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Abstract
The microflora of various foods in Burundi was isolated and identified. Fusarium moniliforme was the predominant fungus isolated from corn and sorghum. Very few molds were isolated from rice and millet. Fusarium semitectum and Fusarium equiseti were the most common species isolated from haricot beans. Fusarium semitectum was also predominant in peanut samples. Peas were predominantly contaminated with Aspergillus ochraceus and Aspergillus wentii. Aspergillus flavus, Aspergillus niger and Aspergillus sydowi were the predominant species isolated from dried Ndagala fish. Penicillium citrinum, Penicillium corylophilum, and Penicillium chrysogenum were the predominant molds isolated from dried crushed cassava tuber and cassava flour.
The ability of these molds to produce aflatoxins, cyclopiazonic acid (CPA) and fumonisins, as well as the presence of these mycotoxins in the foods were investigated. Thirty-seven of 95 isolates of Aspergillus flavus and all five isolates of Aspergillus parasiticus produced aflatoxins. Sixty-seven of the 95 isolates of Aspergillus flavus produced CPA. Ten of 20 isolates of Aspergillus oryzae and Aspergillus tamarii produced CPA. Fifty-one of 56 isolates of Fusarium moniliforme and all four isolates of Fusarium proliferatum produced fumonisins. Relatively high concentrations of fumonisin B$\sb1$ (12.2 to 75.2 $\mu$g/g) were detected in samples of corn and sorghum meal. Neither aflatoxins nor CPA were found in any of the foods.
Bacillus pumilus produced an extracellular metabolite inhibiting mycelial growth and/or mycotoxin production of many Aspergillus, Fusarium and Penicillium species. The metabolite was isolated by precipitation with ammonium sulfate. It was soluble in water and other relatively polar solvents. The metabolite was heat stable (121$\sp\circ$C for 30 minutes) and active over a wide range of pH (2 to 10). It was resistant to hydrolysis by proteases, peptidases and other enzymes. The metabolite was also resistant to denaturation by protein-denaturing detergents. Based on its resistance to hydrolysis by carboxypeptidase A and negative reaction with fluorescamine and ninhydrin, the metabolite appeared to be either a protein/peptide with blocked carboxyl and amine termini or a non-protein/peptide.