Influence of extracellular polymeric substances on microbial activity and cell hydrophobicity in biofilms

Abstract

AbstractBACKGROUND: Over the last few decades, the emphasis in studies on extracellular polymeric substances (EPS) has been on the extraction and quantitative analysis methods relating to activated sludge. However, little is currently known about the relationship between EPS and microbial activity and cell hydrophobicity in heterogeneous biofilms. This paper aims to reveal the relationship between them.RESULTS: Experimental results indicated that EPS content and components varied with depth in the aerobic biofilter. Protein was the main component of EPS at all depths within the biofilter, and the ratio of protein to polysaccharide was higher in the upper media than that in the lower media. Most active biomass was present in the bottom 25% of the biofilter near the inlet. By means of repeatedly washing intact cells, a sharp decline of EPS content of washed cells was obtained, while active biomass rarely decreased. Microbial activity as well as cell hydrophobicity at different filter depths decreased with the decline of EPS.CONCLUSION: Results indicated that EPS on cell surfaces are essential for microbial metabolism as well as for the formation and stability of biofilm, and it is possible to take EPS into consideration for biofilter control and microbial activity assessment. Copyright © 2007 Society of Chemical Industry