Isolation and optimization of growth conditions of yeasts with aflatoxin B1 reducing properties from local cheeses in Iran

Aflatoxin is one of the most important causes of contamination in dairy products, which has shown resistance to removal through various methods. This study aimed to molecularly identify yeasts isolated from local cheeses and screen them based on their ability to reduce aflatoxin B1. To carry out this study, 32 samples of local cheese were prepared from different geographical locations of Tehran and Semnan provinces in Shahryar, Firoozkooh, Chetan and Garmsar. Then the yeast strains were isolated from the samples. Aflatoxin stock solution was prepared and added to the culture medium containing aflatoxin absorbing yeast strains. Adsorbed aflatoxin was measured indirectly by ELISA test. The data of this study showed that 3 strains including Code 6, Code 18, and Code 8 isolated from local cheeses had the ability to detoxify aflatoxin B1. Meanwhile, the highest reduction of aflatoxin B1 in the environment with 46.5% was done by strain code 6. In addition, it was found that the optimum growth temperature of these strains was between 28 and 36 ˚C and their optimum pH was 6.5-5.5. Since the biological removal of aflatoxin has many positive effects on dairy products from various sensory and health aspects, it seems that the yeast strains isolated in the present study were microorganisms with the potential to remove aflatoxin from dairy products, especially local cheese, and should be considered for further studies.