Rate Of Inactivation Research Articles

Altered flexor carpi radialis motor axon excitability properties after cerebrovascular stroke.

Spinal motoneurons may become hyperexcitable after a stroke. Knowledge about motoneuron hyperexcitability remains clinically important as it may contribute to a number of phenomena including spasticity, flexion synergies, and abnormal limb postures. Hyperexcitability seems to occur more often in muscles that flex the wrist and fingers (forearm flexors) compared to other upper limb muscles. The cause of hyperexcitability remains uncertain but may involve plastic changes in motoneurons and their axons. To characterize intrinsic membrane properties of flexor carpi radialis (FCR) motor axons after stroke using nerve excitability testing. Nerve excitability testing using threshold tracking techniques was applied to characterize FCR motor axon properties in persons who suffered a first-time unilateral cortical/subcortical stroke 23 to 308 days earlier. The median nerve was stimulated at the elbow bilaterally in 16 male stroke subjects (51.4 ± 2.9 y) with compound muscle action potentials recorded from the FCR. Nineteen age-matched males (52.7 ± 2.4 y) were also tested to serve as controls. Axon parameters after stroke were consistent with bilateral hyperpolarization of the resting potential. Nonparetic and paretic side axons were modeled by a 2.6-fold increase in pump currents (IPumpNI) together with an increase (38%-33%) in internodal leak conductance (GLkI) and a decrease (23%-29%) in internodal H conductance (Ih) relative to control axons. A decrease (14%) in Na+ channel inactivation rate (Aah) was also needed to fit the paretic axon recovery cycle. "Fanning out" of threshold electrotonus and the resting I/V slope (stroke limbs combined) correlated with blood potassium [K+] (R = -0.61 to 0.62, p< 0.01) and disability (R = -0.58 to 0.55, p < 0.05), but not with spasticity, grip strength, or maximal FCR activity. In contrast to our expectations, FCR axons were not hyperexcitable after stroke. Rather, FCR axons were found to be hyperpolarized bilaterally post stroke, and this was associated with disability and [K+]. Reduced FCR axon excitability may represent a kind of bilateral trans-synaptic homeostatic mechanism that acts to minimize motoneuron hyperexcitability.

Effects of milling condition on nutritional, physicochemical, and textural properties of highland barley grains

AbstractBackground and ObjectivesA lower degree milling to obtain cereal grains with acceptable cooking qualities was recommended for the higher retainment of bioactive compounds. The aim of this work was to investigate effects of milling condition on nutritional, physicochemical and cooking qualities of highland barley (HB) grains.FindingsEffects of tempering results showed that increased water addition amount caused decrease in degree of milling (DOM) and increase in head rice yield (HRY). Effects of milling condition results showed that activities of polyphenol oxidase (PPO) and peroxidase (POD) showed significantly decreasing tendency as DOM increased. When DOM increased from 0% to 8%, the POD activity decreased from 140 to 3.75 Ug−1 min−1, with inactivation rate of 97.3%. Milling also witnessed a 70.1% reduction of PPO activity, from 27.74 to 8.30 Ug−1 min−1. Pasting results showed that viscosity parameters gradually increased and pasting temperature decreased as DOM increased. Texture results showed that the hardness, gumminess and chewiness of HB grains gradually decreased with the increase of DOM, while there was no significant difference in resilience, adhesiveness and springiness.ConclusionsBased on the nutritional, physicochemical and cooking qualities of HB grains, the optimal milling condition of HB grains was fixed at 6% of tempering water, 10 min of tempering time and 10% of DOM.

CO2 concentration as an indicator of indoor ventilation performance to control airborne transmission of SARS-CoV-2

BackgroundThe Wells-Riley equation has been extensively used to quantify the infection risk of airborne transmission indoors. This equation is difficult to apply to actual conditions because it requires measurement of the outdoor air supply rate, which vary with time and are difficult to quantify. The method of determining the fraction of inhaled air that has been exhaled previously by someone in a building using a CO2 concentration measurement can solve the limitations of the existing method. Using this method, the indoor CO2 concentration threshold can be determined to keep the risk of infection below certain conditions. MethodsBased on the calculation of the rebreathed fraction, an appropriate mean indoor CO2 concentration and required air exchange rate to control SARS-CoV-2 airborne transmission was calculated. The number of indoor occupants, ventilation rate, and the deposition and inactivation rates of the virus-laden aerosols were considered. The application of the proposed indoor CO2 concentration-based infection rate control was investigated through case studies in school classrooms and restaurants. ResultsIn a typical school classroom environment with 20–25 occupants and an exposure time of 6–8 h, the average indoor CO2 concentration should be kept below 700 ppm to control the risk of airborne infection indoors. The ASHRAE recommended ventilation rate is sufficient when wearing a mask in classrooms. For a typical restaurant with 50–100 occupants and an exposure time of 2–3 h, the average indoor CO2 concentration should be kept below about 900 ppm. Residence time in the restaurant had a significant effect on the acceptable CO2 concentration. ConclusionGiven the conditions of the occupancy environment, it is possible to determine an indoor CO2 concentration threshold, and keeping the CO2 concentration lower than a certain threshold could help reduce the risk of COVID-19 infection.

In-situ growth pH-adjusted iodine defects engineering BiOI film on 3D-printed polymer substrate for efficient organic pollutant and microorganism purification

Although BiOI has been constructed on FTO or metals to overcome the application shortcomings of powdered photocatalyst, but BiOI film with customizable size and shape will be more suitable for purification environments. In this study, 3D-printed polymer models-likes carbon nanotube, graphene ball, and metal–organic framework are exampled to act as substrates. Compared with the traditional heterostructure film fabricated at complicated temperature and pressure, we report a facile route to synthesize the iodine-defect engineering BiOI film on 3D-printed polymer, under mild room temperature and pressure through only adjusting BiOI solution pH value. The produced iodine vacancies can act as traps to facilitate the separation of electron-holes carriers. Additionally, a self-converted LED device enhances the utilized efficiency of irradiated light. This work reveals good purification efficiency on ca. 99.67% degradation rate towards RhB and >99.99% inactivation rate against E. coli and S. aureus in 1 or 3 h because of the O2−, OH and h+ redox.

Impact of invertebrates on water quality safety and their sheltering effect on bacteria in water supply systems

Invertebrates in drinking water not only affect human health, but also provide migration and shelter for pathogenic microorganisms. Their residues and metabolites also produce DBPs (disinfection by-products), which have adverse effects on the health of residents. In this study, the contributions of the rotifers and nematodes to the BDOC (biodegradable dissolved organic carbon), BRP (bacterial regrowth potential) and DBPs in drinking water were explored, and the sheltering effects of chlorine-resistant invertebrates on indigenous bacteria and pathogenic bacteria were studied, and the health and safety risk of invertebrates in drinking water was also assessed. The contributions of rotifer BAPs (biomass-associated products), UAPs (utilization-associated products) of rotifer, and nematode BAPs to the BRP were 46, 1240, and 24 CFU/mL. Nematodes were found to have a sheltering effect on indigenous bacteria and pathogenic bacteria, allowing them to resist chlorine disinfection and UV (ultraviolet) disinfection. When subjected to a UV dose of 40 mJ/cm2, the inactivation rates of indigenous bacteria and three pathogenic bacteria decreased by 85% and 39–50% when bacteria were sheltered by the living nematodes; while decreased by 66% and 15–41% when they were sheltered by nematode residue. The safety risk posed by invertebrates in the drinking water was mainly due to their ability to promote bacterial regeneration and carry bacteria. This study aims to provide a theoretical basis and technical support for the risk control of invertebrates' pollution, and provides references for ensuring the safety of drinking water and formulating standards for the levels of invertebrates in drinking water.

Negligible risk of surface transmission of SARS-CoV-2 in public transportation.

Exposure to pathogens in public transport systems is a common means of spreading infection, mainly by inhaling aerosol or droplets from infected individuals. Such particles also contaminate surfaces, creating a potential surface-transmission pathway. A fast acoustic biosensor with an antifouling nano-coating was introduced to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on exposed surfaces in the Prague Public Transport System. Samples were measured directly without pre-treatment. Results with the sensor gave excellent agreement with parallel quantitative reverse-transcription polymerase chain reaction (qRT-PCR) measurements on 482 surface samples taken from actively used trams, buses, metro trains and platforms between 7 and 9 April 2021, in the middle of the lineage Alpha SARS-CoV-2 epidemic wave when 1 in 240 people were COVID-19 positive in Prague. Only ten of the 482 surface swabs produced positive results and none of them contained virus particles capable of replication, indicating that positive samples contained inactive virus particles and/or fragments. Measurements of the rate of decay of SARS-CoV-2 on frequently touched surface materials showed that the virus did not remain viable longer than 1-4h. The rate of inactivation was the fastest on rubber handrails in metro escalators and the slowest on hard-plastic seats, window glasses and stainless-steel grab rails. As a result of this study, Prague Public Transport Systems revised their cleaning protocols and the lengths of parking times during the pandemic. Our findings suggest that surface transmission played no or negligible role in spreading SARS-CoV-2 in Prague. The results also demonstrate the potential of the new biosensor to serve as a complementary screening tool in epidemic monitoring and prognosis.

Metal-free nitrogen-doped carbon nanodots as an artificial nanozyme for enhanced antibacterial activity

Bacterial infections have become a considerable obstacle to public health due to the emergence of antibiotic resistance. Herein, we rationally developed a novel and attractive nitrogen-doped carbon nanodots (N-CNDs) as efficient metal-free artificial nanozymes that synergistically and efficiently inhibit bacterial survival by inheriting the bacteriostatic ability of tea polyphenols and light-triggered oxidase-like catalytic activity. The excellent oxidase-mimicking activity exhibited by N-CNDs in the light was mediated by superoxide radicals (•O2−) with a high maximum reaction rate (1.59 μM⋅s−1) and a low Michaelis constant (0.421 mM). Furthermore, the constructed N-CNDs-based nanozyme was demonstrated to serve as a complex biomaterial platform for efficient sterilization by light-driven oxygen molecule generation of •O2−. Remarkably, the inherent antibacterial ability of N-CNDs can effectively inhibit both Gram-positive and Gram-negative bacteria, particularly against Gram-positive S. aureus at a minimum inhibitory concentration (MIC90) of 375 μg⋅mL−1. The inactivation rates of N-CNDs alone agsinst E. coli and S. aureus were 59.72% and 37.15%, respectively. However, the inactivation rates of E. coli and S. aureus by N-CNDs achieved by light were as high as 97.91% and 80.02%, respectively. Encouragingly, a two-way ANOVA revealed that the concentration of N-CNDs and the duration of light exposure had a synergistic effect on antibacterial behavior, which provided favorable conditions for the sustained eradication of exposed bacteria. This synergistic strategy for bacterial eradication based on a novel metal-free carbon-based nanozyme provides a powerful and feasible approach for bacterial contamination management in food safety and environmental protection.

Quality Determination of a High-Pressure Processed Avocado Puree-Based Smoothie Beverage

The aim was to study the quality stability of a high-pressure (HP) processed avocado puree-based smoothie beverage and to determine its shelf life. To achieve this mathematical description of HP process parameters (pressure, temperature, and pH conditions) on polyphenoloxidase (PPO) inactivation of avocado-puree (base of the smoothie beverage), use of the appropriate kinetic models was undertaken. Inactivation rate constants were obtained for combinations of constant pressure (600, 700, 750 MPa) and temperature (25, 35, 45 °C) for pH values 4 and 5. According to the Eyring and Arrhenius equations, activation volumes and activation energies, respectively, representing pressure and temperature dependence of the inactivation rate constant, were calculated for all temperatures and pressures studied. The combined use of HP led to PPO inactivation (&lt;10% remaining PPO activity). An increase in the temperature at pressure 600 or 750 MPa caused an increase in PPO inactivation (4.5 and 9.0%, respectively). The ultimate goal was to produce a HP processed avocado puree-based smoothie beverage (containing acid whey and other ingredients) with superior quality and increased shelf life (under refrigeration). The blended ingredients were HP processed in PET packages (600 MPa-25 °C-10 min, 600 MPa-35 °C-10 min, 750 MPa-25 °C-5 min, 750 MPa-35 °C-5 min) based on PPO inactivation as well as industrial practices. Non-processed as well as thermally (TM) processed (90 °C-5 min) samples were used as control samples. No significant differences were found in sensorial attributes between non-processed and HP samples, although the aroma and acceptability scores decreased significantly for thermally pasteurized smoothies. Based on the data obtained, 600 MPa-25/35 °C-10 min are sufficient to obtain safe smoothies (of pH 5 approximately) (up to 6 months) whose organoleptic properties are equally as acceptable to consumers as freshly made smoothies.

Impact of Chlorine Dioxide on Pathogenic Waterborne Microorganisms Occurring in Dental Chair Units.

Bacterial contamination is a problem in dental unit water lines with the consequence of implementing regular disinfection. In this study, the short-term impact of chlorine dioxide (ClO2) treatment was investigated on the microorganisms Legionella pneumophila and L. anisa, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. The environmental background was proven as an important factor regarding the tolerance to 0.4 mg/L ClO2 as saline and phosphate-buffered saline resulted in a higher bacterial reduction than tap water. Gram-positive microorganisms demonstrated higher robustness to ClO2 than Gram-negative, and microorganisms adapted to tap water showed increased stability compared to cultured cells. At high densities, substantial numbers of bacteria were able to withstand disinfection, whereby the use of 4.6 mg/L ClO2 increased the inactivation rate. A massive cell decrease occurred within the first 5 minutes with subsequent plateau formation or slowed cell reduction upon further exposure. This biphasic kinetics cannot be explained by a ClO2 depletion effect alone, because the probability of bacterial subpopulations with increased tolerance should be taken into account, too. Our results prove high disinfection efficiency to microorganisms that were rather found in correlation to the level of bacterial contamination and background solutions than the chosen concentration for ClO2 treatment itself.

Pulsed light treatment of table grape juice: Influence of matrix pH on microbial and enzyme inactivation kinetics

The influence of pulsed light (PL) treatment and matrix pH was tested in the case of green table grape juice. Escherichia coli, Listeria monocytogenes, and Saccharomyces cerevisiae were inoculated into the table grape juices with matrix pH levels of 3.0, 3.5, and 4.0. Further, the juice was treated at 378–3186 J/cm2. The Weibull model better explained the microbial inactivation data. The shape parameters (β) from the Weibull model for E. coli, L. monocytogenes, and S. cerevisiae are 0.95 ± 0.02, 0.55 ± 0.04, and 0.40 ± 0.03, respectively. A lesser δ-value (scale parameter in J/cm2) was obtained for each microorganism at a lower pH. PL exposure resulted in a lack of cell visibility, cell wall, and cell membrane disruption in bacterial cells. The inactivation of polyphenol oxidase (PPO), peroxidase (POD), and pectin methyl esterase (PME) was studied at an elevated fluence level of 1152–3186 J/cm2. Enzymes in the juice were less sensitive to PL than microorganisms. The enzyme inactivation of >90% was achieved at 3186 J/cm2; thus, the juice was adjudged as the microbially safe and enzymatically stable pasteurized sample. The PL-induced enzyme inactivation followed nth-order kinetics with an inactivation order (n) of 1.1, 1.15, and 0.85 for PPO, POD, and PME, respectively. The enzyme inactivation rate was higher at a low pH. The PL-treated pasteurized juice at pH 3.5 showed the highest sensory acceptance (7.4 out of 9), with a minimal color change, a 7% loss in total phenolics, and a 12% loss in vitamin C and flavonoids.

Actinobacteria produce taste and odor in drinking water reservoir: Community composition dynamics, co-occurrence and inactivation models

Taste and odor (T&O) has become a significant concern for drinking water safety. Actinobacteria are believed to produce T&O during the non-algal bloom period; however, this has not been widely investigated. In this study, the seasonal dynamics of the actinobacterial community structure and inactivation of odor-producing actinobacteria were explored. The results indicated that the diversity and community composition of actinobacteria exhibited significant spatiotemporal distribution. Network analysis and structural equation modeling showed that the actinobacterial community occupied a similar environmental niche, and the major environmental attributes exhibited spatiotemporal dynamics, which affected the actinobacterial community. Furthermore, the two genera of odorous actinobacteria were inactivated in drinking water sources using chlorine. Amycolatopsis spp. have a stronger chlorine resistance ability than Streptomyces spp., indicating that chlorine inactivates actinobacteria by first destroying cell membranes and causing the release of intracellular compounds. Finally, we integrated the observed variability in the inactivation rate of actinobacteria into an expanded Chick-Watson model to estimate its effect on inactivation. These findings will deepen our understanding of the seasonal dynamics of actinobacterial community structure in drinking water reservoirs and provide a foundation for reservoir water quality management strategies.

The β3-subunit modulates the effect of venom peptides ProTx-II and OD1 on NaV 1.7 gating.

The voltage-gated sodium channel NaV 1.7 is involved in various pain phenotypes and is physiologically regulated by the NaV -β3-subunit. Venom toxins ProTx-II and OD1 modulate NaV 1.7 channel function and may be useful as therapeutic agents and/or research tools. Here, we use patch-clamp recordings to investigate how the β3-subunit can influence and modulate the toxin-mediated effects on NaV 1.7 function, and we propose a putative binding mode of OD1 on NaV 1.7 to rationalise its activating effects. The inhibitor ProTx-II slowed the rate of NaV 1.7 activation, whilst the activator OD1 reduced the rate of fast inactivation and accelerated recovery from inactivation. The β3-subunit partially abrogated these effects. OD1 induced a hyperpolarising shift in theV1/2 of steady-state activation, which was not observed in the presence of β3. Consequently, OD1-treated NaV 1.7 exhibited an enhanced window current compared with OD1-treated NaV 1.7-β3 complex. We identify candidate OD1 residues that are likely to prevent the upward movement of the DIV S4 helix and thus impede fast inactivation. The binding sites for each of the toxins and the predicted location of the β3-subunit on the NaV 1.7 channel are distinct. Therefore, we infer that the β3-subunit influences the interaction of toxins with NaV 1.7 via indirect allosteric mechanisms. The enhanced window current shown by OD1-treated NaV 1.7 compared withOD1-treated NaV 1.7-β3 is discussed in the context of differing cellular expressions of NaV 1.7 and the β3-subunit in dorsal root ganglion (DRG) neurons. We propose that β3, as the native binding partner for NaV 1.7 in DRG neurons, should be included during screening of molecules against NaV 1.7 in relevant analgesic discovery campaigns.

Inactivation of pectinmethylesterase in fresh orange juice by cold atmospheric plasma technology: A kinetic study

Preservation of fruit juices requires the inactivation of natural endogenous enzymes, such as pectinmethylesterase (PME). Within this work, cold atmospheric plasma (CAP), and in particular a dielectric barrier plasma jet fed with helium gas, was demonstrated to effectively inactivate PME of freshly squeezed orange juice in short treatment times (2–30 min). By a combination of temperature measurements and a multidimensional heat transfer model, the temperature profile of the whole sample during plasma treatment was extracted. It was found that the thermal phenomena were not a driving factor for PME inactivation. Plasma treatment of orange juices resulted in inactivation of 55–80% of PME with <5.0% of PME inactivation caused by the temperature increase from 20 to 90 °C. The Weibull distribution model compared to the first-order fractional, the sigmoidal logistic and the Hulsheger's kinetic models was found to better describe mathematically (R2 > 0.99; Af = 1.002–1.052) the effect of CAP processing on residual PME activity. Multi-parameter equation fits allowed the prediction of residual PME activity as a function of the applied voltage, helium flow, and treatment time. Generally, higher voltages and lower helium flows applied led to higher PME inactivation rates in fresh orange juice.

Linkages between COVID-19, solar UV radiation, and the Montreal Protocol

There are several connections between coronavirus disease 2019 (COVID-19), solar UV radiation, and the Montreal Protocol. Exposure to ambient solar UV radiation inactivates SARS-CoV-2, the virus responsible for COVID-19. An action spectrum describing the wavelength dependence of the inactivation of SARS-CoV-2 by UV and visible radiation has recently been published. In contrast to action spectra that have been assumed in the past for estimating the effect of UV radiation on SARS-CoV-2, the new action spectrum has a large sensitivity in the UV-A (315–400 nm) range. If this “UV-A tail” is correct, solar UV radiation could be much more efficient in inactivating the virus responsible for COVID-19 than previously thought. Furthermore, the sensitivity of inactivation rates to the total column ozone would be reduced because ozone absorbs only a small amount of UV-A radiation. Using solar simulators, the times for inactivating SARS-CoV-2 have been determined by several groups; however, many measurements are affected by poorly defined experimental setups. The most reliable data suggest that 90% of viral particles embedded in saliva are inactivated within ~ 7 min by solar radiation for a solar zenith angle (SZA) of 16.5° and within ~ 13 min for a SZA of 63.4°. Slightly longer inactivation times were found for aerosolised virus particles. These times can become considerably longer during cloudy conditions or if virus particles are shielded from solar radiation. Many publications have provided evidence of an inverse relationship between ambient solar UV radiation and the incidence or severity of COVID-19, but the reasons for these negative correlations have not been unambiguously identified and could also be explained by confounders, such as ambient temperature, humidity, visible radiation, daylength, temporal changes in risk and disease management, and the proximity of people to other people. Meta-analyses of observational studies indicate inverse associations between serum 25-hydroxy vitamin D (25(OH)D) concentration and the risk of SARS-CoV-2 positivity or severity of COVID-19, although the quality of these studies is largely low. Mendelian randomisation studies have not found statistically significant evidence of a causal effect of 25(OH)D concentration on COVID-19 susceptibility or severity, but a potential link between vitamin D status and disease severity cannot be excluded as some randomised trials suggest that vitamin D supplementation is beneficial for people admitted to a hospital. Several studies indicate significant positive associations between air pollution and COVID-19 incidence and fatality rates. Conversely, well-established cohort studies indicate no association between long-term exposure to air pollution and infection with SARS-CoV-2. By limiting increases in UV radiation, the Montreal Protocol has also suppressed the inactivation rates of pathogens exposed to UV radiation. However, there is insufficient evidence to conclude that the expected larger inactivation rates without the Montreal Protocol would have had tangible consequences on the progress of the COVID-19 pandemic.Graphical abstract

固相法によるモリブデン酸セリウムの作製とその抗ウイルス活性

Single-phase powders of γ-Ce2Mo3O13, Ce8Mo12O49, and Ce2Mo4O15 were prepared using the solid-phase method. Then, the antiviral activity of these powders against the non-enveloped virus bacteriophage Qβ and the enveloped virus bacteriophage Φ6 were evaluated. Moreover, H2O2 assay and catalase inactivation test were performed. Regarding the antiviral activity of the prepared samples, the activity against bacteriophage Φ6 was higher than the activity against bacteriophage Qβ. The antiviral activity order for bacteriophage Φ6 was correlated with the amount of H2O2 generated and the catalase inactivation rate. It depended also on the eluted Ce/Mo ratio. These results imply that the antiviral activity on bacteriophage Qβ is influenced by neutralization of the negative charge of capsid by rare earth ions and by adsorption of heteropolyacids to specific sites of the virus. Results suggest that the oxidation reaction of Ce (IV) or of the H2O2, and the adsorption of heteropolyacids formed by Ce and molybdate ions affect the antiviral activity against bacteriophage Φ6. Among the compounds examined this time, γ-Ce2Mo3O13 exhibited the highest antiviral activity against bacteriophage Φ6.

Optimizing ozone dose and contact time for removal of antibiotic-resistant P. aeruginosa, A. baumannii, E. coli, and associated resistant genes in effluent of an activated sludge process in a municipal WWTP.

This study aimed to investigate the impact of ozonation on inactivation of antibiotic-resistant bacteria (ARB) including E. coli, P. aeruginosa, and A. baumannii, as well as on removal of 16S-rRNA gene and their associated antibiotic-resistant genes (ARGs) indigenously present in effluent of municipal wastewater treatment plant. The Chick-Watson model was used to describe bacterial inactivation rates at specific ozone doses. Maximum reduction of total cultivable A. baumannii, E. coli, and P. aeruginosa were found to be 7.6, 7.1, and 4.7 log, respectively, with the highest ozone dose of 0.48 gO3/gCOD at 12min contact time. According to the study results, complete inactivation of ARB and bacterial regrowth was not observed after 72h incubation. The culture methods overestimated the performance of disinfection processes and propidium monoazide combined with qPCR, and showed the presence of viable but non-culturable bacteria after ozonation. ARGs were more persistent to ozone than ARB. The results of this study highlighted the significance of specific ozone dose and contact time in ozonation process considering the bacterial species and associated ARGs as well as the wastewater physicochemical characteristics, in order to help diminish the entrance of the biological microcontaminants into the environment.

Evaluation of altered environmental conditions as a decontamination approach for SARS-CoV-2 when applied to aircraft related materials.

The purpose of this study was to evaluate the effects of altered environmental conditions, specifically elevated temperature at various levels of expected relative humidity (RH), on the inactivation of SARS-CoV-2 when applied to U.S. Air Force aircraft materials. SARS CoV-2 (USA-WA1/2020) was spiked (∼1×105 TCID50) in either synthetic saliva or lung fluid, dried onto porous (e.g. Nylon strap) and nonporous materials (e.g. bare aluminum, silicone, and ABS plastic), placed in a test chamber and exposed to environmental conditions ranging from 40 to 51.7 °C and RH ranging from 0% to 50%. The amount of infectious SARS-CoV-2 was then assessed at various timepoints from 0 to 2 days. Warmer test temperatures, higher RH, and longer exposure duration resulted in higher inactivation rates per material type. Synthetic saliva inoculation vehicle was more readily decontaminated compared to materials inoculated with synthetic lung fluid. SARS-CoV-2 was readily inactivated below limit of quantitation (LOQ) for all materials inoculated using synthetic saliva vehicle within 6 hours when exposed to environmental conditions of 51.7 °C and RH≥25%. Synthetic lung fluid vehicle did not follow the general trend of an increase in RH resulting in increased efficacy. The lung fluid performed best at the 20%-25% RH range to achieve complete inactivation below LOQ.

Development and optimization of LED systems for surface fungal decontamination of fresh produce

Uneven irradiation is the major challenge of light-emitting diode (LED) antimicrobial technology. This study developed different LED illumination systems with multi-directional light sources, spotlight reflector (SR), and parabolic reflector (PR) to ensure the high antifungal efficiency of LED on artificially inoculated litchi fruit. Results showed that multi-light LEDs enable multi-angle irradiation, therefore, could reach higher inactivation rates under the comparable energy output. Integrating LED with SR could gather the scattering light and improve the inactivation efficiency (LEDs < LEDs + SR). The addition of PR enhanced bottom irradiation, leading to a comparable effect with an extra light source (LED + SR + PR = dual-LEDs). Moreover, when comparing the energy consumption required for 90 % inactivation of fungi, the LED systems combined SR and/or PR required less power consumption than those of LEDs alone. The antifungal effects of developed systems were further validated by natural samples. These results suggest several feasible solutions to improve the antifungal efficiency of LED and also provide practical system designs to broaden the LED application in the food industry.

Influence of pressurization rate and mode on cell damage of Escherichia coli and Staphyloccocus aureus by high hydrostatic pressure

As a non-thermal technology, high hydrostatic pressure (HHP) has been widely investigated for inactivating microorganisms in food. Few studies have been presented on the pressurization/depressurization rate and mode of microbial inactivation. In this study, effect of pressurization rate and mode on Escherichia coli and Staphylococcus aureus cell damage during HHP treatment was investigated. The results showed that fast pressurization + linear mode (FL) treatment has the best bactericidal effect on E. coli and S. aureus, followed by fast pressurization + stepwise mode (FS) and slow pressurization + stepwise mode (SS) treatments. FL treatment caused more morphological damage to the cell wall, cell membrane, and cytoplasmic components compared with FS and SS treatment detected by SEM and TEM. Additionally, the damage to membrane permeability of them was also enhanced after FL treatment. Therefore, our results indicated that FL treatment could be applied to enhance the bactericidal effect of HHP on bacteria by increasing the damage to cell morphological structure and membrane integrity.

Evaluation of steam heat as a decontamination approach for SARS-CoV-2 when applied to common transit-related materials.

The purpose of this study was to evaluate the efficacy of steam heat for inactivation of SARS-CoV-2 when applied to materials common in mass transit installations. SARS CoV-2 (USA-WA1/2020) was resuspended in either cell culture media or synthetic saliva, inoculated (∼1×106 TCID50) onto porous and nonporous materials and subjected to steam inactivation efficacy tests as either wet or dried droplets. The inoculated test materials were exposed to steam heat ranging from 70°C to 90°C. The amount of infectious SARS-CoV-2 remaining after various exposure durations ranging from 1 to 60 s was assessed. Higher steam heat application resulted in higher inactivation rates at short contact times. Steam applied at 1-inch distance (∼90°C at the surface) resulted in complete inactivation for dry inoculum within 2 s of exposure (excluding two outliers of 19 test samples at the 5-s duration) and within 2-30 s of exposure for wet droplets. Increasing the distance to 2 inches (∼70°C) also increased the exposure time required to achieve complete inactivation to 15 or 30 s for materials inoculated with saliva or cell culture media, respectively. Steam heat can provide high levels of decontamination (>3 log reduction) for transit-related materials contaminated with SARS-CoV-2 using a commercially available steam generator with a manageable exposure time of 2-5 s.