电子穿梭体诱导污泥厌氧发酵定向产乙酸的调控机制及效能优化

The volatile fatty acids (VFAs) from anaerobic fermentation is a new and cost-effective way to recover the carbon sources in excess sludge. Comparing with other VFAs, acetic acid is the most popular component for subsequent processes. More dedicated acetic acid production from fermentation indicates profound significance for reclamation of excess sludge. This study adopted anthraquinone-2,6-disulfonic acid (AQDS) as exogenous electron shuttles to regulate anaerobic fermentation process for more acetate production. The microbial pathways and microbial communities are investigated using reverse transcription quantitative PCR (RT-qPCR) and high-throughput sequencing. The mechanisms of AQDS regulation on anaerobic fermentation pathway will be summarized. Furthermore, the severe delay of propionic degradation will be solved by creating certain environmental stresses to promote interspecies electron transfer during propionic degradation. The relationships between enzymes expression, microbial communities and environmental stresses will be studied to elucidate the mechanisms. The each environmental stresses will be optimized for appropriate regulation strategies. Finally, strong alkaline pretreatment will be adopted to enhance the acetate producing efficiency, and the influences of strong alkaline pretreatment on acetate production will be analyzed. The AQDS regulation, environmental stresses, and strong alkaline pretreatment will be reorganized for effective acetate production. This study primarily meets the development of resource recovery from anaerobic fermentation of excess sludge, and could provide theoretical basis for dedicated acetate production in the future.

厌氧发酵产酸是实现剩余污泥资源化的重要途径之一，若实现定向产乙酸，其作为高附加值产品可以促进剩余污泥资源化处置产业价值链的形成。本研究提出外源投加电子穿梭体（蒽醌-2,6-二磺酸钠(AQDS)）调控厌氧发酵过程实现高效定向产乙酸，采用反转录定量PCR(RT-qPCR)及高通量测序技术准确解析混合微生态体系中AQDS调控厌氧发酵产酸的代谢通路并确定其调控机制；为解决定向产乙酸过程中的关键瓶颈问题——丙酸氧化作用滞后，设置能够促进该转化过程中种间电子传递机制的胁迫环境，建立关键酶表达、种群间关系变迁与胁迫环境的关联规律并优化调控策略；最后叠加强碱预处理进一步提高系统产酸量，并探索预处理方式对AQDS定向产乙酸的影响，最终将各调节手段进行整合简化后实现高效定向产乙酸。本研究符合目前剩余污泥厌氧资源化的科技需求，研究成果可以为剩余污泥发酵定向产乙酸提供可靠的理论依据。

本项目以城市污水处理厂剩余污泥为研究对象，探索电子穿梭体对剩余污泥厌氧发酵过程定向产酸的影响，开发高铁酸钾胁迫污泥厌氧发酵定向产酸技术，并进一步利用天然沸石和BP-A型BMED工艺分离发酵液中酸性和碱性组分，以提升发酵液中VFAs品级，提高技术应用前景。研究主要结果表明，通过调控电子穿梭体能够有效地改变剩余污泥厌氧发酵代谢路径，但如无预处理手段协助或添加其他有机底物协同发酵，剩余污泥能够提供的溶解性有机物（即产酸代谢底物）有限，发酵产酸量难以提升，发酵液应用价值受限。基于此，进一步提出厨余和剩余污泥协同厌氧发酵产酸工艺、利用高铁酸钾的强氧化性胁迫剩余污泥厌氧发酵产酸工艺，通过对比底物转化、酸性产物积累、中间产物积累、生物气积累规律，结果表明，厨余协同发酵因提供了更为丰富的溶解性大分子有机底物含量，使得厌氧发酵产酸效率有较大提升，并且促进溶解性多糖含量是协同发酵定向产乙酸的关键。高铁酸钾作为氧化剂，不仅能够促进大分子有机物的溶出，而且能够进一步地促进酸性产物积累，相较其他预处理手段，高铁酸钾能够真正地参与到剩余污泥厌氧发酵产酸过程