Surfactin

Surfactin is a biosurfactant produced by certain Bacillus species, most notably Bacillus subtilis and Bacillus amyloliquefaciens. It is a cyclic lipopeptide consisting of a heptapeptide ring linked to a β-hydroxy fatty acid tail, typically with a 12 to 15 carbon chain. This amphipathic structure confers high surface activity and the ability to reduce interfacial tension and stabilize emulsions. Several natural and engineered variants exist, often labeled surfactin A, B, C, and so on, with variations in the amino acid composition and fatty acid side chain.

In aqueous solution, surfactin lowers the surface tension of water from about 72 mN/m to roughly 27–30 mN/m at low concentrations; the critical micelle concentration lies in the low tens of milligrams per liter. The molecule readily accumulates at interfaces and can form micelles. Through interaction with lipid membranes, surfactin can disrupt membranes, which contributes to antimicrobial and anti-biofilm activities, and it also exhibits strong emulsifying properties.

Biosynthesis is carried out by nonribosomal peptide synthetases encoded by the srfA operon in B. subtilis and related gene clusters in other Bacillus strains. The modular assembly links the cyclic heptapeptide to the β-hydroxy fatty acid tail, producing the cyclic lipopeptide macrocycle.

Applications include bioremediation, enhanced oil recovery, and potential use in agriculture and cosmetics. Research continues on production optimization, formulation stability, and safety. Limitations for commercial use include sensitivity to high salinity and extreme pH, potential cytotoxic effects at high concentrations, and production costs.