Efficacy of saprophytic yeasts on growth of Aspergillus flavus and aflatoxin production

Contamination of pistachio nuts with aflatoxin, which produces strains of Aspergillus section Flavi, has beena concern for the human and animal health and food safety.

Competitive ability of saprophytic yeasts in interfering with toxigenic strain of Aspergillus flavuswas assessed through different experiments. 186 soil samples were collected from different agro-ecological zones of pistachiogrowing areas of Kerman province. A serial dilution method and YMA media were used to isolate yeast strains. Overall, 60yeast isolates were screened for their ability to reduce the biomass of Aspergillus flavus via dual culture assays.

The highest inhibition was achieved by five yeast isolates in the ranges 38 to 82%. Other investigations havedemonstrated the presence of significant interactions between saprophytic yeasts and A. flavus on biomass and aflatoxinproduction. The highest rate of reduction belonged to the IPRIY-43 and IPRIY-39 which reduced the growth of A. flavusinculture media.

Quantitative assessments showed the ability of five selected yeast isolates to reduce aflatoxin production by85-98% in dual culture assays. More investigations are required to understand the ability of yeast isolates to reduce aflatoxinproduction with toxigenic strains of A. flavus and withstand predominant abiotic stresses.