Antibacterial mechanism of apple phloretin on physiological and morphological properties of Listeria monocytogenes

Abstract Green bactericides are excellent strategies for reducing food spoilage. Phloretin was regarded as efficient, broad-spectrum and safe preservative, which showed enormous potential in food industry. Inhibitory mechanism of phloretin on Listeria monocytogenes was systematically elucidated through integrity of cell membrane, intracellular protein content, energy level, and nucleic acid morphological character. SEM and TEM results showed minimal injury of cell membrane, which was further proved by a leakage of potassium ions, ATP and little protein and nucleic acid. There were drastic reduction of intracellular or total protein and ATP compared to cell without phloretin treatment. However, the specific activity of hexokinase and isocitrate dehydrogenase were unaffected after phloretin treatment. From these results, we concluded that phloretin’s bacteriostatic mechanism is decreasing the intracellular protein content and energy level resulting from DNA aggregation. This finding was prospective to fully illustrate the phloretin’s mechanism and develop it into a natural preservative in food industry.

摘要：绿色杀菌剂是减少食品腐败变质的优良策略。根皮素（Phloretin）被认为是高效、广谱且安全的防腐剂，在食品工业中具备巨大应用潜力。本研究通过细胞膜完整性、胞内蛋白含量、能量水平及核酸形态特征，系统阐明了根皮素对单核细胞增生李斯特菌（Listeria monocytogenes）的抑菌机制。扫描电子显微镜（SEM）与透射电子显微镜（TEM）结果显示细胞膜仅受到轻微损伤，这一结论进一步通过钾离子、三磷酸腺苷（ATP）以及少量蛋白与核酸的泄漏得到验证。与未经根皮素处理的菌体相比，经处理后的菌体胞内蛋白、总蛋白及ATP含量均大幅下降。然而，己糖激酶（hexokinase）与异柠檬酸脱氢酶（isocitrate dehydrogenase）的比活性在根皮素处理后未受影响。基于上述结果，本研究得出结论：根皮素的抑菌机制为通过DNA聚集导致胞内蛋白含量与能量水平下降。该研究成果有望全面阐明根皮素的抑菌机制，并推动其开发为食品工业用天然防腐剂。