Effects of natural microbial preparations on the electrokinetic potential of bacterial cells and clay minerals.

A complex mixture of fermentation residues and eutrophication products used commercially as a soil amendment and in various phases of sewage treatment was effective in reducing the electrophoretic mobility of clay minerals (kaolinite and montmorillonite) and cells of Agrobacterium radiobacter. The active fraction(s), which is active at very low concentrations, appears to be a stable (to heat, dialysis, concentration, and storage), net negatively charged polymer which may have several positively charged sites. The material does not significantly alter the viscosity or surface tension of aqueous systems and is probably a microbial metabolite(s).