基于物理及生态双重选择压力的PHA合成菌富集新工艺及餐厨垃圾碳源优化利用研究

Polyhydroxyalkanote (PHA) is considered as the most promising recycled chemical from the new concept wastewater treatment process due to the characteristics of being able to be biodegraded. Food waste has more than 80% of organic component which makes it easily being acidized. Too much volatile fatty acid (VFA) produced would inhibit the anaerobic methanogenesis process. However, these VFA are desirable substrate for mixed microbial culture (MMC) PHA production. Using VFA produced from anaerobic treatment of food waste to produce PHA would provide a possible way for food waste carbon source recycling..Considering the characteristics of the acidification product from food waste and the requirement of PHA synthesis in substrate, in order to solve the key problems in the operation of the combined system, such as high concentration of ammonia and salt in food waste, long enrichment period in PHA accumulating culture selection and the absence of quantitative parameter assessing the process, studies of oriented metabolism regulation in food waste fermentation, optimization of the enrichment process and quantitative simulation, development of continuous feed mode in PHA accumulating process are going to be carried out, when a newly developed PHA accumulating culture enrichment process using both physical and ecological selective pressure is used. The results of the research will reveal the cooperation relationships of physical and ecological selective pressure in culture enrichment process, thus realize an effective and stable enrichment of PHA accumulating culture and reduce the production cost.

聚羟基烷酸（PHA）是新一代污水处理概念中最具发展前途的生物质基化学产品，其良好的生物可降解性使其有望替代传统塑料。餐厨垃圾在厌氧产甲烷过程中由于其有机质含量高易酸化，容易产生产气抑制。而这些小分子有机酸却是混合菌种PHA合成的良好底物。利用餐厨垃圾厌氧发酵中间产物回收PHA，可为餐厨垃圾资源化提供新思路。本项目结合餐厨垃圾发酵产酸产物组成特点及混合菌种PHA合成对底物的需求，在课题组前期研究基础上，针对餐厨垃圾碳源底物中高氨氮及高盐、PHA合成菌富集周期漫长以及系统运行缺乏量化评价指标等关键问题，以基于物理和生态双重选择压力的PHA合成菌富集模式（ADD）为核心工艺，开展餐厨垃圾产酸代谢定向调控、ADD富集工艺优化及量化模拟、连续流的PHA合成模式等方面的研究。研究结果将揭示物理与生态选择压力在PHA合成菌富集过程中的协作制约关系，实现PHA合成合成菌种高效稳定富集，降低PHA合成成本。

本项目开展了以餐厨垃圾为底物混合菌群PHA生产工艺关键因素的影响、生态物理双重压力富集工艺的构建、不同富集模式评价体系的建立等方面的研究。取得如下研究成果：低进水负荷条件下，5.0 g NaCl/L富集的菌群在污泥转化率、PHA比合成速率、污泥生长速率以及底物吸收速率方面具有优势并在对应的批次试验中得到最高PHA合成率50.47%；丁酸型底物富集出的PHA合成菌在不同C/N比和转换进水底物类型的条件下，合成PHA的含量水平都显著高于丙酸型；以未经发酵的粗甘油为底物时，相比于经驯化后以挥发酸为底物的PHA合成菌，污水厂的接种污泥更适于筛选和富集PHA合成菌，以粗甘油为底物时PHA合成效果更佳，合成速率更快，且底物负荷改变会对富集过程中Feast/Famine、甘油氨氮的摄取、生物量浓度及PHA积累产生影响；混合基于传统的好氧动态进料（ADF）模式，将物理选择压应用于PHA合成菌群的筛选，提出了好氧动态排水法（ADD），筛选出的混合菌群具有更高的PHA合成能力以及更短的富集时间；基于底物充盈-匮乏机制微生物新陈代谢模型的基础上，对模型进行改进，提出适用于ADD运行模式的代谢模型并结合实验开展了相应的参数分析和优化；使用三种典型底物（乙酸型、丙酸型和丁酸型）的混合菌群在ADF模式富集期间菌群功能的沿程变化以及对应的菌群更迭，从微生物生态学层面解析了ADF模式和ADD模式下产PHA菌的富集机制，并初步提出了相应的富集评价体系。本项目完成了既定的课题目标，申请发明专利2项，发表高水平学术论文8篇，其中SCI收录6篇。