二甲基二碳酸盐和乳链菌肽对果汁饮料协同杀菌的作用机制研究

The prospect of dimethyl dicarbonate (DMDC) applied in the non-thermal sterilization of juice drinks is very good, whereas some microorganisms showed resistance to DMDC. It was found that DMDC and Nisin showed a synergistic effect on the inactivation of bacteria which were resistant to DMDC, but the mechanism of bactericidal synergism of DMDC and Nisin is still poorly understood. In this project, Escherichia coli and Leuconostoc mesenteroides, which shown difference in the resistance of DMDC and Nisin, will be considered as target microorganisms. Effects of DMDC and Nisin on the functional parameter of cell membrane will be investigated, and it will be analyzed whether the bactericidal synergism of DMDC and Nisin was attributed to the promotion of DMDC to the interaction of nisin and cell membrane. Also the level and type of enzymes modified by DMDC will be studied using the proteomic technology as the target microorganisms was treated by the individual or combined treatment of DMDC and Nisin, and also it will be analyzed whether the bactericidal synergism of DMDC and Nisin was attributed to the increase of microbial enzymes inactivation by DMDC modification. Results of the projiect will provide a theoretical basis for the application of DMDC combined with other non-thermal sterilization technology.

二甲基二碳酸盐（DMDC）在果汁饮料的非热杀菌加工中具有良好的应用前景, 而一些微生物对DMDC具有较强的抗性。项目前期研究发现DMDC和乳链菌肽对DMDC抗性菌具有协同杀菌效应，但两者的协同杀菌机制尚不清楚。本项目以前期发现的对DMDC和乳链菌肽抗性具有明显差异的大肠杆菌和肠膜状明串珠菌为目标菌，研究DMDC和乳链菌肽联合处理对目标菌细胞膜功能的影响，探明DMDC是否通过促进Nisin与细胞膜的相互作用而实现增效杀菌；并采用蛋白组学技术，探讨目标菌经DMDC和乳链菌肽处理后其酶蛋白被DMDC修饰程度和修饰类型的差异，揭示肠膜状明串珠菌对DMDC的抗性机制，明确Nisin是否通过提高DMDC对目标菌中关键酶蛋白的修饰失活而实现增效杀菌。研究结果可以为DMDC与其它非热杀菌技术的联合应用提供理论支撑。

二甲基二碳酸盐（DMDC）在果汁饮料的非热杀菌加工中具有良好的应用前景, 而一些微生物对DMDC具有较强的抗性。项目前期研究发现DMDC和乳链菌肽对DMDC抗性菌具有协同杀菌效应，但两者的协同杀菌机制尚不清楚。本项目以前期发现的对DMDC和乳链菌肽抗性具有明显差异的大肠杆菌和肠膜状明串珠菌为目标菌，研究了二甲基二碳酸盐（DMDC）和Nisin 处理对模拟果汁中肠膜状明串珠菌的杀菌效果及其细胞膜功能的影响。结果表明：DMDC 联合Nisin 作用于该菌时的部分杀菌浓度指数为0.38，小于0.50，两者之间具有很好的协同杀菌作用。扫描电镜分析发现该菌经DMDC 和Nisin 处理后其细胞形态没有发生明显变化。该菌经DMDC 处理后仅有个别菌体细胞的膜通透性出现增加，而该菌经Nisin 处理后，约7%菌体细胞的膜通透性增加。Nisin处理虽能改变该菌的细胞膜通透性，增加胞外极性物质的摄入，但并不能明显促进胞内物质的流失，高浓度的DMDC 处理能导致该菌溶液的紫外吸收值增加约60%。DMDC 和Nisin 两者对该菌细胞内物质的流失、细胞膜的通透性的增加和胞内pH 的下降没有相互促进作用，但DMDC 和Nisin 的联合作用能促进该菌细胞内脱氢酶的进一步失活。研究结果可以为DMDC与其它非热杀菌技术的联合应用提供理论支撑。