EFFECTS OF GROWTH CONDITIONS ON ANTIFUNGAL ACTIVITY OF Bacillus subtilis NN12 AGAINST Fusarium oxysporum AND Fusarium equiseti
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Fusarium spp. are commonly pathogenic to various plants and seriously affect crop yields. To find a safe and effective way to control these fungal pathogens, many Bacillus strains have been widely studied and applied on a variety of plant models. In this study, culture conditions suitable for synthesizing antifungal compounds produced by Bacillus subtilis NN12 strain (Laboratory of Microbiotechology, Industrial university of Ho Chi Minh city) against Fusarium oxysporum and Fusarium equiseti were identified. The culture supplemented with 1% glucose, 0.5% peptone, initial pH 8.0 and 37°C with 150 rpm shaking condition for 18 hours was recorded as the highest antifungal activity of the culture supernatant. The F. oxysporum inhibitory activity of the culture was reduced by high temperatures, while the inhibitory activity affected on F. equiseti was relatively heat-resistant up to 90°C. In addition, antifungal compounds against both F. oxysporum and F. equiseti were shown to be stable in a wide pH spectrum (3.0-11.0) and especially were not affected by proteinase K. The results obtained in this study will provide the basis for future applications of B. subtilis NN12 in agriculture to not only to treat but also to prevent Fusarium diseases.