Micelles versus Ribbons: How Congeners Drive the Self-Assembly of Acidic Sophorolipid Biosurfactants.
Sophorolipids (SLs), a class of microbially derived biosurfactants, are reported by different research groups to have different self-assembled structures (either micelles or giant ribbons) under the same conditions. Here we explore the reasons behind these contradictory results and attribute these differences to the role of specific congeners that are present in minute quantities. We show that a sample composed of a majority of oleic acid (C18:1) sophorolipid in the presence of only 0.5 % (or more) of congeners with stearic acid (C18:0) or linoleic acid (C18:2) results in the formation of micelles that are stable over long periods of time. Conversely, the presence of only 10 to 15 % of congeners with a stearic acid chain gives fibrillar structures instead of micelles. To study the mechanisms responsible, oleic acid SLs devoid of any other congeners were prepared. Very interestingly, this sample can self-assemble into either micelles or fibers depending on minute modifications to the self-assembly conditions. The findings are supported by light scattering, small-angle X-ray scattering, transmission electron microscopy under cryogenic conditions, high-pressure liquid chromatography, and NMR spectroscopy.
Physical and Materials Chemistry Division, CSIR-, National Chemical Laboratory, Dr. Homi Bhabha road, Pune, Maharashtra, India.
Prabhu
P
Dhasaiyan
Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris, UMR 7574, 4, Place Jussieu, 75005, Paris, France.
Patrick
P
Le Griel
Bio Base Europe Pilot Plant, Rodenhuizekaai 1, 9042, Ghent, Belgium.|InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
Sophie
S
Roelants
Bio Base Europe Pilot Plant, Rodenhuizekaai 1, 9042, Ghent, Belgium.
Emile
E
Redant
InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
Inge N A
IN
Van Bogaert
ESRF-The European Synchrotron, High Brilliance Beam line ID02, 38043, Grenoble, France.
Sylvain
S
Prevost
Physical and Materials Chemistry Division, CSIR-, National Chemical Laboratory, Dr. Homi Bhabha road, Pune, Maharashtra, India.
B L V
http://orcid.org/0000-0002-3115-0736
BL
Prasad
Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris, UMR 7574, 4, Place Jussieu, 75005, Paris, France.
Niki
N
Baccile
D006017:Glycolipids / Q000737:chemistry*; D008823:Micelles; D015394:Molecular Structure; D010316:Particle Size; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
D006017:Glycolipids; D008823:Micelles; D013501:Surface-Active Agents
biosurfactants; glycolipids; micelles; self-assembly; sophorolipids