Effect of Neutral Fats and Fatty Acids on Aflatoxin Production ¹

The influence of neutral fats and fatty acids on aflatoxin production by Aspergillus flavus (ATCC 15546) was investigated using a chemically defined medium (glucose-salts-amino acids). The fat-fortified medium was inoculated with A. flavus spores and incubated at 28 C; samples were solvent-extracted at 3-, 6-, 9-, and 14-day intervals and aflatoxin content quantitated fluorometrically. Increasing concentrations of tricaprylin (15% >10% >5%) repressed aflatoxin G₂ synthesis more than B₁ synthesis as compared to the control. Maximum concentrations of G₁ and B₁ were attained within 3 to 6 days and then declined. Increasing amounts of tricaprylin had little influence on B₁ degradation following 3 days of incubation whereas G₁ degradation was pronounced after 3 days. Tristearin fortification of the medium produced results comparable to those obtained with tricaprylin. Within the 14-day incubation period, G₁ degradation rates exceeded those of B₁ in both the control and fortified samples. As compared to the control, both the 15% linoleic acid and the 15% stearic acid fortification of the medium repressed B₁ and G₁ synthesis; however, the difference became less pronounced with incubation time. The 15% stearic acid fortification facilitated greater B₁ yields than the 15% linoleic acid until the 9th day at which time B₁ accumulation in the linoleic acid fortification surpassed that of the stearic acid. The G₁ level in the 15% stearic acid-fortified medium attained 1300 μg within 3 days and declined to a trace at 14 days. Aflatoxin G₁ synthesis in the 15% linoleic acid-fortified medium was completely repressed throughout the entire incubation period.