Abstract

Surfactants are amphipathic molecules which reduce surface and interfacial tensions and widely used in pharmaceutical, cosmetic, food and petroleum industries. Biosurfactants are the structurally diverse group of surface-active molecules synthesized by microorganisms. There are several advantages for biosurfactants in contrast with chemical surfactants, such as lower toxicity; higher biodegradability; better environmental compatibility; higher foaming; high selectivity and specific activity at extreme temperatures, pH, and the ability to be synthesized from renewable feed-stock. In the present study, the production of bioemulsifer byBacillus licheniformis PTCC 1595 was studied. B. licheniformis was grown in the nutrient broth medium and bioemulsifer production was evaluated every 24 h by surface tension and emulsification index (E24). Then B. licheniformis PTCC 1595 was grown in nutrient broth with different conditions in order to get maximum production of bioemulsifer. The best culture medium was found to be nutrient broth medium supplemented with starch, Fe²⁺, Mn²⁺ and olive oil. After growing the bacteria, the microbial biomass was removed from the supernatant by acidic precipitation method. Its amphipathic structure was established by biochemical and spectroscopy methods and it was confirmed to be a lipopeptide structure.

Key words: Bacillus licheniformis, bioemulsifer, surface tension, emulsification index.