus.
abstract: OBJECTIVE
  To evaluate the effect of protective agents upon survival of Lactobacillus delbrueckii ssp. bulgaricus during freeze-drying and storage, and selective amino acids on cell membrane fluidity.
  
  
  RESULTS
  The protective effect of amino-acids and sugars at different concentrations was studied by determining the viability of lyophilized cells after storage under air at 30 degrees C. Survival following freeze-drying was improved by all compounds. During storage, neither proline nor maltose had protective effects on lyophilized Lact. delbrueckii ssp. bulgaricus. Glutamate 5% and aspartate 5% showed similar protection capability during freeze-drying (94-95%) and after storage (92-99%). Fluorescence probes (DPH and TMA-DPH) were used to study the effect of both amino acids on membrane fluidity. Polarization decreased with increasing concentrations of glutamate or aspartate. Lowest values were observed with TMA-DPH.
  
  
  CONCLUSIONS
  Glutamate 5% and aspartate 5% allowed maintaining high viability rates during freeze-drying and storage of Lact. delbrueckii ssp. bulgaricus because of an increase of the membrane fluidity by inserting in the interfacial region of bacterial plasma membrane.
  
  
  CONCLUSIONS
  These results show the first evidence of the mechanisms underlying glutamate and aspartate as lyoprotectors.
authors: Centro de Referencia para Lactobacilos, CERELA, Chacabuco 145. (4000) San Miguel de Tucumán, San Miguel de Tucumán, Argentina.
authors: G I
authors: GI
authors: Martos
authors: C J
authors: CJ
authors: Minahk
authors: G Font
authors: GF
authors: de Valdez
authors: R
authors: R
authors: Morero
mesh_terms: D001224:Aspartic Acid / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects; D002470:Cell Survival; D003451:Cryoprotective Agents / Q000494:pharmacology*; D005612:Freeze Drying; D018698:Glutamic Acid / Q000494:pharmacology; D048668:Lactobacillus delbrueckii / Q000737:chemistry* / Q000187:drug effects / Q000254:growth & development; D008560:Membrane Fluidity / Q000187:drug effects*; D011309:Preservation, Biological
chemical_list: D003451:Cryoprotective Agents; D001224:Aspartic Acid; D018698:Glutamic Acid