Isolation and characterization of lipopeptide antibiotics produced by Bacillus subtilis.

ABSTRACT

AIMS: Antibiotics from Bacillus subtilis JA show strong pathogen inhibition ability, which has potential market application; yet, the composition of these antibiotics has not been elucidated. The aim of this paper is to isolate and identify these antibiotics. METHODS AND RESULTS: The antagonistic activity of JA was tested in vitro; it exhibited strong inhibition against some important phytopathogens and postharvest pathogens. Crude antibiotic production was extracted with methanol from the precipitate by adding 6 mol l(-1) HCl to the bacillus-free culture broth. The crude extract was run on Diamonsil C18 column (5 microm, 250 x 4.6 mm) in HPLC system to separate the antibiotics. Major antibiotics were classified into three lipopeptide families according to electrospray ionization-mass spectrometry analysis. Subsequently, the classification of antibiotics was confirmed with typical collision-induced dissociation fragments. CONCLUSIONS: Three kinds of antibiotics were isolated from B. subtilis JA and were identified to the lipopeptide families, surfactin, iturin and fengycin. These compounds could function as biocontrol agents against a large spectrum of pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY This study provided a reliable and rapid method for isolation and structural characterization of lipopeptide antibiotics from B. subtilis.