LA STEAM EXPLOSION : PRINCIPE ET ACTION SUR LES MATERIAUX LIGNOCELLULOSIQUES

La steam explosion est un procédé thermomécanochimique qui va permettre la déstructuration de la matière lignocellulosique par l’action combinée de la chaleur issue de la vapeur, des hydrolyses induites par la formation d’acides organiques et du cisaillement résultant de la chute brutale de pression. Le procédé est composé de deux phases distinctes. D’une part, le vapocraquage qui consiste à faire pénétrer par diffusion, puis à condenser, la vapeur sous haute pression à l’intérieur de la structure du matériau. L’eau condensée à température élevée va initier l’hydrolyse des groupements acétyles contenus dans les xylanes et induire la formation d’acides organiques. Selon la sévérité des conditions (pression, température), les acides vont catalyser l’hydrolyse des fractions hémicellulosiques, induire des modifications dans la structure des lignines et modifier le degré de cristallinité de la fraction cellulosique. D’autre part, la décompression explosive. Cette phase est provoquée par une chute brutale de pression qui va entraîner la revaporisation d’une partie de l’eau condensée. L’expension brutale de la vapeur va induire des forces de cisaillement qui vont modifier les propriétés physiques (granulométrie, surface spécifique, rétention d’eau…) du matériau.LIGNOFUE

Carbohydrate-Based Surfactants: Structure-Activity Relationships

The aim of the present contribution is: (1) to review CBS in terms of structural classification based on their molecular size (mono-, oligo-, polymeric surfactants), geometry (standard, bipolar or bolaform, and gemini surfactants), and the nature of the polar headgroup (charged or not, cyclic or not), the apolar tail (number and length of alkyl chain), and the linker (amide, ester, ...) and/or the spacer; (2) to present systematically results on structure- activity relationships of uronic acid derivatives (UADs), a particular class of carbohydrate-based surfactants. These concern the impact of each structural entity including the polar headgroup (stereochemistry), apolar tail (chain length, number, and unsaturation), and linkage/spacer, on the performance of UADs to change surface properties, and possibly, to form and stabilize colloidal systems

Mechanism of lipolysis in milk : a modelistic approach using in Langmuir film balance.

Peer reviewe

Impact of the treatment conditions of a formic/acetic acid delignification method on chemical structure and antioxidant activity of beech wood lignin

The interest in lignocellulosic substrates is increasing because they are clearly identified for their high potential of development in energy and value-added molecules production. Indeed lignocellulosic biomass constitutes a promising resource for a sustainable production of organic compounds and biobased products that could progressively replace molecules from the petrochemical industry. Until now lignocellulosic substrates were mainly used for the valorization of cellulose. Hemicelluloses and lignins were less valorized and often degraded after the process. However, due to their phenolic structure, lignins can be valorized in a lot of high-valued applications like vanillin production, replacement of petrochemical polymers, antioxidants for cosmetics and food industry, resins… In this study, a representative sample of beech wood (Fagus sylvatica L.) was collected in the region of Gaume in Belgium. Beech wood was delignified at atmospheric pressure by an organosolv process using a mixture of formic acid/acetic acid/water. The effect of cooking time and temperature was evaluated on the structure, physico-chemical properties and antioxidant activity of the lignins obtained from the black liquor after treatments. The structural and physico-chemical characteristics of the lignins were investigated with different tools like infrared spectrometry, thermogravimetric analysis, gel permeation chromatography after acetylation of lignins, NMR 1H, 13C and HSQC. The antioxidant activity was assessed by a spectrophotometric method using the α,α-diphenyl-β-picrylhydrazyl radical (DPPH)

Impact d'un fractionnement soustractif sur la relation structure-fonction de la gomme de caroube

Le choix d'une température de fractionnement de la gomme de caroube va conditionner les caractéristiques des fractions obtenues et par conséquent les potentialité d'applications de ces dernières

Influence of electrical properties on the evaluation of the surface hydrophobicity of Bacillus subtilis

The surface hydrophobicity of nine Bacillus subtilis strains in different states (spores, vegetative cells, and dead cells) was assessed by water contact angle measurements, hydrophobic interaction chromatography (HIC) and bacterial adhesion to hydrocarbon (BATH). Electrokinetic properties of B, subtilis strains were characterized by zeta potential measurements and found to differ appreciably according to the strain, Correlations between HIC data, BATH data and zeta potential showed that HIC and RATH are influenced by electrostatic interactions. Water contact angle measurements thus provide a better estimate of cell surface hydrophobicity. The water contact angle of B. subtilis varied according to the strain and the state, the spores tending to be more hydrophobic than vegetative cells. (C) 2001 Elsevier Science B.V. All rights reserved