Biodiversity of Aflatoxigenic Aspergillus section Flavi Species According to Food Matrices and Geographic Areas
Résumé
Aflatoxins (AFs) are polyketide-derived metabolites produced by fungi on a wide range of crops (cereals, oilseeds, tree nuts, spices, dried fruits, etc.), both in the field and the post-harvest. As chemical stable molecules, resistant to conventional thermal or technological processes, they will pass through the whole food or feed supply chain to the final processed products. There are more than 20 known AFs and derivatives, yet the most hazardous AFs include the four naturally-occurring AFB1, AFB2, AFG1 and AFG2, and the hydroxylated metabolites of AFB1 and AFB2, and AFM1 and AFM2, which are produced through biotransformation in the liver and excreted in the milk of humans and mammals. AFs are known for their high acute and chronic toxicity to both humans and animals, and are considered among the most dangerous mycotoxins with carcinogenic, hepatotoxic, immunotoxic, teratogenic and mutagenic effects. AFB1 is the most prevalent and toxic aflatoxin, and is classified as a Group 1 human carcinogens. The intake of high amounts of AFs can cause acute intoxication (aflatoxicosis) associated with jaundice, vomiting, hemorrhages, abdominal pain, acute liver failure, problems with absorption of nutrients, and can be lethal. Reported outbreaks in western India (1974) and in Kenya (2004) caused the death of 106 and 125 people, respectively. Chronic exposure to low levels of AFs is associated with high risk of hepatocellular carcinoma (HCC), immunosuppression, teratogenic and mutagenic effects, reduction of nutrient absorption, child stunting, detrimental effects in the endocrinal system, and liver failure. More than five billion people worldwide are at risk of chronic exposure to AFs through contaminated foods. Humans’ exposure to AFs mainly occurs by direct intake of contaminated foods of vegetal or animal origin. Hence, the presence of AFs in foodstuff and feedstuff is a public health issue associated with detrimental effects in economy. In addition, commodities are generally contaminated by several mycotoxins, and this co-occurrence may result in a greater toxicity to humans caused by the possible additive or synergistic effects of these compounds. The main aflatoxin-producing fungi belong to Aspergillus section Flavi of the Circumdati subgenus, and only five AF producers do not belong to this section, A. ochraceoroseus, A. rambellii (A. section Ochraceorosei), A. astellatus, A. olivicola, and A. venezuelensis (A. section Nidulantes). The aim of the present chapter is to describe the characteristics of the aflatoxigenic Aspergillus section Flavi species isolated from food or feed, and to address the biodiversity according to food matrices and geographic areas.
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