Aflatoxin inhibition in Aspergillus flavus for bioremediation purposes
2014
Gomaa, Ola M. | El Nour, Salwa Abou
Although Aspergilli are known for their efficiency in bioremediation, some strains produce aflatoxins as secondary metabolites adding another problem to the already existing environmental problem. A number of fungal isolates were tested for their ability to treat laboratory waste water. A single isolate, Aspergillus flavus, was chosen for its ability to treat a mixture of laboratory wastes in 7 days; the long duration resulted in the production of aflatoxins. This production was assumed to be the result of fungal exposure to stress. The oxidative stress-related transcription factor (OSTRF) Yap1 was present on the genomic level, suggesting the regulation of aflatoxin biosynthesis. Although exposure of the fungus to 2.5 kGy gamma radiation was effective in aflatoxin and mycelial inhibition, green tea phenolic extract (ca. 70 mg/ml phenol) was used because it inhibited aflatoxin production while fungal mycelial growth was not affected. Aflatoxins B1, B2 and G1, G2 were evident in control cultures (0.34 μg/g) along with cultures spiked with hydrogen peroxide (2.4 μg/g) which was considered the positive oxidant. On the other hand, aflatoxins were absent completely in cultures supplemented with gallic acid (positive antioxidant) and green tea phenolic-containing extract. Lipid peroxidation results followed the same trend. The addition of phenolic green tea extract inhibited aflatoxin biosynthesis; moreover, it did not affect the potential of the fungus in bioremediation, or its growth.
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