Biocompatible lecithin-based microemulsions with rhamnolipid and sophorolipid biosurfactants: formulation and potential applications.

The objectives of this research are first to evaluate the hydrophilicity/hydrophobicity of sophorolipid biosurfactants relative to conventional synthetic surfactants and then to formulate and evaluate microemulsions of lecithin/rhamnolipid/sophorolipid biosurfactants with a range of oils (varying EACN values and oil types). We found that sophorolipid biosurfactants are more hydrophobic than sodium bis(2-ethyl) dihexyl sulfosuccinate (SBDHS), which is more hydrophobic than sodium dihexyl sulfosuccinate (SDHS) and rhamnolipid biosurfactant. Sophorolipid thus played an important role as the hydrophobic component in lecithin/rhamnolipid/sophorolipid biosurfactant formulation. This biosurfactant formulation was able to produce Winsor Type I, III and II microemulsions and the corresponding ultralow IFT for limonene, decane, isopropyl myristate and hexadecane. The phase behavior of this formulation with isopropyl myristate did not change significantly with changing temperature (10, 25, 40 degrees C) and electrolyte concentration (0.9% and 4.0% w/v), making it desirable for cosmetic and drug delivery applications. The hexadecane detergency performance of our biocompatible formulation was higher than that of a commercial liquid detergent at the same surfactant active concentrations. This paper thus shows the ability and robustness of mixed biosurfactant systems in formulating microemulsions for a range of oils and their potential applications. Copyright 2010 Elsevier Inc. All rights reserved.