An Improved Test to Study the Changes in Membrane Permeability During Rehydration of Freeze-Dried LC11

Abstract

The objective of this study was to assess changes in membrane permeability during rehydration of freeze-dried Weissella paramesenteroides LC11. Viability was assessed using the electrical conductivity measurement (ms cm^-1 g^-1 dry weight) and the plate count method (cfu g^-1 dry weight). The symptoms of injury included an increase in the electrolyte leakage during the first 4 h of rehydration in Milli Q water and a decrease in the survival rate (about 64%), suggesting an increase in membrane permeability during dehydration. During rehydration of the freeze-dried strain, an increase in the temperature, NaCl or monosodium glutamate concentration and a decrease in H⁺ concentration resulted in an increase in the electrolyte leakage and a decrease in the survival rate (from about 5% to 97%, with respect to the treatment made). However, a decrease in the electrolyte leakage was observed with increasing glycerol, sucrose or maltodextrin and resulted in the maintenance of cell viability. Change in membrane permeability might lead to electrolyte leakage during rehydration and, ultimately, cell death. The electrolyte leakage assay associated with the plate count method, a quick and inexpensive method, could be used to evaluate dried bacteria resistance to dehydration.