The influence of atmospheric gases on aflatoxin formation by Aspergillus parasiticus was investigated using a chemically defined medium and controlled environments in. a fermenter. Maximal yield of aflatoxin was obtained under fermentation conditions lacking agitation or sparging of air. Increasing the rate of aeration enhanced glucose utilization and acid formation, but reduced toxin production. Replacement of air by various mixtures of O2 and CO2, or O2 and N2 suppressed toxin formation. Increasing proportions of CO2 or N2 in the atmosphere enhanced their inhibitory effect on aflatoxin formation, and complete inhibition of toxin synthesis occurred in atmospheres of 100% CO2 or 100% N2. Synthesis of toxin was suppressed more by a high concentration of CO2 than of N2. The optimal condition for toxin formation was quiescent incubation. Suppression of toxin formation can be achieved by introducing high concentrations of CO2 or N2 into the environment.
1Research supported by the College of Agricultural and Life Sciences, University of Wisconsin-Madison and by Public Health Service Grant FD00143 from the Food and Drug Administration.