Adsorption of extracellular polymeric substances (EPS) from pseudomonas putida on various soil particles from an alfisol

Abstract

The adsorption of extracellular polymeric substances (EPS) from Pseudomonas putida on various soil particles from an Alfisol was investigated in batch systems. The interaction mechanisms were discussed using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The functional groups of EPS were phosphoric/carboxylic (pK a = 2.68), carboxyl (pK a = 4.52), phosphoryl (pK a = 7.09), and hydroxyl/amine (pK a = 8.99), respectively. The adsorption isotherms of EPS on soil particles conformed to the Langmuir equation. The amount of EPS-C and EPS-P adsorbed followed the sequence of inorganic clay > organic clay > silt > sand. However, EPS-N adsorption on organic clay was greater than that on inorganic clay slightly. The mass fraction EPS-C and EPS-N adsorption on soil particles increased with the increase of NaCl or CaCl2 concentrations, but the opposite is true for EPS-P. Calcium ions were more efficient than sodium ions in promoting EPS-C and EPS-N adsorption and hindering EPS-P adsorption on soil particles. These results suggest that EPS was adsorbed primarily on fine soil clays which is also in accordance with the prediction by DLVO. Organic matter stimulated EPS-C and EPS-P constituents' adsorption on soil particles while inhibited EPS-N adsorption. The information obtained is of fundamental significance for understanding interfacial reactions between microorganisms and soil particles.