Fresh-cut produce is usually produced under standardized disinfection processes, which are unavailable at the ready-to-eat stage. Currently, chemical sanitizers are used for washing, but their disinfection efficacy is limited. In this study, UV-C (1.03 kJ/m2) was combined with organic acids that are generally recognized as safe (GRAS), including citric, malic, acetic, and lactic acids (LAs), to wash lettuce and cherry tomatoes that are contaminated with Escherichia coli O157:H7 and Salmonella Typhimurium. The results showed that LA was the most effective treatment among the single treatments, with a pathogen reduction and cross-contamination incidence of 2.0-2.3 log CFU/g and 28-35%, respectively. After combining with UV-C, the disinfection efficacy and cross-contamination prevention capacity of the four GRAS acids significantly improved. Among the combination treatments, the highest pathogen reduction (2.5-2.7 log CFU/g) and the lowest cross-contamination incidence (11-15%) were achieved by LA-UV. The analyses of ascorbic acid, chlorophyll, lycopene, antioxidant capacity, and ΔE indicated that neither the single nor combination treatments negatively affected the quality properties. These results provide a potential hurdle technology for fresh produce safety improvement at the ready-to-eat stage.

The study investigated the impact of UV-C irradiation on peach fruit quality during postharvest storage, with a focus on aroma changes and the mechanisms involving lipoxygenase metabolism. Results showed that UV-C irradiation at a dosage of 1.5 kJ/m2 was found to preserve the quality attributes of peach fruit during ambient storage, as evidenced by high flesh firmness, inhibition of weight loss and respiration rate, as well as high values of L* and ascorbic acid. Meanwhile, UV-C irradiation led to an increase in the contents of aroma-related volatiles, particularly esters and lactones, compared to non-irradiated fruit. Our results suggested that the enhanced emission of aroma-related volatiles in UV-C irradiated peach fruit was linked to elevated levels of unsaturated fatty acids. Besides, UV-C induced the expressions and activities of enzymes in the lipoxygenase pathway, thus promoting the synthesis of esters and lactones, which contribute to the enhanced aroma in peach fruit.

Biofilms give rise to a range of issues, spanning from harboring pathogens to accelerating microbial-induced corrosion in pressurized water systems. Introducing germicidal UV-C (200-280 nm) irradiation from light-emitting diodes (LEDs) into flexible side-emitting optical fibers (SEOFs) presents a novel light delivery method to inhibit the accumulation of biofilms on surfaces found in small-diameter tubing or other intricate geometries. This work used surfaces fully submerged in flowing water that contained Pseudomonas aeruginosa, an opportunistic pathogen commonly found in water system biofilms. A SEOF delivered a UV-C gradient to the surface for biofilm inhibition. Biofilm growth over time was monitored in situ using optical conference tomography. Biofilm formation was effectively inhibited when the 275 nm UV-C irradiance was ≥8 μW/cm2. Biofilm samples were collected from several regions on the surface, representing low and high UV-C irradiance. RNA sequencing of these samples revealed that high UV-C irradiance inhibited the expression of functional genes related to energy metabolism, DNA repair, quorum sensing, polysaccharide production, and mobility. However, insufficient sublethal UV-C exposure led to upregulation genes for SOS response and quorum sensing as survival strategies against the UV-C stress. These results underscore the need to maintain minimum UV-C exposure on surfaces to effectively inhibit biofilm formation in water systems.

Stilbenes accumulate in Scots pine heartwood where they have important roles in protecting wood from decaying fungi. They are also part of active defense responses, and their production is induced by different (a)biotic stressors. The specific transcriptional regulators as well as the enzyme responsible for activating the stilbene precursor cinnamate in the pathway are still unknown. UV-C radiation was the first discovered artificial stress activator of the pathway. Here, we describe a large-scale transcriptomic analysis of pine needles in response to UV-C and treatment with translational inhibitors, both activating the transcription of stilbene pathway genes. We used the data to identify putative candidates for the missing CoA ligase and for pathway regulators. We further showed that the pathway is transcriptionally activated by phosphatase inhibitor, ethylene and jasmonate treatments, as in grapevine, and that the stilbene synthase promoter retains its inducibility in some of the tested conditions in Arabidopsis, a species that normally does not synthesize stilbenes. Shared features between gymnosperm and angiosperm regulation and partially retained inducibility in Arabidopsis suggest that pathway regulation occurs not only via ancient stress-response pathway(s) but also via species-specific regulators. Understanding which genes control the biosynthesis of stilbenes in Scots pine aids breeding of more resistant trees.

BACKGROUND: Agaricus bisporus with a completely white appearance is popular with consumers. However, A. bisporus is susceptible to senescence and spoilage, which results in browning and oxidative tissue damage, with limited shelf life. This study investigated the effects of shortwave ultraviolet (UV-C, 1.0 kJ m-2 ) irradiation on quality features, enzymatic browning, and defense properties of A. bisporus stored at 4 °C for 21 days.
RESULTS: After storage, UV-C irradiated A. bisporus had increased quality of sensory, color and hardness characteristics; it exhibited higher content of total phenolic, brown melanin precursors, including γ-glutaminyl-4-hydroxybenzene, γ-glutaminyl-3,4-dihydroxybenzene and tyrosine, lower accumulation of malondiadehyde, hydrogen peroxide and superoxide radical, and maintained membrane integrity in comparison to control samples. Besides, A. bisporus treated by UV-C showed lower degree of browning and higher level of self-defense capacity, which may be ascribed to the enhancement in activities of superoxide dismutase, catalase, phenylalanine ammonia lyase, chitinase and β-1,3-glucanase activity, while inhibiting polyphenol oxidase activity during storage.
CONCLUSIONS: These results indicate that the higher self-defense capacity with UV-C treatment might be the mechanism associated with the delay of senescence in Agaricus bisporus. Therefore, UV-C treatment is suggested as a potential practical application in mushrooms. © 2023 Society of Chemical Industry.

Flavane-3-ol monomers are the precursors of proanthocyanidins (PAs), which play a crucial role in grape resistance. Previous studies showed that UV-C positively regulated leucoanthocyanidin reductase (LAR) enzyme activity to promote the accumulation of total flavane-3-ols in juvenile grape fruit, but its molecular mechanism was still unclear. In this paper, we found that the contents of flavane-3-ol monomers increased dramatically at the early development stage grape fruit after UV-C treatment, and the expression of its related transcription factor VvMYBPA1 was also enhanced significantly. The contents of (-)-epicatechin and (+)-catechin, the expression level of VvLAR1 and VvANR, and the activities of LAR and anthocyanidin reductase (ANR) were improved significantly in the VvMYBPA1 overexpressed grape leaves compared to the empty vector. Both VvMYBPA1 and VvMYC2 could interact with VvWDR1 using bimolecular fluorescence complementation (BiFC) and yeast two hybrid (Y2H). Finally, VvMYBPA1 was proven to bind with the promoters of VvLAR1 and VvANR by yeast one hybrid (Y1H). To sum up, we found that the expression of VvMYBPA1 increased in the young stage of grape fruit after UV-C treatment. VvMYBPA1 formed a trimer complex with VvMYC2 and VvWDR1 to regulate the expression of VvLAR1 and VvANR, thus positively promoting the activities of LAR and ANR enzyme, and eventually improved the accumulation of flavane-3-ols in grape fruit.

The \'Xiaobai\' apricot fruit is rich in nutrients and is harvested in summer, but the high temperature limits its storage period. To promote commercial quality and extend shelf life, we investigated the effectiveness of Ultraviolet C (UV-C) combined with 1-methylcyclopropene (1-MCP) treatment on \'Xiaobai\' apricot fruit stored at 4 ± 0.5 °C for 35 days. The results revealed that the combination treatment of 1-MCP and UV-C performed better than either UV-C or 1-MCP alone in fruit quality preservation. The combination treatment could delay the increase in weight loss, ethylene production, and respiration rate; retain the level of soluble solid content, firmness, titratable acid, and ascorbic acid content; promote the total phenolics and flavonoids accumulation; improve antioxidant enzyme activity and relative gene expression, and DPPH scavenging ability; and reduce MDA, H2O2, O2.- production. The combined treatment improved the quality of apricot fruit by delaying ripening and increasing antioxidant capacity. Therefore, combining UV-C and 1-MCP treatment may be an effective way to improve the post-harvest quality and extend the storage period of the \'Xiaobai\' apricot fruit, which may provide insights into the preservation of \'Xiaobai\' apricot fruit.

This study investigated the possible mechanism of softening and senescence of blueberry after harvest using chitosan/thyme oil coating combined with UV-C (short wave ultraviolet irradiation) treatment. On the 56th day of storage, the CBP, cellulose, and hemicellulose contents in the chitosan/thyme oil coating +UV-C-treated group were 1.41, 1.65, and 1.20 times higher than those in the control group. Compared with the control group, the activities of polygalacturonase (PG), pectin methylesterase (PME), β-glucosidase (β-Gal), and cellulose (Cx) were significantly reduced (p < 0.05) after chitosan/thyme oil coating +UV-C, and their maximum values decreased by 5.41 μg/h g, 5.40 U/g, 12.41 U/g, and 3.85 μg/h g, respectively. Moreover, chitosan/thyme oil coating combined with UV-C treatment inhibited the gene expression of PG, PME, Cx, and β-Gal and then regulated the decrease in PG, PME, Cx, and β-Gal activities, inhibited the degradation of cell wall polysaccharides, and delayed the softening and senescence of postharvest blueberries. The results showed that chitosan/thyme oil coating, UV-C, and chitosan/thyme oil coating + UV-C could significantly inhibit postharvest softening of blueberry; chitosan/thyme oil coating +UV-C had the best effect.

Postharvest rot of potato tubers caused by fungal pathogens is the main cause of significant economic losses, while also raising potential food safety issues. Integrated disease management, utilizing bio-safe and eco-friendly methods, represents a sustainable strategy for reducing postharvest losses in crops, including potato. In the current study, the application of the antagonistic yeast, Wickerhamomyces anomalus, combined with a UV-C treatment was evaluated for the management of postharvest Alternaria rot of potato tubers, caused by Alternaria tenuissima. Both W. anomalus and UV-C as individual treatments reduced the size of A. tenuissima infections on potato tubers, relative to the control, while the combined treatment of W. anomalus and UV-C exhibited the highest level of inhibition. W. anomalus or UV-C alone, and especially when used in combination, induced the expression of defense-related genes, including polyphenol oxidase, peroxidase, and β-1,3-glucanase, and also increased the level of flavonoids and lignin in potato tubers. Our findings indicate that the mechanism of action by which UV-C enhances the biocontrol effect of W. anomalus against postharvest Alternaria rot includes the activation of defense-related response in potato tubers. The integration of biocontrol agents and physical treatments (e.g., UV-C) represents an effective, eco-friendly hurdle technology for managing postharvest rot in potato.

The Taklimakan Desert located in China is the second-largest shifting sand desert in the world and is known for its harsh conditions. Types of γ-rays or UV radiation-resistant bacterial strains have been isolated from this desert. However, there is no information regarding the proportions of the radiation-resistant strains in the total culturable microbes. We isolated 352 bacterial strains from nine sites across the Taklimakan Desert from north to south. They belong to Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes. The phylum Actinobacteria was the most predominant in abundance and Firmicutes had the highest species richness. Bacteroidetes had the lowest abundance and was found in four sites only, while the other three phyla were found in every site but with different distribution profiles. After irradiating with 1000 J/m2 and 6000 J/m2 UV-C, the strains with survival rates higher than 10% occupied 72.3% and 36.9% of all culturable bacteria, respectively. The members from Proteobacteria had the highest proportions, with survival rates higher than 10%. After radiation with 10 kGy γ-rays, Kocuria sp. TKL1057 and Planococcus sp. TKL1152 showed higher radiation-resistant capabilities than Deinococcus radiodurans R1. Besides obtaining several radiation-resistant extremophiles, this study measured the proportions of the radiation-resistant strains in the total culturable microbes for the first time. This study may help to better understand the origin of radioresistance, especially by quantitatively comparing proportions of radiation-resistant extremophiles from different environments in the future.