破乳菌关键表面性质对其油水界面行为的影响机制

Highly-efficient and environment-friendly demulsifying bacteria has become a research hotspot in recent years. In biological demulsification process, added demulsifying cells behave like colloidal particles and exhibit complicated surface properties. However, the related demulsification mechanism remains unclear. The destabilization of oil-water interfacial film of the dispersed droplet is the key premise for the emulsion breaking process. To reveal the demulsification mechanism, it is crucial to clarify the influence of the surface properties of demulsifying bacteria on its interfacial behavior and stability of interfacial film. In this application, a selected demulsifying bacteria, Alcaligenes sp. S-XJ-1, is cultivated using different carbon sources, and the obtained cells are used as the research object. Crucial surface properties are studied followed by in-situ identification of its featured cell surface composition. The quartz crystal microbalance with dissipation (QCM-D) test system based on the single-molecule self-assembled oil monolayer is set up to characterize the interfacial behavior of demulsifying strains with different surface properties. The self-built micropipette technique testing platform is employed to study the effect of the interfacial behavior of demulsifying bacteria on the interfacial film. Finally, the interaction forces between demulsifying cells or between the interface and cells are measured using atomic force microscope (AFM). The obtained results, combined with the extended Derjaguin-Landau-Verwey-Overbeek theory (XDLVO), are cooperatively used to characterize its interfacial mechanical characteristics. Based on the thermodynamic analysis, the influence of the cell surface properties on the interfacial behavior is to be revealed. It is anticipated that this research achievements will make great contributions to the study of biological demulsification mechanism, and will provide reference for other studies focused on microbial interfacial behavior.

高效、环境友好的破乳菌在破乳过程中以胶体颗粒态存在于乳状液，其表面性质复杂，破乳机理尚未揭示。乳状液破乳的关键是液滴油水界面膜的失稳，明确菌体表面性质对其油水界面行为及界面膜稳定性的影响机制是揭示破乳机理的关键。本项目以不同类型碳源培养破乳菌，识别影响破乳性能的关键表面性质，通过原位鉴定明确影响关键表面性质的物质特征；基于自组装单分子油膜构建菌体在油水界面粘附聚集的石英晶体微天平(QCM-D)试验体系，研究不同表面性质破乳菌的界面行为特征；进一步采用自建微吸液管测试平台，研究菌体的油水界面行为对界面膜的影响规律；最后构建基于原子力显微镜(AFM)的菌体在油水界面作用力的测定体系，结合XDLVO理论研究菌体在油水界面的力学特征，并通过热力学分析揭示破乳菌表面性质对其油水界面行为的影响机制。研究成果为最终揭示破乳菌的破乳机理奠定基础，并为其他领域的菌体界面行为研究提供借鉴。

高效、环境友好的破乳菌在破乳过程中以胶体颗粒态存在于乳状液，其表面性质复杂，破乳机理尚未揭示。乳状液破乳的关键是液滴油水界面膜的失稳，明确菌体表面性质对其油水界面行为及界面膜稳定性的影响机制是揭示破乳机理的关键。本研究以不同碳源培养的破乳菌Alcaligenes sp.S-XJ-1为研究对象，分析了其表面特征物质、表面性质及二者对W/O乳化液破乳效果影响；阐明了菌体细胞表面的疏水性是影响其破乳活性的关键表面性质，通过原位鉴定明确了菌表的蛋白质类及低聚谷氨酸类物质是破乳关键活性物质；从基因和蛋白组学层面证明了破乳菌代谢碳源的机制及合成破乳活性物质的机制。建立了基于动态光散射技术的乳化液破乳过程原位定量分析方法，准确地将破乳菌的破乳过程分为液滴絮凝聚并、分散液滴沉降、脱油脱水三个阶段，并证明了絮凝聚并阶段是菌体破乳的关键环节；构建了基于CLSM、cry-SEM及QCM-D的乳化液破乳过程中微观结构演变的观测平台，揭示了破乳菌在油水界面粘附、聚集成簇、不均匀分布等特征是促进液滴聚并的关键，并证明了液滴-液滴、液滴-界面聚集的破乳菌对乳化液网状结构的动态影响过程，菌体表面疏水性越强其对乳状液微观结构演变响应越快；基于微吸液管实验平台搭建菌体与界面相互作用实验测试平台，分析液滴与液面、液滴与液滴间的接触、碰撞等过程，研究发现破乳菌的存在使界面膜形态发生明显变化，界面膜各个位点的机械强度不再均一，易发生液滴聚并，且表面疏水性强的菌体对界面膜机械强度的降低作用更加明显。最后结合XDLVO理论研究菌体在油水界面的力学特征，通过热力学分析揭示破乳菌表面性质对其油水界面行为的影响机制。研究成果为不同碳源培养生物破乳菌的性质及特征物质分析提供了思路，为菌体界面行为研究提供了方法借鉴，为最终揭示破乳菌的破乳机理奠定理论基础。