Isolation, Identification, and Potential Biotechnological Application on Soil Porosity of the Microbial...

Microbial exopolysaccharides (EPS) exhibit high viscosity, offering significant potential for reducing soil porosity. In this paper, a kind of Bacillus polymyxa producing EPS was selected and its chemical and physical properties, including the morphology, molecular weight, monosaccharide composition, structure, and rheological properties, were studied. Subsequently, the effect of EPS on soil porosity was investigated by the permeability coefficient and X-ray computed tomography (X-CT), and the mechanism by which EPS reduced soil porosity was elucidated. The EPS was a porous ellipsoid with a molecular weight of 7.89 × 10⁴ Da, mainly composed of mannose, galactose, and glucose with a molar ratio of 7.35:1.96:1.00. The rheological properties were fitted using a power law model, and the EPS solution exhibited pseudoplasticity at different concentrations and pH conditions. Compared with the blank group, the permeability coefficient of the microbial group decreased by 66.27% after 504 h, and the porosity measured of the microbial group by X-CT decreased by 68.20% after 240 h. In general, the results suggest that the EPS is a promising natural polymer with great application potential in soil and groundwater remediation, which is conducive to promoting the development and progress of green barrier remediation materials.