Escherichia coli and Lactobacillus plantarum responses to osmotic stress |
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Authors: | I Poirier P-A Maréchal C Evrard P Gervais |
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Institution: | (1) Laboratoire de génie des Procédés Alimentaires et Biotechnologiques, E.N.S.B.A.N.A., 1, esplanade Erasme, F-21000 Dijon, France Tel.: +33-3-80396654 Fax: +33-3-80396611 e-mail: gervais@satie.u-bourgogne.fr, FR |
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Abstract: | Escherichia coli and Lactobacillus plantarum were subjected to final water potentials of −5.6 MPa and −11.5 MPa with three solutes: glycerol, sorbitol and NaCl. The water
potential decrease was realized either rapidly (osmotic shock) or slowly (20 min) and a difference in cell viability between
these conditions was only observed when the solute was NaCl. The cell mortality during osmotic shocks induced by NaCl cannot
be explained by a critical volume decrease or by the intensity of the water flow across the cell membrane. When the osmotic
stress is realized with NaCl as the solute, in a medium in which osmoregulation cannot take place, the application of a slow
decrease in water potential resulted in the significant maintenance of cell viability (about 70–90%) with regard to the corresponding
viability observed after a sudden step change to same final water potential (14–40%). This viability difference can be explained
by the existence of a critical internal free Na+ concentration.
Received: 20 May 1998 / Received revision: 31 July 1998 / Accepted: 31 July 1998 |
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