Influence of cooling rate on Saccharomyces cerevisiae destruction during freezing: unexpected viability at ultra-rapid cooling rates.
The purpose of this work was to study cell viability as a function of cooling rate during freezing. Cooling rate strongly influences the viability of cells during cold thermal stress. One of the particularities of this study was to investigate a large range of cooling rates and particularly very rapid cooling rates (i.e., faster than 20000 degrees C min (-1)). Four distinct ranges of cooling rates were identified. The first range (A(')) corresponds to very slow cooling rates (less than 5 degrees C min (-1)), and results in high cell mortality. The second range (A) corresponds to low cooling rates (5-100 degrees C min (-1)), at which cell water outflow occurs slowly and does not damage the cells. The third range (B) corresponds to rapid cooling rates (100-2000 degrees C min (-1)), at which there is competition between heat flow and water flow. In this case, massive water outflow, which is related to the increase in extracellular osmotic pressure and the membrane-lipid phase transition, can cause cell death. The fourth range (C) corresponds to very high cooling rates (more than 5000 degrees C min (-1)), at which the heat flow is very rapid and partially prevents water exit, which seems to preserve cell viability.
Dumont
Frédéric
F
Laboratoire de Génie des Procédés Alimentaires et Biotechnologiques, ENSBANA, 1, Esplanade Erasme, 21000, Dijon, France.
Marechal
Pierre André
PA
Gervais
Patrick
P
D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology; D003470:Culture Media; D005615:Freezing; D007424:Intracellular Fluid; D009997:Osmotic Pressure; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000187:drug effects; D013816:Thermodynamics; D013997:Time Factors
D003451:Cryoprotective Agents; D003470:Culture Media