副干酪乳杆菌Z17-壳聚糖复配对大肠杆菌O157:H7的抑菌效果及作用机制

目的：研究副干酪乳杆菌Z17-壳聚糖复配对草莓中大肠杆菌O157:H7抑菌活性及作用机制。方法：采用流式细胞术、傅里叶变换红外光谱、拉曼光谱及扫描电子显微镜技术分析副干酪乳杆菌Z17-壳聚糖对大肠杆菌O157:H7细胞膜的影响。结果：质量分数1.0%壳聚糖溶液与副干酪乳杆菌Z17复配处理能有效去除草莓上的大肠杆菌O157:H7，减菌率达99%；壳聚糖溶液与副干酪乳杆菌Z17共同作用3 h使大肠杆菌O157:H7 DNA胞外释放量达（381.00±3.53）ng/μL，细胞膜破损率为58.3%；细胞壁膜中脂肪酸、蛋白、肽聚糖、糖苷环、多糖结构成分被破坏；细胞膜局部位移变薄，大分子物质黏附于菌体细胞表面，细胞表面出现孔洞，胞内物质泄漏，最终导致菌体死亡。结论：副干酪乳杆菌Z17-壳聚糖能够有效地抑制草莓中大肠杆菌O157:H7，其抑菌作用靶点为大肠杆菌O157:H7的细胞膜，研究可为大肠杆菌O157:H7的生物防治提供参考。

Antibacterial Effect and Mechanism of Mixture of Culture Supernatant of Lactobacillus paracei Z17 with Chitosan against Escherichia coli O157:H7

To investigate the synergistic antibacterial activity and mechanism of culture supernatant of Lactobacillus paracei Z17 combined with?chitosan against Escherichia coli O157:H7 in strawberry, flow cytometry, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM) were used to study the damage to the cell membrane of E. coli O157:H7 caused by Lactobacillus paracei Z17-chitosan mixture. The results showed that combined treatment with 1.0% chitosan solution and Lactobacillus parace Z17 could decontaminate E. coli O157:H7 on strawberries by 99%. The extracellular release of DNA from E. coli O157:H7 was (381.00 ± 3.53) ng/μL and the proportion of cells with a damaged membrane was 58.3% after combined treatment for 3 h. Fatty acids, proteins, peptidoglycans, glycoside rings and polysaccharides were destroyed in the cell wall membrane. The cell membrane exhibited local displacement and became thinner, and large molecules were adhered to the cell surface, with holes in it, leading to leakage of intracellular contents and eventually cell death. In conclusion, L. paracei Z17-chitosan mixture can inhibit E. coli O157:H7 on strawberries by targeting the cell membrane of E. coli O157:H7, which may be useful for the biocontrol of E. coli O157:H7.