Inhibition of aflatoxin production of Aspergillus parasiticus NRRL 2999 by Bacillus pumilus.

Six isolates of Bacillus pumilus were tested for their ability to inhibit aflatoxin production of Aspergillus parasiticus NRRL 2999 in yeast extract sucrose (YES) broth. Aflatoxin production was inhibited in both simultaneous and deferred antagonism assays, suggesting that the inhibitory activity was due to extracellular metabolites(s) produced in cell-free supernatant fluids of cultured broth. The inhibition was not due to organic acids or hydrogen peroxide produced by B. pumilus since the inhibitory activity was not lost after pH adjustment or treatment of supernatant fluids with catalase. A range of media tested for the production of inhibitory metabolite(s) in supernatant fluids showed that all media supported bacterial growth and production of the metabolite(s). The metabolite(s) were produced over a wide range of temperature (25 to 37 degrees C) and pH (4 to 9) of growth of B. pumilus. They were stable over a wide range of pH (4 to 10) and were not inactivated after autoclaving at 121 degrees C for 30 minutes.