Antibacterial Activity of the Lipopeptide Biosurfactant Produced by Bacillus mojavensis PTCC 1696

Bacillus mojavensis PTCC 1696 (a member of Bacillus subtilis group) has been isolated from the Iranian oil field (Masjed-I Soleyman), to examine its ability to produce biosurfactant (lipopeptide type) [28]. The present study was designed to characterize the antibacterial activity of the isolated biosurfactant. The antibacterial activity towards several bacteria including clinical isolates and type strains species was examined. For detecting the extent of antibacterial activity, the agar disc diffusion method was used, where the measured diameter of the zone of inhibition was used as an index for determining the antibacterial activity. Among the test microorganisms, the antibacterial activity was highest in Pseudomonas aeruginosa ATCC 27853. At concentration as low as 16 μg/ml, the inhibitory effect of the lipopeptide biosurfactant was detectable. The stability of the test biosurfactant also was examined over a wide range of temperatures (40–100°C)and pH values (2-11). The stability was further tested using protease and lipase, where the substance showed clear sensitivity towards lipase. The potentiality of this antibacterial agent in clinical applications is of interest and needs to be further recognized.