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

Background: Contamination of pistachio nuts with aflatoxin, which produces strains of Aspergillus section Flavi, has been a concern for the human and animal health and food safety. Materials and Methods: Competitive ability of saprophytic yeasts in interfering with toxigenic strain of Aspergillus flavus was assessed through different experiments. 186 soil samples were collected from different agro-ecological zones of pistachio growing areas of Kerman province. A serial dilution method and YMA media were used to isolate yeast strains. Overall, 60 yeast isolates were screened for their ability to reduce the biomass of Aspergillus flavus via dual culture assays. Results: The highest inhibition was achieved by five yeast isolates in the ranges 38 to 82%. Other investigations have demonstrated the presence of significant interactions between saprophytic yeasts and A. flavus on biomass and aflatoxin production. The highest rate of reduction belonged to the IPRIY-43 and IPRIY-39 which reduced the growth of A. flavusin culture media. Conclusions: Quantitative assessments showed the ability of five selected yeast isolates to reduce aflatoxin production by 85-98% in dual culture assays. More investigations are required to understand the ability of yeast isolates to reduce aflatoxin production with toxigenic strains of A. flavus and withstand predominant abiotic stresses.