氧化还原介体强化厌氧消化系统中丙酸降解特性及机制研究

Propionate is important intermediates during anaerobic digestion of organic polymers. Its accumulation would significantly inhibit treatment efficiency and operation stability of an anaerobic reactor. Redox mediators（ROMs）can enhance pollutants anaerobic biodegradation by accelerating the electron transfer between the electron-donor and -acceptor. This electron transfer could be performed by the conversion cycle of itself oxidized state and reduced state. Firstly, the ROMs are used to regulate the fermentation type of anaerobic digestion systems for reducing propionate yield. And the regulating mechanism also would be clarified. In addition, the effects of redox mediators on the electron transport between propionate oxidized bacteria and methanogens would be investigated for enriching interspecific electron transfer theory. Furthermore, the efficiency of ROMs to catalyze propionate degradation was studied. The mechanism of ROMs to catalyze propionate degradation would be revealed by analyzing quantity, methylation and activity of key enzymes during propionate oxidization process. It would lay the foundation for constructing the electron transfer model of ROMs to catalyze propionate transformation. In conclusion, this study will provide a new idea and new technology for reducing propionate accumulation in anaerobic digestion system.

丙酸是有机物厌氧消化过程中重要的中间代谢产物，它的积累对厌氧消化系统的处理效能和运行稳定性均具有显著的抑制作用，而氧化还原介体（ROMs）可通过其自身氧化态与还原态的循环转换来加速电子在电子供体与电子受体间的传递，促进污染物的厌氧生物降解。首先，利用ROMs具有的电子传递功能，通过对其定向调控厌氧消化发酵类型研究，来减少丙酸产生量，并揭示ROMs定向调控厌氧消化发酵类型的规律。其次，利用ROMs的电子传递功能，研究其对互营丙酸氧化菌和产甲烷菌种间电子传递的促进作用，丰富种间电子传递理论。最后，利用ROMs具有的生物催化功能，研究其催化强化丙酸厌氧降解的效率，并通过对丙酸厌氧降解过程中关键酶表达的定量分析、甲基化分析及酶活测定，阐明ROMs催化强化丙酸厌氧降解的机制，为构建ROMs催化丙酸降解电子传递模型奠定基础。总之，本项目的研究将为有效控制厌氧消化系统中丙酸积累提供了新思路和新技术。

丙酸的积累对厌氧消化系统的处理效能和运行稳定性均具有显著的抑制作用，本项目利用氧化还原介体（ROMs）具有的电子传递功能和生物催化功能，通过定向调控发酵类型和提高丙酸的降解速率，有效避免丙酸的积累，提高了厌氧消化反应器的运行效能和稳定性。实验结果表明：石墨烯（GO）可以定向调控颗粒污泥的发酵类型，使发酵类型由混合酸发酵向丁酸型发酵转化，且80 mg/L的GO促进作用最强。蒽醌-2,6-二磺酸（AQDS）、GO都能够调控絮状污泥发酵类型，使发酵类型由丁酸型发酵向乙醇型发酵转化，其中GO的浓度为80 mg/L、AQDS浓度为400 mg/L时，促进作用最强。GO介导下颗粒污泥中的产酸发酵优势菌为Clostridium sensu stricto，该菌的相对丰度是空白组的13.6倍。AQDS、GO介导下絮状污泥中的产酸发酵优势菌分别为Pseudomonas、Clostridium sensu stricto。AQDS的加入促进了Pseudomonas的富集，进而提高了乙醇产量，而GO通过对Clostridium sensu stricto的富集提高了乙醇产量，实现了从丁酸型发酵向乙醇型发酵的转化。GO可以促进厌氧生物处理系统中丙酸的生物降解，且当GO浓度80 mg/L时，其促进丙酸厌氧降解效果最为显著，且GO介导下的活性污泥中优势功能菌以Pseudomonas、Acinetobator等产氢产乙酸菌为主，产氢产乙酸菌的富集使得GO对丙酸厌氧降解具有显著的促进作用。总之，本项目研究成果将为有效控制厌氧消化系统中丙酸积累提供新的技术。