Disinfection Using Pressurized Carbon Dioxide Microbubbles to Inactivate Escherichia coli, Bacteriophage MS2 and T4 (original) (raw)
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Inactivation of Escherichia coli and bacteriophage T4 by high levels of dissolved CO2
Applied Microbiology and Biotechnology, 2011
Little information is available regarding the effectiveness of water disinfection by CO 2 at low pressure. The aim of this study was to evaluate the use of high levels of dissolved CO 2 at 0.3-0.6 MPa for the inactivation of microorganisms. Bacteriophage T4 was chosen as the model virus and Escherichia coli was selected as the representative bacterium. The results of the study showed a highly effective log inactivation of E. coli and bacteriophage T4 at low and medium initial concentrations by high levels of dissolved CO 2 at 0.3 MPa with a treatment time of 20 min. When the pressure was increased to 0.6 MPa, inactivation of both microorganisms at high initial concentrations was improved to different extents. Neither pressurized air nor O 2 effectively inactivated both E. coli and bacteriophage T4. The pH was not a key factor affecting the inactivation process by this method. The results of scanning electron microscopy of E. coli and transmission electron microscopy of bacteriophage T4 suggested that "CO 2 uptake at high pressure and bursting of cells by depressurization" were the main reasons for lethal effect on micro-organisms. This technology has potential for application in the disinfection of water, wastewater, and liquid food in the future.
Virus and bacteria inactivation by CO2 bubbles in solution
npj Clean Water
The availability of clean water is a major problem facing the world. In particular, the cost and destruction caused by viruses in water remains an unresolved challenge and poses a major limitation on the use of recycled water. Here, we develop an environmentally friendly technology for sterilising water. The technology bubbles heated un-pressurised carbon dioxide or exhaust gases through wastewater in a bubble column, effectively destroying both bacteria and viruses. The process is extremely cost effective, with no concerning by-products, and has already been successfully scaled-up industrially.
Escherichia coli inactivation mechanism by pressurized CO 2
Canadian Journal of Microbiology, 2006
The effects of pressurized CO 2 on the survival of Escherichia coli and the mechanism of cell inactivation were studied. Bacterial cultures were inoculated in nutrient broth and incubated at 30°C for 18 h. Exposure of the cells to CO 2 under pressures ranging from 2.5 to 25 MPa and at temperatures between 8 and 40°C was performed in a double-walled reactor with a 1 L capacity. The effect of the treatment on the cells was evaluated by plating and by transmission and scanning electron microscopy observation. Vapour CO 2 generated a bacteriostatic effect. In liquid or supercritical state, CO 2 provided a bactericidal effect. The bactericidal effect increased with pressure and temperature. The mechanism of cell inactivation by liquid CO 2 involved two stages. First, cell stress caused by the CO 2 penetration provoked cell wall collapse and cellular content precipitation. Second, the cell death caused by supercritical extraction of intracellular substances and cell envelope perforation resulted in leaking of intracellular constituents. In supercritical conditions, the cell inactivation process had one single phase: cellular death.
Substantia, 2021
A CO2 bubble column (CBC) has been developed as a body-temperature lab-scale water sterilization process for the inactivation of pathogens. Both CO2 and combustion gas bubbles inactivated Escherichia coli C-3000 (ATCC15597) with extraordinary efficiency in solutions with low alkalinity. The mechanisms of inactivation were not known. To characterise the phenomena a new first-order kinetic equation that correlates E.coli inactivation rates with a total alkalinity of the solutions has been developed as a first step towards understanding. This leads us to propose a new mechanism of inactivation.
Inactivation of Escherichia coli by Carbon Dioxide under Pressure
Journal of Food Science, 1996
Thermal inactivation of Escherichia coli was studied under CO 2 pressures of 1.2, 2.5, and 5 MPa at 25, 35, and 45ЊC. Two phases were observed in the destruction curves. The earlier stage was characterized by a slow rate of inactivation, which increased sharply at the later stage. An increase of pressure and/or temperature enhanced the antimicrobial effects of CO 2 under pressure. The effects on cell structure were studied by scanning electron microscopy and the specific mechanism of action appeared to be related to enzyme inactivation.
Effect of high pressurized carbon dioxide on Escherichia coli
Tanzania journal of science, 2009
Carbon dioxide at high pressure can retard microbial growth and sometimes kill microorganisms depending on values of applied pressure, temperature and exposure time. In this study the effect of high pressurised carbon dioxide (HPCD) on Escherichia coli was investigated. Culture of E. coli was subjected to high pressurised carbon dioxide at 15, 25 and 35 bar, and varying exposure times of 20, 40, 60 and 90 minutes at room temperature (27 o C). Microbial inactivation increased with pressure and exposure time. For the first 20 minutes reduction of viable microbial cells was 18%, 30% and 36% at 15, 25 and 35 bar, respectively. Higher microbial inactivation values were achieved at 40, 60, and 90 minutes. Decimal reduction times were 127, 93 and 75 minutes at 15, 25, and 35 bar, respectively. The pH values of treated samples decreased with increasing pressure and treatment time from approximately neutral to 5.71 at 15 bar, and 5.02 at 35 bar. It was concluded that high pressurised carbon dioxide has antimicrobial effect on E. coli bacteria. With further studies, HPCD microbial deactivation can be used for foods preservation as a alternative technology to conventional heat pasteurisation and sterilization.
Thermal pasteurization is a well known and old technique for reducing the microbial count of foods. Traditional thermal processing, however, can destroy heat-sensitive nutrients and food product qualities such as flavor, color and texture. For more than 2 decades now, the use of highpressure carbon dioxide (HPCD) has been proposed as an alternative cold pasteurization technique for foods. This method presents some fundamental advantages related to the mild conditions employed, particularly because it allows processing at much lower temperature than the ones used in thermal pasteurization. In spite of intensified research efforts the last couple of years, the HPCD preservation technique has not yet been implemented on a large scale by the food industry until now. This review presents a survey of published knowledge concerning the HPCD technique for microbial inactivation, and addresses issues of the technology such as the mechanism of carbon dioxide bactericidal action, the potential for inactivating vegetative cells and bacterial spores, and the regulatory hurdles which need to be overcome. In addition, the review also reflects on the opportunities and especially the current drawbacks of the HPCD technique for the food industry.
Inactivation of Salmonella typhimurium by high pressure carbon dioxide
Food Microbiology, 2000
Thermal inactivation of Salmonella typhimurium was studied under CO 2 pressures of15, 30 and 60 atm at 25, 35 and 458C. Two phases were observed in the destruction curves. The earlier stage was characterized by a slow rate of inactivation in the number of S. typhimurium, which increased sharply at the later stage. It was suggested that the cell death resulted from the lowered pH due to solubilization of CO 2. An increase of pressure and/or temperature enhanced the antimicrobial e¡ects of CO 2. Salmonella typhimurium suspended in physiological saline (PS) was completely inactivated under 60 atm CO 2 treatment in 35 and 15 min at 25 and 358C, respectively. On the other hand, it was completely inactivated when suspended in PS containing brain^heart infusion broth for140 and100 min. A minimum Dvalue was obtained under 60 atm CO 2 pressure at 458C. Inactivation rates of S. typhimurium were sensitive to pressure, temperature, exposure time, initial number of cells, and the suspending medium.
High carbon dioxide pressure inactivation kinetics of Escherichia coli in broth
Food Microbiology, 2001
The inactivation kinetics of Escherichia coli by high pressure carbon dioxide was investigated. Inactivation rates increased with increasing pressure (25, 50, 75 and 100 atm), temperature, and exposure time. Microbial inactivation followed ¢rst order reaction kinetics, with inactivation rates (k) and decimal reduction times (D) that varied from 0?0848 to 0?4717 min 71 and from 4?90 to 27?46 min, respectively, at treatment temperatures (20, 30 and 408C). The inactivation rates of E. coli were described by the apparent activation volume (DV*) and a 'pressure z value' , and they were greatly dependent on both temperature and pressure.
INACTIVATION OF STAPHYLOCOCCUS AUREUS EXPOSED TO DENSE-PHASE CARBON DIOXIDE IN A BATCH SYSTEM
Journal of Food Process Engineering, 2009
ABSTRACTThe inactivation of Staphylococcus aureus exposed to dense-phase carbon dioxide (DPCD) was investigated, and the kinetics of come-up time (CUT) in pressurization was monitored with come-down time (CDT) and temperature fluctuation in depressurization. CUT was about 2.5, 3.5, 4.0 and 4.0 min; CDT was 3.4, 3.7, 4.5 and 4.5 min; lowest temperature of samples in depressurization was 4, −1, −15 and −22C, corresponding to 10, 20, 30 and 40 MPa at 37C. The inactivation behavior of S. aureus was closely related to the variables of process pressure, holding-pressure time (HPT), process temperature and process cycling. The log reduction of S. aureus at 40 MPa for 30-min HPT was significantly greater (P < 0.05), but the inactivation effect at 10, 20 and 30 MPa was similar. The log reduction of S. aureus at 30 and 40 MPa for 60-min HPT was similar and significantly greater (P < 0.05), while the inactivation effect at 10 and 20 MPa was similar. The inactivation of S. aureus against HPT conformed to a fast–slow biphase kinetics; the two stages were well fitted to a first-order model with higher regression coefficients R2 = 1.000 and 0.9238; their respective D values (decimal reduction time) were 16.52 and 70.42 min. As the process temperature increased, the log reduction of S. aureus increased significantly (P < 0.05); the inactivation kinetics of S. aureus versus process temperature was characterized with a fast inactivation rate from 32 to 45C and a slow inactivation rate from 45 to 55C. As compared to one-process cycling for a total of 60-min HPT, four-process cycling resulted in a significant reduction of S. aureus, and its maximal reduction was near to 5 log cycles, indicating that more process cycling caused more inactivation of S. aureus under identical pressure and temperature with equal HPT. However, the maximal reduction was 0.09 and 0.12 log cycles for two- and four-process cyclings with 0-min HPT, indicating that pressurization and depressurization had a lesser effect on the inactivation of S. aureus, while HPT was significant in DPCD to inactivate S. aureus.The inactivation of Staphylococcus aureus exposed to dense-phase carbon dioxide (DPCD) was investigated, and the kinetics of come-up time (CUT) in pressurization was monitored with come-down time (CDT) and temperature fluctuation in depressurization. CUT was about 2.5, 3.5, 4.0 and 4.0 min; CDT was 3.4, 3.7, 4.5 and 4.5 min; lowest temperature of samples in depressurization was 4, −1, −15 and −22C, corresponding to 10, 20, 30 and 40 MPa at 37C. The inactivation behavior of S. aureus was closely related to the variables of process pressure, holding-pressure time (HPT), process temperature and process cycling. The log reduction of S. aureus at 40 MPa for 30-min HPT was significantly greater (P < 0.05), but the inactivation effect at 10, 20 and 30 MPa was similar. The log reduction of S. aureus at 30 and 40 MPa for 60-min HPT was similar and significantly greater (P < 0.05), while the inactivation effect at 10 and 20 MPa was similar. The inactivation of S. aureus against HPT conformed to a fast–slow biphase kinetics; the two stages were well fitted to a first-order model with higher regression coefficients R2 = 1.000 and 0.9238; their respective D values (decimal reduction time) were 16.52 and 70.42 min. As the process temperature increased, the log reduction of S. aureus increased significantly (P < 0.05); the inactivation kinetics of S. aureus versus process temperature was characterized with a fast inactivation rate from 32 to 45C and a slow inactivation rate from 45 to 55C. As compared to one-process cycling for a total of 60-min HPT, four-process cycling resulted in a significant reduction of S. aureus, and its maximal reduction was near to 5 log cycles, indicating that more process cycling caused more inactivation of S. aureus under identical pressure and temperature with equal HPT. However, the maximal reduction was 0.09 and 0.12 log cycles for two- and four-process cyclings with 0-min HPT, indicating that pressurization and depressurization had a lesser effect on the inactivation of S. aureus, while HPT was significant in DPCD to inactivate S. aureus.PRACTICAL APPLICATIONSDense-phase carbon dioxide (DPCD) is a novel technology to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. This study showed that DPCD effectively inactivated Staphylococcus aureus inoculated in 7.5% sodium chloride broth, and the inactivation behavior of S. aureus was closely related to the pressure, holding-pressure time, temperature and process cycling. Based on this observation, the technology of DPCD can be applied in the pasteurization of foods such as milk and various fruit juices, especially thermal-sensitive materials.Dense-phase carbon dioxide (DPCD) is a novel technology to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. This study showed that DPCD effectively inactivated Staphylococcus aureus inoculated in 7.5% sodium chloride broth, and the inactivation behavior of S. aureus was closely related to the pressure, holding-pressure time, temperature and process cycling. Based on this observation, the technology of DPCD can be applied in the pasteurization of foods such as milk and various fruit juices, especially thermal-sensitive materials.