Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants - Sorbonne Université Access content directly
Journal Articles ACS Nano Year : 2012

Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants


An increasing need exists for simple, bioderived, nontoxic, and up-scalable compounds with stimuli-responsive properties. Acidic sophorolipids (SL) are glucose-based biosurfactants derived from the yeast broth of Candida bombicola (teleomorph: Starmerella bombicola). The specific design of this molecule, a sophorose head with a free end-COOH group at the end of the alkyl chain, makes it a potentially interesting pH-responsive compound. We have specifically investigated this assumption using a combination of small angle neutron scattering (SANS), transmission electron microscopy under cryogenic conditions (Cryo-TEM), and nuclear magnetic resonance (NMR) techniques and found a strong dependence of SL self-assembly on the degree of ionization, α, of the COOH group at concentration values as low as 5 and 0.5 wt %. At least three regimes can be identified where the supramolecular behavior of SL is unexpectedly different: (1) at low α values, self-assembly is driven by concentration, C, and micelles are mainly identified as nonionic objects whose curvature decreases (sphere-to-rod) with C; (2) at mid α values, the formation of COO– groups introduces negative charges at the micellar surface inducing an increase in curvature (rod-to-sphere transition). Repulsive electrostatic long-range interactions appear at this stage. In both regimes 1 and 2, the cross-section radius of the micelles is below 25 Å. This behavior is concentration independent. (3) At α = 1, individual micelles seem to favor the formation of large netlike tubular aggregates whose size is above 100 nm. Such a complex behavior is very unique as it is generally not observed for common alkyl-based surfactants in concentration ranges below 5–10 wt %.
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hal-01455100 , version 1 (03-02-2017)



Niki Baccile, Florence Babonneau, Jacques Jestin, Gerard Pehau-Arnaudet, Inge van Bogaert. Unusual, pH-Induced, Self-Assembly Of Sophorolipid Biosurfactants. ACS Nano, 2012, 6 (6), pp.4763-4776. ⟨10.1021/nn204911k⟩. ⟨hal-01455100⟩
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