-were the predominant Aspergillus species identified as exogenous mycoflora. Aspergillus flavus (26.6%) was the predominant Aspergillus species identified as endogenous mycoflora. Flotation method with MGA 0.25 recommended for isolating of hyaline fungi from wheat cereals. In this study one isolate from Fusarium species was isolated on the basis of morphology and ribosomal internal transcribed spacer classified as Fusarium langsethiae but on the basis of partial translation elongation factor-1alpha gene grouped with Fusarium sporotrichioides. To our knowledge, this is the first report about F. cf. langsethiae in Iran and Asia.
In this study, two techniques were used to compare the specific activity and total concentration of mycelial glutathione S-transferase (GST) in fungal strains isolated from natural sources. The fungi identified as Aspergillus parasiticus and Aspergillus flavus have been divided into two groups based on their ability to produce aflatoxins. Altogether 26 fungi were isolated, among which 12 were capable of producing varying levels of aflatoxin and 14 were proved to be non-toxigenic. GST specific activity in mycelial preparation was measured spectrophotometrically using 2,1-chloro-2,4-dinitrobenzene as the substrate. The results showed that the mean GST activity in toxigenic isolates was 25.06 +/- 9.8 micromol/mg protein/min which was 2.8-fold greater than that measured in non-toxigenic isolates (8.84 +/- 5.5 micromol/mg protein/min). Moreover, the GST concentration was compared in toxigenic and non-toxigenic isolates using an Enzyme Linked Immunosorbent Assay based on antigen (fungal preparation) and antibody (antibody produced against fungal GST in rabbit). The results of ELISA showed that the mean GST level in toxigenic and non-toxigenic fungi was 1.17 +/- 0.55 and 0.40 +/- 0.24, respectively. These results further confirm that the aflatoxin production in the fungal strains is correlated with GST expression and using ELISA, it is possible to discriminate aflatoxin-producing fungi from their non-toxigenic counterparts.
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