Addition of ethanol to supercritical carbon dioxide enhances the inactivation of bacterial spores in the biofilm of Bacillus cereus |
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Authors: | Hyong Seok Park Hee Jung Choi Myoung-Dong Kim Kyoung Heon Kim |
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Affiliation: | 1. Department of Biotechnology, Korea University Graduate School, Seoul 136-713, Republic of Korea;2. Department of Internal Medicine, Division of Infectious Diseases, Ewha Womans University School of Medicine, Seoul 158-710, Republic of Korea;3. Department of Food Science and Biotechnology, Kangwon National University, Chuncheon 200-701, Republic of Korea |
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Abstract: | Supercritical carbon dioxide (SC-CO2) was used to inactivate Bacillus cereus spores inside biofilms, which were grown on stainless steel. SC-CO2 treatment was tested using various conditions, such as pressure treatment (10–30 MPa), temperature (35–60 °C), and time (10–120 min). B. cereus vegetative cells in the biofilm were completely inactivated by treatment with SC-CO2 at 10 MPa and at 35 °C for 5 min. However, SC-CO2 alone did not inactivate spores in biofilm even after the treatment time was extended to 120 min. When ethanol was used as a cosolvent with SC-CO2 in the SC-CO2 treatment using only 2–10 ml of ethanol in 100 ml of SC-CO2 vessel for 60–90 min of treatment time at 10 MPa and 60 °C, B. cereus spores in the biofilm were found to be completely inactivated in the colony-forming test. We also assessed the viability of SC-CO2-treated bacterial spores and vegetative cells in the biofilm by staining with SYTO 9 and propidium iodide. The membrane integrity of the vegetative cells was completely lost, while the integrity of the membrane was still maintained in most spores. However, when SC-CO2 along with ethanol was used, both vegetative cells and spores lost their membrane integrity, indicating that the use of ethanol as a cosolvent with SC-CO2 is efficient in inactivating the bacterial spores in the biofilm. |
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Keywords: | Supercritical carbon dioxide Sterilization Spore Biofilm Cosolvent |
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