Comparison of Direct and Indirect Effects of Non-Thermal Atmospheric-Pressure Plasma on Bacteria (original) (raw)
Related papers
Inactivation of Bacteria in Flight by Direct Exposure to Nonthermal Plasma
IEEE Transactions on Plasma Science, 2000
Plasma treatment is a promising technology for fast and effective sterilization of surfaces, waterflow, and airflow. The treatment of airflow is an important area of healthcare and biodefense that has recently gained the interest of many scientists. In this paper, we describe a dielectric barrier grating discharge (DBGD) which is used to study the inactivation of airborne Escherichia coli inside a closed air circulation system. Earlier published results indicate approximately 5-log reduction (99.999%) in the concentration of the airborne bacteria after single DBGD exposure of 10-s duration. This paper investigates plasma species influencing the inactivation. The two major factors that are studied are the effect of charged and short-lived species (direct exposure to plasma) and the effect of ozone. It is shown that for a 25% reduction in direct exposure, the inactivation falls from 97% to 29% in a single pass through the grating. The influence of ozone was studied by producing ozone remotely with an ozone generator and injecting the same concentration into the system, as that produced by the DBGD plasma. The results show a 10% reduction in the bacterial load after 10-s exposure to ozone; thus, ozone alone may not be one of the major inactivating factors in the plasma.
Journal of Applied …, 2009
Atmospheric pressure dielectric barrier discharge ͑DBD͒ plasma has been employed on Gram-negative bacteria, Escherichia coli BL21. Treatment was carried out using plasma generated with different compositions of gases: CH 4 / N 2 ͑1:2͒, O 2 , N 2 / O 2 ͑1:1͒, N 2 , and Ar, and by varying plasma power and treatment time. E. coli cells were exposed under the DBD plasma in triplicates, and their surviving numbers were observed in terms of colony forming units. It has been observed that the CH 4 / N 2 plasma exhibits relatively higher sterilization property toward E. coli compared to plasma generated by using O 2 , N 2 / O 2 , N 2 , and Ar gas mixtures. The time to kill up to 90% of the initial population of the E. coli cells was found to be about 2-3 min for CH 4 / N 2 and O 2 gas mixture DBD plasma. A prolongation of treatment time and an increase in the dissipated power significantly improved the E. coli killing efficiency of the atmospheric pressure DBD plasma.
Food Engineering Reviews, 2020
Microbial inactivation efficacy of plasma generated by a custom-made floating electrode dielectric barrier discharge (FE-DBD) or cold plasma at three different frequencies (1 kHz, 2 kHz, and 3.5 kHz) was experimentally evaluated for its inactivation of the pathogen surrogate Enterobacter aerogenes on a glass surface to obtain inactivation kinetics. COMSOL Mul-tiphysics® was used to numerically simulate the amount and the distribution of reactive species within an FE-DBD system. Microbial inactivation kinetics was predicted using species concentrations and microbial inactivation rates from the literature and compared with experimental data. The results showed that the FE-DBD plasma treatment achieved a microbial reduction of 4.3 ± 0.5 log CFU/surface at 3.5 kHz, 5.1 ± 0.09 log CFU/surface at 2 kHz, and 5.1 ± 0.05 log CFU/surface at 1 kHz in 2 min, 3 min, and 6 min, respectively. The predicted values were 4.02 log CFU/surface, 4.10 log CFU/surface, and 4.56 log CFU/surface at 1 kHz, 2 kHz, and 3.5 kHz, respectively. A maximum 1 log difference was observed between numerical predictions and the experimental results. The difference might be due to synergistic interactions between plasma species, UV component of FE-DBD plasma, and/or the electrical field effects, which could not be included in the numerical simulation.
Inactivation of Bacteria and Biomolecules by Low-Pressure Plasma Discharges
Plasma Processes and Polymers, 2010
The inactivation of bacteria and biomolecules using plasma discharges were investigated within the European project BIODECON. The goal of the project was to identify and isolate inactivation mechanisms by combining dedicated beam experiments with especially designed plasma reactors. The plasma reactors are based on a fully computer-controlled, low-pressure inductively-coupled plasma (ICP). Four of these reactors were built and distributed among the consortium, thereby ensuring comparability of the results between the teams. Based on this combined effort, the role of UV light, of chemical sputtering (i.e. the combined impact of neutrals and ions), and of thermal effects on bacteria such as Bacillus atrophaeus, Aspergillus niger, as well as on biomolecules such as LPS, Lipid A, BSA and prions have been evaluated. The particle fluxes emerging from the plasmas are quantified by using mass spectrometry, Langmuir probe measurements, retarding field measurements and optical emission spectroscopy. The effects of the plasma on the biological systems are evaluated using atomic force microscopy, ellipsometry, electrophoresis, specially-designed western blot tests, and animal models. A quantitative analysis of the plasma discharges and the thorough study of their effect on biological systems led to the identification of the different mechanisms operating during the decontamination process. Our results confirm the role of UV in the 200-250 nm range for the inactivation of microorganisms and a large variability of results observed between different strains of the same species. Moreover, we also demonstrate the role of chemical sputtering corresponding to the synergism between ion bombardment of a surface with the simultaneous reaction of active species such as O, O 2 or H. Finally, we show that plasma processes can be efficient against different micro-organisms, bacteria and fungi, pyrogens, model proteins and prions. The effect of matrices is described, and consequences for any future industrial implementation are discussed.
Design an Atmospheric Pressure Non-Thermal Plasma Device for Killing Bacteria
Abstract In this work, a dielectric barrier discharge DBD plasma system has been designed and fabricated . This system produces non-thermal atmospheric pressure plasma , where two planar stainless steel electrodes with a diameter (4.5cm ) were used . Besides an upper electrode was covered by a sheet of Pyrex with thickness (1.2 mm) as an electrical insulator . For comparison purpose, another electrode with a diameter (2.5cm) was used as an upper electrode . The distance between the electrodes was fixed at two values: 1mm and 2mm . Characteristics of the system such as I-V curve and breakdown voltage at many different conditions were studied . The study also included the effect of both area of electrodes and the distance between the electrodes on the current of the system and breakdown voltage, It was found that by increasing the distance between the electrodes the breakdown voltage increased. It was also found that the current values increases on the decrease in the distance between the electrodes . Also it was found that by increasing the area of electrode the value of breakdown voltage increases and the current value decreases . This work also included the application of the plasma produced from the system in the field of bacterial sterilization , where samples of Gram- positive bacteria (Staphylococcus aureus) and Gram- negative bacteria (Escherichia coli) were exposed to intervals (1-20)second . It was found that the percentage of the killing of Gram- positive bacteria (S. aureas) was 100% at time (14)second , whereas ,the percentage of the killing of Gram-negative bacteria (E.coli) was 100% at (10) second. This shows that Gram-positive bacteria is more resistant than Gram-negative bacteria to sterilization by DBD plasma system.
Plasma interaction with microbes
New Journal of Physics, 2003
The germicidal effects of a non-equilibrium atmospheric pressure plasma generated by a novel resistive barrier discharge on representatives of the two classes of bacteria (Gram-negative and Gram-positive) are discussed. The plasma exposure, while being lethal to both bacterial classes, also produced gross structural damage in the Gram-negative E. coli while none was observed in the more structurally robust Gram-positive Bacillus subtilis. An electrophysical process involving the role of the electrostatic tension on a charged body in a plasma is invoked to explain both observations. Since the efficacy of this electrophysical process depends not only on the tensile strength of the bacterial cell wall but also on its shape and texture, the need for more experimental studies, using a wide range of bacteria belonging to various morphological groups, is suggested. Ways to further test the validity of this electrophysical lysis mechanism for Gramnegative bacteria on one hand, and also to extend its operation to the more robust Gram-positive bacteria on the other, are suggested.
Applied Biochemistry and Biotechnology, 2010
We developed and employed a new geometrical structure of dielectric barrier discharge in atmospheric pressure for bacterial broad spectrum sterilization. We utilized a plasma source having an AC power supply at 50 HZ and 5,400 V (rms value). We prepared suspensions of the Gram-negative bacteria species (Escherichia coli, Pseudomonas aeruginosa) and a Gram-positive of Bacillus cereus with Luria-Bertani broth media up to OD 600 nm =0.25 of McFarland standard. Afterglow of non-thermal atmospheric pressure plasma treated these suspensions. The influence of the atmospheric plasma afterglow on the species was assayed in different time durations 5, 10, and 15 min. The spectroscopic results of this investigation indicated that the survival reduction of the species can reach to 100% for P. aeruginosa in an exposure time of 10 min, E. coli and B. cereus in an exposure time of 15 min.
The interaction of a direct-current cold atmospheric-pressure air plasma with bacteria
Plasma Science, …, 2009
A direct-current cold atmospheric-pressure air plasma microjet (PMJ) based on the microhollow cathode discharge design is used to inactivate six types of bacteria within a small well-defined area on a large petri dish. We show that the PMJ is very effective in inactivating bacteria in their vegetative state as well as in the spore state within the area of plasma exposure. We also observed that bacteria in their vegetative state were inactivated efficiently outside the area of direct plasma exposure. Different bacteria responded differently to an increase in the plasma exposure (dose). Lastly, we observed two types of colony forming unit (CFU) distributions after plasma treatment; one distribution is diffusionlike with a gradual increase of the surviving CFU as one moves radially away from the area of direct plasma exposure, and the other distribution shows an essentially uniform reduction in surviving CFU across the entire petri dish.
Atmospheric-pressure, nonthermal plasma sterilization of microorganisms in liquids and on surfaces
Pure and Applied Chemistry, 2008
Gas discharge plasma inactivation of microorganisms at low (close to ambient) temperature is a promising area of investigation that is attracting widespread interest. This paper describes atmospheric-pressure, nonthermal plasma (NTP) methods for cold sterilization of liquids and thermal sensitive surfaces. These methods are based on the use of direct current (DC) gas discharge plasma sources fed with steady-state high voltage. Parameters characterizing the plasma sources used (plasma-forming gas, gas flow rate, electric power consumed, etc.) are given. The results for plasma sterilization of different microorganisms (vegetative cells, spores, fungi, biofilms) are presented. An empirical mathematical approach is developed for describing NTP inactivation of microorganisms. This approach takes into account not only the destruction of different components of the cells, but their reparation as well.
Plasma Medicine, 2013
Nonthermal plasmas (NTPs) represent a new class of sterilizing agents. A full set of NTP bioactive factors includes electric components (E, charged particles and electric field), neutral active particles (R), and UV. A specific construction of the direct current (DC) corona source was used that allowed dissection of NTP bioactive factors and quantitative evaluation of their individual and combined action on bacterial pathogens Pseudomonas aeruginosa and Staphylococcus aureus. 10 and 120 s were required for the positive and negative coronas, respectively, to kill 10 5 colony-forming units (CFU) P. aeruginosa. 10 s was required for both positive and negative coronas to kill 10 5 CFU S. aureus. For the positive corona, the bactericidal activity of components decreased as R+UV>E+UV>>UV and E+UV>R+UV>>UV for P. aeruginosa and S. aureus, respectively. For the negative corona, the bactericidal activity decreased as R+UV>>E+UV=UV=0 and R+UV>>E+UV>UV≈0 for P. aeruginosa and S. aureus, respectively. Despite low, if any, activity of electric components in the negative corona, the whole plasma effect was much higher than the effect of neutral particles and UV alone. The obtained results demonstrated that different combinations of bioactive plasma components exerted diverse species-specific bactericidal effects. It is synergy among plasma bioactive factors that supplies high bactericidal activity of NTP.