厌氧发酵产酸菌群对餐厨垃圾特征组分的响应及调控研究

Anaerobic acidogenic bacteria are adaptable to the environment. Volatile fatty acids (VFA) produced during anaerobic acidogensis are important precursors for production of biodiesel and fuel alkanes by chemical post-processing reactions. Therefore, VFA production from food waste based on the carboxylate platform become one of research topics on recycling wastes. High contents of salt and grease are the important characteristics of food waste, which is different from the other municipal organic wastes. Studies have shown that the activity of methane-producing bacteria and the stability of anaerobic system will be negatively affected by the accumulation of salt and grease. However, the effects of salt and grease stress on acidogenic microbial community and their regulation are still unclear. Based on our previous study, the responsive characteristics of acidogens to high contents of salt and grease of food waste will be investigated to obtain the optimum process parameters for efficient VFA production. Based on metabolomics research, the typical metabolic characterizations and specific pathways of components of food waste under salt and grease stress will be determined to discuss the metabolic regulation of organics in food waste for the enhancement of VFA production. The global metabolomic responses of acidogenic microbial community to environmental changes will be identified. Combined with quorum sensing, the characterization of informative flow in population dynamics will be analyzed to illustrate the ecological regulation mechanism of anaerobic acidogenic fermentation under salt and grease stress. The dynamic mathematical model of anaerobic acidogenic fermentation will be developed. The results of this study will provide theoretical basis and technical support for the application of anaerobic acidogenic fermentation of solid wastes.

厌氧发酵产酸菌对环境适应能力强，其产生的挥发性脂肪酸属于短链羧酸类，是合成生物能源的前体，因此基于羧酸盐平台的餐厨垃圾产酸成为废物资源化研究的方向之一。高盐分和高油脂是餐厨垃圾区别于其他城镇有机垃圾的重要特点。已有研究发现，高盐高油脂对厌氧发酵产甲烷菌存在严重抑制，导致厌氧消化系统不稳定，但其对厌氧发酵产酸菌的影响及调控方式尚不清楚。本项目拟在已有研究基础上，研究厌氧发酵产酸功能菌群对餐厨垃圾高盐高油脂的响应特征，确定高效产酸的工艺条件；基于代谢物组学，掌握油脂及盐胁迫下餐厨垃圾组分的典型代谢特征和特异代谢途径，探讨提高产酸效率的代谢调控方式；解析油脂及盐胁迫下厌氧发酵产酸菌群的生态代谢响应，以群体感应为切入，分析种群动态中的信息流特征，探讨油脂及盐胁迫下厌氧发酵产酸过程的生态调控机制；完善厌氧发酵产酸的动力学模型。项目预期成果将为固体废物厌氧发酵产酸工艺的应用实践提供理论基础和技术支撑。

高盐分和高油脂是餐厨垃圾区别于其他城镇有机垃圾的重要特点。已有研究发现，高盐高油脂对厌氧发酵产甲烷菌存在严重抑制，导致厌氧消化系统不稳定，但其对厌氧发酵产酸菌的影响及调控方式尚不清楚。本项目在已有研究基础上，研究厌氧发酵产酸菌群对餐厨垃圾高盐高油脂的响应特征；分析油脂及盐胁迫下餐厨垃圾组分的典型代谢特征和特异代谢途径；以群体感应为切入，分析群体感应与产酸之间的相关性，探讨油脂及盐胁迫下厌氧发酵产酸过程的生态调控机制；完善厌氧发酵产酸的动力学模型。研究结果表明，在5种不同的NaCl浓度下，10g/LNaCl浓度VFAs的产量最高为0.542g/g餐厨垃圾，乳酸在反应器中的停留时间以及产生量都随NaCl浓度增加而增加，产酸发酵类型也从丁酸型转变为丙酸型。高盐条件下在发酵结束时反应器中存在大量的丙酸杆菌Propionibacterium。厌氧颗粒污泥能很好地适应10g/L和15g/LNaCl浓度，且盐度促进了AHLs的分泌，C4-HSL作为检测到的主要信号分子，浓度高达1.96μg/L，并与VFAs的产生呈现正相关。在5种不同的油脂浓度下，随着油脂浓度升高，餐厨垃圾体系的产酸量下降，但深入分析却发现，发酵过程中油脂和垃圾之间存在协同产酸作用，即油脂促进了垃圾中蛋白质的水解产酸，同时垃圾的存在也促进了油脂的水解产酸，但油脂产酸量较垃圾中糖和蛋白的产酸量低。50%油脂浓度下产丙酸菌Veillonella为优势菌株，同时还富集了利用糖类和蛋白质产乳酸的菌属Streptococcus和Lactococcus，使得对蛋白质的利用增多，而VFAs产率的升高可能是这两种菌属产生乳酸，并进一步转化为乙酸和丙酸。高盐促使丙酮酸向缬氨酸、异亮氨酸和亮氨酸的转化途径增强，促进了丙酸的生成。低盐条件下吲哚乙酸远远高于高盐，可促进乙酸的生成。葡萄糖的产酸主要以丁酸为主，蛋白以乙酸为主，甘油以丙酸为主，混合基质以丙酸和丁酸为主。通过计算可知，葡萄糖产乙酸、丙酸和丁酸的3种产酸途径比例为1:0.6:1.1，而甘油的产酸过程极有可能通过“甘油-乳酸-VFAs”途径实现。项目成果为固废厌氧发酵产酸工艺的应用实践提供理论基础和技术支撑。