Submitted to: Association Official Analytical Chemists Annual Intrl Meeting & Exposition
Publication Type: Abstract Only
Publication Acceptance Date: September 21, 1995
Publication Date: N/A
Technical Abstract: A new method of growing A. flavus was developed to evaluate compounds occurring in corn kernels for inhibition or stimulation of growth and aflatoxin B1 (AFT B1) production. The suspended disc culture system consists of a humidified vial with a septum cap pierced by a pin on which a glass fiber disc is affixed. The disc contains the medium, inoculum and test compound. The method is particularly useful for testing hydrophobic compounds without solubilizers and compounds available in very small amounts. Discs of glass fiber, quartz fiber and filter paper were evaluated for AFT B1 production and coefficient of variation (CV). The best overall performance was obtained with glass fiber filters containing binder. AFT B1 production is ca. 5 times greater for glass fiber discs than for liquid medium layers with equivalent surface area to volume. Discs as small as 6 mm, using 8 ul of medium, had a lower CV (15%) than liquid cultures with 20-30 times more medium. Corn kernel metabolites and related compounds which have been studied with this system include the following: 4-Acetybenzoxazolinone (4-ABOA) inhibited AFT B1 production 35% at 0.08 mg/ml and 75% at 0.4 mg/ml with little effect on growth. 6-Methoxybenzoxazolinone (MBOA) produced complete inhibition of growth and toxin production at 0.68 mg/ml, a reduction of 45% at 0.4 mg/ml but only 8.5% in growth. Benzoxazolinone (BOA) produced declines in both AFT B1 and growth at levels of 0.016 mg/ml and 0.08 mg/ml with no growth or toxin at 0.4 mg/ml. Cyanidin at 5.0 and 2.0 mg/ml inhibited toxin by 37% and 87%. Growth was increased by 12% at 20 mg/ml and decreased by 18% and 9% at 1.25 and 5 mg/ml.