Effect of Combined Physical Stresses on Cells: The Role of Water

Abstract

The role of water in microorganism viability was envisaged through the application of combined physical perturbations. The combination of different physical parameters could enable one to balance the property variations (especially water related) resulting from the increase of one parameter alone. The fi rst example shows that the combination of osmotic level and temperature can enable yeast cell survival to be optimized when following membrane fl uidity variations. This analysis has enabled a better comprehension of cell inactivation during rehydration and dehydration. The second example deals with the combination effect of high hydrostatic pressure, low temperature, and medium water activity (a w ) on Escherichia coli resistance. The synergetic effect of high pressure and low temperature was observed only at a pressure level lower than 300 MPa and with high water content. Otherwise, low temperature, as well as low a w , protect the microorganisms from inactivation even at an extreme pressure level (P 600 MPa). © 2010 Blackwell Publishing.