Fourteen strains of the genera Rhodococcus, Nocardia, and Corynebacterium were found to produce substances which flocculate kaolin clay.
Rhodococcus erythropolis produces a kind of the microbial flocculant. It had very interesting and unique flocculating characteristics. It could efficiently flocculate all suspended solids in aqueous solution tested. Among those effectively tested were microorganisms such as E. coli and alcohol yeast, activated sludge, Microcystis aeruginosa (AOKO), kaolin clay, muddy water, river dredging muddy water, river bottom sediment (HEDORO), ash from a steam-power station, and chacoal. These results indicated that the flocculant from R. erythropolis had a wide flocculating activity against both organic and inorganic materials. Cationic ions such as Ca²⁺ also significantly increased the flocculating activity.

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