The pH-Sensitive Conversion of Molecular Aggregates of Rhamnolipid Biosurfactant

Abstract

Rhamnolipid B and its precursor A, both microbial and membranous constituent, reversibly changed morphologies of their molecular aggregates from vesicles under acidic conditions, to lamella, lipid particles, and finally to micelles under weakly acidic conditions within a narrow pH range of about 5–7.

The physicochemical properties and chemical composition of trehalose lipids produced by Rhodococcus erythropolis 51T7

“…However, at pH 4, the carboxyl groups do not carry any charge. Ishigami et al (1987) described similar behaviour. Sánchez et al (2007) found a CMC value of 0.110 mM at pH 7.4 and 0.010 mM at pH 4 with purified dirhamnolipids.…”

“…In aqueous media, biosurfactants, like surfactants, have different types of aggregates depending on their structure (Sánchez et al, 2007;Imura et al, 2007). Furthermore, it has been reported that biosurfactant aggregation properties depend on the pH of the medium (Israelachvili et al, 1976;Ishigami et al, 1987Ishigami et al, , 1993Champion et al, 1995).…”

Enhanced aqueous solubilization of tetrachloroethylene by a rhamnolipid biosurfactant

“…The data was then used to estimate the critical micelle concentration (CMC). The rhamnolipid solutions were prepared in phosphate buffer to control pH which is known to have a significant influence on the morphology of the surfactant aggregates [28,29]. Micelles are the predominant species at a pH greater than 6.8 [28].…”

“…The rhamnolipid solutions were prepared in phosphate buffer to control pH which is known to have a significant influence on the morphology of the surfactant aggregates [28,29]. Micelles are the predominant species at a pH greater than 6.8 [28]. Further, Zhang and Miller [9] observed a maximum reduction in surface tension of rhamnolipid solutions at pH 7.…”

Interfacial and micellar behavior of glucose lipid

“…This phenomenon may be attributed to a gradual growth of ionic micelle with the increase of GL concentration owing to the bulky molecular structure. Rhamnolipid A and B also showed a similar behavior to GL in the gradual association because of the similarity of their chemical structures,both being liposaccharides with c~,~-hydrophilic moieties(Ishigami et al 1987). Surface and interracial tensions of GL in PBS buffer (pH 7.35) are summarized inTable l. GL exhibits a high surface activity in spite of the molecular bulkiness.…”