Choukri Hbid

Purification Of Antifungal Lipopeptides By Reversed-Phase High-Performance Liquid-Chromatography

A rapid procedure for the purification of antifungal lipopeptides from Bacillus subtilis, a potential agent for biocontrol of plant diseases, was tested. It consists of a solid-phase extraction on C18 gel followed by reversed-phase chromatography using a biocompatible PepRPC HR 5/5 column with a pharmacia fast protein liquid chromatographic system. This is a very effective method for isolating and fractionating iturin A and surfactin, two lipopeptides of different nature, co-produced by Bacillus subtilis strain S499. The presence of homologous lipopeptides was easily detected.

Foaming properties of surfactin, a lipopeptide biosurfactant fromBacillus subtilis

Foaming properties of surfactin were investigated and compared to those of sodium dodecyl sulfate (SDS) and bovine serum albumin (BSA). Foams were formed by a bubbling technique. Evolution of the foam volume and the liquid in the foam was monitored with optical and conductimetric methods to characterize foam formation and stability. Excellent foaming properties of surfactin were shown by its higher ability to form and stabilize the foam at a concentration as low as 0.05 mg/mL, in comparison with SDS and BSA. Surfactin produced a foam with intermediate maximum density and stabilized the liquid in foam, as well as BSA.

Foaming properties of a natural cyclic lipoheptapeptide belonging to a special class of amphiphilic molecules

Abstract The foaming properties of surfactin, a natural cyclic lipoheptapeptide from Bacillus subtilis, were investigated in comparison and in association with those of bovine serum albumin (BSA). An apparatus combining bubbling, optical and conductimetric methods was used to study continuously foam formation and stability in terms of the quantity and density offoam. The increase in surfactin concentration from 0.05 to 0.2 mg/ml had little effect on its foaming capacity, measured by the bubbling time to produce the required foam volume, but improved the foam maximum density significantly. Surfactin produced foam with higher maximum density and stability, and forms more regular and smaller bubbles than BS A. In addition, a synergistic effect was observed on the stability of liquid in foam prepared with a mixture of 50:50 surfactin/BS A. The liquid half-life of BSA foam was enhanced up to 40% when surfactin was added to the solution.

Influence of the Production of Two Lipopeptides, Iturin A and Surfactin S1, on Oxygen Transfer During Bacillus subtilis Fermentation

Bacillus subtilis produces three types of lipopeptides: Iturins, Fengycins, and Surfactins. These amphiphilic molecules influence the volumetric oxygen transfer (KLa) like chemical surfactant.KLa values were from two-to fivefold lower when both Iturin A and Surfactin S1 were coproduced, and from 0.57-to 0.8-fold lower when only Iturin A was produced. The addition of an oxygen vector (n-Dodecane) during fermentation increasedKLa values (7.5-fold) and biomass production (twofold), and decreased Iturin A and Surfactin S1 production. However, at high stirring conditions and in the presence ofn-Dodecane, Iturin A production was improved.