Effects of solution pH and ions on suicidal germination of bacillus subtilis spores induced by medium high temperature-medium high hydrostatic pressure treatment

Abstract

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.