Thermal Death of Escherichia coli Suspended in Solutions Containing Sodium Ion at Several pH Values

Abstract

Thermal death of Escherichia coli suspended in solutions contained sodium ion at several pH values (pH 5.4-7.4) was investigated. The thermal death of Escherichia coli suspended in phosphate-buffered saline (PBS; pH 7.4) was accelerated in comparison with that of Escherichia coli suspended in distilled water. The presence of sodium and potassium ions in PBS was found to accelerate the thermal death of Escherichia coli; the thermal death of Escherichia coli suspended in sodium chloride solution or sodium monohydrogen phosphate solution was accelerated at a neutral pH of the bacterial suspension in comparison with a mild acidic pH. These results indicate that the thermal death of Escherichia coli at neutral pH was accelerated by the addition of sodium ions.