基于多相流（CFD）剪应力调控胞内第二信使分子的膜污染控制方法及机理研究

膜污染是限制膜生物反应器技术广泛应用的重要因素，微生物群体在膜表面形成生物膜是其主要形式。而环二鸟苷酸（c-di-GMP）是广泛存在于细菌胞内的通用第二信使分子，参与调控生物膜的形成。本项目拟采用计算流体力学（CFD）和环境工程实验并重的方法，以气液固多相流场在膜表面产生的剪应力为外部信号源，全面研究其通过调节胞内c-di-GMP水平而影响细菌成膜行为（如EPS分泌），最终控制膜污染发生的微生物学机制。在此基础上，利用间歇性活塞流及连续性气泡流作为外部控制手段，构建基于CFD剪应力对c-di-GMP调控的新型膜污染控制方法。并根据关键基因及相应目标菌群对剪应力的响应特征等方面，揭示剪应力通过c-di-GMP水平控制膜污染的分子生物学机制。研究结果将结合宏观信号源剪应力和微观c-di-GMP两个调控层面对膜污染过程进行深层次研究，以及为相应控制方法的开发提供理论与应用基础。

Membrane fouling is the major factor limiting the wide application of membrane bioreactor (MBR) technology. The formation of microbial biofilm on membrane surface is the main reason of membrane fouling. The bis-(3’-5’)-cyclic dimeric guanosine monophosphate (c-di-GMP) is found as the universal intracellular second messenger molecule in the bacteria, which is involved in the regulation of biofilm formation. The gas-liquid-solid multiphase flow generated by aeration can induce shear stress on the membrane surface, which has direct and significant correlation with c-di-GMP and biofilm formation. By combination of computational fluid dynamics (CFD) and environmental engineering experimental methods, this project quantifies the complex correlation rule of shear stress with time and space, the aim is to use shear stress as external signal source, comprehensively investigate its impact on intracellular second messengers c-di-GMP level, and the mediating effect on biofilm formation (such as EPS production). Therefore, the shear stress will be used as external signal source to control membrane fouling through regulation of c-di-GMP level. Based on this, the novel strategies of intermittent slug flow and continuous bubbly flow will be developed and constructed. Moreover, according to the response characteristics to shear stress, the key functional gene composition, expression patterns and the corresponding targeted bacteria community will be identified. The molecular biological mechanism of shear stress controlling membrane fouling through c-di-GMP level will be illustrated. This project is expected to provide new insights in the membrane fouling mechanism from the intracellular c-di-GMP level regulation by shear stress, from both macroscopic and microcosmic aspects. Furthermore, it would provide theoretical and application basis for new strategies developments on fouling control based on shear stress and c-di-GMP regulation.