Abstract：
Fulvic acids (FAs) is formed during the bioconversion of organic matter (OM) to biogas during anaerobic digestion (AD) and has a complex structure and redox function. However, the evolutionary mechanisms of FAs during AD and its interactions with acid and methane production have not been sufficiently investigated, especially at different stages of AD. Intermittent AD experiments by chicken manure and rice husk showed significant structural changes and reduced aromatization of FAs (e.g., O-H stretch6, 14.10-0%; SR, 0.22-0.60). The electron donating capacity (EDC) [9.76-45.39 μmole-/(g C)] and electron accepting capacity (EAC) [2.55-5.20 μmole-/(g C)] of FAs showed a tendency of decreasing and then increasing, and FAs had a stronger electron transfer capacity (ETC) in the methanogenic stage. Correlation analysis showed that the EDC of FAs was influenced by their own structure (C-O stretch2, C-H bend1, C-H bend4, and N-H bend) and also had an inhibitory effect on propionic production, which further inhibited acetic production. The EAC of FAs was affected by molecular weight and had a promoting effect on methane production. Structural equation modelling identified three possible pathways for AD. The C-O stretch2 structure of FAs alone inhibits the production of propionic. In addition, pH can directly affect the EDC of FAs. This study provides a theoretical basis for the structural and functional evolution of FAs in AD of chicken manure on the mechanism of methane production.
摘要：
富里酸（FAs）是在厌氧消化（AD）过程中将有机物（OM）生物转化为沼气的过程中形成的，具有复杂的结构和氧化还原功能。然而,AD过程中FAs的进化机制及其与酸和甲烷产生的相互作用尚未得到充分研究，尤其是在AD的不同阶段。通过鸡粪和稻壳进行的间歇性AD实验显示出明显的结构变化和减少的FAs芳构化（例如，O-H拉伸6，14.10-0%；SR，0.22-0.60）。FAs的给电子能力(EDC)[9.76-45.39μmol-/(gC)]和电子接受能力(EAC)[2.55-5.20μmol-/(gC)]呈先降低后升高的趋势,FAs在产甲烷阶段具有较强的电子转移能力(ETC)。相关分析表明，FAs的EDC受其自身结构（C-O拉伸2，C-H弯曲1，C-H弯曲4和N-H弯曲）的影响，对丙酸的产生也有抑制作用，这进一步抑制了乙酸的生产。FAs的EAC受分子量影响，对甲烷产生有促进作用。结构方程模型确定了AD的三种可能途径。单独的FAs的C-O拉伸2结构抑制丙酸的产生。此外,pH可以直接影响FAs的EDC。本研究为鸡粪AD中FAs的结构和功能演化对甲烷产生机理的研究提供了理论依据。
