Toxigenic properties of mycotoxin-producing fungi

Microscopic fungi that infect plants during the growing season and agricultural products during storage can get into food and animal feed and pollute them with their toxic metabolites - mycotoxins. The species composition and proportion of each species in the complex of fungi may vary with changes in growing or storage conditions, which is accompanied by changes in the spectrum of mycotoxins. In addition to known and controlled pollutants of this kind, the levels of previously unaccounted toxic fungal metabolites may increase, requiring a further study and assessment of the risk of their occurrence in food. The review is devoted to the consideration of fungi from the genera Fusarium, Aspergillus and Penicillium, whose representatives can produce mycotoxins both already regulated in plant products and predicted. The review also includes species Alternaria spp., the study of which revealed a frequent occurrence and a wide range of produced toxic metabolites, not yet normalized in food. Most mycotoxic fungi can multiply and accumulate toxic metabolites in a wide range of habitats of these microorganisms. We showed that microorganisms are extremely widespread in nature, and under favorable conditions with high humidity and optimal temperature (See Table 1) can affect various food products, animal feed and vegetable resources causing significant economic damage. Since it is difficult to identify toxin-producing fungi contaminating different substrates including food products and animal feed, mycotoxinology studies are conducted in accordance with a strict procedure including detection of species composition of fungi and their distribution by geographical zones, and determination of substrates contaminated with mycotoxins, as well as the composition of mycotoxins and the mechanism of their action on humans and animals. The paper presents data on the properties of toxigenic fungi of the genera Aspergillus, Alternaria, Fusarium and Penicillium, the most important from the point of view of food and animal feed safety. A special attention is paid to the problem of detecting producers of emerging mycotoxins among these fungi (See Table 2), which include fusaproliferin, beauvericin, enniatins, moniliformin, tenuazonic acid, tentoxin, alternariol and its methyl ether, mycophenolic acid, citrinin, fusaric acid, sterigmatocystin, emodin and asperglaucid (Gruber-Dorninger C et al., 2017, Jestoi M, 2008, Fraeyman S et al., 2017, Serrano AB, 2015). The review discusses the problems and prospects of applying the methods of DNA-identification of toxigenic fungi, touched upon in works of Gagkaeva TYu et al., 2017, Stakheev AA et al., 2018, Dupont J, 2010, Gromovykh TI et al., 2014, Rodr^guez A et al., 2011. We enumerate the difficulties that prevent a widespread introduction of PCR- diagnostics including the specifics of fungal DNA extraction, peculiarities of qualitative PCR for multinuclear cells of filamentous fungi, and the necessity to differentiate inactivated and viable mold forms. We showed that molecular methods of micromycete identification should be improved in order to search for target DNA sequences and markers which correlate with mycotoxigenic strains in the studied substrate. An important part of the research was to identify mycotoxin biosynthesis genes and evaluate their expression. Selection and improvement of DNA methods of food control for toxigenic fungi are needed for adequate risk evaluation of food contamination with mycotoxins, ensuring its safety and preventing mycotoxicosis. The paper contains 2 Tables and 81 References.

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