Factors influencing the inhibition of aflatoxin production in corn by Aspergillus niger

Abstract

A. niger, a mold commonly associated with A. flavus in damaged corn, interferes with the production of aflatoxin when grown with A. flavus on autoclaved corn. The pH of corn-meal disks was adjusted using NaOH-HCl, citric acid-sodium citrate or a water extract of A. niger fermented corn. Aflatoxin formation was completely inhibited below pH 2.8-3.0, irrespective of the system used for pH adjustment. When grown in association with A. flavus NRRL 6432 on autoclaved corn kernels, A.niger NRRL 6411 lowered substrate pH sufficiently to suppress aflatoxin production. The biodegradation of alfatoxin B1 or its conversion to alfatoxin B2a were eliminated as potential mechanisms by which A. niger reduces aflatoxin contamination. A water extract of corn kernels fermented with A. niger caused an additional inhibition of aflatoxin formation apart from the effects of pH.