Inhibitory Effect of a Soil Isolate of Bacillus amyloliquefaciens on Aflatoxin B1 Production by Aspergillus parasiticus in Laboratory Conditions

The concern about the presence of aflatoxin and its risk for human and animal health has resulted in the introduction of different methods to eliminate or reduce this toxin. One of these methods is biological control of the fungus by other microorganisms.
We isolated a strain of Bacillus amyloliquefaciens from the soil of a pistachio orchard, Damghan, Iran. This strain was applied as a biological control to examine the inhibition of growth and toxin production by Aspergillus parasiticus NRRL2999. After 72 hours of incubation of the bacterium at 30°C, we separated the supernatant as a potential source for antifungal compounds. Different doses of the supernatant were co-cultured with the fungus suspension in glucose yeast extract broth (GYB) at 28°C for 4 days. After the incubation period, we measured the inhibition of fungal growth by dry weight assessment of the fungal mass. We performed qualitative and quantitative assessment to determine the amount of aflatoxin B1 by TLC and HPLC, respectively.
Increased bacterial culture supernatant as the antagonist in fungal growth medium resulted in decreased fungal growth. AFB1 production was 2.35 ppm in control samples, whereas the amount considerably decreased in samples treated by the bacterial supernatants. The toxin reduction was dose-dependent.
The results of this study have shown that this bacterial strain, by taking into consideration its native origin, can be used as a biological control against aflatoxigenic fungi.