Deposition Kinetics of Extracellular Polymeric Substances (EPS) on Silica in Monovalent and Divalent Salts

Abstract

The deposition kinetics of extracellular polymeric substances (EPS) on silica surfaces were examined in both monovalent and divalent solutions under a variety of environmentally relevant ionic strength and pH conditions by employing a quartz crystal microbalance with dissipation (DCM-D). Soluble EPS (SEPS) and bound EPS (BEPS) were extracted from four bacterial strains with different characteristics. Maximum favorable deposition rates (k(fa)) were observed for all EPS at low ionic strengths in both NaCl and CaCl2 solutions. With the increase of ionic strength, k(fa) decreased due to the simultaneous occurrence of EPS aggregation in solutions. Deposition efficiency (alpha; the ratio of deposition rates obtained under unfavorable versus corresponding favorable conditions) for all EPS increased with increasing ionic strength in both NaCl and CaCl2 solutions, which agreed with the trends of zeta potentials and was consistent with the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Comparison of alpha for SEPS and BEPS extracted from the same strain showed that the trends of alpha did not totally agree with trends of zeta potentials, indicating the deposition kinetics of EPS on silica surfaces were not only controlled by DLVO interactions, but also non-DLVO forces. Close comparison of alpha for EPS extracted from different sources showed alpha increased with increasing proteins to polysaccharides ratio. Subsequent experiments for EPS extracted from the same strain but with different proteins to polysaccharides ratios and from activated sludge also showed that alpha were largest for EPS with greatest proteins to polysaccharides ratio. Additional experiments for pure protein and solutions with different pure proteins to pure saccharides ratios further corroborated that larger proteins to polysaccharides ratio resulted in greater EPS deposition.

Preconditioning with Cations Increases the Attachment of Anoxybacillus flavithermus and Geobacillus Species to Stainless Steel

“…1 and 2). Our results contradict those of other studies, which showed that bacterial attachment and biofilm cohesion increase as the ionic strength of the surrounding solution increases (5,6). Perhaps the addition of cations at concentrations of 2 mM saturated the surfaces of the bacteria and the stainless steel coupons such that further increases in ionic strength may have had no further enhancing effect on biofilm formation.…”

“…Thus, there is an extent of electrostatic repulsion between bacteria and the stainless steel surface to which they attach (3). Factors such as the ionic strength (6), the ratio of the concentrations of monovalent to divalent cations in solution (7), and the proportion of divalent cation bridges in a biofilm matrix (2) have the potential to alter the extent of electrostatic repulsion in a biofilm.…”

Influence of the shear stress and salinity on Anammox biofilms formation: modelling results

“…The same behaviour was reported by Poortinga et al [35]. Furthermore, Zhu et al [36] reported that deposition of extracellular poly-meric substances (EPS) increased with increasing ionic strength, which confirmed the prediction by DLVO theory. EPS play an important role in cell aggregation, cell adhe-sion, and biofilm formation [37].…”

Influence of natural organic matter on the deposition kinetics of extracellular polymeric substances (EPS) on silica

“…QL2 (gram-positive, non-motile), and Bacillus subtilis (gram-positive, motile). Bacteria were grown and harvested according to protocols described in previous publications [20,23] as well as in the Supplementary Information. After harvest, the cell pellets were re-suspended in Milli-Q water for the subsequent EPS extraction process.…”

“…Subsequently, using atomic force microscopy (AFM), Kwon et al [13] compared the interactions of silica surfaces with three different homopolymers selected to represent different components of EPS. Very recently, Zhu et al [23] employed QCM-D to investigate the deposition kinetics of EPS on silica surface under a wide range of environmentally relevant solution ionic strengths and pH.…”