Nisin and grape seed extract (GSE) have been widely used as food preservatives; however, the mechanism against pathogens at molecular level has not been well elucidated. This work aimed to investigate their antimicrobial effect against Listeria monocytogenes and to elucidate the mechanism by NMR-based metabolomics. Nisin exhibited enhanced in vitro antilisterial effect when combined with GSE (4.49 log CFU/mL reduction). Marked change in cell membrane permeability was observed in the combination group using confocal laser scanning microscopy; this was verified by increased leakage of protein and nucleic acid. The underlying antimicrobial mechanism was revealed by NMR coupled with multivariate analysis. Significant decreases in threonine, cysteine, ATP, NADP, adenine were observed, whereas a few of metabolites such as lactic acid and γ-aminobutyric acid (GABA) increased after nisin-GSE treatment (P < 0.05). Pathway analysis further manifested that the nisin-GSE inhibited the survival of L. monocytogenes by blocking the TCA cycle, amino acid biosynthesis and energy-producing pathway. Lastly, nisin and GSE were applied to shrimp and binary combination showed remarkably antilisterial activity (1.79 log CFU/g reduction). GABA shunt and protein degradation from shrimp compensated the unbalanced glycolysis and amino acid metabolism by providing energy and carbon source for L. monocytogenes inoculated on shrimp. Thus, they were more tolerant to nisin and GSE stresses as compared to the broth-grown culture.

中文翻译：

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通过基于NMR的代谢组学方法阐明了乳链菌肽和葡萄籽提取物对肉汤和虾中单核细胞增生李斯特菌的抗菌机制。

日清和葡萄籽提取物（GSE）已被广泛用作食品防腐剂。然而，在分子水平上针对病原体的机制尚未得到很好的阐明。这项工作旨在研究其对单核细胞增生李斯特菌的抗菌作用，并通过基于NMR的代谢组学阐明其机制。当与GSE结合使用时，乳链菌肽显示出增强的体外抗利斯特作用（降低4.49 log CFU / mL）。使用共聚焦激光扫描显微镜观察联合组细胞膜通透性的显着变化。蛋白质和核酸泄漏的增加证实了这一点。通过NMR和多变量分析揭示了潜在的抗菌机制。观察到苏氨酸，半胱氨酸，ATP，NADP，腺嘌呤显着下降，乳酸链球菌素-GSE处理后乳酸和γ-氨基丁酸（GABA）等代谢产物增加（P <0.05）。途径分析进一步表明，乳链菌肽-GSE通过阻断TCA循环，氨基酸生物合成和能量产生途径而抑制了单核细胞增生李斯特菌的存活。最后，将乳链菌肽和GSE应用于虾，二元组合显示出明显的抗李斯特菌活性（降低1.79 log CFU / g）。虾的GABA分流和蛋白质降解通过为虾上接种的单核细胞增生李斯特菌提供能量和碳源，从而补偿了不平衡的糖酵解和氨基酸代谢。因此，与肉汤培养相比，它们更能耐受乳链菌肽和GSE胁迫。途径分析进一步表明，乳链菌肽-GSE通过阻断TCA循环，氨基酸生物合成和能量产生途径而抑制了单核细胞增生李斯特菌的存活。最后，将乳链菌肽和GSE应用于虾，二元组合显示出明显的抗李斯特菌活性（降低1.79 log CFU / g）。虾的GABA分流和蛋白质降解通过为虾上接种的单核细胞增生李斯特菌提供能量和碳源，从而补偿了不平衡的糖酵解和氨基酸代谢。因此，与肉汤培养相比，它们更能耐受乳链菌肽和GSE胁迫。途径分析进一步表明，乳链菌肽-GSE通过阻断TCA循环，氨基酸生物合成和能量产生途径而抑制了单核细胞增生李斯特菌的存活。最后，将乳链菌肽和GSE应用于虾，二元组合显示出明显的抗李斯特菌活性（降低1.79 log CFU / g）。虾的GABA分流和蛋白质降解通过为虾上接种的单核细胞增生李斯特菌提供能量和碳源，从而补偿了不平衡的糖酵解和氨基酸代谢。因此，与肉汤培养相比，它们更能耐受乳链菌肽和GSE胁迫。虾的GABA分流和蛋白质降解通过为虾上接种的单核细胞增生李斯特菌提供能量和碳源，从而补偿了不平衡的糖酵解和氨基酸代谢。因此，与肉汤培养相比，它们更能耐受乳链菌肽和GSE胁迫。虾的GABA分流和蛋白质降解通过为虾上接种的单核细胞增生李斯特菌提供能量和碳源，从而补偿了不平衡的糖酵解和氨基酸代谢。因此，与肉汤培养相比，它们更能耐受乳链菌肽和GSE胁迫。