Cereal flour (rye, wheat, maize) contaminated with aflatoxin B, was subjected to spontaneous fermentation or by using a probiotic prepn. contg. Lactobacillus sp. bacteria and yeast Saccharomyces cerevisiae. The process was carried out at 37 degrees C for 24 h. Mycotoxin concn. during fermentation was measured after 6, 12 and 24 h by enzyme-linked immunosorbent assay. After 6 h, the amt. of toxin decreased by 39-55% and after 24 h by 53-73%. The microorganisms included in the probiotic prepn. were able to detoxify aflatoxin B, in vitro. The mycotoxin binding process took place by phys. adsorption.