Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/22/1999
Publication Date: N/A
Technical Abstract: Finding inhibitors of Aspergillus flavus growth and aflatoxin B1 (AFB1) in corn kernels is an active research area. If an inhibitor is present in only one tissue of the kernel, will that affect toxin production when the fungus spreads to adjacent tissues? A model system was used to address this question. Two discs separated by 3-3.5 mm were mounted on a pin and incubated in a vial. Lower discs contained medium and spores and either received inhibitor or served as a control. The upper disc received only medium. Mycelia from the lower disc infected the upper. Alpha-carotene (1 mg/ml) and delphinidin (5 mM) were used as inhibitors. The results indicated that once the control discs are infected by inhibited mycelium, removal of the inhibitor and infecting mycelia does not affect inhibition. Alpha-carotene inhibition was similar for both the infected discs containing inhibitor and those colonized by this mycelium but lacking inhibitor. Delphinidin showed a sharply lower level of inhibition in the secondarily infected discs. Dose/response curves were derived for D- talose, 2-deoxy- and 6-deoxy-D-glucose (2DG and 6DG), and xylose, sugars previously shown to inhibit conversion of triglyceride to AFB1 by A. flavus. The concentration for 50% inhibition (I50) for talose was 146 ug/ml for AFB1 and 318 ug/ml for growth. For 6DG, the I50 was 527 ug/ml and 1430 ug/ml for 2DG. The I50 for xylose was 1%. Mixtures of sucrose and xylose (from 4.5%:0.5% to 2.5:2.5, sucrose:xylose) were investigated in medium containing 10% corn oil to determine if the occurrence of xylose in the germ could affect AFB1 level.