Department of Food Science and Technology, University of California-Davis, Davis, California, USA.
Department of Food Science and Technology, University of California-Davis, Davis, California, USA
Appl Environ Microbiol. 2019 Aug 14;85(17). doi: 10.1128/AEM.01033-19. Print 2019 Sep 1.
The need for more effective antimicrobials is critical for the food industry to improve food safety and reduce spoilage of minimally processed foods. The present study was initiated to develop an efficient and novel antimicrobial approach which combines physical treatments (UV-A or mild heat) and generally recognized as safe lauroyl arginate ethyl (LAE) to inactivate surrogate strains, including and Synergistic inactivation of bacteria resulted in an ∼6-log reduction of target bacteria, while individual treatments resulted in <1.5-log inactivation under the same set of conditions. In addition, the synergistic mechanism between LAE and UV-A/mild heat was evaluated by supplementing with a variety of antioxidants for suppressing oxidative stress and measurement of cell membrane damage by nucleic acid release. These results demonstrate that the synergistic antimicrobial activity of LAE and mild physical stresses was suppressed by supplementation with antioxidants. The research also compared LAE with another membrane-targeting lipopeptide antimicrobial agent, polymyxin B, to understand the uniqueness of LAE-induced synergy. Briefly, differences in modes of action between LAE and polymyxin B were characterized by comparing the MIC, damage to liposomes, and oxidative stress generation. These differences in the mode of action between LAE and polymyxin B suggested that both compounds target cell membrane but significantly differ in mechanisms, including membrane disruption and oxidative stress generation. Overall, this study illustrates synergistic antimicrobial activity of LAE with light or mild heat and indicates a novel oxidative stress pathway that enhances the activity of LAE beyond membrane damage. This study highlights an effective antimicrobial processing approach using a novel combination of lauroyl arginate ethyl (LAE) and two different physical treatments, light (UV-A) and mild heat. Both combinations demonstrated synergistic inactivation against a model Gram-negative bacterium or a Gram-positive bacterium or both by a >5-log reduction. Further mechanistic study revealed that oxidative stress is responsible for synergistic inactivation between LAE and UV-A, while both membrane damage and oxidative stress are responsible for the synergistic combination between LAE and mild heat. The mode of action of LAE was further compared to that of polymyxin B and analyzed using artificial membrane model systems and the addition of antioxidants. The proposed combination of LAE and common physical treatments may improve food preservation, food safety, and current sanitation processes for the food industry and the inactivation of pathogenic strains in biomedical environments.
需要更有效的抗菌剂对于改善食品安全和减少低加工食品变质至关重要。本研究旨在开发一种有效的新抗菌方法,该方法结合物理处理(UV-A 或温和加热)和普遍认为安全的月桂酰精氨酸乙酯(LAE)来灭活替代菌株,包括 和 。细菌的协同失活导致目标细菌减少了约 6 个对数级,而在相同条件下,单独处理导致细菌减少小于 1.5 个对数级。此外,通过添加各种抗氧化剂来抑制氧化应激并通过核酸释放测量细胞膜损伤,评估了 LAE 和 UV-A/温和加热之间的协同作用机制。这些结果表明,抗氧化剂的补充抑制了 LAE 和温和物理应激的协同抗菌活性。该研究还将 LAE 与另一种靶向细胞膜的脂肽抗菌剂多粘菌素 B 进行了比较,以了解 LAE 诱导协同作用的独特性。简而言之,通过比较 MIC、脂质体损伤和氧化应激生成,LAE 和多粘菌素 B 的作用模式之间的差异。LAE 和多粘菌素 B 之间作用模式的这些差异表明,两种化合物都靶向细胞膜,但在机制上有很大差异,包括膜破坏和氧化应激的产生。总体而言,本研究说明了 LAE 与光或温和热协同抗菌活性,并指出了一种新的氧化应激途径,该途径通过超越细胞膜损伤来增强 LAE 的活性。这项研究强调了一种使用新型月桂酰精氨酸乙酯(LAE)和两种不同物理处理(光(UV-A)和温和加热)的新型组合的有效抗菌处理方法。这两种组合都表现出对革兰氏阴性菌或革兰氏阳性菌或两者的协同失活作用,减少超过 5 个对数级。进一步的机制研究表明,氧化应激是 LAE 和 UV-A 之间协同失活的原因,而膜损伤和氧化应激都是 LAE 和温和热之间协同组合的原因。还使用人工膜模型系统和添加抗氧化剂进一步比较了 LAE 的作用模式和多粘菌素 B 的作用模式。LAE 和常见物理处理的组合可能会改善食品保存、食品安全以及食品工业的当前卫生过程,并在生物医学环境中失活致病菌株。