Toxin-producing fungi of the genus Penicillium in coarse fodders

Abstract

The search for toxin-producing microscopic fungi, affecting plant and animals products, food and feed continues to be relevant in scientific research. A long-term study of this problem has shown that the threat of the occurrence of toxicoses of humans and animals is associated mainly with micromycetes of genus Fusarium, Aspergillus and Penicillium (CAST, 1989). In coarse feed, which form the basis of the ration of ruminants, these fungi have a leading position. Among Fusarium fungi the highly toxic species F. sporotrichioides dominates in hay and straw (E.A. Piryazeva et al., 2016), and 7 species of Aspergillus are capable to contaminate that with CPA, STE and MPA (G.P. Kononenko et al., 2017). The purpose of this work was to elucidate the toxin-forming potential of 11 species of the genus Penicillium fungi which prevail in mycobiota of coarse feed. The strains were cultured for 7 days at 25 С on a panel including Czapek Dox agar (CDA), wort agar (WA), Czapek Yeast Autolysate Agar (CYA), yeast extract sucrose agar (YES) and moistened rice grain (RG). Further, in the extracts, the amounts of ochratoxin A (OA), citrinin (CIT), mycophenolic acid (MPA), PR-toxin (PR), cyclopiazonic acid (CPA), emodin (EMO) and ergot alkaloids (EA) were determined by indirect competitive enzyme-linked immunosorbent assay (ELISA) using certified commercial and research test systems. On the basis of obtained results, the species P. aurantiovirens, P. palitans, as well as P. martensii and P. meleagrinum are classified as non-producing. Among the representatives of P. cyclopium, we found weak producers of MPA and CIT, as well as isolates that do not form any of the analyzed mycotoxins. High accumulation (10 µg/g and more) is revealed in P. brevicompactum, P. stoloniferum (MPA), P. roqueforti (PR + MPA), P. chrysogenum (PR) and average level (1-10 µg/g) is characteristic of P. urticae (CPA) and P. expansum (CIT). Isolates lacking production capacity were found only among P. chrysogenum and P. expansum, toxin production by other species was stable. In the representatives of P. roqueforti, producing jointly PR and MPA, the amount of MPA was, as a rule, less than PR. EMO, OA and EA in the metabolites of fungi were not found. In this paper it was shown for the first time that the species P. expansum, P. brevicompactum, P. stoloniferum, P. roqueforti, P. chrysogenum and P. urticae from a typical complex of fungi of this genus can be related to extensive and intensive contamination of coarse fodder by CIT, MPA, PR and CPA. It has been established that the use of a growth media panel for testing the toxicity of Penicillium fungi is an indispensable technique for an exhaustive assessment of their potential, and, in addition to agar media, it is expedient to use substrates of plant origin. Virtually all producing species had the highest intensity of toxin accumulation on RG, and for P. chrysogenum, PR production could be detected only on this substrate. Specific features of the profile of toxic metabolites in isolates belonging to one species are discussed, as well as the problem of the possible contribution of other species of Penicillium to the contamination of coarse fodder by mycotoxins.