Ionophorous and sequestering properties of surfactin, a biosurfactant from Bacillus subtilis

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 1993-05, Vol.1 (1), p.57-62
• Main Authors: Thimon, Laurence, Peypoux, Françoise, Wallach, Jean, Michel, Georges
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biosurfactant; Cation binding; Fundamental and applied biological sciences. Psychology; Ionophore; Molecular biophysics; Sequestering agent; Surface properties. Adsorption; Surfactin
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/0927-7765(93)80018-T

Surfactin is a bacterial lipopeptide containing two carboxylic groups. Its sequestering properties (surfactin binds calcium and magnesium ions) were determined in aqueous solution at pH 9.5. The calculated association constants were K = 1.5 × 10 5 M −1 for Ca 2 − and 1.9 × 10 4 M −1 for Mg 2+. Its complexing properties were determined by the two-phase distribution system; the aqueous phase contained Ca 2+ or Rb + ions and the lipidic phase contained surfactin. At pH 9, surfactin forms a 1:1 complex with Ca 2+ and a 2:1 complex with Rb + and it shows a higher affinity for divalent cations than for monovalent cations. Surfactin is non-selective in binding monovalent cations but is slightly more effective in binding Ca 2+ than Mg 2+ or Ba 2+. Surfactin is also a mobile carrier to transport monovalent and divalent cations across a solvent barrier and mediates the exchange between H − and inorganic cation.