Inactivation of Geobacillus stearothermophilus Spores by High-Pressure CarbonDioxideTreatment

Abstract

ABSTRACT High-pressure CO 2 treatment has been studied as a promising method for inactivating bacterial spores. In the present study, we compared this method with other sterilization techniques, including heat and pressure treatment. Spores of Bacillus coagulans , Bacillus subtilis , Bacillus cereus , Bacillus licheniformis , and Geobacillus stearothermophilus were subjected to CO 2 treatment at 30 MPa and 35°C, to high-hydrostatic-pressure treatment at 200 MPa and 65°C, or to heat treatment at 0.1 MPa and 85°C. All of the bacterial spores except the G. stearothermophilus spores were easily inactivated by the heat treatment. The highly heat- and pressure-resistant spores of G. stearothermophilus were not the most resistant to CO 2 treatment. We also investigated the influence of temperature on CO 2 inactivation of G. stearothermophilus. Treatment with CO 2 and 30 MPa of pressure at 95°C for 120 min resulted in 5-log-order spore inactivation, whereas heat treatment at 95°C for 120 min and high-hydrostatic-pressure treatment at 30 MPa and 95°C for 120 min had little effect. The activation energy required for CO 2 treatment of G. stearothermophilus spores was lower than the activation energy for heat or pressure treatment. Although heat was not necessary for inactivationby CO 2 treatment of G. stearothermophilus spores, CO 2 treatment at 95°C was more effective than treatment at 95°C alone.