Atmospheric plasma provides the advantages of high microbial inactivation that can be performed under ambient conditions. It is consequently regarded as potential alternative to traditional food ...preservation methods.
In this study we systematically tested the influence of argon as plasma carrier gas with admixtures of oxygen (0–0.34vol.%) and nitrogen (0–0.3vol.%) towards its emission intensity of UV-C light, excited OH and N2-species and atomic oxygen. A mixture of argon, 0.135vol.% oxygen and 0.2vol.% nitrogen emitted four fold more UV photons than pure argon. However, sporicidal effects on Bacillus atrophaeus (3.1 log10) and Bacillus subtilis spores (2.4 log10) were found for pure argon plasma, which were similar as compared to the sporicidal effect of the plasma with highest UV-emission. To distinguish lethal effects caused by emitted UV-light and reactive species, UV-sensitive mutant spore strains (PS578 and FB122) were exposed to plasmas with different UV-emission intensities and a significant impact of UV-light on the first phase of spore inactivation was confirmed.
As an efficient method for the inactivation of microorganisms at low temperatures and atmospheric pressure, plasma is already commercially used for the sterilization of medical devices. The results presented in this study could be useful for a process optimization regardless if the plasma is applied for food preservation or surface decontamination. Especially the impact of emitted UV photons from the plasma on the first inactivation phase of endospores attached to surfaces, depicts a high potential of such plasmas for a rapid spore inactivation.
•A systematically testing of argon plasma with admixtures of oxygen and nitrogen was done.•Highest UV-emission for a mixture of argon with 0.135vol.% O2 and 0.2vol.% N2.•Similar sporicidal effects were found for a pure argon plasma compared to the one with highest UV-emission.•UV-sensitive spore strains confirmed the sporicidal effect of emitted UV-photons.•Biphasic spore inactivation was found, with a dominant effect of UV-photons on the first inactivation phase.
Plasma activated water (PAW), a physicochemical approach that can efficiently enable the inactivation effect of Bacillus cereus endospores, is receiving numerous attentions in food and other areas. ...However, the potential RONS featuring PAW that inactivates bacteria is an open issue. Here, we for the first time thoroughly clarified the functioning chemicals on antimicrobial ability in PAW by adding each corresponding scavenger at an optimized dose, including superoxide anion (O2−), singlet oxygen (1O2), hydroxyl radical (OH), hydrogen peroxide (H2O2), nitrite ions (NO2−), nitric oxide (NO) and peroxynitrite (ONOOH). An overall reduction of 1.74 log CFU/mL is determined by the sporicidal effects of PAW; however, when adding their corresponding scavengers, the effect was attenuated to different extents. The internal correlations are constructed using Spearman analysis based on the inactivation of endospores for determining their specific contributions in such a complex PAW system and corresponding effective factors are calculated. The Spearman coefficients of NO2−, O2−, H2O2, and NO were 0.476, 0.405, 0.168, and 0.143, revealing that the log CFU/mL reduction of B. cereus endospore was positively proportional to the contents of NO2−, O2−, H2O2, and NO. This study addresses the fundamental issues related to the chemicals in PAW and may initiate wide interest in PAW in physiochemistry and biology.
•Seven RONS components were detected in PAW.•Seven RONS components in PAW acted as the sporicidal contributors.•Sporicidal effects of RONS species were sequentially ranked by correlation analysis.•NO2− and O2− displayed the most important roles in the sporicidal effect on spores.
The introduction of novel composites suited for additive manufacturing machines offers a solution for the current slow adoption of the technology. Many composites offer secondary functions and ...mechanical improvements to suit unique applications better. This article presents the creation of a set of novel nanocomposites consisting of zinc oxide (ZnO) and a photocurable resin using a masked stereolithography additive machine. These nanocomposites are produced in 1%, 2.5%, 5%, and 7.5% concentrations and are characterized based on their mechanical and surface properties. Using ZnO allows for the creation of mechanically stronger parts with reduced wettability while offering antibacterial properties throughout the entire part. Best results were observed at a 5% concentration of ZnO with a nearly 25% strength increase and 45% decrease in wettability. Additionally, SEM analysis demonstrated proper dispersion with minimal agglomerations present. In the sporicidal effect analysis, the ZnO (with 7.5% concentration) reduced 31.5% of Clostridioides difficile spores. These results demonstrate the capability of producing antibacterial nanocomposites using low-cost additive manufacturing to enhance public health options.
The thermal resistance of Clostridium sporogenes PA 3679 ATCC 7955 was determined in soymilk (pH 7) and 0.1% peptone water (pH 7) by the capillary tube method. In the continuous flow high-pressure ...throttling, the temperature of soymilk increased due to instantaneous pressure release and the additional heat was supplied by a heat exchanger to achieve the set temperature. The soymilk was immediately cooled after a short preset hold time to below 40 °C. A significant increase in the heat resistance was observed in C. sporogenes spores when heated in soymilk in comparison to 0.1% peptone water. The D₁₂₁-value for spores in soymilk was approximately 3-folds higher than peptone water. The z-value was also much higher in soymilk as compared to that in 0.1% peptone water. Continuous flow high-pressure throttling (HPT) from 207 or 276 MPa to atmospheric pressure reduced the microbial populations in inoculated soymilk up to 6 log cycles when the holding times were 10.4, 15.6, and 20.8 s and the process temperatures were 85, 121, 133, and 145 °C, respectively. The sporicidal effect increased as the operating pressure, time, and temperature were increased. More injured spores were found at 207 MPa than at 276 MPa, indicating that lower pressure caused cell injury whereas high pressure caused cell death.
Summary
Alicyclobacillus acidoterrestris
is a typical endospore‐forming microorganism, whose spores are able to germinate in Not From Concentrate juice causing its spoilage. In this work, dielectric ...barrier discharge atmospheric cold plasma (DBD‐ACP) at the voltage of 30 kV was used to inactivate
Alicyclobacillus acidoterrestris
spores in NFC juice (2–8 min). The results showed spores reduced nearly 3‐log CFU mL
−1
after 8 min treatment, and the morphology of spores were severely disrupted, causing the release of their contents. Furthermore, proteomic analysis showed totals of 122 and 170 different expression proteins were detected in group C (control)/Ct1 (30 kV, 4 min) and C/Ct2 (30 kV, 8 min), respectively, indicating that metabolic activities of spores including amino acid and energy metabolic, protein biosynthesis, DNA replication and spore germination are inhibited. This study confirms the inactivation of
Alicyclobacillus acidoterrestris
spores by DBD‐ACP and provides some new perspectives on the inactivation mechanisms of spores by DBD‐ACP.
Previous studies have shown that the combination disinfectant,
Ortho
-phthalaldehyde and benzyldimethyldodecylammonium chloride (ODB), can effectively kill a variety of microorganisms, such as
...Escherichia coli
,
Staphylococcus aureus
, and
Candida albicans
. To observe the sporicidal ability and mechanism of ODB for spores,
Bacillus subtilis
spores were used as the research object in this experiment. TEM images revealed that ODB destroyed the integrity of the coat, cortex, and inner membrane of the spores after 0.5-h treatment, and the nuclear material was also broken and exuded after 4-h treatment. The broken structure led to the release of dipicolinic acid (DPA) in large amount. The results show that
B. subtilis
spores can be effetely killed by ODB through destroying the structure of the spores.
This study purpose was to evaluate the in vitro inhibitory properties of Italian acacia honey extracts against pathogenic aquatic oomycete/fungal isolates that cause different diseases in crayfish, ...resulting in an elevated mortality rate. The antimycotic activity of acacia honey aqueous extracts was evaluated against the strain UEF88662 of Aphanomyces astaci (oomycete) and the strain SMM2 of Fusarium avenaceum (fungus). The extracts preparation was carried out with water by a cheap, not complex and organic solvent‐free procedure, with low environmental impact and the higher possibility of large‐scale reproducibility. The anti‐oomycete and antifungal activities were quantitatively evaluated by growth, survival and sporulation microbiological assays. The extracts displayed a dose‐dependent inhibitory efficacy on oomycete and fungal growth and survival, as well as on the production of oomycete and fungal spores. Supported by future in vivo studies, our results encourage the use of natural extracts like honey as innovative tools to counteract mycotic infections.
Significance and Impact of the Study
The continuous spread of aquatic fungal disease as the ‘crayfish plague’ and the ‘burn spot disease’ has severe ecological and commercial repercussions. Critical factor to prevent further spread is the availability of effective antifungals possibility derived from local natural resources to use in innovative strategies of control and eradication of these diseases. This study provides relevant information about the in vitro anti‐oomycete and antifungal activity of Italian acacia honey aqueous extracts against two highly infectious and dangerous pathogenic species, Aphanomyces astaci and Fusarium avenaceum, that are responsible for important crayfish diseases.
Significance and Impact of the Study: The continuous spread of aquatic fungal disease as the ‘crayfish plague’ and the ‘burn spot disease’ has severe ecological and commercial repercussions. Critical factor to prevent further spread is the availability of effective antifungals possibility derived from local natural resources to use in innovative strategies of control and eradication of these diseases. This study provides relevant information about the in vitro anti‐oomycete and antifungal activity of Italian acacia honey aqueous extracts against two highly infectious and dangerous pathogenic species, Aphanomyces astaci and Fusarium avenaceum, that are responsible for important crayfish diseases.
The sporicidal effect of 20 different radio-frequency plasma processes produced by combining five different gas mixtures O(2), Ar/H(2) (50/50%), Ar/H(2) (5/95%), O(2)/H(2) (50/50%), O(2)/H(2) (95/5%) ...with four power/pressure settings were tested. Sporicidal effects of oxygen-containing plasmas were dependent on power at low pressure settings but not at high pressure settings. In the absence of oxygen no power dependency was observed at either high or low pressure settings. Survivor curves obtained with the use of nonoxygen plasmas typically had a tailing tendency. Only a mixture-optimized Ar/H(2) (15/85%) plasma process was not encumbered by tailing, and produced a decimal reduction time (D value) below 2 min for Bacillus stearothermophilus spores. Scanning electron microscopy showed that a CF(4)/O(2) plasma did more damage to the substrate than the 15/85% Ar/H(2) plasma. The present results indicate that UV irradiation inactivation is swift and power and pressure independent. Additionally, it is produced at low energy. However, it is not complete. Inactivation through etching is highly power and pressure dependent; finally, inactivation by photodesorption is moderately power and pressure dependent. A sterilization process relying on this mechanism is very advantageous because it combines a highly sporicidal effect with low substrate damage.
