Far-UV-C irradiation promotes synergistic bactericidal action against adhered cells of Escherichia coli and Staphylococcus epidermidis

The contamination of indoor areas is a global health problem that can cause the dispersion of infectious diseases. In that sense, it is urgent to find new strategies applying a lower concentration of the traditional chemicals used for cleaning and disinfection. Ultraviolet radiation (UV), in particular far-UV-C (200-225 nm), has emerged as a successful, powerful, easy-to-apply, and inexpensive approach for bacterial eradication that still requires scientific assessment. This study investigated new strategies for disinfection based on far-UV-C (222 nm) combined with chlorine and mechanical cleaning, providing an innovative solution using low doses. The bactericidal activity of far-UV-C (222 nm) was tested at an intensity of irradiation from 78.4 μW/cm2 to 597.7 μW/cm2 (for 1 min) against Escherichia coli and Staphylococcus epidermidis adhered on polystyrene microtiter plates. It was further tested in combination with mechanical cleaning (ultrasounds for 1 min) and free chlorine (0.1, 0.5, and 1 mg/L for 5 min). The triple combination consisting of mechanical cleaning + free chlorine (0.5 mg/L) + far-UV-C (54 mJ/cm2) was tested against cells adhered to materials found in hospital settings and other public spaces: polyvinyl chloride (PVC), stainless steel (SS), and polyetheretherketone (PEEK). Disinfection with far-UV-C (54 mJ/cm2) and free chlorine at 0.5 mg/L for 5 min allowed a total reduction of culturable E. coli cells and a logarithmic reduction of 2.98 ± 0.03 for S. epidermidis. The triple combination of far-UV-C, free chlorine, and mechanical cleaning resulted in a total reduction of culturable cells for both adhered bacteria. Bacterial adhesion to PVC, SS, and PEEK occurred at distinct extents and influenced the bactericidal activity of the triple combination, with logarithmic reductions of up to three. The overall results highlight that, based on culturability assessment, far-UV-C (54 mJ/cm2) with chlorine (0.5 mg/L; 5 min) and mechanical cleaning (1 min) as an efficient disinfection strategy using mild conditions. The combination of culturability and viability assessment of disinfection is recommended to detect regrowth events and increase the effectiveness in microbial growth control.

Involvement of UV-C-induced genomic instability in stimulation рlant long-term protective reactions

The study of the mechanisms affecting single stress factor impact on long-term metabolic rearrangements is necessary for understanding the principles of plant protective reactions. The objective of the study was to assess the involvement of UV-C-induced genomic instability in induction рlant long-term protective reactions. The study was carried out on two genotypes of chamomile, Perlyna Lisostepu (PL) variety and its mutant, using UV-C pre-sowing seed radiation exposure at dose levels 5-15 kJ/m2. Multiple DNA damages under different exposure doses were studied on plant tissues during the flowering stage using - ISSR-RAPD DNA marker PCR. In the cluster analysis of changes within the amplicon spectra as an integral group the Jacquard similarity index was used. The results of the study suggest that genomic instability is a link between the direct effects of UV-C exposure and stimulation of metabolic rearrangements at the final stages of ontogeny. A hypothetical scheme for the transformation of primary UV-C DNA damage into long-term maintenance of genomic instability signs has been proposed.

Development of porcine embryos cultured in media irradiated with ultraviolet-C

Sterilization of the culture medium using ultraviolet (UV)-C reduces the potential adverse effects of microorganisms and allows for long-term use. In the present study, we investigated the effects of a medium directly irradiated with UV-C prior to in vitro culture on the development and quality of porcine in vitro-fertilized embryos and the free amino acid composition of the culture media. The culture media (porcine zygote medium [PZM-5] and porcine blastocyst medium [PBM]) were irradiated with UV-C at 228 and 260 nm for 1 and 3 days, respectively. Next, the culture media were irradiated with UV-C at 228 nm for 3, 7, or 14 days. After in vitro fertilization, the embryos were cultured in the UV-C-irradiated media for 7 days. Free amino acid levels in culture media irradiated with 228 and 260 nm UV-C for 3 days were analysed. The blastocyst formation rate of embryos cultured in media irradiated with 260 nm UV-C for 3 days was significantly lower than that of embryos cultured in non-irradiated control media. However, 228 nm UV-C irradiation for up to 14 days did not affect blastocyst formation rates and quality in the resulting blastocysts. Moreover, 260 nm UV-C irradiation significantly increased the taurine concentration in both culture media and decreased methionine concentration in the PBM. In conclusion, UV-C irradiation at 228 nm before in vitro culture had no detrimental effects on embryonic development. However, 260 nm UV-C irradiation decreased embryo development and altered the composition of free amino acids in the medium.

Porcine embryo development and inactivation of microorganisms after ultraviolet-C irradiation at 228 nm

It is important to prevent contamination inside the incubator as a method of preventing microbial infections during the embryo culture. In the present study, we examined the effects of ultraviolet-C (UV-C) irradiation, used for microorganism inactivation, on embryo development and the growth of bacteria, including Escherichia coli and Staphylococcus aureus, and the fungus Cladosporium cladosporioides. In the embryo irradiation experiment, we examined the effects of the plastic lid of the culture dish, irradiation distances (10, 20, and 25 cm), and different irradiation wavelengths (228 and 260 nm) during embryo culture for 7 days on the development and quality of porcine in vitro-fertilized embryos. None of the embryos cultured in dishes without plastic lids developed into blastocysts after irradiation with 228 nm UV-C. When porcine embryos were cultured in a culture dish with lids, the 228 nm UV-C irradiation decreased blastocyst formation rates of the embryos but not their quality, irrespective of the UV-C irradiation distance. Moreover, irradiation with 260 nm UV-C, even with plastic lids, had more detrimental effects on embryo development than irradiation with 228 nm UV-C. Investigation of the inactivating effects of UV-C irradiation at 228 nm and 260 nm on the growth of the bacteria and fungus showed that 260 nm UV-C reduced the viability to a greater extent than 228 nm UV-C. Moreover, the disinfection efficacy for the bacteria increased when the irradiation duration increased and the distance decreased. In conclusion, porcine embryos can develop into blastocysts without loss of quality even after continuous long-duration irradiation (7 days) with 228 nm UV-C, which can inactivate the growth of bacteria and the tested fungus; however, the development rate of the embryo is reduced.

Effect of combining UV-C irradiation and vacuum sealing on the shelf life of fresh strawberries and tomatoes

This research presents the effect of combining UV-C irradiation and vacuum sealing on the shelf life of strawberries and quartered tomatoes and compares it with the effect of the sole use of UV-C irradiation or vacuum sealing. A constant UV-C dose of 360 J/m² was used for the samples' irradiation, and all the vacuum-sealed samples were stored at a reduced pressure of 40 kPa. Organoleptic analysis, microbial population quantification of yeast and mold, Pseudomonas sp., weight loss, and pH measurements were obtained to identify the spoilage occurrence, monitor the samples' quality, and quantify the shelf life. Sensory evaluation was conducted by 12 consumer panelists to evaluate the aroma, taste, color, texture, and the overall acceptance of the samples. The results revealed that the combination of UV-C irradiation and vacuum sealing prolongs the shelf life of perishables more than the sole use of UV-C irradiation or vacuum sealing. The achieved shelf-life increase using this combination was 124.41% and 54.41% for strawberries and quartered tomatoes, respectively, while acceptable sensory characteristics were maintained throughout the storage period. Hence, this food preservation method can be further improved and integrated in the daily life of modern consumers and the operations of fresh produce retailers, as it could effectively reduce the spoilage rates of fresh produce and help achieve the UN SDG 12.3, which aims to reduce food loss and waste by 50% by 2030 at the consumer and retail levels. PRACTICAL APPLICATION: The system can be further developed and introduced to the market as a kitchen appliance for households or as a predistribution step for fresh produce distribution centers. The shelf-life extension capability of this system, which does not involve any use of chemical substances, would make it an attractive solution for households and food retailers.

Effects of UV-C Irradiation and Vacuum Sealing on the Shelf-Life of Beef, Chicken and Salmon Fillets

One-third of the world's food supply is lost, with meat being a major contributor to this loss. Globally, around 23% of all meat and 35% of all seafood products are lost or wasted. Meats and seafood products are susceptible to microbial spoilage during processing, storage, and distribution, where microbial contamination causes significant losses throughout the supply chain. This study examined the efficacy of UV-C irradiation and vacuum-sealing in preventing microbiological deterioration in beef, chicken, and salmon fillets. The samples were sterilized using a constant UV-C irradiation dose of 360 J/m² and stored under a reduced pressure of 40 kPa. A microbiological analysis was conducted daily to examine the microbial contamination, which included counting the colonies of Pseudomonas spp., aerobic bacteria, lactic acid bacteria (LAB), Salmonella, and Escherichia coli, as well as monitoring the increase in pH levels. The results demonstrated a statistically significant difference (p > 0.05) in the aerobic bacteria counts between the storage conditions and storage days in all samples, which is a primary indicator of microbial spoilage. In contrast, the differences varied in the Pseudomonas spp. and LAB counts between the storage conditions and storage days, and there was no significant difference (p < 0.05) in the pH levels between the storage conditions. The results indicate that the combination of UV-C irradiation and vacuum sealing effectively inhibits microbial growth and extends the shelf-life of beef, chicken, and salmon fillets by 66.6%.

Degradation of Alternaria mycotoxins by UV-C irradiation: Effect of selected process and exposure to food components

Alternariol (AOH) and alternariol monomethyl ether (AME) are two Alternaria mycotoxins with high occurrence rates in food systems. This study aimed to investigate the photodegradation of AOH and AME by ultraviolet-C (UV-C) irradiation. The effect of UV-C intensity, pH, treatment time, solvents and the exposure of food components were evaluated. After treated by UV-C irradiation at 3500 μW/cm² for 90 min, AOH samples in methanol, aqueous solution and solid state were degraded by 89.1%, 72.9% and 53.2%, respectively, while the degradation percentages of AME were 86.6%, 50.1% and 11.1%, respectively. Increasing irradiation intensity and prolonging irradiation time could significantly facilitate the degradation of AOH and AME. An alkaline environment (pH = 11) was more conducive to the degradation of toxins. In addition, 2.5 mg mL^-1 citric acid or malic acid increased the photodegradation of AOH and AME to 94.6% and 95.3%, 93.2% and 70.5%, respectively. However, protein, polyphenols and vitamin C exerted inhibitory effects on the degradation, while 10% glucose or sucrose reduced the photodegradation of AOH and AME to 65.9% and 40.3%. UV-C treatment could effectively reduce the content of AOH and AME, with the highest efficiency achieved in methanol and alkaline environment. By contrast, UV-C irradiation is more effective in degrading toxins in some liquid foods rich in organic acids but lacking in protein. The utilization of UV-C radiation appears to be a potentially useful approach for decreasing the underlying risk of Alternaria mycotoxin contamination in foods.

Composition identification and UV-C irradiation growth inhibition effect of green shading on the greenhouse cover

Greenhouse cover pollution with green shading composed of dust, microalgae and bacteria is a severe problem in tropical areas. The shading results in lower greenhouse indoor light intensity reducing the yield and quality of protected horticulture crops. However, few studies have focused on environmentally efficient ways to remove green shading to increase greenhouse production. In this study, five purified microalgae were isolated from the green shading of three greenhouse roofs and were identified using morphological and molecular assessments. The effects of Ultraviolet-C irradiation (UV-C, 254 nm) at doses of 100, 200 and 300 mJ cm^-2 on the growth of GLY-1 microalgae were investigated. The results indicated that five purified microalgae all appeared to belong to the genus of Jaagichlorella. The purified microalgae cell density and chlorophyll content decreased respectively by 26.89-74.44 % and 42.02-77.31 % at 1-3 d after UV-C treatment with doses ranging from 100 to 300 mJ cm^-2. The inhibition of the growth rate of microalgae was significantly positively correlated with the UV-C irradiation dose and significantly negatively correlated with treatment time. In summary, UV-C irradiation treatment at 300 mJ cm^-2 and 3 d could substantially inhibit microalgae growth in green shading on greenhouse covers. UV-C irradiation could be an effective method for solving the problem of greenhouse cover pollution with microalgae.

Inactivation methods for human coronavirus 229E on various food-contact surfaces and foods

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the cause of the COVID-19 outbreaks, is transmitted by respiratory droplets and has become a life-threatening viral pandemic worldwide. The aim of this study was to evaluate the effects of different chemical (chlorine dioxide [ClO₂] and peroxyacetic acid [PAA]) and physical (ultraviolet [UV]-C irradiation) inactivation methods on various food-contact surfaces (stainless steel [SS] and polypropylene [PP]) and foods (lettuce, chicken breast, and salmon) contaminated with human coronavirus 229E (HCoV-229E). Treatments with the maximum concentration of ClO₂ (500 ppm) and PAA (200 ppm) for 5 min achieved >99.9% inactivation on SS and PP. At 200 ppm ClO₂ for 1 min on lettuce, chicken breast, and salmon, the HCoV-229E titers were 1.19, 3.54, and 3.97 log₁₀ TCID₅₀/mL, respectively. Exposure (5 min) to 80 ppm PAA achieved 1.68 log₁₀ reduction on lettuce, and 2.03 and 1.43 log₁₀ reductions on chicken breast and salmon, respectively, treated with 1500 ppm PAA. In the carrier tests, HCoV-229E titers on food-contact surfaces were significantly decreased (p < 0.05) with increased doses of UV-C (0–60 mJ/cm²) and not detected at the maximum UV-C dose (Detection limit: 1.0 log₁₀ TCID₅₀/coupon). The UV-C dose of 900 mJ/cm² proved more effective on chicken breast (>2 log₁₀ reduction) than on lettuce and salmon (>1 log₁₀ reduction). However, there were no quality changes (p > 0.05) in food samples after inactivation treatments except the maximum PAA concentration (5 min) and the UV-C dose (1800 mJ/cm²).

Removal of virus aerosols by the combination of filtration and UV-C irradiation

The COVID-19 pandemic remains ever prevalent and afflicting-partially because one of its transmission pathways is aerosol. With the widely used central air conditioning systems worldwide, indoor virus aerosols can rapidly migrate, thus resulting in rapid infection transmission. It is therefore important to install microbial aerosol treatment units in the air conditioning systems, and we herein investigated the possibility of combining such filtration with UV irradiation to address virus aerosols. Results showed that the removal efficiency of filtration towards f2 and MS2 phages depended on the type of commercial filter material and the filtration speed, with an optimal velocity of 5 cm/s for virus removal. Additionally, it was found that UV irradiation had a significant effect on inactivating viruses enriched on the surfaces of filter materials; MS2 phages had greater resistance to UV-C irradiation than f2 phages. The optimal inactivation time for UV-C irradiation was 30 min, with higher irradiation times presenting no substantial increase in inactivation rate. Moreover, excessive virus enrichment on the filters decreased the inactivation effect. Timely inactivation is therefore recommended. In general, the combined system involving filtration with UV-C irradiation demonstrated a significant removal effect on virus aerosols. Moreover, the system is simple and economical, making it convenient for widespread implementation in air-conditioning systems.

Monitoring Stimulated Darkening from UV-C Light on Different Bean Genotypes by NMR Spectroscopy

The use of UV-C cool white light on bean (Phaseolus vulgaris L.) seeds significantly increases the biochemical seed coat post-harvest darkening process, whilst preserving seed germination. The aim of this work consists in monitoring the effect caused by the incidence of UV-C light on different bean genotypes using NMR spectroscopy. The genotype samples named IAC Alvorada; TAA Dama; BRS Estilo and BRS Pérola from the Agronomic Institute (IAC; Campinas; SP; Brazil) were evaluated. The following two methodologies were used: a prolonged darkening, in which the grain is placed in a room at a controlled temperature (298 K) and humidity for 90 days, simulating the supermarket shelf; an accelerated darkening, where the grains are exposed to UV-C light (254 nm) for 96 h. The experiments were performed using the following innovative time-domain (TD) NMR approaches: the RK-ROSE pulse sequence; one- and two-dimensional high resolution (HR) NMR experiments (¹H; ¹H-¹H COSY and ¹H-¹³C HSQC); chemometrics tools, such as PLS-DA and heat plots. The results suggest that the observed darkening occurs on the tegument after prolonged (90 days) and accelerated (96 h) conditions. In addition, the results indicate that phenylalanine is the relevant metabolite within this context, being able to participate in the chemical reactions accounted for by the darkening processes. Additionally, it is possible to confirm that a UV-C lamp accelerates oxidative enzymatic reactions and that the NMR methods used were a trustworthy approach to monitor and understand the darkening in bean seeds at metabolite level.

Rapid, dose-dependent and efficient inactivation of surface dried SARS-CoV-2 by 254 nm UV-C irradiation

Background: The COVID-19 pandemic urges for cheap, reliable, and rapid technologies for disinfection and decontamination. One frequently proposed method is ultraviolet (UV)-C irradiation. UV-C doses necessary to achieve inactivation of high-titre SARS-CoV-2 are poorly defined.

Aim: We investigated whether short exposure of SARS-CoV-2 to UV-C irradiation sufficiently reduces viral infectivity and doses necessary to achieve an at least 6-log reduction in viral titres.

Methods: Using a box and two handheld systems designed to decontaminate objects and surfaces, we evaluated the efficacy of 254 nm UV-C treatment to inactivate surface dried high-titre SARS-CoV-2.

Results: Drying for 2 hours did not have a major impact on the infectivity of SARS-CoV-2, indicating that exhaled virus in droplets or aerosols stays infectious on surfaces for at least a certain amount of time. Short exposure of high titre surface dried virus (3–5*10^6 IU/ml) with UV-C light (16 mJ/cm²) resulted in a total inactivation of SARS-CoV-2. Dose-dependency experiments revealed that 3.5 mJ/cm² were still effective to achieve a > 6-log reduction in viral titres, whereas 1.75 mJ/cm² lowered infectivity only by one order of magnitude.

Conclusions: SARS-CoV-2 is rapidly inactivated by relatively low doses of UV-C irradiation and the relationship between UV-C dose and log-viral titre reduction of surface residing SARS-CoV-2 is nonlinear. Our findings emphasize that it is necessary to assure sufficient and complete exposure of all relevant areas by integrated UV-C doses of at least 3.5 mJ/cm² at 254 nm. Altogether, UV-C treatment is an effective non-chemical option to decontaminate surfaces from high-titre infectious SARS-CoV-2.

Light Tailoring: Impact of UV-C Irradiation on Biosynthesis, Physiognomies, and Clinical Activities of Morus macroura-Mediated Monometallic (Ag and ZnO) and Bimetallic (Ag-ZnO) Nanoparticles

A nano-revolution based on the green synthesis of nanomaterials could affect all areas of human life, and nanotechnology represents a propitious platform for various biomedical applications. During the synthesis of nanoparticles, various factors can control their physiognomies and clinical activities. Light is one of the major physical factors that can play an important role in tuning/refining the properties of nanoparticles. In this study, biocompatible monometallic (AgNPs and ZnONPs) and bimetallic Ag-ZnONPs (0.1/0.1 and 0.1/0.5) were synthesized under UV-C light irradiation from the leaf extract of Morus macroura, which possesses enriched TPC (4.238 ± 0.26 mg GAE/g DW) and TFC (1.073 ± 0.18 mg QE/g DW), as well as strong FRSA (82.39%). These green synthesized NPs were evaluated for their anti-diabetic, anti-glycation, and biocompatibility activities. Furthermore, their anti-cancerous activity against HepG2 cell lines was assessed in terms of cell viability, production of reactive oxygen/nitrogen species, mitochondrial membrane potential, and apoptotic caspase-3/7 expression and activity. Synthesized NPs were characterized by techniques including ultraviolet-visible spectroscopy, SEM, EDX, FTIR, and XRD. UV-C mediated monometallic and bimetallic NPs showed well-defined characteristic shapes with a more disperse particle distribution, definite crystalline structures, and reduced sizes as compared to their respective controls. In the case of clinical activities, the highest anti-diabetic activity (67.77 ± 3.29% against α-amylase and 35.83 ± 2.40% against α-glucosidase) and anti-glycation activity (37.68 ± 3.34% against pentosidine-like AGEs and 67.87 ± 2.99% against vesperlysine-like AGEs) was shown by UV-C mediated AgNPs. The highest biocompatibility (IC50 = 14.23 ± 1.68 µg/mL against brine shrimp and 2.48 ± 0.32% hemolysis of human red blood cells) was shown by UV-C mediated ZnONPs. In the case of anti-cancerous activities, the lowest viability (23.45 ± 1.40%) with enhanced ROS/NOS production led to a significant disruption of mitochondrial membrane potential and greater caspase-3/7 gene expression and activity by UV-C mediated bimetallic Ag-ZnONPs (0.1/0.5). The present work highlights the positive effects of UV-C light on physico-chemical physiognomies as well as the clinical activities of NPs.

Effectiveness of photocatalysis of MMT-supported TiO2 and TiO2 nanotubes for rhodamine B degradation

The aim of this paper is to synthesize montmorillonite/TiO₂-nanoparticles (MMT/TiO₂ and montmorillonite/TiO₂-nanotubes (MMT/TiO_2-NTs) photocatalysts through a simple wet agitation method based on TiO₂ nanoparticles and MMT. They are likely to accumulate the effect of adsorption and photodegradation. Then, the photocatalysts are applied to degrade the rhodamine B in dye effluents. The structural characterizations of photocatalysts are investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The photocatalytic activities and effectiveness of photocatalysts are evaluated through rhodamine B degradation at different concentrations under dark and UV-C irradiation conditions. The results show that the synthesized TiO_2-NTs have an average tube diameter of 5 nm and a tube length at least about 110 nm, which are intercalated into MMT sheets in MMT/TiO_2-NTs photocatalyst. Meanwhile, TiO₂ nanoparticles are immobilized on the surface of MMT sheets in the MMT/TiO₂ photocatalyst. The photocatalytic effectiveness of rhodamine B degradation of TiO_2-NTs shows a significantly enhance compared to that of TiO₂ nanoparticles. However, photocatalytic performance of MMT/TiO_2-NTs is lower than that of MMT/TiO₂. The degradation effectiveness of MMT/TiO₂ photocatalyst reaches to 100% for 3 ppm and 90% at 10 ppm of rhodamine B, while these values are 97.5% and 85.5%, respectively, recorded for MMT/TiO_2-NTs.

[Screening for UV-C irradiation-enhanced transcription factors that regulate the metabolism of phenolic compounds in tomato fruit]

Solanum lycopersicum phenylalanine ammonia-lyase 5 (SlPAL5) gene regulates the metabolism of phenolic compounds. The study of transcription factors that regulate the expression of SlPAL5 gene is of great significance to elucidate the regulatory mechanism underlying the biosynthesis of phenolic compounds in tomato fruit induced by UV-C irradiation. Here, yeast one-hybrid library of tomato fruit was constructed, and the yeast one-hybrid technology was used to screen the transcription factors that regulate the expression of SlPAL5, the key gene related to the synthesis of phenolic compounds in tomato fruit. As a result, a transcription factor, SlERF7, was obtained and sequenced, followed by the blast homology analysis. Further experiments confirmed that SlERF7 interacted with the promoter of SlPAL5 gene. In addition, UV-C irradiation significantly increased the expression level of SlERF7. These results indicate that SlERF7, which is regulated by UV-C irradiation, might be involved in regulating the transcription of SlPAL5, which provided foundations for further studying the regulation mechanism of the biosynthesis of phenolic compounds in tomato fruit induced by UV-C irradiation.

Assessment of the Arsenic Removal From Water Using Lanthanum Ferrite

The catalytic performance of a perovskite-type lanthanum ferrite LaFeO3 to remove arsenic from water has been investigates for the first time. LaFeO3 was prepared by citrate auto-combustion of dry gel obtained from a solution of the corresponding nitrates poured into citric acid solution. Kinetic studies were performed in the dark with As(V) and in the dark and under UV-C irradiation at pH 6-7 with As(III) (both 1 mg L-1 ), and As : Fe molar ratios (MR) of 1 : 10 and 1 : 100 using the LaFeO3 catalyst. As(V) was removed from solution after 60 min in the dark in 7 % and in 47 % for MR=1 : 10 and MR=1 : 100, respectively, indicating the importance of the amount of the iron material on the removal. Oxidation of As(III) in the dark was negligible after 60 min in contact with the solid sample, but complete removal of As(III) was observed within 60 min of irradiation at 254 nm, due to As(III) photooxidation to As(V) and to As(III) sorption to a minor extent. Morphological and microstructural studies of the catalyst complement the catalytic testing. This work demonstrates that LaFeO3 can be used for the removal of As(III) from highly arsenic contaminated water.

The Regulation of LexA on UV-Induced SOS Response in Myxococcus xanthus Based on Transcriptome Analysis

SOS response is a conserved response to DNA damage in prokaryotes and is negatively regulated by LexA protein, which recognizes specifically an "SOS-box" motif present in the promoter region of SOS genes. Myxococcus xanthus DK1622 possesses a lexA gene, and while the deletion of lexA had no significant effect on either bacterial morphology, UV-C resistance, or sporulation, it did delay growth. UV-C radiation resulted in 651 upregulated genes in M. xanthus, including the typical SOS genes lexA, recA, uvrA, recN and so on, mostly enriched in the pathways of DNA replication and repair, secondary metabolism, and signal transduction. The UV-irradiated lexA mutant also showed the induced expression of SOS genes and these SOS genes enriched into a similar pathway profile to that of wild-type strain. Without irradiation treatment, the absence of LexA enhanced the expression of 122 genes that were not enriched in any pathway. Further analysis of the promoter sequence revealed that in the 122 genes, only the promoters of recA2, lexA and an operon composed of three genes (pafB, pafC and cyaA) had SOS box sequence to which the LexA protein is bound directly. These results update our current understanding of SOS response in M. xanthus and show that UV induces more genes involved in secondary metabolism and signal transduction in addition to DNA replication and repair; and while the canonical LexA-dependent regulation on SOS response has shrunk, only 5 SOS genes are directly repressed by LexA.

Physiotherapy elastic band disinfection by UV-C irradiation in an intensive care unit

BACKGROUND

The transmission of healthcare-associated pathogens is mainly related to the massive flow of patients with infections in hospitals, presenting surfaces as potential transmission sources of these microorganisms. The physiotherapist who works in the intensive care area has become a specialist in daily routine in critical care with ventilatory support and post-surgical recovery. Furthermore, for this, the instruments are used in the patient's hands and body. Chemicals such as chlorine derivatives, triclosan, chlorhexidine and, 70 % alcohol are currently used to decontaminate surfaces. This study evaluated ultraviolet C (UV-C) irradiation efficiency in the physiotherapy object's disinfection in daily use in the Hospital Intensive Care Unit (ICU).

METHODS

the microbiological quantification carried out using the elastic band during physiotherapy in a cross-sectional study with 21 patients. The methodology compared the cleaning protocol (70 % alcohol) with a new irradiation method in elastic band in the ICU.

RESULTS

The results showed microbial reductions in the elastic band using both 70 % alcohol and UV-C irradiation (254 nm), with 60 s of illumination, totaling a light dose of 0.78 J/cm²; however, the UV-C irradiation showed better results.

CONCLUSION

This study showed that disinfection by UV-C irradiation could be introduced in an intensive care hospital environment for physiotherapeutic conduct.

Factors inducing bryophyte growth on prehistoric pigments and effect of UV-C treatment

In La Glacière cave (France), the touristic activity has been conducted to an environmental parameter change that has led to photosynthetic organism proliferation (microalgae, diatoms, cyanobacteria, bryophytes). The present study is focused on bryophyte development occurring in the show cave that was responsible of limestone biodeterioration. In order to understand the colonization process of limestone, we have maintained limestone blocks under optimal Lampenflora growth conditions. Moreover, some limestone blocks were painted with several pigments that were used in the prehistory (e.g., red ocher, bone char). Microorganisms and bryophyte growth were monitored during 1 year, and then, the block samples were treated using UV-C light (254 nm). Thus, obtained results were compared with in situ treatment in La Glacière cave. Results have showed dense bryophyte propagation on the several blocks. However, the growth rate was correlated with the chemical composition of the pigment. In fact, the presence of some chemical elements such as As, Cr, Ti, and Co contributed to reduce bryophyte growth. Finally, moss treatment using UV-C light has demonstrated high efficiency under in situ condition, while a fast recolonization has been observed for samples maintained in laboratory. This difference was explained by the high bryophyte density under laboratory conditions that make UV-C light penetration difficult.

Selective removal of phenanthrene for the recovery of sodium dodecyl sulfate by UV-C and UV-C/PDS processes: Performance, mechanism and soil washing recycling

Soil washing is commonly used to remediate PAHs contaminated sites. However, the effluent after washing containing PAHs and surfactant may cause secondary pollution and remediation cost is still high, unless PAHs are selectively removed from the effluent and the surfactant is recovered and recycled. Herein, ultraviolet irradiation (254 nm, UV-C) and its combination with peroxydisulfate (UV-C/PDS) were applied to selectively degrade PHE in the synthetic soil washing effluent. At natural pH of 8.6, 98.2 % of PHE was removed within 30 min under 6 W UV-C irradiation. After adding 2 mM PDS, the time was shortened to 8 min but still achieving 98.7 % PHE removal and less toxic treated effluent than UV-C alone. The ¹O₂ was the main oxidizing species in UV-C alone system, while ¹O₂ as well OH and SO₄^- were responsible for PHE removal in the UV-C/PDS system. The possible intermediates of PHE degradation were recognized using liquid chromatography-mass spectrometry technique and the degradation pathways in both systems were proposed. Soil washing recycling experiments verified the recovered SDS could be reused directly without surfactant supplement and the soil washing efficiency changed insignificantly during three cycles. It indicates UV-C/PDS coupled with soil washing is a promising remediation technology.

Synergetic suppression effects upon the combination of UV-C irradiation and berberine on Microcystis aeruginosa and Scenedesmus obliquus in reclaimed water: Effectiveness and mechanisms

The risk of harmful algal blooms (HABs) in the water recharged with reclaimed water is a bottleneck for water reuse. The suppression effects and mechanisms of the combination of UV-C and berberine on Microcystis aeruginosa and Scenedesmus obliquus in reclaimed water were investigated. Mono UV-C irradiation at 75 mJ cm^-2 could suppress the growth of M. aeruginosa for 7 d and that at 90 mJ cm^-2 could suppress the growth of S. obliquus for 5 d. UV-C irradiation combined with 0.2-2 mg L^-1 berberine lengthened the inhibition period of M. aeruginosa to 10- > 22 d and that of S. obliquus to 7- > 22 d and induced more rapid lethal effects on the harmful microalgal cells, in significant synergetic patterns. The combination of UV-C and berberine suppressed total, intracellular and extracellular microcystin-LR (MC-LR) more effectively and decreased the MC-LR quota significantly, which further reduced the risks of microcystin production and release. Furthermore, synergetic mechanisms of the combined treatments were systematically investigated from the aspects of photosynthetic system (photosynthetic activity and pigments), metabolic activity (ATP and membrane potential), oxidation stress (reactive oxygen species (ROS) and glutathione (GSH)), and apoptosis-like cell death (phosphatidylserine (PS) ectropion, caspase-3 activity and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive rate). The combination treatment provided a joint attack of UV-C and berberine on photosynthetic transport chain of photosynthetic system II (PS II), and a synergetic pathway to achieve more severe disruptions in energy metabolism as well as aggravated oxidative stress. The accumulated ROS enhanced increases in programmed cell death (PCD) indicators of both microalgal species, which contributed to the enhancement effects on growth suppression. The results showed that the combination treatment achieved lower dose requirements of both UV-C irradiation and berberine for inducing the same inhibition effects on microalgal cells, which was promising to be applied in the HABs control of reclaimed water.

UV-C Irradiation as a Tool to Reduce Biofilm Growth on Pompeii Wall Paintings

This study focuses on the experimentation of a method based on the use of UV-C irradiation to eliminate the biofilms present in a tomb located in the necropolis of Porta Nocera, in Pompeii. For this study, the autotrophic component of the biofilm was isolated in the laboratory, while, contemporarily, the characterization of the composition of the pigments of the frescoes took place on original fragments, which had already detached from the tomb and were examined in situ. These preliminary analyses were necessary for the recreation of test samples in the laboratory, which closely matched the original surfaces. Artificial biofilms were used for experimental exposure to UV-C radiation. The exposure to UV-C radiation was carried out at different distances for a fixed time interval. The effectiveness of the biocidal action was assessed by employing optical microscopy techniques, through a careful visual assessment of the area occupied by the biofilm on the different test samples, using a photographic survey, as well as by means of colorimetric measurements using spectrometric techniques. In order to obtain an additional parameter to evaluate the death rate of microorganism cultures exposed to the UV-C radiation, the concentrations of the photosynthetic pigments were also measured by spectrophotometry. Results showed that biofilms were completely eradicated by radiation, and no change in pigment color was observed.

Continuous Flow UV-C Irradiation Effects on the Physicochemical Properties of Aloe vera Gel and Pitaya (Stenocereus spp.) Blend

Physicochemical properties of a blend of 10% Aloe vera gel with 5% pitaya juice subjected to UV-C doses of 16.5, 27.7, and 40 mJ/cm2 were evaluated at pH 3.5 and 5.5. Unprocessed treatments were used as the control. The a* color parameter decreased and luminosity increased at pH 3.5. The decrease in the reddish color was consistent with the decrease in total betalains content and stabilized at pH 5.5. The NMR analyses of UV-C treatments showed changes in betalains signal patterns. Polyphenolics content was significantly reduced in the UV-C treatments at pH 5.5. UV-C processing decreased the antioxidant activity 1.25 times compared to unprocessed treatments. Total sugar content was reduced as the UV-C dose increased. Doses above 16.5 mJ/cm2 resulted in a higher simple sugar content at a pH 3.5. The UV-C continuous flow technology can be applied to stabilize betalains in Aloe vera-pitaya blends at a UV-C dose of 16.5 mJ/cm2 and pH 5.5.

UV-C irradiation for harmful algal blooms control: A literature review on effectiveness, mechanisms, influencing factors and facilities

UV-C irradiation has drawn much attention in recent years as a candidate for controlling harmful algal blooms (HABs). In this review, we have collated the recent knowledge about the UV-C irradiation technique for suppressing HABs, including the effectiveness, mechanisms, influencing factors, growth recovery pattern, and UV-C irradiation facilities. Most microalgal species have been proved to be effectively suppressed by UV-C irradiation and the suppression effects had positive correlation with UV-C dose. However, the effectiveness on difference algal species varied dramatically. The understanding for growth suppression mechanisms upon UV-C irradiation has been significantly deepened beyond pyrimidine dimers. The suppression effects on algal cell density were the results of UV-induced damage on nucleic acid, light harvesting and electron transfer and transportation, nitrogen fixation and assimilation, toxin synthesis, settle ability, antioxidative capacity and cellular membrane integrity. While several influencing factors, such as algal sensitivities, UV transmittance (UVT), salinity, pH, and microalgal growth recovery should be paid attention to in practical application. UV-C facilities with high maturity, especially flow-through reactors, make it possible to develop ship-born UV-C facilities and put UV-C irradiation technique into real practice on controlling HABs.

Lycorine and UV-C stimulate phenolic secondary metabolites production and miRNA expression in Chlamydomonas reinhardtii

Studying stress pathways on the level of secondary metabolites that are found in very small concentration in the cells is complicated. In the algae, the role of individual metabolites (such as carotenoids, phenolic compounds, organic acids, and vitamins) and miRNAs that participate in plant's defence are very poorly understood during stressful conditions. Therefore, in the present experiment, the model organism Chlamydomonas reinhardtii was exposed to stress conditions (Lyc and UV-C irradiation) to detect these substances, even at very low concentrations. The purpose was to monitored changes at each response level with a future view to identifying their specific roles under different stress factors. In stress-treated cultures, numerous transcriptomic and metabolomic pathways were triggered in C. reinhardtii. Although Lyc significantly decreased the concentration of AA, suggesting that Lyc has a similar function in C. reinhardtii as in plants. The negative effect of UV-C radiation was based on the production of ROS and enhancement of antioxidant responses, resulting in increased levels of polyphenols and simple phenolic compounds. Both treatments did lead to extensive changes in transcript levels and miRNA expression patterns.

The growth suppression effects of UV-C irradiation on Microcystis aeruginosa and Chlorella vulgaris under solo-culture and co-culture conditions in reclaimed water

Harmful algal blooms (HABs) are serious problems in landscape waters sourced from reclaimed water. In this study, the suppression effects of UV-C irradiation on microalgal growth were researched to find a possible preventive approach. Microcystis aeruginosa and Chlorella vulgaris were exposed to UV-C irradiation and then cultured in real reclaimed water for 7-18 d. UV-C irradiation at 50-200 mJ cm^-2 could inhibit the growth of M. aeruginosa, C. vulgaris, and both microalgae in co-culture for 3-14, 1-3, and 1-5 d respectively. In addition, UV-C irradiation could cause damage to the cell integrity. At 100-200 mJ cm^-2 UV-C, the proportion of microalgal membrane damage (P_md) in M. aeruginosa cells increased rapidly to 56%-76% from day 3, whereas that in C. vulgaris cells increased to 23%-62% within 3 d. The photochemical efficiency (represented by Y value) of the irradiated groups was negatively affected immediately after UV-C irradiation and recovered gradually during the incubation. The Y value of M. aeruginosa cells began to recover from days 3 to 14, whereas that of C. vulgaris recovered much more quickly, from days 0.1 to 1. Overall, the irradiation-induced suppressive effects on algal growth correlated positively with the UV-C doses. Because M. aeruginosa was more sensitive to UV-C irradiation, UV-C irradiation not only controlled the total biomass of the mixed algae but also selectively reestablished the dominance of the nontoxic C. vulgaris.

Inactivation of Bacillus cereus Spores on Stainless Steel by Combined Superheated Steam and UV-C Irradiation Treatment

Bacillus cereus spore contamination on food contact surfaces is of great concern in the food industry. Thus, in the present study, superheated steam (SHS) was used alone or combined with UV-C irradiation for inactivation of B. cereus spores inoculated on stainless steel coupons. Temperatures higher than 250°C were needed to effectively inactivate B. cereus spores by SHS treatment alone, while a synergistic bactericidal effect resulted from the sequential treatment of SHS before or after UV-C irradiation. The increased dipicolinic acid ratio obtained by the combined treatment had a significant role in the synergistic bactericidal effect. Therefore, the combined treatment of SHS and UV-C could be used effectively to inactivate B. cereus on stainless steel. It is recommended to use hurdle technology with reduced energy consumption to ensure microbiological safety on food contact surfaces.

Effects of a rotational UV-C irradiation system and packaging on the shelf life of fresh pistachio

BACKGROUND

In this study, fresh pistachio was exposed to UV-C irradiation (2.1 and 4.5 kJ m^-2 ) in a rotating cylindrical system with seven germicidal UV-C lamps and immediately packed in perforated and non-perforated polyethylene terephthalate (PET). The fruit were evaluated for weight loss, total phenolic content, enzyme activities, color indices (L*, a*, b* and browning index), and microbial counts during 35 days of storage at 4 °C.

RESULTS

UV-C treatment caused a significant decrease (P < 0.05) in the weight loss of fresh pistachios compared to the control. The activity of catalase and peroxidase enzymes was significantly higher (P < 0.05) in irradiated samples packed in non-perforated PET in comparison to those of untreated samples. Irradiation did not inhibit the activity of polyphenol oxidase in treated samples, although a slight decrease in polyphenol oxidase activity was observed in irradiated samples compared to control. The fruit treated with 2.1 kJ m^-2 of UV-C and the control packed in non-perforated PET were lighter (L*), redder (a*), and less yellow (b*) compared to 4.5 kJ m^-2 treated samples. Furthermore, a dose of 4.5 kJ m^-2 UV-C significantly decreased sensory attributes of fresh pistachios compared to the other irradiation level and control.

CONCLUSION

UV-C irradiation at a dose of 2.1 kJ m^-2 and packing in non-perforated PET are recommended for fresh pistachio preservation based on the physicochemical, microbial, and sensory parameters. © 2019 Society of Chemical Industry.

High Hydrostatic Pressure Processing Better Preserves the Nutrient and Bioactive Compound Composition of Human Donor Milk

BACKGROUND

When mother's milk is insufficient, pasteurized human donor milk (DM) is the recommended supplement for hospitalized very-low-birth-weight infants. The current method of pasteurization (Holder, 62.5°C, 30 min) negatively affects heat-sensitive nutrients and bioactive proteins.

OBJECTIVES

Objectives of this study were to compare changes in DM composition after thermal pasteurization (Holder and flash-heating) and nonthermal methods [UV-C irradiation and high hydrostatic pressure (HHP)]. We hypothesized that nonthermal techniques would result in fewer changes to composition.

METHODS

Holder, flash-heating (brought to boil), UV-C irradiation (250 nm, 25 min), and HHP (500 MPa, 8 min) were studied. Pools of milk from 17 women known to contain bacteria at >5 × 107 colony forming units (CFU)/L were collected from the Rogers Hixon Ontario Human Milk Bank and underwent each pasteurization technique. Macronutrients, heat-sensitive micronutrients (vitamin C, folate), and bioactive components [bile-salt-stimulated lipase (BSSL), lysozyme, lactoferrin] were measured in raw and pools of pasteurized milk. Milk was cultured to determine how well each technique produced a culture negative result (detection limit <1 × 103 CFU/L).

RESULTS

Folate was reduced by 24-27% after Holder, flash-heating, and UV-C (P < 0.05); no reduction was observed after HHP. All pasteurization methods reduced vitamin C (60-75%, P < 0.001). BSSL was abolished after Holder and flash-heating (P < 0.001), reduced after UV-C (48%, P < 0.001), but unaffected by HHP. Lysozyme activity was reduced after flash-heating (44%) and UV-C (74%, P < 0.004) but unaffected by Holder or HHP. Lactoferrin was reduced by all methods (P < 0.02) but most severely by flash-heating (74%) and least severely by HHP (25%). Holder and UV-C reduced lactoferrin by ∼48%. All pasteurization methods reduced the number of culture positive DM samples (P < 0.001).

CONCLUSIONS

HHP better preserves human milk composition than Holder pasteurization. Future research on the feasibility of HHP for pasteurizing human milk is warranted because its implementation may improve the nutritional status and health of DM-fed infants.

UV-C suppression on hazardous metabolites in Microcystis aeruginosa: Unsynchronized production of microcystins and odorous compounds at population and single-cell level

The effectiveness of UV-C towards the toxin and odor of M. aeruginosa at population and single cell levels were investigated in three ways. In the absence of UV-C, MC-LR and β-cyclocitral production show similar pattern of incremental rate with growth rate on population level shown as intracellular concentrations of MC-LR (C_MC) and β-cyclocitral (C_BCC), but the cellular quota of MC-LR (Q_MC) and β-cyclocitral (Q_BCC) at single-cell level reached the maximum values, 37.5 ± 1.2 fg cell^-1 and 4.3 ± 0.1 fg cell^-1, just after the early exponential phase. Second, upon UV-C irradiation, the C_MC consistently decreased by 10-41% with increase of UV-C dosage (50-200 mJ cm^-2) while C_BCC increased by 2-14%. Third, during the 14 days' post-UV incubation, UV-C at 75-200 mJ cm^-2 induced remarkable suppressing effects on both C_MC and C_BCC for 3-14 days. The suppressing effects on Q_MC and Q_BCC were induced by UV-C at 100 mJ cm^-2 and above, with shorter suppressing periods by 1-4 days and lower decremental rates by 21%-30% than that of C_MC and C_BCC, indicating interruptions on biosynthesis processes partially contribute to suppression effects of C_MC and C_BCC. The suppression effect on either C_BCC or Q_BCC, with higher decrement rates while lower recovery rates, was more severe than C_MC and Q_MC.

Resistance of a multiple-isolate marine culture to ultraviolet C irradiation: inactivation vs biofilm formation

Ultraviolet (UV) irradiation is an emerging strategy for controlling the formation of undesired biofilms in water desalination facilities using reverse osmosis (RO). However, most studies examining these pretreatments are limited as they have been conducted on single-species cultures, while biofilms are composed of multiple-species communities. The goal of this study was to investigate the effect of UV-C irradiation on a model community composed of six environmental isolates from a marine biofilm formed in RO seawater desalination plant. There was a high variance in the susceptibility of the single-isolate cultures to UV-C, from no response (isolate Eryth23) to complete inactivation (isolate Vib3). The most active wavelength was around 260 nm, resulting in a loss of viability of single-isolate cultures and loss of vitality of the mixed-isolate cultures. With respect to biofilm formation, the activity of this wavelength was completely different compared to its activity on planktonic suspension. Irradiation with 260 nm did not inhibit the total biofilm formation by the six-isolate culture; moreover, isolates such as the resistant Eryth23 or the susceptible Pseudoalt17, even gained abundance in the mixed isolate biofilm. The only decrease in total biofilm was obtained from irradiation at 280 nm, which was less active against the planktonic culture. These results indicate that the complexity of the biofilm-forming microbial community may contribute to its resistance to UV-C irradiation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study examined the resistance of a multiple-isolate native marine culture to UV-C irradiation, in terms of viability, vitality and the ability to form biofilm. Results of this study showed that even though most of the cells were inactivated both in single-isolate and in multiple-isolate cultures, still the multiple-isolate cultures manages to form biofilms, surprisingly with higher biomass than without irradiation. The significance of the study is in its conclusion that studies on UV-C irradiation of biofilm-forming model micro-organisms are not always applicable to natural multiple-species communities.

Comment on "Photo-assisted degradation of 2, 4, 6-trichlorophenol by an advanced reduction process based on sulfite anion radical: Degradation, dechlorination and mineralization" [Chemosphere 191 (2018) 156-165]

The sulfite-mediated photoreduction (SMP) with UV-C light showed promising performances especially for dechlorination of chlorinated organic compounds (e.g., 2, 4, 6-trichlorophenol (TCP)). The investigation of SMP for TCP is commented and proposed in order to clarify the mechanisms involved.

Wide band gap Ga2O3 as efficient UV-C photocatalyst for gas-phase degradation applications

α, β, γ, and δ polymorphs of 4.6-4.8 eV wide band gap Ga₂O₃ photocatalysts were prepared via a soft chemistry route. Their photocatalytic activity under 254 nm UV-C light in the degradation of gaseous toluene was strongly depending on the polymorph phase. α- and β-Ga₂O₃ photocatalysts enabled achieving high and stable conversions of toluene with selectivities to CO₂ within the 50-90% range, by contrast to conventional TiO₂ photocatalysts that fully deactivate very rapidly on stream in similar operating conditions with rather no CO₂ production, no matter whether UV-A or UV-C light was used. The highest performances were achieved on the high specific surface area β-Ga₂O₃ photocatalyst synthesized by adding polyethylene glycol (PEG) as porogen before precipitation, with stable toluene conversion and mineralization rate into CO₂ strongly overcoming those obtained on commercial β-Ga₂O₃. They were attributed to favorable physicochemical properties in terms of high specific surface area, small mean crystallite size, good crystallinity, high pore volume with large size mesopore distribution and appropriate surface acidity, and to the possible existence of a double local internal field within Ga³⁺ units. In the degradation of hydrogen sulfide, PEG-derived β-Ga₂O₃ takes advantage from its high specific surface area for storing sulfate, and thus for increasing its resistance to deactivation and the duration at total sulfur removal when compared to other β-Ga₂O₃ photocatalysts. So, we illustrated the interest of using high surface area β-Ga₂O₃ in environmental photocatalysis for gas-phase depollution applications.

UV-C as an efficient means to combat biofilm formation in show caves: evidence from the La Glacière Cave (France) and laboratory experiments

Ultra-violet C (UV-C) treatment is commonly used in sterilization processes in industry, laboratories, and hospitals, showing its efficacy against microorganisms such as bacteria, algae, or fungi. In this study, we have eradicated for the first time all proliferating biofilms present in a show cave (the La Glacière Cave, Chaux-lès-Passavant, France). Colorimetric measurements of irradiated biofilms were then monitored for 21 months. To understand the importance of exposition of algae to light just after UV radiation, similar tests were carried out in laboratory conditions. Since UV-C can be deleterious for biofilm support, especially parietal painting, we investigated their effects on prehistoric pigment. Results showed complete eradication of cave biofilms with no algae proliferation observed after 21 months. Moreover, quantum yield results showed a decrease directly after UV-C treatment, indicating inhibition of algae photosynthesis. Furthermore, no changes in pigment color nor in chemical and crystalline properties has been demonstrated. The present findings demonstrate that the UV-C method can be considered environmentally friendly and the best alternative to chemicals. This inexpensive and easily implemented method is advantageous for cave owners and managers.

Vitamin D2, Ergosterol, and Vitamin B2 Content in Commercially Dried Mushrooms Marketed in China and Increased Vitamin D2 Content Following UV-C Irradiation

Mushrooms are a great source of vitamin D and vitamin B₂; however, the content of these vitamins in dried mushrooms has not fully been investigated. Thus, the objectives of this study were to determine the contents of vitamin D₂, ergosterol, and vitamin B₂ in commercially dried edible mushrooms in China and to investigate the effect of UV-C irradiation on fresh mushrooms. Among the 35 species of dried mushrooms considered for this study, the average ergosterol content was 1.98 mg/g, while the average vitamin D₂ content was 16.88 µg/g. The average vitamin B₂ content in dried mushrooms was 12.68 µg/g. Fresh shaggy ink caps and oyster mushrooms, when exposed to UV-C at 254 nm at a dose of 0.25 J/cm² for 10, 30, and 60 min, showed significantly (p < 0.05) increased vitamin D2 content (229.7 and 67.0 µg/g, respectively) as compared to its fresh counterparts. The conversion of ergosterol to vitamin D₂ induced by UV-C irradiation at 0.25 J/cm² was significant (p < 0.05). In conclusion, dried commercial mushrooms have higher contents of ergosterol and vitamin D₂ than fresh mushrooms. UV-C radiation can be used to increase vitamin D₂ content in mushrooms.

UV-C-Induced alleviation of transcriptional gene silencing through plant-plant communication: Key roles of jasmonic acid and salicylic acid pathways

Plant stress responses at the epigenetic level are expected to allow more permanent changes of gene expression and potentially long-term adaptation. While it has been reported that plants subjected to adverse environments initiate various stress responses in their neighboring plants, little is known regarding epigenetic responses to external stresses mediated by plant-plant communication. In this study, we show that DNA repetitive elements of Arabidopsis thaliana, whose expression is inhibited epigenetically by transcriptional gene silencing (TGS) mechanism, are activated by UV-C irradiation through airborne plant-plant and plant-plant-plant communications, accompanied by DNA demethylation at CHH sites. Moreover, the TGS is alleviated by direct treatments with exogenous methyl jasmonate (MeJA) and methyl salicylate (MeSA). Further, the plant-plant and plant-plant-plant communications are blocked by mutations in the biosynthesis or signaling of jasmonic acid (JA) or salicylic acid (SA), indicating that JA and SA pathways are involved in the interplant communication for epigenetic responses. For the plant-plant-plant communication, stress cues are relayed to the last set of receiver plants by promoting the production of JA and SA signals in relaying plants, which exhibit upregulated expression of genes for JA and SA biosynthesis and enhanced emanation of MeJA and MeSA.

Abscisic acid induces biosynthesis of bisbibenzyls and tolerance to UV-C in the liverwort Marchantia polymorpha

Environmental stresses are effective triggers for the biosynthesis of various secondary metabolites in plants, and phytohormones such as jasmonic acid and abscisic acid are known to mediate such responses in flowering plants. However, the detailed mechanism underlying the regulation of secondary metabolism in bryophytes remains unclear. In this study, the induction mechanism of secondary metabolites in the model liverwort Marchantia polymorpha was investigated. Abscisic acid (ABA) and ultraviolet irradiation (UV-C) were found to induce the biosynthesis of isoriccardin C, marchantin C, and riccardin F, which are categorized as bisbibenzyls, characteristic metabolites of liverworts. UV-C led to the significant accumulation of ABA. Overexpression of MpABI1, which encodes protein phosphatase 2C (PP2C) as a negative regulator of ABA signaling, suppressed accumulation of bisbibenzyls in response to ABA and UV-C irradiation and conferred susceptibility to UV-C irradiation. These data show that ABA plays a significant role in the induction of bisbibenzyl biosynthesis, which might confer tolerance against UV-C irradiation in M. polymorpha.

Mechanisms of photosynthetic inactivation on growth suppression of Microcystis aeruginosa under UV-C stress

This study aims to investigate the effects of UV-C irradiation on photosynthetic processes of Microcystis aeruginosa to unravel the mechanism(s) involved in how and in what ways UV-C mediates growth suppression and cellular recovery. Changes in the concentration of photosynthetic pigments, photochemical efficiency, PS II core protein (D1) content, and the coding genes expressions were measured. The results indicate that UV-C doses at 20-200 mJ cm(-2) lead to rapid reduction in gene expression of both psbA (for D1) and cpc (for phycocyanin), but the suppression was short term and recoverable within 3 d of post-UV incubation. Conversely, UV-C doses at ≥50 mJ cm(-2) could induce marked decline in photochemical efficiency (represented by the optimal PS II quantum yield, FV/FM, and the effective PS II quantum yield, Y) as well as decreases in D1 content and water soluble pigments (phycoerythrins, phycocyanins, allophycocyanins) in M. aeruginosa during the post UV-C incubation period. The results suggest that interruption of both the light energy harvesting apparatus (especially the water soluble pigments) and the photochemical process mainly accounted for the growth suppression effect in UV-C irradiated M. aeruginosa.

The impact of UV-C irradiation on spoilage microorganisms and colour of orange juice

The effect of UV-C irradiation on inactivation of spoilage microorganisms and colour of freshly squeezed orange juice were investigated. Orange juice samples were intentionally fermented in order to increase the natural microflora which were mostly composed of yeasts and then exposed to UV-C irradiation at an intensity level of 1.32 mW/cm(2) and sample depth of 0.153 cm for several exposure times by using a collimated beam apparatus. Applied UV dose was in the range of 0 and 108.42 mJ/cm(2). Resistance of yeast to UV light and existence of suspended particles limited the effectiveness of the process. Survival data obtained for yeasts was either described by the Weibull or traditional first-order model and goodness-of-fit of these models was investigated. Weibull model produced a better fit to the data with higher adjusted determination coefficient (R(2) adj) and lower mean square error (MSE) values which were 0.99 and 0.003, respectively. Time and UV dose of first decimal reduction were obtained as 5.7 min and 31 mJ/cm(2), respectively. The data suggests that biodosimetric studies performed by using inoculated microorganisms for assesment of the efficiency of UV irradiation treatment in the shelf life extension of juices must be carefully evaluated. UV-C irradiation had no influence on the colour of orange juice.

UV-C irradiation delays mitotic progression by recruiting Mps1 to kinetochores

The effect of UV irradiation on replicating cells during interphase has been studied extensively. However, how the mitotic cell responds to UV irradiation is less well defined. Herein, we found that UV-C irradiation (254 nm) increases recruitment of the spindle checkpoint proteins Mps1 and Mad2 to the kinetochore during metaphase, suggesting that the spindle assembly checkpoint (SAC) is reactivated. In accordance with this, cells exposed to UV-C showed delayed mitotic progression, characterized by a prolonged chromosomal alignment during metaphase. UV-C irradiation also induced the DNA damage response and caused a significant accumulation of γ-H2AX on mitotic chromosomes. Unexpectedly, the mitotic delay upon UV-C irradiation is not due to the DNA damage response but to the relocation of Mps1 to the kinetochore. Further, we found that UV-C irradiation activates Aurora B kinase. Importantly, the kinase activity of Aurora B is indispensable for full recruitment of Mps1 to the kinetochore during both prometaphase and metaphase. Taking these findings together, we propose that UV irradiation delays mitotic progression by evoking the Aurora B-Mps1 signaling cascade, which exerts its role through promoting the association of Mps1 with the kinetochore in metaphase.