Influence of formic acid on fungal flora of barley and on aflatoxin production in Aspergillus flavus link.

In recent years Aspergillus flavus and aflatoxin production have been noted on several occasions in grain preserved with formic acid. Samples of mouldy barley treated with formic acid and stored in an open bin were investigated for the presence of fungi. In the lower part of the bin there was a clear dominance of Fusarium sporotrichioides, and deoxynivalenol and neosolaniol were detected. A. flavus and A. fumigatus were also present. Paecilomyces variotii occurred, almost as a pure culture, in the upper part of the bin, but no patulin was found. Cultivation of four fungal isolates from these genera on laboratory substrates containing formic acid showed P. variotii to be the most tolerant to formic acid, withstanding 150 mM, but still without patulin production. F. sporotrichioides and A. fumigatus tolerated only 6 mM formic acid. The growth of A. flavus was reduced and atypical at 60 mM formic acid. Pretreatment of A. flavus spores with formic acid increased aflatoxin production about 800 times.