Biocontrol Activity of Bacillus megaterium against the Fungus Aspergillus flavus Isolated from Poultry Feeds in Algeria

摘要

Aims: This study aimed to evaluate the antagonist effect of the bacteria Bacillus megaterium against the toxigenic fungus Aspergillus flavus using different methods . Methodology: According to the method described by Vincent et al. (1991) and Arras (1993) we have determined the effect of B. megaterium on the growth of A. flavus using fungal disc and fungus spore respectively. In order to see the effect of cell free supernatant of B. megaterium on the dry mass of A. flavus , culture bacteria of 5 days old was centrifuged; filtered and cell-free supernatant was incubated with 5 mm circular plug of A. flavus . After incubation at 28°C for 9 days. The dry mass was determined by weighting every 72 h and compared with the control. Elucidation of antagonistic mechanism of B. megaterium was examined using the following tests: Hydrogen Cyanide production, production of Ammonia (NH₃) and production of extracellular enzymes such: Protease, Chitinase and Amylase. Results: The results showed that B. megaterium is an antagonistic bacterium that has been shown high effectiveness against the fungus A. flavus isolated form poultry feeds in Algeria. Results indicated an almost entirely decrease (47.56%) of mycelial growth using fungal disc and (40.75%) using fungus spore. In cell-free supernatant in vitro assay, B.megaterium showed significant inhibitory activity against A. flavus when the dry mass of mycelium decrease from 1.25 g to 0.83 g compared with the control. Conclusion: This research shows that B. megaterium is quite important and effective as biocontrol agent against the toxigenic mold A. flavus in poultry feeds. This inhibition action is probably due to the synergistic effects of the factors such as the production of antibiotics and the extracellular enzymes such as protease, cellulase, chitinase and amylase.