Antifungal activity of secondary metabolites purified from Bacillus subtilis isolated in Vietnam and evaluated on in vitro and in vivo models

Abstract

The supernatant from Bacillus subtilis possessed significant antifungal activity against Fusarium oxysporum and Rhizoctonia solani, two harmful pathogenic fungi. In this study, antifungal compounds were purified from the extracellular extract of B. subtilis including volatile organic compounds (VOCs) and membranes protein. The antifungal compound was purified from B. subtilis by using a silica gel column with a solvent system of chloroform: ethyl acetate (7:3, v/v). Based on spectral data, the chemical structure was identified as (3R,4R)- and (3S,4S)- 3.4-dihydroxyl-3-methyl-2-pentanone (acetylbutanediol)—volatile organic compounds. The 3.4-dihydroxyl-3-methyl-2-pentanone showed high antifungal activity against Fusarium oxysporum and Rhizoctonia solani. Additionally, we isolated a novel antifungal protein with a molecular mass of 40 kDa. The results of Matrix-assisted laser desorption/ionization-Time of flight (MALDI-TOF) mass suggested that the functional molecule was outer membrane proteins (OMPs). The purified secondary metabolites retained antifungal activity against R. solani after being treated at 100 °C for 30 min. Treatment with the crude broth produced from Bacillus subtilis highly inhibited the growth of tested pathogens. Hence, it exhibited the potential of the antifungal compounds from B. subtilis for use as a biocontrol agent against fungi.