Solubilization of moderately hydrophobic 17α-ethinylestradiol by mono- and di-rhamnolipid solutions

Rhamnolipids are typically produced as multicomponent mixtures of homologues and are notably promising for environmental remediation. Because different mixtures exhibit dissimilar surface-active and micellization properties, which may affect their functional behaviors, the individual contribution of each rhamnolipidic homologue to the solubilization has largely been unexplored. In this study, enhanced solubilization of moderately hydrophobic 17α-ethinylestradiol (EE2) by two independent rhamnolipidic fractions (i.e., RL-F1 and RL-F2, which are mono- and di-rhamnolipids, respectively) was investigated. The results of the solubilization experiments indicated that RL-F2 exhibited a higher maximum dissolving capability of EE2 compared to RL-F1. However, a higher mass transfer rate was observed for RL-F1. To confirm the results of the solubilization experiments, dynamic light scattering, transmission electron microscopy, and UV-spectral analysis were performed. The type of rhamnolipid and the aggregate morphology strongly influenced the incorporation of solubilizate into the surfactant aggregates. The results of this study may be used to understand the rhamnolipid-facilitated transport of contaminants in aquatic environments, as well as the selection of rhamnolipids, with high specificity for practical applications.