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Characterization of electrostatic binding sites of extracellular polymers by linear programming analysis of titration data
Author(s) -
Liu Hong,
Fang Herbert H. P.
Publication year - 2002
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.10432
Subject(s) - titration , chemistry , extracellular polymeric substance , titration curve , phosphoric acid , amine gas treating , binding site , chromatography , nuclear chemistry , inorganic chemistry , organic chemistry , biochemistry , biofilm , biology , bacteria , genetics
Electrostatic binding sites of extracellular polymeric substances (EPS) were characterized from titration data using linear programming analysis. Test results for three synthetic solutions of given solutes comprising amino, carboxyl, and phenolic groups indicated that this method was able to identify the electrostatic binding sites. For the six sites with p K a between 3 and 10, the estimated p K a deviated 0.11 ± 0.09 from the theoretical values, and the estimated concentrations deviated 3.0% ± 0.9% from the actual concentrations. Two EPS samples were then extracted from a hydrogen‐producing sludge (HPS) and a sulfate‐reducing biofilm (SRB). Analysis of charge excess data in titration from pH 3 to 11 indicated that the EPS of HPS comprised of five electrostatic binding sites with p K a ranging from 3 to 11. The p K a values of these binding sites and the possible corresponding functional groups were p K a 4.8 (carboxyl), p K a 6.0 (carboxyl/phosphoric), p K a 7.0 (phosphoric), p K a 9.8 (amine/phenolic), and p K a 11.0 (hydroxyl). EPS of the SRB comprised five of similar binding sites (with corresponding p K a values of 4.4, 6.0, 7.4, 9.4, and 11.0), plus one extra site at p K a 8.2, which was likely corresponding to the sulfhydryl group. The total electrostatic binding site concentration of EPS extracted from HPS were 10.88 mmol/g‐EPS, of which the highest concentration was from the site of p K a 11.0. The corresponding values for the EPS extracted from SRB were 16.44 mmol/g‐EPS and p K a 4.4. The total concentrations of electrostatic binding sites found in this study were 20‐ to 30‐fold of those reported for bacterial cell surface, implying that EPS might be more crucial in biosorption of metals than bacterial cell surface in wastewater treatment and in bioremediation. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 806–811, 2002.