Surface binding of aflatoxin B1 by lactic acid bacteria

Specific lactic acid bacterial strains remove toxins from liquid media by physical binding. The stability of the aflatoxin B-1 complexes formed with 12 bacterial strains in both viable and nonviable (heat- or acid-treated) forms was assessed by repetitive aqueous extraction. By the fifth extraction, up to 71% of the total aflatoxin B-1 remained bound. Nonviable bacteria retained the highest amount of aflatoxin B-1. Lactobacillus rhamnosus strain GG (ATCC 53103) and L. rhamnosus strain LC-705 (DSM 7061) removed aflatoxin B-1 from solution most efficiently and were selected for further study. The accessibility of bound affatoxin B-1 to an antibody in an indirect competitive inhibition enzyme-linked immunosorbent assay suggests that surface components of these bacteria are involved in binding. Further evidence is the recovery of around 90% of the bound affatoxin from the bacteria by solvent extraction. Autoclaving and sonication did not release any detectable aflatoxin B-1. Variation in temperature (4 to 37 degreesC) and pH (2 to 10) did not have any significant effect on the amount of affatoxin B-1 released, Binding of aflatoxin B-1 appears to be predominantly extracellular for viable and heat-treated bacteria. Acid treatment may permit intracellular binding. In all cases, binding is of a reversible nature, but the stability of the complexes formed depends on strain, treatment, and environmental conditions.