Effects of Solution pH and Ions on Suicidal Germination of Bacillus subtilis Spores Induced by Medium High...

Spores of Bacillus subtilis suspended in water or aqueous solution of NaCl, CaCl₂, sodium lactate, or calcium lactate at pH 4 - 7 was subjected to spore inactivation by simultaneous combination of medium high hydrostatic pressure (MHHP; 100 MPa) treatment for germination and medium high temperature (MHT; 65℃) treatment for pasteurization of germinated vegetative cells. The spores at pH 4 in NaCl solution and those at pH 5 and 6 in Na lactate solutions were less killed than in water by MHHP+MHT treatment. Spore inactivation was promoted by calcium ion in NaCl solution at pH 4 and in Na lactate solutions at pH 5 and pH 6, while it was more suppressed at pH 5 and pH 6 in Na lactate solutions than at pH 4 in NaCl solution. The spores treated by MHHP+MHT in NaCl or Na lactate solution at pH 4 were further killed by subsequent MHT treatment.