Dry biofilms on polystyrene surfaces: the role of oxidative treatments for their mitigation.

Candida auris and Staphylococcus aureus are associated with a wide range of infections, as they exhibit multidrug resistance - a growing health concern. In this study, gaseous ozone, and ultraviolet-C (UVC) radiation are applied as infection control measures to inactivate dry biofilms of these organisms on polystyrene surfaces. The dosages utilised herein are 1000 and 3000 ppm.min for ozone and 2864 and 11592 mJ.cm-2 for UVC. Both organisms showed an increased sensitivity to UVC relative to ozone exposure in a bespoke decontamination chamber. While complete inactivation of both organisms (>7.5 CFU log) was realized after 60 mins of UVC application, this could not be achieved with ozonation for the same duration. However, a combined application of ozone and UVC yielded complete inactivation in only 20 mins. For both treatment methods, it was observed that dry biofilms of S. aureus were more difficult to inactivate than dry biofilms of C. auris. Compared to dry biofilms of C. auris, micrographs of wet C. auris biofilms revealed the presence of an abundance of extracellular material after treatments. Interestingly, wet biofilms were more difficult to inactivate than dry biofilms. These insights are crucial to preventing recalcitrant and recurrent infections via contact with contaminated polymeric surfaces.

Oxidative treatment can inactivate dry biofilms formed by C. auris and S. aureus.Both organisms showed an increased sensitivity to UVC compared to ozone.Dry biofilms of S. aureus were more difficult to inactivate than dry biofilms of C. auris.Wet biofilms of C. auris display a spongy appearance compared to its dry biofilms.Wet biofilms of C. auris proved more difficult to inactivate than its dry biofilms.

Assessing the association between necrotizing enterocolitis and the type of initial central venous access in preterm infants.

AIM: Umbilical venous catheters (UVC) have been associated with an increased risk of necrotizing enterocolitis (NEC). We aimed to assess the relationship between the type of initial central venous access in preterm infants and NEC. METHODS: Using the Canadian Neonatal Network database, we identified preterm infants <30 weeks gestation born between 2014 and 2021 in one of 32 participating centres who had a peripherally inserted central catheter (PICC) as initial vascular access. These infants were matched in a 1:1 ratio based on gestational age, sex and birth weight to infants in two other groups: (i) those who initially had an UVC and (ii) those who had an UVC followed by a PICC. RESULTS: A total of 497 infants were included in this study: 165 in the PICC group, 164 in the UVC group and 165 in the UVC + PICC group. There was no association between the type of initial central venous access and NEC. CONCLUSION: Although this retrospective study did not find an association between the type of initial central venous access and NEC, larger prospective studies are required to evaluate this association.

Far-UVC light (222 nm) efficiently inactivates clinically significant antibiotic-resistant bacteria on diverse material surfaces.

In recent years, there has been a gradual increase in the prevalence of drug-resistant bacteria, primarily attributed to the widespread use of antibiotics. This has resulted in heightened mortality rates, morbidity, and exorbitant healthcare costs associated with antibiotic-resistant bacterial infections. In order to mitigate the spread of antibiotic-resistant bacteria, environmental disinfection plays a crucial role. Ultraviolet radiation C (UVC) light disinfection has emerged as a potent technique to limit the transmission of nosocomial pathogens and prevent healthcare-associated infections. Different types of high-touch surfaces were used. A serial disinfected experiment with different 222 nm UVC dosages was conducted on clinically isolated antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus species (VRE), carbapenem-resistant Escherichia coli (CREC), carbapenem-resistant Klebsiella pneumonia (CRKP), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA) on different material surfaces. The bactericidal efficacy was evaluated by The Clinical & Laboratory Standards Institute (CLSI) guidelines. 222 nm UVC irradiation had a potent bactericidal efficacy on clinical antibiotic-resistant bacteria on different high-touch surfaces that are commonly found in the environment and healthcare facilities. 222 nm UVC irradiation time was tested from 10 s to 1 h. Different surfaces affect the efficiency of 222 nm UVC. The more adsorptive a material is, the higher the dosage of 222 nm UVC irradiation energy is required for effective disinfection. The use of 222 nm UVC lamps for disinfection on different materials has been shown to be a useful method. However, it is crucial to pay attention to the energy required for effective sterilization. IMPORTANCE: This study is crucial, providing compelling evidence on Far-ultraviolet radiation C (Far-UVC) light's efficacy against clinically significant antibiotic-resistant bacteria-a pressing issue in microbiology and infection control. Our research employs antibiotic-resistant strains from clinically isolated bacteria, emphasizing real-world relevance. Simultaneously, we assess Far-UVC light (222 nm) across diverse material surfaces commonly found in clinical settings. This dual approach ensures practical applicability and broad relevance. Our comprehensive setup and rigorous methodologies unequivocally demonstrate Far-UVC light's potency in combating antibiotic-resistant bacteria. Since 222 nm far-UVC has a disinfection capability and is harmless to mammalian cells, this dual effectiveness positions Far-UVC as a secure tool for infection control, with potential applications in healthcare settings, mitigating antibiotic-resistant bacteria spread, and reducing healthcare-associated infections.

UV-C light-activated gallic acid and non-thermal technologies for inactivating Salmonella Typhimurium inoculated in aqueous solution and whole cow milk.

This study aimed to evaluate the effect of UV-C light-activated gallic acid (GA) alone and combined with ultrasound (US) or ultraviolet-C light (UV-C, 254 nm) on the inactivation of Salmonella Typhimurium in aqueous solution for being later applied to whole cow milk. First-order, Weibull, and Beta models were used to describe the inactivation kinetics of S. Typhimurium by GA alone and combined with non-thermal technologies. Results indicated that GA concentration, the UV-C light activation process, and the combination of US and UV-C light significantly affected (p < 0.05) the inactivation of S. Typhimurium in aqueous solution, which was properly described by the first order (R2 > 0.84), Weibull (R2 > 0.96), and Beta (R2 > 0.83) models. The activation process of GA increased its antimicrobial activity in the range of 40.87-101.44 %. Moreover, with the highest concentration of GA and the application of US or UV-C light, >5 log reductions were achieved. Nevertheless, although these combinations were applied to whole cow milk, a low reduction (2.0-log cycles) was obtained, regardless of the GA activation and non-thermal technologies. Therefore, the effect of GA, whether UV-C light activated or not, on S. Typhimurium depends on the food matrix. This highlights that in whole cow milk, this treatment was insufficient to ensure safety, even when combined with non-thermal technologies. INDUSTRIAL RELEVANCE: UV-C light and US are non-thermal technologies used as alternatives to thermal treatments. These technologies can be used on their own or in combination; however, in many cases, the necessary microbial reduction is not attained, thus the use of complementary techniques or processes is required. GA is a phenolic compound with low antimicrobial activity; however, UV-C light may activate its antimicrobial activity. In this sense, this study shows the potential application of GA and non-thermal technologies for inactivating S. Typhimurium in an aqueous solution and the first approach of this methodology in whole cow milk as a liquid food product.

Human exposure to air contaminants under the far-UVC system operation in an office: effects of lamp position and ventilation condition.

The far-UVC (222 nm) system has emerged as a solution for controlling airborne transmission, yet its effect on indoor air quality, particularly concerning positioning, remains understudied. In this study, we examined the impact of far-UVC lamp position on the disinfection and secondary contaminant formation in a small office. We employed a three-dimensional computational fluid dynamics (CFD) model to integrate UV intensity fields formed by different lamp positions (ceiling-mounted, wall-mounted, and stand-alone types) along with the air quality model. Our findings reveal that the ceiling-mounted type reduces human exposure to airborne pathogens by up to 80% compared to scenarios without far-UVC. For all the lamp positions, O3 concentration in the breathing zone increases by 4-6 ppb after one hour of operation. However, it should be noted that a high concentration zone (> 25 ppb) forms near the lamp when it is turned on. Moreover, ventilation plays a crucial role in determining human exposure to airborne pathogens and secondary contaminants. Increasing the ventilation rate from 0.7 h-1 to 4 h-1 reduces airborne pathogen and secondary contaminant concentrations by up to 90%. However, caution is warranted as higher ventilation rates can lead to elevated O3 indoors, especially under conditions of high outdoor O3 concentrations.

Decontamination of Fused-Silica Surfaces by UVC Irradiation as Potential Application on Touchscreens.

The contamination of surfaces by antibiotic-resistant pathogens presents an escalating challenge, especially on touchscreens in public settings such as hospitals, airports, and means of transport. Traditional chemical cleaning agents are often ineffective and leave behind harmful residues. Thus, the application of optical radiation is gaining relevance as a rapid, effective, and environmentally friendly disinfection method. This study examines the contamination of publicly accessible touchscreens and the efficacy of an irradiation approach for the radiation disinfection of microorganisms on quartz surfaces with UVC LEDs. In this setup, the LED radiation is laterally coupled into a quartz plate that serves as cover glass of a simplified touchscreen model. The process allows for the irradiation of microorganisms on the surface, without the user being exposed to hazardous radiation. To assess the efficacy of the disinfection process, a range of bacteria, mostly ESKAPE surrogates, such as Staphylococcus carnosus, Acinetobacter kookii, Escherichia coli, Enterococcus mundtii, and additionally Micrococcus luteus, were spread over a quartz plate with a homebuilt nebulization system. After operating the side-mounted LEDs for 30 s, a reduction in all bacteria except M. luteus by more than three orders of magnitude was observed. In the case of M. luteus, a significant reduction was achieved after 60 s (p < 0.05). This result demonstrates the potential of side-mounted UVC LEDs for rapid disinfection of touchscreens between two users and thus for reducing the spread of pathogens without irradiating humans.

Can a Shorter Dwell Time Reduce Infective Complications Associated with the Use of Umbilical Catheters?

BACKGROUND: Umbilical venous catheters (UVCs) are the standard of care in neonatal intensive care units (NICUs) to administer fluids, parenteral nutrition and medications, although complications may occur, including central line-associated blood stream infections (CLABSIs). However, the dwell time to reduce CLABSI risk remains an open issue. METHODS: We performed a single-center retrospective study of newborns hospitalized in the Modena NICU with at least one UVC inserted over a 6-year period (period 1: January 2011-December 2013; period 2: January 2019-December 2021). We selected a non-consecutive 6-year period to emphasize the differences in UVC management practices that have occurred over time in our NICU. The UVC dwell time and catheter-related complications during the first 4 weeks of life were examined. RESULTS: The UVC dwell time was shorter in period 2 (median 4 days vs. 5 days, p < 0.00001). Between the two periods, the incidence of CLABSIs remained unchanged (p = 0.5425). However, in period 2, there was an increased need for peripherally inserted central catheters (PICCs) after UVC removal, with a rise in PICC infections after UVC removal (p = 0.0239). CONCLUSIONS: In our NICU, shortening UVC dwell time from 5 to 4 days did not decrease the UVC-related complications. Instead, the earlier removal of UVCs led to a higher number of PICCs inserted, possibly increasing the overall infectious risk.

A multicenter study comparing the bacterial reduction on flexible endoscopes without a working channel between UV-C light disinfection versus standard endoscope Washer Disinfection: a randomized controlled trial.

BACKGROUND: To prevent cross-contamination between patients, adequate reprocessing is necessary when using flexible endoscopes (FEs) without a working channel. The current reprocessing process using an Endoscope Washer Disinfector (EWD) is time-consuming. Ultraviolet light group C (UV-C) exposition is an alternative and fast disinfection method and has previously been shown to adequately reduce Colony Forming Units (CFUs) on FEs without a working channel. The objective of this study was to examine whether UV-C light is as effective in reducing CFUs on contaminated FEs without a working channel compared to the EWD. METHODS: FEs without a working channel were collected in three different Otorhinolaryngology Departments in the Netherlands. After pharyngolaryngoscopy, a manual pre-cleaning with tap water was performed and a culture was collected by rolling the distal 8-10 cm of the FE over an agar plate. Next, the FE was randomly assigned to be disinfected with UV-C light (D60) or the EWD (gold standard). After disinfection, another culture was taken. The primary outcome was microbiological contamination, defined by Colony Forming Units (CFU). RESULTS: 600 FEs without a working channel were randomized. After clinical use and manual pre-cleaning, 239/300 (79.7%) FEs in the UV-C group and 262/300 (87.3%) FEs in the EWD group were contaminated (i.e., > 0 CFU). FEs without culture confirmed contamination were excluded from further analysis. After UV-C light disinfection, 195/239 (81.6%) FEs showed 0 CFUs, compared to 187/262 (71.4%) FEs disinfected with the EWD (p < 0.01). A multivariate logistics regression analysis showed an increased odds of 0 CFUs when using UV-C light (OR 1.83, 95% CI 1.19-2.79; p < 0.01), conditional on participating hospitals and types of FE. CONCLUSIONS: UV-C light disinfection of FEs without a working channel appears more effective in reducing CFUs compared to the EWD and might be a good alternative disinfection method. TRIAL REGISTRATION: Not applicable.

Far-UVC (UV222) based photolysis, photooxidation, and photoreduction of chlorophenols using a KrCl-excimer lamp: Degradation, dechlorination, and detoxification.

The KrCl-excimer lamp, emitting far-UVC light at 222 nm (UV222), offers a promising alternative to conventional UVC light at 254 nm (UV254) for the photolysis of organic pollutants and the activation of radical sensitizers. This study was aimed to investigate the efficiencies of UV222 in the treatment of halogenated aromatics, focusing on its performance in degradation, dechlorination and detoxification. Chlorophenols, representative recalcitrant and toxic halogenated aromatics, were used as target pollutants. The pathways of direct photolysis, photooxidation and photoreduction under UV222 illumination were compared. UV222 outperformed UV254 in photolyzing chlorophenols (1.4-34.1 times faster), especially protonated chlorophenols, due to substantially higher UV absorption (17.1-108.0 times) and quantum yields (2.1-3.4 times). The quantum yields of chlorophenols were influenced by the inducive electron-withdrawing effect of Cl-substitutes. Moreover, UV222 improved the dechlorination of chlorophenols to 95 % compared to 60 % by UV254. The introduction of radical sensitizer (e.g., H2O2, nitrate, and sulfite) reduced 4-chlorophenol photolysis by competing for UV222 absorption, though the sensitizers partially increased radical oxidation via generating •OH or eaq-. UV222 photolysis of 4-chlorophenol increased the toxicity by 88.6 times through forming toxic intermediates (e.g., hydroquinone and resorcinol). Notably, •OH and eaq- (i.e., UV222/H2O2 and UV222/sulfite) increased the dechlorination and •OH (i.e., UV222/H2O2) detoxified the mixture solution. Moreover, UV222 photolysis remained effective for 4-chlorophenol removal in real paper-mill wastewater, indicating the potential application of KrCl* lamp UV222.

Assessment of quality and antioxidant capacity of peach in response to different UV-C dose irradiation.

The effects of different doses of UV-C irradiation (0, 0.5, 1.0, 2.0, and 4.0 kJ m-2) on the quality and antioxidant capacity of peach fruit were examined. Results showed that irradiation at 2.0 kJ m-2 led to higher firmness and total soluble solids, as well as lower weight loss and decay index. Additionally, peach fruits irradiated with 2.0 kJ m-2 UV-C exhibited increased production of reactive oxygen species, which in turn stimulated the synthesis of total phenolics and total flavonoids and enhanced the activities of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase. Overall, the best abiotic stress effect was observed with 2.0 kJ m-2 UV-C irradiation, resulting in improved shelf quality and increased antioxidant capacity of peach fruits during storage. PRACTICAL APPLICATION: This study provides a theoretical basis for the application of UV-C irradiation in peach fruit preservation.

Reactive Oxygen Species Generated in Situ During Carbamazepine Photodegradation at 222 nm Far-UVC: Unexpected Role of H2O Molecules.

When 222 nm far-UVC is used to drive AOPs, photolysis emerges as a critical pathway for the degradation of numerous organic micropollutants (OMPs). However, the photodegradation mechanisms of the asymmetrically polarized OMPs at 222 nm remain unclear, potentially posing a knowledge barrier to the applications of far-UVC. This study selected carbamazepine (CBZ), a prevalent aquatic antiepileptic drug that degrades negligibly at 254 nm, to investigate its photodegradation mechanisms at 222 nm. Accelerated CBZ treatment by 222 nm far-UVC was mainly attributed to in situ ROS generation via self-sensitized photodegradation of CBZ. By quenching experiments and EPR tests, •OH radicals were identified as the major contributor to the CBZ photodegradation, whereas O2•- played a minor role. By deoxygenation and solvent exchange experiments, the H2O molecules were demonstrated to play a crucial role in deactivating the excited singlet state of CBZ (1CBZ*) at 222 nm: generating •OH radicals via electron transfer interactions with 1CBZ*. In addition, 1CBZ* could also undergo a photoionization process. The transformation products and pathways of CBZ at 222 nm were proposed, and the toxicities of CBZ's products were predicted. These findings provide valuable insights into OMPs' photolysis with 222 nm far-UVC, revealing more mechanistic details for far-UVC-driven systems.

Extending the acute skin response spectrum to include the far-UVC.

Guidance on maximal limits for ultraviolet (UV) exposure has been developed by national and international organizations to protect against adverse effects on human skin and eyes. These guidelines consider the risk of both acute effects (i.e., erythema and photokeratitis) and delayed effects (e.g., skin and ocular cancers) when determining exposure limits, and specify the dose a person can safely receive during an 8-h period without harmful effects. The determination of these exposure limits relies on the action spectra of photobiological responses triggered by UV radiation that quantify the effectiveness of each wavelength at eliciting each of these effects. With growing interest in using far-UVC (200-235 nm) radiation to control the spread of airborne pathogens, recent arguments have emerged about revisiting exposure limits for UV wavelengths. However, the standard erythema action spectrum, which provides some of the quantitative basis for these limits, has not been extended below 240 nm. This study assists to expand the erythema action spectrum to far-UVC wavelengths using a hairless albino mice model. We estimate that inducing acute effects on mouse skin with 222 nm radiation requires a dose of 1162 mJ/cm2, well above the current ACGIH skin exposure limit of 480 mJ/cm2.

Lighting the way: an economical alternative to feeder cell irradiation for T-cell expansion.

A robust T-cell expansion process involves co-culturing T-cells with non-proliferating feeder cells combined with anti-CD3 antibody and IL-2. Although ionizing irradiation effectively inhibits feeder cell proliferation, the high operating costs limit cell therapy research to well-funded institutions. UVC, known for causing DNA damage-induced cell death and commonly used for environmental sterilization, presents a cost-effective alternative to ionizing irradiation for generating non-proliferating feeder cells. UVC irradiation of K562 artificial antigen presenting cells (aAPCs) resulted in significant DNA damage, evidenced by increased γ-H2AX phosphorylation within 15 minutes and elevated 8-OHdG levels at 24 hours. This indicates the occurrence of DNA double-strand breaks and oxidative damage. Following UVC irradiation, glucose uptake and ATP production were significantly reduced, whereas aCD3 retention at the surface of the cell increased twofold. Selective inhibition of glucose uptake and ATP production similarly enhanced aCD3 retention by approximately 10-fold and 6-fold, respectively. This suggests that UVC-induced energy deprivation dampens aCD3 internalization, potentially enhancing T-cell activation through prolonged aCD3 and T-cell receptor interaction. Tumor-infiltrating lymphocytes (TILs) expanded with UVC-irradiated PBMCs demonstrated comparable viability, expansion, immunophenotype, and effector function to those expanded with ionizing irradiation. UVC irradiation was equally effective in suppressing feeder cell proliferation and facilitating the expansion of functionally potent T-cells compared to traditional ionizing irradiation. Implementing UVC irradiation in T-cell expansion can significantly reduce costs, enhancing the accessibility and feasibility of cell therapy research across various institutions.

Fluorescence of Intrinsic Milk Chromophores as a Novel Verification Method of UV-C Treatment of Milk.

The European Food Safety Authority (EFSA) has approved the use of a 1045 J/L UV-C dose as an adjunct to pasteurization to increase the shelf life and vitamin D3 content of milk. However, there are no verification methods analogous to the alkaline phosphatase test for pasteurized milk to ensure that the desired UV-C dose has been correctly applied. The aim is to develop a real-time in-line detector based on fluorescence spectroscopy. In this study, 22 different UV-C doses (ranging from 0 to 2000 J/L) were applied to milk to assess the impact of photooxidation on intrinsic photosensitive chromophores. Fluorescence spectroscopy (90°-angle) was employed as the method of analysis for monitoring the changes in the fluorescence spectra of chromophores in milk without sample pretreatment. Three important chromophore areas (CAs) were identified: CA 1 (riboflavin), CA 3 (vitamin A and dityrosine) and CA 4 (tryptophan), with statistically significant changes at around 1045 J/L and 1500 J/L. The findings of our preliminary study support our hypothesis that the fluorescence of intrinsic chromophores can be used as verification of the applied UV-C dose.

Salmonella Inactivation Model by UV-C Light Treatment in Chicken Breast.

This study aims to evaluate the effectiveness of inactivating Salmonella enteritidis in fresh chicken breast by irradiation using a combination of short-wave UV (0, 3, 6, 9, 12, and 15 J/cm2) and a natural antimicrobial such as caffeine (0, 5, 10, 15, and 20 nM/g) at 14 °C as alternative proposals to conventional techniques to reduce pathogens in food. The effect of temperature was studied in an initial phase (2 to 22 °C). The most suitable models were double Weibull in 60% of cases, with an adjustment of R2 0.9903-0.9553, and Weibull + tail in 46.67%, with an adjustment of R2 of 0.9998-0.9981. The most effective combination for the reduction in Salmonella was 12 J/cm2 of UV light and 15 nM/g of caffeine, with a reduction of 6 CFU/g and an inactivation rate of 0.72. The synergistic effect was observed by increasing caffeine and UV light. Furthermore, the physico-chemical characteristics of the food matrix were not affected by the combination of both technologies. Therefore, these results suggest that this combination can be used in the food industry to effectively inactivate Salmonella enteritidis without deteriorating product quality.

Microbiological evaluation of ultraviolet C light-emitting diodes for disinfection of medical instruments.

Background: Despite the many guidelines for reprocessing of medical instruments, challenges persist such as microbial resistance to biocides, corrosive effects on materials, and time-consuming reprocessing procedures. Ultraviolet (UV) C light-emitting diode (LED) chambers might provide a solution but the integration in healthcare is still in its infancy. Here, we evaluated the efficacy of a novel ZAPARAY™ UVC LED chamber as a time and energy-efficient alternative for reprocessing of medical instruments for which current disinfection protocols exhibit limitations. Methods: We verified the disinfection efficacy of the UVC LED chamber on a Petri dish and contaminated several medical devices with Staphylococcus aureus ATCC 25923. The bacterial reduction was assessed after 5 min of UVC LED exposure. Additionally, we investigated the impact of rinsing before UVC exposure. Results: We demonstrated a bacterial reduction of 9 log10 on a Petri dish. Non-rinsed dental tools exhibited varied reduction levels ranging from a 3.23 log10 to a 6.25 log10 reduction. Rinsing alone yielded an average reduction of 2.7 log10 and additional UVC exposure further reduced the bacterial load by an average of 3.65 log10. We showed an average 4.90 log10 reduction on thermistors, 2 log10 or less on orthodontic pliers, and no reduction on handpieces. Conclusions: This study demonstrates that UVC LED chambers may be used as a standardized substitute for specific (manual) disinfection procedures of certain medical devices, offering a time-efficient and more sustainable alternative. However, its use should be preceded by efficacy testing for each specific type of instrument.

Kinetic modelling of UVC and UVC/H2O2 oxidation of an aqueous mixture of antibiotics in a completely mixed batch photoreactor.

The removal kinetics of an aqueous mixture of thirteen antibiotics (i.e., ampicillin, cefuroxime, ciprofloxacin, flumequine, metronidazole, ofloxacin, oxytetracycline, sulfadimethoxine, sulfamethoxazole, sulfamethazine, tetracycline, trimethoprim and tylosin) by batch UVC and UVC/H2O2 processes has been modeled in this work. First, molar absorption coefficients (ε), direct quantum yields (Φ) and the rate constants of the reaction of antibiotics with hydroxyl radical (kHO•) (model inputs) were determined for each antibiotic and compared with literature data. The values of these parameters range from 0.3 to 21.8 mM-1 cm-1 for ε, < 0.01 to 67.8 mmol·E-1 for Φ and 3.8 × 109 to 1.7 × 1010 M-1 s-1 for kHO•. Second, a regression model was developed to compute the rate constants of the reactions of the antibiotics with singlet oxygen (k1O2) from experimental data obtained in batch UVC experiments treating a mixture of the antibiotics. k1O2 values in the 1-50 × 106 M-1 s-1 range were obtained for the antibiotics studied. Finally, a semi-empirical kinetic model comprising a set of ordinary differential equations was solved to simulate the evolution of the residual concentration of antibiotics and hydrogen peroxide (model outputs) in a completely mixed batch photoreactor. Model predictions were reasonably consistent with the experimental data. The kinetic model developed might be combined with computational fluid dynamics to predict process performance and energy consumption in UVC and UVC/H2O2 applications at full scale.

A multi-analytical approach to evaluate the removal efficiency of polystyrene nanoparticles in water treatment processes.

The removal of nanoplastics (NP) from water using various treatment processes has gained significant attention recently. This study comprehensively characterizes the degradation of polystyrene nanoparticles (concentration: 200 ppm, diameter: 140 nm) through UVC irradiation. For the first time, we compared four analytical methods to monitor removal efficiency: Py-GCMS, UV-Visible spectroscopy, TOC, and Turbidity. Additionally, DLS, TEM, and SEC were used to understand changes in particle size, morphology, and molecular weight. Results showed that Py-GCMS overestimated the removal rate by a factor of 2 compared to Turbidity and UV-Visible measurements, which were in agreement. Furthermore, after 200 h of irradiation, the styrene signal disappears from the pyrogram, although the mineralization rate reaches only 50%, as determined by total organic carbon (TOC) analysis. The particle size decreased slowly, reaching 100 nm after 150 h, while a significant decrease in molecular weight indicated high chain-scission. These findings emphasize the importance of a multi-analytical approach to accurately assess NP removal efficiency and understand degradation mechanisms.

Enhancement of phenolic compounds in vanilla curing with the application of UVC light, microwaves and ultrasound.

Short-wave ultraviolet light at 254 nm (UVC light) was evaluated at different doses (0.9, 2.16, 4.50 and 7.16 J/m2) to increase phenolic compounds and analyze its effect on the native microbial flora present on vanilla (Vanilla planifolia) beans (VB). Subsequently, microwave and ultrasound treatments were applied, individually or in combination, at different powers levels (1100 and 600 W) and amplitudes (50 and 90%) during the curing process. In the UVC light treatment, a dose 2.16 J/m2 was the optimal, resulting in a 74% increases in total phenolic compounds (TPC) in VB compared to the control. During the curing process of the irradiated VB, the combination of microwave (600 W) and ultrasound (50% amplitude) resulted in 37.909 ± 0.52 mg GAE/g d.m. of TPC, while non-irradiated pods showed 29.869 ± 0.54 mg GAE/g d.m. at 50 days. This methodology offers several advantages, such as eliminating the need for tedious handling and skilled labor. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-024-06061-6.

Evaluation of the antimicrobial effect of a far-uv radiation lamp in a real-life environment.

Background: Using far-Ultraviolet-C (UVC) radiation with an emission maximum of 222 nm, has the potential to kill bacteria while not being harmful to humans and can be used continuously in public areas. Elevators pose a high risk of infection transmission, as they are small, crowded spaces with poor ventilation. In such a setting continuous decontamination would be very useful. This study aimed to measure the effectiveness of a far-UVC lamp installed in a frequently used elevator by comparing the bacterial load found in that elevator with the bacterial load in a control elevator. Methods: Microbial load was measured by different methods; ATP bioluminescence, surface samples were collected by contact slides, contact plates, and swabbing. Air samples were also collected. Results: No significant differences were found in the microbial content between the control elevator and the UV-lamp elevator, regardless of whether the UV-lamp was always on, or was used with a motion sensor to turn off when someone entered the elevator. Conclusions: The results suggest that the far-UVC requires a longer time to kill the bacteria, while the people traffic were continuously re-contaminating the elevators.