Carboxyméthylcellulose

La carboxyméthylcellulose ou CMC (aussi appelée carmellose) est un gel d'origine synthétique. C'est un éther de cellulose très hygroscopique. Elle est souvent utilisée sous la forme de son sel de sodium, la carboxyméthylcellulose de sodium. Indiquée contre la sécheresse oculaire, elle est utilisée dans la composition de larmes de substitution, comme additif alimentaire (émulsifiant texturant , par exemple dans certains beurres alimentaires) ou encore comme agent antiredéposition. La CMC est utilisée comme résine d'échange de cation en chromatographie à échange d'ions pour la purification des protéines. Cet additif présent dans de nombreuses préparations agroindustrielles est pointé du doigt. En effet, près de de personnes dans le monde souffrent d'inflammations intestinales chroniques comme la maladie de Crohn ou la rectocolite hémorragique. Les facteurs génétiques ne suffisent pas à expliquer ces troubles et des causes environnementales sont suspectées. Une équipe de l'INSERM a

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Surface modified microfibrillated cellulose‐poly(vinylidene fluoride) composites: β‐phase formation, viscoelastic and dielectric performance

Dragan Damjanovic, Yves Leterrier, Véronique Michaud, Mohammed Arif Poothanari

The effect of silylation of microfibrillated cellulose (MFC) surfaces on β‐phase formation in poly(vinylidene difluoride) (PVDF) and the resulting viscoelastic and dielectric performance of MFC‐PVDF composites is investigated. Two different organosilanes, namely aminated (A) and fluorinated (F), were used. Composites of PVDF and MFC at concentrations up to 10 wt%, both untreated and silylated, were prepared by solvent casting. The two different surface modifications did not markedly change the melting and crystallization enthalpy of the polymer. However, only A‐MFC was found to promote β‐phase compared to the untreated MFC and the F‐MFC, which was attributed to the formation of hydrogen bonds at the interface between the amine groups of A‐MFC and the fluorine groups of PVDF. The elastic modulus and the permittivity of all composites increased with the amount of MFC up to a maximum value, depending on the MFC modification, and then decreased. This effect was due to the formation of MFC aggregates and porosity, as further confirmed by a comparison of experimental moduli with a classical composite mechanical model. The highest elastic modulus and highest permittivity were obtained for the untreated MFC and A‐MFC composites with 5 and 1 wt%.

2021

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A cellulolytic fungal biofilm enhances the consolidated bioconversion of cellulose to short chain fatty acids by the rumen microbiome

Robert Lawrence Shahab

The ability of the multispecies biofilm membrane reactors (MBM reactors) to provide distinguished niches for aerobic and anaerobic microbes at the same time was used for the investigation of the consolidated bioprocessing of cellulose to short chain fatty acids (SCFAs). A consortium based consolidated bioprocess (CBP) was designed. The rumen microbiome was used as the converting microbial consortium, co-cultivated with selected individual aerobic fungi which formed a biofilm on the tubular membrane flushed with oxygen. The beneficial effect of the fungal biofilm on the process yields and productivities was attributed to the enhanced cellulolytic activities compared with those achieved by the rumen microbiome alone. At 30 degrees C, the MBM system with Trichoderma reesei biofilm reached a concentration 39% higher (7.3g/L SCFAs), than the rumen microbiome alone (5.1g/L) using 15g/L crystalline cellulose as the substrate. Fermentation temperature was crucial especially for the composition of the short chain fatty acids produced. The temperature increase resulted in shorter fatty acids produced. While a mixture of acetic, propionic, butyric, and caproic acids was produced at 30 degrees C with Trichoderma reesei biofilm, butyric and caproic acids were not detected during the fermentations at 37.5 degrees C carried out with Coprinopsis cinerea as the biofilm forming fungus. Apart from the presence of the fungal biofilm, no parameter studied had a significant impact on the total yield of organic acids produced, which reached 0.47g of total SCFAs per g of cellulose (at 30 degrees C and at pH6, with rumen inoculum to total volume ratio equal to 0.372).

2019

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Membranes from polycation-polyanion complexes

Christine Wandrey

Membranes suitable for microfiltration, ultrafiltration, and dialysis consist of polycation-polyanion complexes prepd. by casting an aq. soln. of CM-cellulose (I) and cellulose sulfate (II) into a film and then treating with a cationic polyelectrolyte. Thus, 2.5% solns. of I with degree of substitution 1.0 and II were mixed in amts. to give I-II ratio 2:1, cast into a 2.0 mm layer on a glass plate, topped with a 2.0 mm layer of 20-5% polyethylenimine soln., dried, removed from the plate, and washed. The resulting membrane had throughput 16.0 L/h-m2 and sepn. efficiency 79.5% when used in a Millipore US cell at 0.2 MPa to sep. a 1 g/L aq. soln. of dextran with mol. wt. 500,000. [on SciFinder (R)]

(Akademie der Wissenschaften der DDR, Institut fuer Polymerenchemie, Ger. Dem. Rep.).1981

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