Characterization of Lectins and Bacterial Adhesins in Activated Sludge Flocs

Abstract

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.

Investigation of the Fate and Dynamics of Extracellular Polymeric Substances (EPS) during Sludge-Based Photogranulation under Hydrostatic Conditions

“…Literature shows that EPS accounts for a large fraction of organic matter in activated sludge. ,,, Thus, knowing the fate of EPS from sludge inoculum could be important to understand the C recycle and photogranulation in hydrostatic cultivation. Furthermore, studying the dynamics of EPS generated during the phototrophic growth could reveal more about photogranulation and these will be presented and discussed in the later sections of the current study.…”

Molecular Insights into Extracellular Polymeric Substances in Activated Sludge

“…By combing spectral analysis with other molecular characterization techniques such chromatography and mass spectrometry, several types of important glycoconjugates have been identified in granular sludge. − In particular, glycosaminoglycans that contain hexosamine and uronic acid/galactose backbone unit and sialic acids residues are considered important structural components of EPS. ,, These macromolecules can self-interlink or bind with other EPS molecules (e.g., polysaccharides and pili) to form a hybrid matrix network that provides mechanical stability to sludge. Notably, the glycosaminoglycans can have variable building blocks, functional groups, and spatial distributions.…”

Response Mechanism of Extracellular Polymeric Substances Synthesized by Alternaria sp. on Drought Stress in Alfalfa (Medicago sativa L.)

“…Polysaccharides contain many hydrophilic groups, while some of the functional groups also can scavenge oxygen free radicals . The proteins in EPS participate in the formation of the extracellular matrix network, enabling microorganisms to establish connections with the surrounding environment . In comparison to the factors influenced by microorganisms the emphasis is more on analyzing the role of EPS in water retention, film formation, and its potential impact on plant signal transduction.…”

“…3 The proteins in EPS participate in the formation of the extracellular matrix network, enabling microorganisms to establish connections with the surrounding environment. 40 In comparison to the factors influenced by microorganisms the emphasis is more on analyzing the role of EPS in water retention, film formation, and its potential impact on plant signal transduction. EPS can assist the fungi in attaching to plant roots, and this promotes colonization by the endophytic fungi.…”