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

Morphological and structural differences between glucose, cellulose and lignocellulosic biomass derived hydrothermal carbons

International audienceHydrothermal carbonization (HTC) has demonstrated that it is an effective technique for the production of functionalized carbon materials from simple carbohydrates, such as monosaccharides and disaccharides. The chemical structure of the HTC carbon has been identified in detail by means of solid-state MAS 13C NMR investigations. However, it has not yet been clearly shown what the effects are of the processing temperature and time on the chemical structure and morphology of the generated HTC carbon. This study shows, with the help of SEM, elemental and yield analysis and solid-state MAS 13C NMR, the effects of these two key variables on the final nature of the produced material, allowing the development of a mechanistic model. According to the chosen set of processing parameters, the chemical structure of the HTC carbon can be tuned from polyfuran rich in oxygen containing functional groups to a carbon network of extensive aromatic domains. The same kind of investigation using lignocellulosic biomass as a carbon precursor shows a striking difference between the HTC mechanism of glucose and cellulose. The biopolymer, when it is treated under mild hydrothermal conditions (180–280 °C), tends to react according to a reaction scheme which leads to its direct transformation into an aromatic carbon network and which has strong similarities with classical pyrolysis

One-step hydrothermal synthesis of nitrogen-doped nanocarbons : albumine directing the carbonization of glucose

International audienceWe present a simple and green one-step pathway towards nitrogen-doped carbon nanostructures with controlled mesoporosity through hydrothermal treatment of glucose in the presence of model proteins. Performing the reaction with different amounts of egg white ovalbumin protein (OvA), carbonaceous nanoparticles or continuous nanosponges with high specific surface areas can be efficiently produced. The nitrogen content of the structures is rather high (up to 8 wt %) and can be kept constant up to 950 °C, while oxygen elimination and graphitization of the carbon material occurs. We demonstrate here that sustainable natural resources can be efficiently used in the synthesis of pure high-potential nanomaterials

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

Structural Insights on Nitrogen-Containing Hydrothermal Carbon Using Solid-State Magic Angle Spinning 13C and 15N Nuclear Magnetic Resonance

International audienceHere, 13C and 15N solid state NMR is used as the main and most effective characterization technique on nitrogen-containing hydrothermal carbons obtained from glucose and glycine. This study represents a model system for other types of nitrogen-containing hydrothermal carbons, which were shown to have interesting energy-storage properties (Zhao et al. Adv. Mater. 2010, 22, 5202). These materials are obtained either from N-containing carbohydrates or from pure carbohydrates in the presence of natural amino-containing compounds such as proteins or aminoacids. In contrast to what is generally known for this model system, high molecular weight heterogeneous polymers (e.g., melanoidins) that are formed when sugars and amino acids combine through the Maillard reaction, we found an extended nitrogen-containing aromatic network, which is chemically bound to a polyfuran network known to be one of the main components of the biomass-derived hydrothermal carbons. In contrast to the hydrothermal carbons obtained from pure carbohydrates, these types of N-containing materials have an increased level of aromatic character already present at 180 °C, after the hydrothermal treatment