Production and Characterization of Fengycin by Indigenous Bacillus subtilis F29-3 Originating from a Potato Farm

Abstract

Fengycin, a lipopeptide biosurfactant, was produced by indigenous Bacillus subtilis F29-3 isolated from a potato farm. Although inhibiting the growth of filamentous fungi, the fengycin is ineffective against yeast and bacteria. In this study, fengycin was isolated from fermentation broth of B. subtilis F29-3 via acidic precipitation (pH 2.0 with 5 N HCl) followed by purification using ultrafiltration and nanofiltration. The purified fengycin product was characterized qualitatively by using fast atom bombardment-mass spectrometer, Fourier transform infrared spectrometer, ultraviolet-visible spectrophotometer, 13C-nuclear magnetic resonance spectrometer and matrix assisted laser desorption ionization-time of flight, followed by quantitative analysis using reversed-phase HPLC system. This study also attempted to increase fengycin production by B. subtilis F29-3 in order to optimize the fermentation medium constituents. The fermentation medium composition was optimized using response surface methodology (RSM) to increase fengycin production from B. subtilis F29-3. According to results of the five-level four-factor central composite design, the composition of soybean meal, NaNO3, MnSO4*4H2O, mannitol-mannitol, soybean meal-mannitol, soybean meal-soybean meal, NaNO3-NaNO3 and MnSO4*4H2O-MnSO4*4H2O significantly affected production. The simulation model produced a coefficient of determination (R2) of 0.9043, capable of accounting for 90.43% variability of the data. Results of the steepest ascent and central composite design indicated that 26.2 g/L of mannitol, 21.9 g/L of soybean meal, 3.1 g/L of NaNO3 and 0.2 g/L of MnSO4*4H2O represented the optimal medium composition, leading to the highest production of fengycin. Furthermore, the optimization strategy increased the fengycin production from 1.2 g/L to 3.5 g/L.