Trametes versicolor Inhibits aflatoxin production by Aspergillus parasiticus

Trametes versicolor is a non-toxic basidiomycete with medicinal properties, widely used in China and other far eastern countries. A protein-bound polysaccharide (PSK) and a low-cytotoxic polysaccharopeptide (PSP) from this mushroom are used with some success as scavenger of free radicals, T-cell proliferation inducer and antiviral agent in gastric cancer. Aspergillus parasiticus can produce on different foods and feeds, aflatoxins, which are dangerous pollutants, mutagenic and cancerogenic. Previous studies showed a close relationship between oxidative stress and aflatoxin production, in fact, antioxidants and scavengers of reactive species can inhibit aflatoxin production induced by peroxidation. In this work, lyophilised culture filtrates and some purified fractions from T. versicolor were assayed as inhibitors of aflatoxin production. Different strains of T. versicolor were cultured in malt extract broth for 15 days in a rotary shaker at 25°C. Culture filtrates were collected and lyophilised. Subsequently, the filtrates underwent purification, ethanol precipitation, dialysis and tripsin treatment to collect glicoproteins and polysaccharides (EPS, EPSt). Fractions were analysed by the crocin test to assay their antioxidant power. All the fractions were separately added to A. parasiticus cultures and incubated at 28°C for 3 and 6 days. Fungal growth, as dry weight and aflatoxin production, by HPLC analyses, were assessed. Fungal growth was not affected by the added fractions. The results obtained show that EPS fractions were the best inhibitors of aflatoxin production by comparison with lyophilised and tripsinated fractions. The data obtained with crocin the test allow some speculations on aflatoxins inhibition.