A NEW DESIGN INTENDED TO RELATE HIGH-PRESSURE TREATMENT TO YEAST-CELLMASS-TRANSFER

A new optical device has been developed to allow the observation of mi croorganisms during a high pressure treatment up to 700 MPa. To measur e cell volume variation during the high pressure application, an image analysis system was connected with the light microscope. With this de vice, growth of Saccharomyces cerevisiae was studied at moderate press ure (10 MPa) through the observation of individual cell budding. Cell volume variations were also measured on the yeast Saccharomycopsis fib uligera on fixed cells as well on a population sample and a shrinkage in average cell volume was observed consequently to a pressure increas e of 250 MPa. The observed compression rate (25%) under pressure and t he partial irreversibility of cell compression (10%) after return to a tmospheric pressure lead to the conclusion that a mass transfer betwee n cell and cultivation medium occurred. The causes of this transfer co uld be explained by a modification of membrane properties, i.e., disru ption or increase in permeability.