title: Addition of ethanol to supercritical carbon dioxide enhances the inactivation of bacterial spores in the biofilm of Bacillus cereus.
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 100ml 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.
authors: Department of Biotechnology, Korea University Graduate School, Seoul 136-713, Republic of Korea.
authors: Hyong Seok
authors: HS
authors: Park
authors: Hee Jung
authors: HJ
authors: Choi
authors: Myoung-Dong
authors: MD
authors: Kim
authors: Kyoung Heon
authors: KH
authors: Kim
mesh_terms: D001409:Bacillus cereus / Q000187:drug effects*; D018441:Biofilms; D002245:Carbon Dioxide / Q000737:chemistry / Q000494:pharmacology*; D000431:Ethanol / Q000494:pharmacology*; D050296:Microbial Viability; D011312:Pressure; D013171:Spores, Bacterial / Q000187:drug effects*; D013193:Stainless Steel; D013696:Temperature
chemical_list: D013193:Stainless Steel; D002245:Carbon Dioxide; D000431:Ethanol
keywords: Biofilm; Cosolvent; Spore; Sterilization; Supercritical carbon dioxide