Trametes versicolor: a possible tool for aflatoxin control.
The genotoxic, mutagenic and cancerogenic aflatoxins produced by Aspergillus parasiticus are not yet efficiently controlled besides the increasing researches on this topic. Aflatoxin production by A. parasiticus is related to oxidative stress and some antioxidants can inhibit their production. Some basidiomycetes as Trametes versicolor used as "healing mushrooms" present beta-glucans and glycoproteins which are responsible for the stimulation of the host immune response. In this work T. versicolor culture filtrates, from different isolates, have been tested on A. parasiticus cultures to assay their inhibiting effect on aflatoxin production. Filtrates from T. versicolor were lyophilised and exopolysaccharides and glycoproteins were extracted by subsequent steps and added (2% w/v) to liquid cultures of a toxigenic A. parasiticus strain. Fungal growth and aflatoxins production by A. parasiticus were analysed both in filtrates and in mycelia and no interference on the output of toxins from mycelia was evidenced. Furthermore antioxidant capacity (by crocin test) of the T. versicolor extracts was analysed. All the strains assayed are able to inhibit the toxin production from 40% to above 90% in liquid cultures as well as in maize and wheat seeds inoculated with A. parasiticus. Antioxidant activity and beta-glucans amount in T. versicolor extracts showed a close relationship with aflatoxin inhibition ability and demonstrated that beta-glucans could be involved in aflatoxin inhibition. Molecular data indicate the almost complete inhibition of norA mRNA expression and a delay of aflR mRNA transcription. Filtrates and fractions from T. versicolor could be promising agents in the challenge against aflatoxins.