Thermal denaturation of bacterial cells examined by differential scanning calorimetry

Thermal stability of vegetative cells of Listeria monocytogenes, Escherichi a coli and Lactobacillus plantarum was studied by counting viable fractions and determining DSC curves of their suspensions. DSC curves in the 5-99 de grees C range showed a series of endothermic transitions between 50 and 60 degrees C, where the heat destruction of cells occurred. Heat denaturation of DNA required a higher temperature than cell killing. Thermal death was s trongly influenced by the pH, composition and NaCl content of the suspendin g buffer. A mathematical model developed by us enabled comparison of DSC pe ak temperatures and temperatures required for loss of viability.