[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.