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Characterization of Lectins and Bacterial Adhesins in Activated Sludge Flocs

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Bacterial lectins are carbohydrate-binding proteins that are involved in bacterial adhesion and aggregation. To investigate whether lectins are involved in floc formation of activated sludge, hemaaggultination (HA) and HA inhibition assays were conducted on extracellular polymeric substances (EPS) extracted from activated sludges. Six sludges from both full-scale and synthetic chemical-fed laboratory activated sludge systems were subjected to EPS extraction and lectin assay. Activated sludge EPS resulted in strong agglutination with trypsin-treated human red blood cells. While simple monosaccharides failed to exhibit inhibition of agglutination, several glycoproteins clearly reversed agglutination, indicating that glycoprotein (oligosaccharide)-specific lectins are present in activated sludge. This inhibitory pattern was the same for both the field and laboratory-grown activated sludges, indicating that these lectins are indigenously generated by activated sludge microorganisms. The major lectin activities were found to be present in a hydrophobic region of EPS. The activities remained unaffected after heat and urea treatment of EPS, but were significantly reduced by the ethylenediaminetetraacetic acid (EDTA) treatment. These results share similar properties with previously studied pure culture bacterial lectins and support the conclusion that lectin-mediated bacterial aggregation is one of the mechanisms responsible for activated sludge bioflocculation.

Keywords: activated sludge; adhesins; bioflocculation; extracellular polymeric substance; hemaagglutination; lectin

Document Type: Research Article


Publication date: August 1, 2009

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  • Water Environment Research® (WER®) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year.

    Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.
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