Abstract

The aim of this study is to investigate the antimicrobial effect of the lipopeptide biosurfactant produced by Bacillus licheniformis strain M104 grown on whey. The biosurfactant was investigated for potential antimicrobial activity by using disc-diffusion method against several Gram positive bacteria (Bacillus subtilis, Bacillus thuringiensis (2 strains), Bacillus cereus, Staphylococcus aureus (2 strains), and Listeria monocytogenes), Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli (2 strains), Salmonella typhimurium, Proteous vulgaris and Klebsiella pneumoniae) and a yeast (Candida albicans). The biosurfactant showed profoundly distinct antibacterial activity toward tested bacteria and displayed an antifungal activity against tested yeast. Maximum antimicrobial activity of the biosurfactant was shown against S. aureus. The biosurfactant had a broad inhibition effect on intracellular components of S. aureus. The antimicrobial effect of lipopeptide biosurfactant produced by B. licheniformis was found to be time and concentration dependent. When biosurfactant was added to S. aureus medium in a concentration of (48 μg/ml), the maximum reduction of acid soluble phosphorous (53.06%), total lipid (90.47%) total proteins (53.43%), ribonucleic acid (RNA) (83.29%) anddeoxyribonucleic acid (DNA) (48.50%) were recorded after 12 h of incubation period. From these results, it can be concluded that biosurfactants are a suitable alternative in potential applications of medical fields.

Key words: Biosurfactant, Bacillus licheniformis, cheese whey, antimicrobial activity,Staphylococcus aureus.