Characterization of the Mineral Fraction Associated to Extracellular Polymeric Substances (EPS) in Anaerobic Granular Sludges
Abzac, P. D'; Bordas, F. ; Joussein, E. ; Hullebusch, E. ; Lens, P.N.L. ; Guibaud, G. - \ 2010
Environmental Science and Technology 44 (2010)1. - ISSN 0013-936X - p. 412 - 418.
waste-water - extraction methods - heavy-metals - part i - removal - sulfate - reactor - mechanisms - dynamics - sorption
The extracellular polymeric substances (EPS) extracted from four anaerobic granular sludges contain an important mineral fraction (20-77% of the EPS dry weight). The composition of the mineral fraction of EPS depends strongly of the extraction method applied and to a lesser extend of the origin of the anaerobic sludge. Centrifugation, sonication, and heating extraction procedures yield a similar mineral composition. However, extraction using a cationic exchange resin (CER) leads to an increase of the Na+ content in the EPS extract because the CER promotes an exchange of divalent and trivalent inorganic elements in the EPS extracts toward Na+. Chemical extraction protocols were also shown to contaminate the EPS extracts by impurities or carry over of the extractant itself (e.g., ethanol). A part of the mineral fraction is bound to the EPS organic matter and structures the EPS matrix in the granules. Scanning electron microscopic analysis (SEM-EDX) showed that in addition, solid particles such as CaCO3 and Ca5OH(PO4)(3) containing various metallic elements (i.e., Al, Fe, Cu, Mn...) are present in the EPS as well. This inorganic fraction, too often neglected in EPS studies, can influence the physicochemical properties of EPS.
Evaluation of size exclusion chromatography (SEC) for the characterization of extracellular polymeric substances (EPS) in anaerobic granular sludges
Simon, S. ; Pairo, B. ; Villain, M. ; Abzac, P. D'; Hullebusch, E. ; Lens, P.N.L. ; Guibaud, G. - \ 2009
Bioresource Technology 100 (2009)24. - ISSN 0960-8524 - p. 6258 - 6268.
activated-sludge - extraction methods - part i - exopolymers - biofilms - polysaccharides - complexation - separation - protocols - hplc
The extracellular polymeric substances (EPS) extracted from three granular and one flocculant anaerobic sludges were characterised by size exclusion chromatography (SEC) using two serially linked chromatographic columns in order to obtain more detailed chromatograms. A Superdex peptide 10/300 GL (0.1-7 kDa) and Superdex 20010/300GL (10-600 kDa) from Amersham Biosciences were used in series with a mobile phase at pH 7 with an ionic strength of 0.223 M (phosphate buffer 50 mM and NaCl 150 mM). A part of the EPS molecules displays hydrophobic and/or ionic interactions with the column packing. Interactions could be modified by changing the mobile phase ionic strength or polarity (addition of acetonitrile). The detection wavelength (210 or 280 nm) affects strongly the EPS chromatogram. For a sludge originating from the same type of biofilms (i.e., anaerobic granules), the differences in EPS fingerprints are mainly due to differences in the absorbance of the chromatographic peaks, linked to EPS molecules content and composition. The EPS fingerprint changes significantly when the EPS originate from another type of anaerobic sludges. In addition, EPS fingerprints were affected by the extraction method used (centrifugation only; heat and centrifugation or cationic exchange resin and centrifugation). This phenomenon was observed mainly for the largest and smallest molecules and molecules which display interactions with column packing.