CELL WATER PERMEABILITY AND CRYOTOLERANCE OF SACCHAROMYCES-CEREVISIAE

Electron particle sizing (Coulter counter) was used to measure cell and protoplast volumes of Saccharomyces cerevisiae grown under different conditions designed to increase its cryotolerance. Membrane water permeabilities were estimated from those measurements. A relationship was obtained between the lower water permeability of yeast grown under microaerobic batch conditions and its weaker cryotolerance in water (cooling rate of 39.6-degrees-C/min), as compared to fed-batch cells. For the latter, cell water permeability was not related to the observed differences in survival for frozen-thawed cells grown under strong or partial (with temporary limitation of dissolved oxygen in growth media) aerobic conditions.