Effect of High Pressure Gaseous and Supercritical Carbon Dioxide Treatments on Bacterial Spores

Effects of high pressure gaseous carbon dioxide treatment (35°C, 6.5 MPa) (HGCT) and supercritical carbon dioxide treatment (35°C, 30 MPa) (HSCT), followed by heat treatment at 70°C (criterion for germination), on Bacillus coagulans and B. licheniformis spores were investigated. In both strains, HSCT was more effective in inactivating the bacterial spores than HGCT. Approximately 10% of the spores of B. coagulans were inactivated, and 40% of the B. coagulans spores germinated with HGCT for 120 min. Approximately 90% of the spores of B. coagulans were inactivated and germinated with HSCT for 120 min. Approximately 20% of the spores of B. licheniformis were inactivated, and 70% of the B. licheniformis spores germinated with HGCT for 120 min. Approximately 80% of the spores of B. licheniformis were inactivated, and 90% of the B. licheniformis spores germinated with HSCT at 120 min. These results suggest that the spores germinate more effectively with HSCT than HGCT, and germinated spores are more sensitive to HSCT than HGCT.