Rhamnolipid Self-Aggregation in Water–Bioglycerol Mixtures: Byproduct Valorization for Sustainable Formulation Design

Increasing biodiesel production poses a significant challenge in managing its primary byproduct, bioglycerol. Advancements in production techniques have markedly enhanced bioglycerol potential applications across various sectors, including as cosolvent in industrial formulations. In the context of ecosustainable formulation design, this study addresses the self-aggregation of rhamnolipids, biosurfactants with a wide range of physicochemical and biological activities, in bioglycerol aqueous mixtures, studied by integrating surface tension and NMR self-diffusion measurements. Preliminary analysis of the properties of water–bioglycerol mixtures indicates that bioglycerol impurities (mainly potassium acetate) have only a small effect on surface tension and no discernible effect on bulk properties such as density, viscosity, and refractive index. The aggregation of rhamnolipids is unaffected by bioglycerol at concentrations up to 40–50 wt%. At higher cosolvent levels, the cmc increases and the micellar size decreases, an indirect effect of the decreasing polarity of the medium. These results provide the basic knowledge to promote the exploration of rhamnolipids and bioglycerol as valuable ingredients in formulations for various applications.