Foaming properties of lipopeptides produced by Bacillus subtilis: effect of lipid and peptide structural attributes

To study the effect of lipid and peptide structural attributes of Bacillus subtilis lipopeptides on
their foaming properties, the formation, stability, and appearance of foams prepared with surfactins (C13 C15) and iturins A (C14 C17) were characterized. The density and stability of lipopeptide foams depend on both the alkyl chain hydrophobic character and peptide molecular intrinsic properties. A lipidic chain length of 14 carbon atoms provides lipopeptides with the best foaming properties in terms of foam density and liquid stability in foams. Increases in alkyl chain length above 15 carbon atoms result in a drastic decrease of iturin A foam density. With the same alkyl chain, surfactin produces denser foam whereas iturin A exhibits better foaming stability. These results demonstrate the importance of the peptide structural attributes of B. subtilis on their foaming properties.