Characteristics of extracellular polymeric substances of phototrophic biofilms at different aquatic habitats

• Three different phototrophic biofilms grown under different environmental conditions (natural lake, drinking water plant and wastewater treatment plant) shown variable EPS concentrations and compositions.
• Polysaccharides and protein were the main components in LB-EPS and TB-EPS, but their fractions were variant in the three phototrophic biofilms.
• FTIR and EEM spectra were used to identify the structure and composition of LB-EPS and TB-EPS produced by the three phototrophic biofilms.

Three different phototrophic biofilms obtained from a natural lake (Sample 1), drinking water plant (Sample 2) and wastewater treatment plant (Sample 3) were investigated. Diatoms and green algae were the dominant algae of three biofilms, and the biomass was highest in biofilm of Sample 2. The three phototrophic biofilms also had variable extracellular polymeric substances (EPS) concentrations and compositions. Total EPS concentration of 14.80 mg/g DW was highest in biofilm of Sample 2, followed by biofilms of Samples 3 and 1 (13.11 and 12.29 mg/g DW). Tightly bound EPS (TB-EPS) were the main fraction, and polysaccharides and protein were the main components of total EPS in all three biofilms. However, the compositions of loosely bound EPS (LB-EPS) and TB-EPS were different in three biofilms. Fourier-transform infrared and fluorescence spectra indicated different structure and compositions of LB-EPS and TB-EPS. These results demonstrated the characteristics of EPS produced by phototrophic biofilms varied and had compact relation to their growth environmental conditions.