贫营养条件下EPS、SMP和微生物多样性的研究

为了考察活性污泥在营养缺乏的条件下，胞外聚合物（EPS）、溶解性微生物产物（SMP）和微生物种群结构自身的变化情况，为优化MBR系统运行、延缓膜污染等提供理论依据，对天津大学游泳馆MBR中的污泥混合液进行贫营养实验,测定了污泥混合液中EPS和SMP的含量，通过聚合酶链式反应-变性梯度凝胶电泳（PCR-DGGE）技术和克隆测序技术对微生物多样性进行分析，根据序列数据进行同源性分析并构建系统进化树.实验初期，EPS和SMP的浓度由15.04 mg/g和0 mg/g分别上升到17.99 mg/g和3.29 mg/g.随着实验的进行，EPS有很大的降低，最终只有2.40 mg/g；SMP则一直在3.5 mg/g左右变化.实验表明，EPS和SMP对外界环境变化具有一定的缓冲作用，并且在营养缺乏的条件下微生物能够以降解EPS和SMP来维持自身生命活动.由于对EPS和SMP的利用，污泥的Shannon多样性指数由最初的0.81上升到最高时的1.09，随后开始降低，并最终稳定在0.95.克隆测序的结果表明，污泥中微生物的种类比较丰富，并且优势菌种大部分为未经培养菌种.部分菌种能够通过产生蛋白质和多糖水解酶来实现对EPS和SMP的降解，主要属于拟杆菌(Bacteroidetes)、黄杆菌(Flavobacterium）、腐螺旋菌(Saprospiraceae)和厚壁门菌(Firmicutes)等.

EPS,SMP and Microbial Biodiversity Under the Oligotrophic Environment

In order to investigate the extracellular polymeric substances (EPS), soluble microbial product (SMP) and microbial biodiversity of the sludge lacking of nutrition, to provide evidence for optimizing MBR's operation and lessening membrane fouling, a series of experiments were undertaken under the oligotrophic environment using the sludge from the MBR of Tianjin University. The contents of EPS and SMP were determined, and microbial biodiversity was analyzed by PCR-DGGE technology and cloning-sequencing. Furthermore, the sequences were used for homology analysis and then the phylogenetic tree was constructed. In the initial stage, the EPS and SMP contents raised from 15.04 mg/g and 0 mg/g to 17.99 mg/g and 3.29 mg/g, respectively. Along with the experiment progress, the EPS content dropped to 2.40 mg/g; but the SMP content varied around 3.5 mg/g. This indicates that the EPS and SMP possess the buffer action towards the variation of the environment, and the microorganism can utilize the EPS and SMP under the condition of oligotrophic. Because of the utilization of the EPS and SMP, the Shannon index of the sludge raised from 0.81 to 1.09. Then, it began to decline and stabilized at 0.95 finally. The clone and sequence results reflect that the microbial structure is very rich, and most of the dominant species are uncultured bacterium. Some of the bacterium, which are mostly belong to Bacteroidetes, Flavobacterium, Saprospiraceae and Firmicutes, can degrade the EPS and SMP by secreting protein and polysaccharide hydrolyzing enzymes.