Organic acids and essential oils are commonly used in the poultry industry as antimicrobials and for their beneficial effects on gut health, growth performance, and meat quality. A common postharvest storage fungal colonist, Aspergillus flavus, contaminates corn, the primary component of poultry feed, with the highly detrimental mycotoxin, aflatoxin. Aflatoxin adversely affects poultry feed intake, feed conversion efficiency, weight gain, egg production, fertility, hatchability, and poultry meat yield. Both organic acids and essential oils have been reported to inhibit the growth of A. flavus. Thus, we evaluated if the inhibitory synergy between combined essential oils (cinnamon, lemongrass, and oregano) and organic acids (acetic, butyric, and propionic) prevents A. flavus growth. The study confirmed that these compounds inhibit the growth of A. flavus and that synergistic interactions do occur between some of them. Overall, cinnamon oil was shown to have the highest synergy with all the organic acids tested, requiring 1000 µL/L air of cinnamon oil and 888 mg/kg of butyric acid to fully suppress A. flavus growth on corn kernels. With the strong synergism demonstrated, combining certain essential oils and organic acids offers a potentially effective natural method for controlling postharvest aflatoxin contamination in poultry feed.

The mycotoxigenic fungi, Aspergillus flavus and Fusarium verticillioides, commonly co-colonize maize in the field, yet their direct interactions at the chemical communication level have not been well characterized. Here, we examined if and how the two most infamous mycotoxins produced by these species, aflatoxin and fumonisin, respectively, govern interspecies growth and mycotoxin production. We showed that fumonisin producing strains of F. verticillioides suppressed the growth of A. flavus while non-producers did not. Additionally, while aflatoxin did not inhibit F. verticillioides growth, it did suppress fumonisin production. Fumonisin B₁ concentration levels plummeted when challenged with a high dose of aflatoxin B₁ or with an aflatoxin producing strain. With these findings, expression of the genetic regulators of secondary metabolism was investigated for both fungi. While no strong effect was seen on genes in the aflatoxin biosynthetic gene cluster when exposed to fumonisin B₁, the fumonisin repressor FvZBD1, which is adjacent to the cluster, was induced with expression proportionate to concentration when F. verticillioides was challenged with aflatoxin B₁. We also assessed the expression of the global regulators of fungal secondary metabolism, veA and laeA, and found that their expression is altered in both A. flavus and F. verticillioides when exposed to their competitor’s mycotoxin. This work gives insight into the ecological roles of mycotoxins and why these fungi may produce them as weapons in the interspecies battle for resource acquisition.