Adsorption layer structure at soil mineral/biopolymer/supporting electrolyte interface - The impact on solid aggregation

This paper focused on the protein and polysaccharide adsorption mechanism on the surface of common soil mineral - silica (SiO2), as well as the biopolymer adsorption effect on the solid aggregation. For the experiments, the proteins of various internal stability were selected, i.e. bovine serum albumin (BSA), ovalbumin (OVA) and lysozyme (LSZ). Moreover, the study involved exopolysaccharide (EPS) synthesized by soil bacteria Sinorhizobium meliloti. The adsorption layer structure on the silica surface and the solid aggregation tendency in the biopolymer presence were established and explained based on the turbidimetric, adsorption and zeta potential measurements. The measured biopolymer adsorbed amounts, biopolymer conformation on the SiO2 surface and solid aggregation were strongly dependent on the pH conditions. The stimulating effect on SiO2 aggregate formation was stated at pH 4.6 for BSA, OVA and LSZ, whereas at pH 7.6 - for LSZ and EPS. The strongest impact was noticed at pH 7.6 in the lysozyme presence (the TSI value increased by 40 units). The presented results can contribute to a better understanding of mineral-organic associations formation under selected soil conditions. Moreover, they may be helpful in developing innovative substances limiting destructive erosion effect. (C) 2019 Elsevier B.V. All rights reserved.