(11d) Biosurfactant Adsorption and Self-Assembly: A Comparative Study

Biosurfactants are naturally occurring amphiphiles that reduce surface and interfacial tension in aqueous solutions and water-oil mixtures. On the basis of their ability to mobilize and disperse hydrocarbons, biosurfactants are involved in the bioremediation of oil spills, and are being actively pursued as alternatives to synthetic surfactants in cleaning, personal care, and cosmetic products. [Jahan, R.; Bodratti, A. M.; Tsianou, M.; Alexandridis, P., Biosurfactants, natural alternatives to synthetic surfactants: Physicochemical properties and applications. Adv. Colloid Interface Sci. 2020, 275, 102061. DOI: 10.1016/j.cis.2019.102061] We examine here the micellization of mono-rhamnolipids and di-rhamnolipids in aqueous solutions and their adsorption on solid surfaces, and discuss the effects of rhamnolipid headgroup, rhamnolipid purification, and presence of salt in water. Further, we compare the rhamnolipid solution and surface association behavior to that of other biosurfacatns (sophorolipids and surfactin) and synthetic surfactants (sodium dodecyl sulfate (SDS) and sodium dioctyl sulfosuccinate (AOT)). An improved fundamental understanding of biosurfactant self-assembly and adsorption properties is important for their utilization in environmental and consumer products applications.