Studies on the Population of Toxigenic Fungi in Foodstuffs

Abstract

The present studies were undertaken to determine the population of toxigenic fungi in domestic milled rice harvested in 1965. Of a total of 835 isolates, the toxigenicity of 82 representative strains has been investigated by subcutaneous administration with cultural filtrates of the fungi and methanol extracts obtained from mold-rice substrates. The experimental animals, male mice weighing 15-18g, were subcutaneously injected with 0.5ml/mouse of the cultural filtrates and with 25mg, 250mg and 1, 250mg/kg of the methanol extracts, respectively, in a single dose. Results of the tests indicated that fungal metabolites from one strain of Penicillium expansum and Penicillium islandicum were highly toxic, and fungal metabolites from one strain of P. cyclopium, P. cylclopium var. echinulatum, P. martensii, P. decumbens, P. expansum and Aspergillus versicolor, and 2 strains of P. roqueforti were mildly toxic. Toxic effects were not found in the other fungi, including the groups belonging to Ascomycetes and Fungi Imperfecti. Thus, highly toxic fungi were found in 2 of representative strains, a frequency of 2.4%. The incidence of mild toxic fungi was 9.7%. This is the first report of the prevalence of toxic fungi in domestic rice. Known mycotoxins such as patulin, luteroskyrin, and islanditoxin and two different unknown were detected. Except for a few cases of Fusarium toxicoses, human mycotoxin poisoning has not ever been happened in Japan. These facts could be considered as evidence for a qualitative interpretation of mycotoxicosis in the Japanese people who consume rice as their main food.