Anti-fungal substances of Bacillus subtilis against Ganoderma boninense

ABSTRACT

Aims@#To determine the optimum culture incubation time for β-glucanase and chitinase production by Bacillus subtilis as well as optimum pH and temperature condition for enzymatic activity against Ganoderma boninense. The suitable solvent (methanol, ethyl acetate or hexane) for the extraction of bacterial metabolites from B. subtilis were also determined. @*Methodology and results@#In vitro antagonistic activity of antifungal metabolites derived from B. subtilis to inhibit the growth of G. boninense was evaluated based on time of culture incubation, extraction solvent of the metabolites, and enzymatic treatments conditions including pH and temperature. The results showed that β-glucanase could be optimally produced (with a specific activity 4.222 U/mg-protein) after 28 h of incubation. The optimum pH and temperature for the activity of β-glucanase were 7.5 and 45 °C respectively when 1% laminarin used as the substrate. B. subtilis showed optimum chitinase activity (0.0514 U/mL) after 8 h of incubation. Optimum pH and temperature of chitinase were at pH 6.0 and 40 °C, respectively using 1% colloidal chitin as the substrate. β-glucanase crude enzyme showed strongest antifungal activities against the mycelial growth of G. boninense better than crude enzyme of chitinase with an inhibition rate of 47.75% at 5 days of incubation. Furthermore, cultivation of B. subtilis over 48 h produced antifungal metabolites which could inhibit the growth of G. boninense the most. The best solvent to extract metabolite from B. subtilis was identified as ethyl acetate that rendered an inhibition value of 38.91%. @*Conclusion, significance and impact of study@#Bacillus subtilis could be a potential biological control agent against G. boninense.