Micellar and Solubilization Properties of Biological Surfactant Surfactin

ABSTRACT

We studied aqueous solutions of surfactin in the concentration range of 0.001–200 g/L using NMR diffusometry, tensometry and optical microscopy methods. According to tensometry data, the system forms monolayers of surfactant molecules at the water‐air phase boundary at C  = 0.02 g/L. According to NMR diffusometry data, the micelles are formed in the entire volume of the solution at C  = 0.28 g/L. According to UV spectrophotometry data, the formation of micelles begins at C  = 0.23 g/L. We calculated the effective hydrodynamic radii of surfactin molecules, micelles and vesicles, and aggregation numbers. In addition, solubilization characteristics were determined: the proportion of solubilizate molecules in micelles p , micelle‐water partition coefficient, molar solubilization ratio of the surfactin micelles to benzene, toluene, ethylbenzene and xylene. This study shows that vesicles formed at high concentrations C  > 100 g/L of surfactin demonstrate high solubilization capacity and have high solubilization characteristics, p  = 0.98, which are maintained with an increase in the concentration of the solubilizate (benzene) up to 125 g/L.