THE INHIBITION OF MYCOTOXINS BIOSYNTHESIS BY a-HETEROPOLYSACCHARIDES OF TRAMETES VERSICOLOR.

The contamination of food commodities by mycotoxins (aflatoxins, ochratoxin A, Fusarium toxins) which are health hazardous and carcinogenic secondary metabolites produced by different fungi (Aspergillus flavus, A. carbonarius, Fusarium verticillioides), has to be strictly controlled to safeguard human and animal health. Extant control methods are mainly based on chemical strategy (pesticides and fungicides). However, the use of substances synthesised by some basidiomycetes with a lower impact on the environment and on human health have produced encouraging results. Trametes versicolor is a basidiomycete known for its therapeutic effects mainly based on the production of several glycoproteins and exoglucans which display anti-tumoral action and anti-oxidative effects. The semi-purified exo-polysaccharides and glycoproteins secreted by this mushroom had previously shown the ability to inhibit the biosynthesis of different mycotoxins (aflatoxins, ochratoxin A, Fusarium toxins). In this study, the exo-polysaccharidic component secreted T. versicolor was purified by chromatographic separation techniques (Sephacryl S-300) and analysed by 1H- and 13C-NMR. Two-dimensional HSQC and COSY analysis have revealed the presence of highly complexed a-glucans with a mol. wt of ca. 50 kDa. We hypothesise that these fungal polysaccharides can act as non-self signals capable of modulating secondary metabolism in mycotoxigenic fungi. The results obtained are promising in view of the implementation of a more environment friendly strategy, so as to achieve a better control of different toxins that are often concomitantly present in foods and feeds.