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The Journal of Supercritical Fluids, 2013
The aim of the present study was to determine an effective sterilization method for safe handling and recycle-reuse of clinical solid waste materials. Supercritical fluid carbon dioxide (SC-CO 2 ) was applied in the inactivation of gram positive Staphylococcus aureus (S. aureus) and gram negative Serratia marcencens (S. marcescens) in clinical solid waste. The colony forming activity of the bacteria was completely lost at pressures 10-40 MPa, temperatures 35-80 • C and treatment period between 5 and 120 min. An increase in pressure at constant temperature and vice versa with the increasing treatment time enhanced the SC-CO 2 inactivation efficiency. The inactivation process was illustrated by the modified Gompertz equation. The SC-CO 2 inactivation of bacteria was compared with the steam autoclaved bacteria. Regrowth of the bacteria was observed in the autoclaved sample while no re-growth was detected in the SC-CO 2 treated clinical solid waste. Results from SEM image analysis, cellular protein and enzymatic activity of untreated, autoclaved and SC-CO 2 treated S. marcescens and S. aureus cells confirmed that SC-CO 2 is an effective sterilization method.
Waste Management, 2015
Clinical solid waste (CSW) poses a challenge to health care facilities because of the presence of pathogenic microorganisms, leading to concerns in the effective sterilization of the CSW for safe handling and elimination of infectious disease transmission. In the present study, supercritical carbon dioxide (SC-CO 2 ) was applied to inactivate gram-positive Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and gramnegative Escherichia coli in CSW. The effects of SC-CO 2 sterilization parameters such as pressure, temperature, and time were investigated and optimized by response surface methodology (RSM). Results showed that the data were adequately fitted into the second-order polynomial model. The linear quadratic terms and interaction between pressure and temperature had significant effects on the inactivation of S. aureus, E. coli, E. faecalis, and B. subtilis in CSW. Optimum conditions for the complete inactivation of bacteria within the experimental range of the studied variables were 20 MPa, 60°C, and 60 min. The SC-CO 2 -treated bacterial cells, observed under a scanning electron microscope, showed morphological changes, including cell breakage and dislodged cell walls, which could have caused the inactivation. This espouses the inference that SC-CO 2 exerts strong inactivating effects on the bacteria present in CSW, and has the potential to be used in CSW management for the safe handling and recycling-reuse of CSW materials.
The expansions of communities and cities over the last two decades have led to the increase of the number of health care facilities, and thus, clinical wastes are generated in significant amounts. Clinical wastes are a potential source for many pathogens such as viruses, parasites, fungi and bacteria. Therefore, clinical wastes should be treated before disposal into the environment. The incineration is the most common technology applied for the treatment process. However, the negative effects of incineration on humans and the environment have led scientists to define alternative technologies for the safe disposal of clinical waste. Numerous treatment technologies have been investigated as an alternative for incineration, such as autoclave and microwave. These technologies generally depend on temperature while the recent direction is to use a non-thermal sterilization processes. SC-CO2 is one of the nonthermal sterilization technologies, which depends on pressure and low temperature. Currently, SC-CO2 has been extensively used for the inactivation of microorganisms in food and pharmaceutical industries. However, the application of SC-CO2 in treating clinical wastes has been on a rise. Studies conducted on the inactivation of fungi in food, normal saline and growth media indicate that SC-CO2 has the ability to inactivate these organisms. In clinical wastes, SC-CO2 has been found to be effective in the inactivation of pathogenic bacteria. Therefore, this review paper focuses on the potential of using SC-CO2 as alternative technology for inactivating fungi in clinical wastes.
Food Science and Technology
High hydrostatic pressure technology is a relatively new method for the food industry and is considered more as an alternative to traditional storage methods such as thermal processes. Inactivation of spores, models, yeasts, and viruses has been demonstrated by this method. Although issues related to the safety and longevity of food, as well as their legal permits, require extensive case studies, the available experimental findings can be useful in expanding the potential applications of high pressure in the food industry. In this paper, CO 2 is used as a fluid. Increasing the pressure in Weibull and log-logistic models from 2.5 MPa to 10 MPa has reduced the processing time from 700 minutes to 70 and 60 minutes, respectively. The log-logistic model in predicting the process of inactivation of microbes compared to the Weibull model has been the lowest, and also the log-logistic model has a suitable ability to predict the shoulder of the chart if the Weibull model does not have this ability and its error is almost high. Increasing the increase in pressure has increased the level of inactivation of Salmonella typhimurium and Listeria monocytogenes, except Listeria monocytogenes at a pressure of 6.05 MPa, which reduced inactivation.
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.
A new era for sterilization based on supercritical CO 2 technology
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2019
The increasing complexity in morphology and composition of modern biomedical materials (e.g., soft and hard biological tissues, synthetic and natural-based scaffolds, technical textiles) and the high sensitivity to the processing environment requires the development of innovative but benign technologies for processing and treatment. This scenario is particularly applicable where current conventional techniques (steam/dry heat, ethylene oxide, and gamma irradiation) may not be able to preserve the functionality and integrity of the treated material. Sterilization using supercritical carbon dioxide emerges as a green and sustainable technology able to reach the sterility levels required by regulation without altering the original properties of even highly sensitive materials. In this review article, an updated survey of experimental protocols based on supercritical sterilization and of the efficacy results sorted by microbial strains and treated materials was carried out. The application of the supercritical sterilization process in materials used for biomedical, pharmaceutical, and food applications is assessed. The opportunity of supercritical sterilization of not only replace the above mentioned conventional techniques, but also of reach unmet needs for sterilization in highly sensitive materials (e.g., single-use medical devices, the next-generation biomaterials, and medical devices and graft tissues) is herein unveiled.
Supercritical CO2 technology: The next standard sterilization technique?
Materials Science and Engineering: C, 2019
Sterilization of implantable medical devices is of most importance to avoid surgery related complications such as infection and rejection. Advances in biotechnology fields, such as tissue engineering, have led to the development of more sophisticated and complex biomedical devices that are often composed of natural biomaterials. This complexity poses a challenge to current sterilization techniques which frequently damage materials upon sterilization. The need for an effective alternative has driven research on supercritical carbon dioxide (scCO 2) technology. This technology is characterized by using low temperatures and for being inert and non-toxic. The herein presented paper reviews the most relevant studies over the last 15 years which cover the use of scCO 2 for sterilization and in which effective terminal sterilization is reported. The major topics discussed here are: microorganisms effectively sterilized by scCO 2 , inactivation mechanisms, operating parameters, materials sterilized by scCO 2 and major requirements for validation of such technique according to medical devices' standards.
Bacterial inactivation on solid food matrices through supercritical CO2: A correlative study
Journal of Food Engineering, 2014
In this paper the effectiveness of dense phase carbon dioxide (DPCD) treatment to inactivate different bacterial strains inoculated on the surface of solid food matrices is studied. The bacterial survival is investigated on three distinct matrices: Salmonella enterica spiked on fresh cut coconut (Cocos nucifera), Escherichia coli on fresh cut carrot (Daucus carota) and Listeria monocytogenes on dry cured ham surface. Bacterial inactivation experiments are carried out in order to develop and identify mathematical models whose relative performance is assessed in terms of goodness-of-fit and a posteriori statistics obtained after parameters estimation. Operational maps illustrating the time required to achieve an assigned inactivation degree are built in order to guide the choice of the best operating conditions to be used in the process.