电发酵强化剩余污泥制备己酸效能及机理研究

Caproic acid is a high value-added product for chemical industry use. Recently, it is an attractive topic for researchers to convert caproic acid from organic wastes through the bio-technology. Waste activated sludge (WAS) generated from waste water treatment plant is one typical organic waste, which contains plenty of organic carbon and various strains for hydrolysis and fermentation. However, low yield of caproic acid is normally occurred from the valorization process of WAS. The key challenges are: 1) electron donor driven for chain elongation is insufficient in the WAS fermentation system; and 2) the metabolic pathway diversifies in the mixed microbial consortium of sludge, which undermines the caproic acid production due to the by-product fermentative pathway. According to the above challenges, the current study proposes to employ lactic acid as the endogenous electron donor and to simplify the metabolic pathway through electro-fermentation. Therefore, the current study aims to enrich the functional microbial consortium from WAS and focus on elaborating the mechanism of optical purity and supplementary method of lactic acid affecting chain elongation. Accordingly, the electro-fermentation will be optimized for chain elongation from lactic acid. Furthermore, the mechanism of electro-fermentation simplifying metabolic pathway and promoting the conversion of WAS to caproic acid will be illustrated from view of metabolic pathway and enzyme activity, community structure and function gene expression. The extracellular electron transfer (EET) in the electro-fermentation and the synergy with mediate EET will be also explored. This study benefits to the conversion of WAS to high value-added caproic acid and contributes the theory of electro-fermentation regulation EET. In sum, the whole work is reliable for the practical use and shows significant intellectual merit.

己酸是一种高附加值的化工原料。近年来，利用生物技术将有机废物资源化制备己酸，引起了国内外研究者的广泛关注。污水厂产生的剩余污泥是典型的有机废物，含丰富的有机碳源及水解发酵菌群。然而，剩余污泥资源化制备己酸产率偏低，关键问题在于：1）污泥发酵体系缺乏驱动碳链加长的电子供体；2）代谢通路复杂，发酵副产物代谢途径降低了己酸产率。围绕上述问题，本项目将乳酸作为内源电子供体，从电发酵纯化代谢产物的角度出发，富集剩余污泥中碳链加长功能微生物，着重研究乳酸光学纯度及供给来源对碳链加长的影响机理；在此基础上，进一步开展电发酵强化乳酸碳链加长的效能研究，从代谢酶活性、菌群演变及功能基因表达方面，探明电发酵纯化代谢通路强化己酸生成的机理，解析电发酵胞外电子传递及介导协同发酵机制。开展这方面研究有助于剩余污泥制备高附加值己酸，丰富电发酵调控胞外电子传递的相关理论，具有一定的现实意义与学术价值。

剩余污泥与餐厨垃圾是典型的有机废物，含丰富的有机碳源及水解发酵菌群。然而，有机废物资源化制备己酸产率偏低。关键问题在于：1）污泥发酵体系缺乏驱动碳链加长的电子供体；2）代谢通路复杂，发酵副产物代谢途径降低了己酸产率。本课题首先研究了菌源以及不同电子供体对发酵体系碳链增长产己酸的影响，发现酒曲是剩余污泥/餐厨垃圾联合发酵促进了乳酸碳链增长的最佳菌群；在此基础上，进一步开展了电发酵强化乳酸碳链加长产己酸的效能研究，利用阴极（-0.1V），己酸产率从3.9 g COD/L增加到13.5 g COD/L，揭示了乙醇、乳酸、短链脂肪酸的转化规律，实现了产己酸功能菌Caproiciproducens的富集；项目于昆山正仪污水处理厂（10吨/天）开展示范应用。基于上述成果，共发表期刊论文12篇，其中SCI 检索12 篇，授权国家发明专利10项，培养研究生13名。