Aurore Richel

Synthesis and optical properties of opal and inverse opal photonic crystals

We describe the synthesis of two complementary photonic crystals: opal and an inverted opal structure consisting of air spheres in a titania matrix. From optical measurements and comparison with the literature, the mechanical strength and effective refractive index are increased by sintering for opal and because of compression for the inverse opal. However, this is at the expense of reducing the PBG in the [1 1 1] direction.

Ruthenium catalysts bearing N-heterocyclic carbene ligands in atom transfer radical reactions

The catalytic activity of ruthenium-p-cymene complexes bearing N-heterocyclic carbene ligands in atom transfer radical addition (ATRA) or polymerisation (ATRP) strongly depends on the substituents of the carbene ligand, thereby providing a nice illustration of the importance of organometallic engineering and ligand fine tuning in homogeneous catalysis.

Effect of Metals, Metalloids and Metallic Nanoparticles on Microalgae Growth and Industrial Product Biosynthesis: A Review

Microalgae are a source of numerous compounds that can be used in many branches of industry. Synthesis of such compounds in microalgal cells can be amplified under stress conditions. Exposure to various metals can be one of methods applied to induce cell stress and synthesis of target products in microalgae cultures. In this review, the potential of producing diverse biocompounds (pigments, lipids, exopolymers, peptides, phytohormones, arsenoorganics, nanoparticles) from microalgae cultures upon exposure to various metals, is evaluated. Additionally, different methods to alter microalgae response towards metals and metal stress are described. Finally, possibilities to sustain high growth rates and productivity of microalgal cultures in the presence of metals are discussed.

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

The enormous quantity of food wastes discarded annually forces a look into alternatives for this interesting feedstock. Thus, food bio-waste valorisation is one of the current imperatives of society. This review is the most comprehensive overview of currently existing technologies and processes in this field. It tackles classical and innovative physical, physico-chemical and chemical methods of food waste pre-treatment and extraction for the recovery of added value compounds and detection by modern technologies and is an outcome of the COST Action EUBIS, TD1203 Food Waste Valorisation for Sustainable Chemicals, Materials and Fuels.

Non Digestible Oligosaccharides Modulate the Gut Microbiota to Control the Development of Leukemia and Associated Cachexia in Mice

We tested the hypothesis that changing the gut microbiota using pectic oligosaccharides (POS) or inulin (INU) differently modulates the progression of leukemia and related metabolic disorders. Mice were transplanted with Bcr-Abl-transfected proB lymphocytes mimicking leukemia and received either POS or INU in their diet (5%) for 2 weeks. Combination of pyrosequencing, PCR-DGGE and qPCR analyses of the 16S rRNA gene revealed that POS decreased microbial diversity and richness of caecal microbiota whereas it increased Bifidobacterium spp., Roseburia spp. and Bacteroides spp. (affecting specifically B. dorei) to a higher extent than INU. INU supplementation increased the portal SCFA propionate and butyrate, and decreased cancer cell invasion in the liver. POS treatment did not affect hepatic cancer cell invasion, but was more efficient than INU to decrease the metabolic alterations. Indeed, POS better than INU delayed anorexia linked to cancer progression. In addition, POS treatment increased acetate in the caecal content, changed the fatty acid profile inside adipose tissue and counteracted the induction of markers controlling β-oxidation, thereby hampering fat mass loss. Non digestible carbohydrates with prebiotic properties may constitute a new nutritional strategy to modulate gut microbiota with positive consequences on cancer progression and associated cachexia.

Extraction by three processes of arabinoxylans from wheat bran and characterization of the fractions obtained

Arabinoxylans (AXs) were extracted from destarched wheat bran (DWB) according to different processes, with a view to their production at industrial scale. Two fractions (F3a and F3b, respectively, purified on 10kDa and 100kDa ultrafiltration membranes) were obtained with low yields by treating DWB with an endoxylanase and this process left a solid residue exhausted in enzyme-extractable AXs (EDWB). F1 and F2 AX fractions were obtained by treatment with sodium hydroxide of, respectively, DWB and EDWB. The fraction F4 resulted from a hydrothermal treatment of EDWB in a pressure reactor, followed by ethanol precipitation. The different AX fractions were characterized and compared for the composition in monosaccharides, for the contents in fats and in ferulic, phytic and uronic acids, for the molecular mass distribution and the degrees of methylation and acetylation. The alkaline extractions gave one deesterified AX population with molecular mass (MM) higher than 670kDa and arabinose/xylose ratios (Ara/Xyl) around 1. The enzyme and thermal treatments yielded AXs with two main populations in size-exclusion chromatography (the largest one at 5-12.5kDa and a second one at 140-160kDa), having overall Ara/Xyl of, respectively, 0.7 and 0.5 for both processes. These data bring information about the influence of the process on the characteristics of AX fractions obtained from pretreated wheat bran. Here are also reported processes that enabled to recover enzyme-unextractable AXs from DWB, including an original and up-scalable hydrothermal extraction. Phytate contents of isolated AXs are described for the first time.

Evaluation of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for Second-Generation Lignin Analysis

Matrix-Assisted Laser Desorption/Ionization time-of-flight (MALDI-TOF) mass spectrometry is evaluated as an elucidation tool for structural features and molecular weights estimation of some extracted herbaceous lignins. Optimization of analysis conditions, using a typical organic matrix, namely α-cyano-4-hydroxycinnamic acid (CHCA), in combination with α-cyclodextrin, allows efficient ionization of poorly soluble lignin materials and suppression of matrix-related ions background. Analysis of low-mass fragments ions (m/z 100–600) in the positive ion mode offers a “fingerprint” of starting lignins that could be a fine strategy to qualitatively identify principal inter-unit linkages between phenylpropanoid units. The molecular weights of lignins are estimated using size exclusion chromatography and compared to MALDI-TOF-MS profiles. Miscanthus (Miscanthus x giganteus) and Switchgrass (Panicum Virgatum L.) lignins, recovered after a formic acid/acetic acid/water process or aqueous ammonia soaking, are selected as benchmarks for this study.

Is non-host pollen suitable for generalist bumblebees?

Current evidence suggests that pollen is both chemically and structurally protected. Despite increasing interest in studying bee–flower networks, the constraints for bee development related to pollen nutritional content, toxicity and digestibility as well as their role in the shaping of bee–flower interactions have been poorly studied. In this study we combined bioassays of the generalist bee Bombus terrestris on pollen of Cirsium, Trifolium, Salix, and Cistus genera with an assessment of nutritional content, toxicity, and digestibility of pollen. Microcolonies showed significant differences in their development, non‐host pollen of Cirsium being the most unfavorable. This pollen was characterized by the presence of quite rare δ7‐sterols and a low digestibility. Cirsium consumption seemed increase syrup collection, which is probably related to a detoxification mixing behavior. These results strongly suggest that pollen traits may act as drivers of plant selection by bees and partly explain why Asteraceae pollen is rare in bee generalist diet.

Comprehensive comparison of the chemical and structural characterization of landfill leachate and leonardite humic fractions

AbstractHumic substances (HS) are complex and heterogeneous mixtures of organic compounds that occur everywhere in the environment. They represent most of the dissolved organic matter in soils, sediments (fossil), water, and landfills. The exact structure of HS macromolecules has not yet been determined because of their complexity and heterogeneity. Various descriptions of HS are used depending on specific environments of origin and research interests. In order to improve the understanding of the structure of HS extracted from landfill leachate (LHS) and commercial HS from leonardite (HHS), this study sought to compare the composition and characterization of the structure of LHS and HHS using elemental composition, chromatographic (high-performance liquid chromatography (HPLC)), and spectroscopic techniques (UV–vis, FTIR, NMR, and MALDI-TOF). The results showed that LHS molecules have a lower molecular weight and less aromatic structure than HHS molecules. The characteristics of functional groups of both LHS and HHS, however, were basically similar, but there was some differences in absorbance intensity. There were also less aliphatic and acidic functional groups and more aromatic and polyphenolic compounds in the humic acid (HA) fraction than in the fulvic acid (FA) and other molecules (OM) fractions of both origins. The differences between LHS and HHS might be due to the time course of humification. Combining the results obtained from these analytical techniques cold improve our understanding of the structure of HS of different origins and thus enhance their potential use. Graphical AbstractChemical and structural and characterization of landfill leachate and leonardite humic fractions

Effects of Size and Dispersity of Microcrystalline Celluloses on Size, Structure and Stability of Nanocrystalline Celluloses Extracted by Acid Hydrolysis

Nanocrystalline celluloses (NCCs) were separated from four commercial microcrystalline celluloses (MCCs) by an acid hydrolysis–sonication treatment. Transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectrum, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were conducted to investigate the NCCs. MCCs with different morphologies and particle sizes showed different aggregation degrees. The aggregation of MCCs followed the order MCC1 > MCC3 > MCC2 > MCC4, which is the same order of the heights of the resulting NCCs. The best uniformity and thermal stability were characterized for NCC3, which was produced by MCC3 with smallest original particle size and good dispersity among the four MCCs. This result suggests that both the original particle size and dispersity of MCCs had significant effects on separated NCCs.