Characterization of extracellular polymeric substances from biofilm in the process of starting-up a partial nitrification process under salt stress

Abstract

In this study, the characteristics of extracellular polymeric substance (EPS) fractions of biofilm during the process of establishing a partial nitrification under salt stress were analyzed in terms of concentrations, molecular weight distribution, and three-dimensional excitation-emission matrix (EEM) ？uorescence spectroscopy. <br />A partial nitrification was formed successfully with a salinity of 1%. Results indicated that the amount of total EPS increased from 54.2 mg？g-1 VSS-1 on day 1 to 99.6 mg？g-1 VSS-1 on day 55 due to the NaCl concentration changed from 0 to 10.0 g？L-1 in a biofilm reactor. The changes of loosely bound EPS (LB-EPS) compounds under different salt concentrations appeared to be more significant than those of the tightly bound EPS (TB-EPS). A clear release of polysaccharides in the LB-EPS fraction was detected during the enhancement of salinity. This was considered as a protective response of bacteria to the salinity. Three ？uorescence peaks were identi？ed in the EEM ？uorescence spectra of the EPS fraction samples. Two peaks were assigned to the protein-like ？uorophores, and the third peak was located at the excitation/emission wavelengths of 275nm/425-435 nm of the spectra of EPS fractions till the salinity maintained constant at 1%. This information is valuable for understanding the characteristics of EPS isolated from biomass in a saline nitrogen removal system