丙酸厌氧转化的铁促进行为及机制研究

Volatile fatty acid inhibition, making the food waste anaerobic digestion (AD) failure, is mainly due to the accumulation of propionate. Previous researches had confirmed that supplementation of iron could relieve propionate accumulation effectively. However, whether it is caused by the acceleration of propionate conversion as well as the effect mechanism is unclear. Focusing on the syntrophic microbe for the anaerobic conversion of propionate, this study will investigate the quantitative effect of different morphology iron on propionate conversion and gas production by using laboratory simulation and dynamic analysis firstly, to represent the directional enhance effect of propionate conversion. Subsequently, the iron-mediated conversion path of propionate will be determined using isotopic tracer, to reveal the internal relations among the conversion path, iron morphology and environmental parameters. Finally, the interrelationship among iron, microbial distribution and metabolism will be explored by using electronic flow distribution calculation, high-throughput sequencing and fluorescence quantitative PCR etc., to analysis the coupling relationship of iron morphology, microbial community structure and propionate conversion efficient. Based on it, the promotion mechanism of propionate conversion enhanced by iron will be clarified, from three levels of key microbe species, interspecies electron transfer and key enzyme activity change. Results of this study will perfect the theoretical and practical research of propionate accumulation control by iron in AD system, and also can supply theoretical reference and application basis for breaking the bottleneck of food waste AD industrialization with low efficiency and poor stability.

丙酸积累是餐厨垃圾等厌氧消化体系酸抑制致系统失衡的关键，现有研究发现外源添加铁有助于控制丙酸积累,但是否归因于丙酸转化的促进作用及其影响机制仍不清楚。本课题紧扣丙酸转化互营微生物，首先通过实验室模拟和动力学分析，定量表征不同形态的铁对丙酸厌氧转化和系统产气量的影响，以明晰铁对丙酸厌氧转化的促进作用；其次，利用稳定同位素示踪，探究铁介导的丙酸转化途径，揭示其与铁形态和系统环境参数间的内在联系；最终采用电子流分配计算、高通量测序和荧光定量PCR等，探明铁与微生物分布及代谢间的交互作用，解析铁的形态变化-微生物群落结构-丙酸转化效率的耦联关系，进而从关键微生物种类及丰度、种间电子传递方式、关键酶活性变化三个层面解析铁介导下丙酸厌氧转化行为的促进机制。项目预期研究结果将完善厌氧消化体系铁控制丙酸积累的理论和应用研究，为突破餐厨垃圾厌氧消化效率低、稳定性差的产业化瓶颈提供理论参考和应用基础。

厌氧消化效率低、稳定化差是制约城市有机废物产清洁能源的限速瓶颈。其中，丙酸积累是挥发性脂肪酸（VFA）抑制厌氧消化系统效率和稳定性的关键，因此，丙酸厌氧转化及其促进机制是提升有机废物能源回收率的重要方向之一。研究紧扣丙酸厌氧转化互营微生物和外源添加铁的互作行为，明确了铁的添加形态（溶解态Fe2+和纳米磁铁矿）与丙酸转化的定量关系，确定了不同形态铁的最佳添加量；进一步通过微生物生理生态行为机制的解析，提出了铁促丙酸厌氧转化的三种机制，即微生物优势菌群（Methanosaeta和Methanosarcina）富集强化乙酸营养性产甲烷代谢路径、硫酸盐还原协同耦合机制和电子通络蛋白中介的电子传递加速机制；在此基础上，建立了强化丙酸厌氧转化的可行性策略，包括适宜的外源铁添加、硫酸盐还原作用协同、电化学反应器MEC强化以及选择性光催化耦合，并采用实际样品进行了验证，从而为突破城市有机废物厌氧消化产业化瓶颈提供了新的思路和参考。