The aim of this study was to use a polyphasic approach to identify Aspergillus section Flavi isolated from Brazil nuts collected in the Amazon forest: investigation of macro- and microscopic morphology, production of extrolites, heat-resistance fungi, and sequencing of DNA regions. The following Aspergillus section Flavi species were identified: Aspergillus flavus (75.5%), Aspergillus nomius (22.3%), and Aspergillus parasiticus (2.2%). All A. nomius and A. parasiticus isolates produced aflatoxins B and G, but not cyclopiazonic acid (CPA). A. flavus isolates were more diversified and a high frequency of mycotoxigenic strains was observed. The polyphasic approach permitted the reliable identification of section Flavi species. The rate of mycotoxigenic strains was high (92.7%) and mainly included A. flavus strains producing elevated levels of aflatoxins and CPA. These results highlight the possibility of co-occurrence of both toxins, increasing their potential toxic effect in this commodity.

Brazil nut (Bertholletia excelsa) is an important commodity from the Brazilian Amazon, and approximately 37,000 tons (3.36 × 10⁷ kg) of Brazil nuts are harvested each year. However, substantial nut contamination by Aspergillus section Flavi occurs, with subsequent production of mycotoxins. In this context, the objective of the present investigation was to evaluate the presence of fungi and mycotoxins (aflatoxins and cyclopiazonic acid) in 110 stored samples of cultivated Brazil nut (55 samples of nuts and 55 samples of shells) collected monthly for 11 months in Itacoatiara, State of Amazonas, Brazil. The samples were inoculated in duplicate onto Aspergillus flavus and Aspergillus parasiticus agar and potato dextrose agar for the detection of fungi, and the presence of mycotoxins was determined by high-performance liquid chromatography. The most prevalent fungi in nuts and shells were Aspergillus spp., Fusarium spp., and Penicillium spp. A polyphasic approach was used for identification of Aspergillus species. Aflatoxins and cyclopiazonic acid were not detected in any of the samples analyzed. The low water activity of the substrate was a determinant factor for the presence of fungi and the absence of aflatoxin in Brazil nut samples. The high frequency of isolation of aflatoxigenic Aspergillus section Flavi strains, mainly A. flavus, and their persistence during storage increase the chances of aflatoxin production on these substrates and indicates the need for good management practices to prevent mycotoxin contamination in Brazil nuts.