厌氧膜生物反应器互营产甲烷路径解析与调控

Anaerobic digestion was one of the key technologies treating livestock manure. However, the anaerobic digestion was sensitive to environmental pressure and serious volatile fatty acids accumulation occurred with environmental disturbance. These drawbacks significantly limit the efficiency of established biogas project and the new construction of biogas plants. As a result, maintaining the balance of acetate producing and consuming was the core of anaerobic process management. Especially, acetate degradation through combined syntrophic oxidation and hydrogen methanogenesis fundamentally determined the performance and stability of an anaerobic membrane bioreactor. However, the mechanism of the syntrophic acetate methanogenesis was still unclear. In this project, an innovative technology, SIP-FISH-nanoSIMS, is proposed to investigate the syntrophic metabolism anaerobic microorganism in a single cell level. The accumulation of individual and total volatile fatty acids will be investigated using thermodynamic methodology by including the acid and hydrogen producing bacteria, syntrophic acetate oxidation bacterial and hydrogentropic methanogens into a complete eco-environment. The dynamics of methanogenesis pathway will be analyzed by considering the co- existense of bulk liquid and attached microbe flocs and biofilms. A series experiment will be carried out to obtain the kinetics parameters to establish the competition kinetic model. External electron acceptors will be used to increase the ability of utilizing hydrogen. Sulfate and iron will be chosen as agent. Regulation strategies will be finally established to reduce the accumulation of volatile fatty acid under stressed environmental conditions. The fruits of the project will provide new findings to anaerobic fundamental theories and will promote the development of the anaerobic membrane biotechnology.

厌氧发酵是畜禽废弃物处理的重要技术手段，但环境耐受性差和易酸败的不足限制了工程技术的效果和推广应用。维持乙酸的代谢平衡是发酵过程控制的核心，传统理论忽视了乙酸互营产甲烷路径，但这一路径却是控制厌氧膜生物反应器高效和稳定运行的关键。为此，本研究采用SIP-FISH-nanoSIMS方法在近单细胞尺度上解析乙酸互营产甲烷的生物链，从“产氢产乙酸细菌+乙酸氧化菌+嗜氢产甲烷菌”的完整生态链角度解析有机酸积累的热力学机制；探索膜使用周期内附着生长的生物膜和悬浮生长的混合液产甲烷路径的动态变化机制；建立乙酸互营产甲烷与裂解产甲烷的竞争动力学模型，引入具有硫酸盐还原和异化铁还原作用的外源电子受体，提高系统的嗜氢能力，实现从有机酸积累到高速产气和低有机酸残留的定向调控。本课题的研究成果将有助于丰富甲烷发酵的基础理论，为厌氧膜生物反应器推广应用提供技术支撑。

厌氧发酵是畜禽粪污处理的重要技术手段，但环境耐受性差和易酸败的不足限制了工程技术的效果和推广应用。维持乙酸的代谢平衡是发酵控制的核心，传统理论忽视了乙酸互营产甲烷路径，但这一路径却是控制厌氧膜生物反应器高效和稳定运行的关键。课题组围绕关键科学问题，针对厌氧膜生物反应器处理粪水和高浓度有机废水的情景，开展了大量研究工作，完成了各项研究内容。针对发现的新现象，研究团队及时调整方向，获得了新的发现，提出了新的科学问题。研究团队搭建了多套平板膜和中空纤维厌氧膜生物反应器，开展了长期运行实验、微生物群落结构解析、添加外源电子受体、13C乙酸稳定同位素示踪、乙酸和氢的代谢活性和代谢动力学解析等研究，取得主要成果有：i) 揭示了不同工况下厌氧膜生物反应器乙酸产甲烷路径的演替机制；ii) 建立了厌氧膜生物反应器处理高氨氮粪水的产甲烷路径调控方法；iii) 获得了厌氧膜生物反应器互营产甲烷路径的代谢生物链；iv) 建立了厌氧膜生物反应器的固定化生物膜结构，实现了生物量的分离，延缓了膜污染的形成。研究发现，厌氧膜生物反应器在高负荷、高氨氮、高温和高固体条件下会促进嗜氢产甲烷路径的发生。但是，乙酸直接裂解产甲烷仍然具有动力学优势，提高严格嗜乙酸甲烷菌的环境耐受性是调控乙酸代谢速率的关键，这为路径调控指明了方向。通过氨吹脱强化乙酸裂解产甲烷是促进甲烷转化的重要手段，可将容积负荷提高37%。膜面上形成的生物膜有助于分解挥发性脂肪酸，但也容易形成膜污染。在反应器内设置固定床生物膜载体，可将21%的生物量由发酵液转移到载体上，避免了沼气爆气循环的剪切扰动，为共生菌系的团聚和氢的种间电子传递提供了良好的微环境，促进脂肪酸的深度降解，同时也延缓了膜污染的形成。研究成果共发表SCI论文11篇，中文论文5篇，培养3名博士生和2名博士生，与日本东北大学等高水平研究机构建立了稳定的合作关系。