植物乳杆菌SCB2505代谢物对液化沙雷氏菌的抑菌机理

Antibacterial mechanism of Lactobacillus plantarum SCB2505 metabolites against Serratia liquefaciens

液化沙雷氏菌是畜产食品在低温贮藏中的一种常见致腐菌和食源性病原菌。该实验通过最小抑菌浓度(minimum inhibitory concentration,MIC)和生长曲线分析植物乳杆菌SCB2505代谢物对液化沙雷氏菌的抑菌活性,并通过高温、过氧化氢酶及蛋白酶、pH处理和乳酸排除实验分析抑菌物质组成,再通过生物被膜抑制率、细胞壁和细胞膜完整性、菌体形态变化的研究来分析其抑菌机理。结果表明,植物乳杆菌SCB2505代谢物对液化沙雷氏菌的MIC为8 mg/mL,其抑菌物质的高温耐受性较好,pH越低其抑菌效果越好,但相同pH的乳酸溶液不具有抑菌活性,过氧化氢酶和蛋白酶对其抑菌圈大小有显著影响,推测抑菌物质可能为乳酸盐、细菌素与过氧化氢的复合物。植物乳杆菌SCB2505代谢物能明显抑制液化沙雷氏菌生物被膜合成,破坏细胞壁和细胞膜的完整性,使得菌体皱缩凹陷,甚至裂解死亡。该研究结果说明植物乳杆菌SCB2505代谢物作为天然防腐剂在动物食品防腐领域具有较好的应用前景。

Serratia liquefaciens is a common spoilage bacteria and food-borne pathogen in animal-based food during low-temperature storage.In this study,the antibacterial activity of Lactobacillus plantarum SCB2505 metabolites against S.liquefaciens SCB2649 was investigated by measuring the minimum inhibitory concentration(MIC)and growth curve.The composition of antibacterial substances was analyzed by high-temperature heat treatment,catalase and protease treatment,pH adjustment treatment,and lactic acid exclusion experiments.The antibacterial mechanism was studied by measuring the biofilm inhibition rate,the integrity of the cell wall and cell membrane,and the changes in cell morphology.Results showed that the MIC of L.plantarum SCB2505 metabolites against S.liquefaciens was 8 mg/mL.The antibacterial substances were found to well tolerate high temperature,hereby the relative antibacterial activity was 89.09%after heat treatment at 121℃.Catalase and protease could reduce the antibacterial activity of metabolites,but the relative antibacterial activity was still greater than 90%.pH adjustment had a significant effect on its antibacterial activity,whereby the lower the pH,the higher the antibacterial activity.However,it was verified that hydrogen ion concentration was not the main factor affecting the antibacterial activity,and it was speculated that the antibacterial substance was a complex of lactic acid,bacteriocin and hydrogen peroxide.The L.plantarum SCB2505 metabolites can inhibit the biofilm synthesis of S.liquefaciens,destroy the integrity of the cell wall and cell membrane,leading to shrinking and sagging of the cells,and even lysing and dead of the cells.These results show that the L.plantarum SCB2505 metabolites have a good application prospect as natural preservatives in the field of animal-based food preservation.