Development of a Cradle-to-Grave Approach for Acetylated Acidic Sophorolipid Biosurfactants

International audienceMicrobial production of biosurfactants represents one of the most interesting alternatives to classical petrol-based compounds due to their low toxicity, high biodegradability, and biological production processes from renewable bioresources. However, some of the main drawbacks generally encountered are the low productivities and the small number of chemical structures available, which limit widespread application of biosurfactants. Although chemical derivatization of (microbial) biosurfactants offers opportunities to broaden the panel of available molecules, direct microbial synthesis is still the preferred option and the use of engineered strains is becoming a valid alternative. In this multidisciplinary work we show the entire process of conception, upscaling of fermentation (150 L) and sustainable purification (filtration), application (foaming, solubilization, antibacterial), and life cycle analysis of acetylated acidic sophorolipids, directly produced by the Starmerella bombicola esterase knock out yeast strain, rather than purified using chromatography from the classical, but complex, mixture of acidic and lactonic sophorolipids

Surface charge of acidic sophorolipid micelles: effect of base and time

International audienceAcidic sophorolipids, SL–COOH, bio-derived glycolipids, are known to form micelles whose interactions vary as a function of pH. Upon partial ionization of the COOH group, intermicellar interactions take place. Here, we explore the nature of these interactions by using small angle neutron scattering (SANS) on SL–COOH solutions to which increasing amounts of NaOH are added. The effect of the nature of the base is also explored by replacing NaOH with aqueous NH3, KOH and Ca(OH)2. Time effects up to 36 days are also discussed. All SANS data have been successfully fitted using an appropriate model of core–shell prolate ellipsoids of revolution with an interaction potential, U(r), which combines hard-sphere and screened Coulomb (described by a repulsive Yukawa potential) potentials. Modelling quantifies the effect of the base in terms of micellar size, effective surface charge and interfacial hydration, thus showing the possibility of tuning them at will

One-Step Introduction of Broad-Band Mesoporosity in Silica Particles Using a Stimuli-Responsive Bioderived Glycolipid

Stimuli-responsive glycolipid biosurfactants belonging to the family of acidic sophorolipids (SL) have been used to introduce a broad range of pore size in the mesoscale regime (2–30 nm) in silica particles using a one-pot co-assembly sol–gel route in water. The pore size distribution is tailored by the sole interaction between an amino-modified silane, aminopropyltriethoxy silane (APTES), and SL. No additional compounds (e.g., block copolymers, polymers, organic solvents, pore-swelling agents) have been used to promote the formation of mesopores larger than 2 nm. Materials morphology and porosity have been characterized by high resolution TEM, SEM, and nitrogen physisorption, while the interaction between the glycolipid and silica is demonstrated by FT-IR and solid-state NMR

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

pH-triggered formation of nanoribbons from yeast-derived glycolipid biosurfactants

International audienceIn the present paper, we show that the saturated form of acidic sophorolipids, a family of industrially scaled bolaform microbial glycolipids, unexpectedly forms chiral nanofibers only at pH below 7.5. In particular, we illustrate that this phenomenon derives from a subtle cooperative effect of molecular chirality, hydrogen bonding, van der Waals forces and steric hindrance. The pH-responsive behaviour was shown by Dynamic Light Scattering (DLS), pH-titration and Field Emission Scanning Electron Microscopy (FE-SEM) while the nanoscale chirality was evidenced by Circular Dichroism (CD) and cryo Transmission Electron Microscopy (cryo-TEM). The packing of sophorolipids within the ribbons was studied using Small Angle Neutron Scattering (SANS), Wide Angle X-ray Scattering (WAXS) and 2D H-1-H-1 through-space correlations via Nuclear Magnetic Resonance under very fast (67 kHz) Magic Angle Spinning (MAS-NMR)

LSL administration causes a dose-dependent effect on cell viability and morphology.

<p>(a) Following 24h of treatment with LSL we observed a significant reduction in O.D.570 values at doses between 20–100μg/ml (p<0.0001) in the control cell lines CCD-841-CoN and MRC5. (b) There was a significant reduction in O.D.570 values at doses between 30–100μg/ml in HCT116, Caco2 and LS180 (p < 0.05) and at doses above 60μg/ml inn HT29 and HT115 cells (p < 0.001). Graphs show a representative data set from three independent experimental replicates. Values indicate mean ± SEM (n = 6). Statistical significance was assessed one-way ANOVA (*p < 0.05; **p < 0.001; ***p < 0.0001). (c) Light micrographs from CCD-841-CoN colonic epithelial cells (top) treated with vehicle-only control (left) where cells show a typical bipolar morphology. After treatment with 40μg/ml (central) or 70μg/ml (right) LSL the remaining adherent cells are rounded and there are large regions devoid of cells. In HT29 cultures treated with vehicle-only (bottom right) the cells are densely packed with a cobblestone-like morphology. Following treatment with 40μg/ml LSL (middle), there are no discernable changes in cell morphology, however treatment with 70μg/ml LSL (right) leads to cell rounding and conspicuous cell free areas. Scale bar = 50μm for all images.</p