Germination and inactivation of Bacillus subtilis spores under combined conditions of hydrostatic pressure and medium temperature

The combined effect of mild heating and pressurization on germination and inactivation of Bacillus subtilis spores was investigated. The spore count decreased remarkably at 60 degrees C + 80 MPa in glucose broth as opposed to phosphate buffer. These results suggested that the spores germinated due to pressure and germination-inducing components in the glucose broth, and that the germinated spores were then inactivated by mild heating. The induction of germination started at 10 MPa at 40 degrees C or 20 MPa at 60 degrees C with the number of spores decreasing by two log-cycles in one hour. The relationship between the logarithm of spore number and pressure became linear in the pressure range of 50-300 MPa. The germination ratio was 0.95 log-cycles 100 MPa at 40 degrees C or 0.82 log-cycles/100 MPa at 60 degrees C for half an hour in glucose broth.