Abstract Due to the lack of thermal inactivation steps, the fresh produce industry is actively looking for new, environmentally friendly and effective non-thermal control strategies to eliminate foodborne pathogens on produce surfaces and to prevent cross-contamination. Photodynamic inactivation of bacteria has emerged as a novel alternative approach to inactivate microorganisms on fresh produce. In this study, the photo-sensitizing efficacy of vitamin K3 (VK3) under UV-A and simulated sunlight and their antimicrobial efficacy against common foodborne pathogens in broth and on lemon surfaces were investigated. The minimal bactericidal concentration (MBC) of VK3 against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Enteritidis PT30 in darkness was 625.0, 156.3, and 625.0 μg/ml, respectively. When treatments were carried out under light, the MBC values of VK3 (VK3 + light) were reduced in strain, light source, and exposure time dependent manners. The enhanced antimicrobial effect can be attributed to the production of reactive oxygen species of VK3, including hydroxyl radical and singlet oxygen under light exposure. Based on scanning electron microscope examination, VK3 + light treatment damaged the cell integrity of L. monocytogenes and Salmonella; and altered the cell morphology of E. coli O157:H7 including filament formation and fewer fimbriae/flagella. When applied on artificially inoculated lemon surfaces, VK3 + light treatments at MBC levels immediately reduced the levels of L. monocytogenes and E. coli O157:H7 by more than 5.0 Log10 CFU/disk and S. Enteritidis PT30 by ∼4.0 Log10 CFU/disk. Bacterial populations of all tested strains were reduced to below the limit of detection (1.0 Log10 CFU/disk) after one day of storage at 4 °C; the numbers of positive samples after enrichment further decreased as the storage time increased, demonstrating the continuous antimicrobial effects the VK3 generated on lemon surfaces. In summary, the results of this study demonstrated the promising antimicrobial effects of VK3 + light treatments and their great application potential for fresh produce industry.

中文翻译：

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维生素 K3 对单核细胞增生李斯特菌、大肠杆菌 O157:H7 和肠炎沙门氏菌的光驱动抗菌活性

摘要 由于缺乏热灭活步骤，新鲜农产品行业正在积极寻找新的、环保且有效的非热控制策略，以消除农产品表面的食源性病原体并防止交叉污染。细菌的光动力灭活已成为灭活新鲜农产品上微生物的一种新的替代方法。在这项研究中，研究了维生素 K3 (VK3) 在 UV-A 和模拟阳光下的光敏功效及其对肉汤和柠檬表面常见食源性病原体的抗菌功效。VK3 在黑暗中对单核细胞增生李斯特菌、大肠杆菌 O157:H7 和肠炎沙门氏菌 PT30 的最小杀菌浓度 (MBC) 分别为 625.0、156.3 和 625.0 μg/ml。当在光照下进行处理时，VK3 (VK3 + 光) 的 MBC 值以应变、光源和曝光时间相关的方式降低。增强的抗菌作用可归因于 VK3 活性氧的产生，包括在光照下的羟基自由基和单线态氧。扫描电镜观察，VK3+光处理破坏了单核细胞增生李斯特菌和沙门氏菌的细胞完整性；并改变了大肠杆菌 O157:H7 的细胞形态，包括细丝形成和更少的菌毛/鞭毛。当应用于人工接种的柠檬表面时，MBC 水平的 VK3 + 光处理立即将单核细胞增生李斯特氏菌和大肠杆菌 O157:H7 的水平降低了超过 5.0 Log10 CFU/盘和肠炎沙门氏菌 PT30 的水平约 4.0 Log10 CFU/盘. 在 4 °C 下储存一天后，所有测试菌株的细菌数量都减少到检测限以下（1.0 Log10 CFU/盘）；随着储存时间的增加，富集后阳性样品的数量进一步减少，证明了 VK3 在柠檬表面产生的持续抗菌作用。总之，这项研究的结果证明了 VK3 + 光处理的有希望的抗菌作用及其在新鲜农产品行业的巨大应用潜力。