PURPOSE: An aqueous dispersion, containing a fermentaion product obtained by multiplying a petroleum assimilable microorganism in a growth culture medium containing fine zeolite powder, water and a hydrocarbon as a carbon source, and having good dispersibility and improved redispersibility without forming hard cakes even on storage for a long term.

CONSTITUTION: An aqueous dispersion, containig a fermentation product obtained by multiplying a petroleum assimilable microorganism, e.g. a microorganism selected from the group of the genuses Pseudomonas, Corynebacterium, Nocardia, Arthrobacter, Bacillus and Alcaligenes in a growth culture medium containing fine zeolite powder, water and a hydrocarbon as a sole carbon source, and having characteristics of good dispersibility and further improved redispersibility even on storage for a long term without forming hard cakes. The aqueous dispersion is prepared by multiplying the petroleum assimilable microorganism in the growth culture medium containing the hydrocarbon as a sole carbon source under 6W8pH condition, ad mixing the resultant fermentation liquor or a supernatant liquid ith zeolite powder or if necessary an adequate amount of water.