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Suriyarak S.,University of Hohenheim | Gibis M.,University of Hohenheim | Schmidt H.,University of Hohenheim | Villeneuve P.,CNRS Agropolymers Engineering and Emerging Technologies | Weiss J.,University of Hohenheim
Journal of Food Protection | Year: 2014

Antimicrobial activity and mechanism of action of rosmarinic acid (RA) and dodecyl rosmarinate (RE12) against Staphylococcus carnosus LTH1502 were studied as a function of pH (5.8 to 7.2) and in the presence of salts (KCl and MgCl 2, 0 to 500 mM). Microbial cultures were exposed to unesterified RA and to esterified RE12, and cell number was determined by plate counting. Cells exposed to RA and RE12 at the minimum bactericidal concentration (200 and 0.05 mM, respectively) were examined using scanning electron microscopy to observe potential morphological changes. Activity of RA was found to be strongly dependent on pH, salt type, and concentration, whereas RE12 led to the compound's activity becoming independent of pH, salt concentration, and type. Scanning electron microscopy images showed that morphology of cells treated with RE12 after incubation of 1 h was irrevocably altered. Our results suggest that esterification (i) altered the mechanism of action by increasing the compound's affinity for cell membranes and (ii) decreased the compound's susceptibility to changes in environmental conditions that alter its charge. Highly specific changes in structure-activity relationships can be observed when esterifying a naturally active phenol such as RA with an alkyl chain that has a carbon chain length of 12. Copyright ©, International Association for Food Protection. Source

Barakat A.,French National Institute for Agricultural Research | Barakat A.,CNRS Agropolymers Engineering and Emerging Technologies | Gaillard C.,French National Institute for Agricultural Research | Steyer J.-P.,French National Institute for Agricultural Research | Carrere H.,French National Institute for Agricultural Research
Waste and Biomass Valorization | Year: 2014

In order to determine the parameters influencing lignocellulosic biomass biodegradability, binary and ternary model systems were constructed, consisting of cellulose nanowhiskers gel, xylan matrix derived from lignocellulosic plants and synthetic lignin. The adsorption of two xylan polymers with different arabinose/xylose ratios (Ara/Xyl) on the cellulose nanowhiskers resulted in the synthesis of nanocomposites each of different Ara/Xyl ratios and crystallinity indexes. Organized and associated cellulose-xylan-lignin nanocomposites were formed following the polymerization of guäiacyl (G) and syringyl (S) lignin monomers using a peroxidase/H2O2 system in cellulose nanowhiskers-xylan gel. The anaerobic digestion of cellulose nanowhiskers, xylans and cellulose-xylan nanocomposites indicated that the biomethane production depended strongly on the xylan Ara/Xyl ratio and on the cellulose crystallinity. However, the anaerobic digestion of cellulose-xylan-lignin nanocomposites showed that the digestion rate decreased significantly in the presence of lignin. Moreover, there was an even more considerable decrease in digestion rate in the presence of GS-type lignin compared to G-type lignin. © Springer Science+Business Media Dordrecht 2013. Source

Monlau F.,French National Institute for Agricultural Research | Trably E.,French National Institute for Agricultural Research | Barakat A.,French National Institute for Agricultural Research | Barakat A.,CNRS Agropolymers Engineering and Emerging Technologies | And 3 more authors.
Environmental Science and Technology | Year: 2013

Because of their rich composition in carbohydrates, lignocellulosic residues represent an interesting source of biomass to produce biohydrogen by dark fermentation. Nevertheless, pretreatments should be applied to enhance the solubilization of holocelluloses and increase their further conversion into biohydrogen. The aim of this study was to investigate the effect of thermo-alkaline pretreatment alone and combined with enzymatic hydrolysis to enhance biohydrogen production from sunflower stalks. A low increase of hydrogen potentials from 2.3 ± 0.9 to 4.4 ± 2.6 and 20.6 ± 5.6 mL of H2 g-1 of volatile solids (VS) was observed with raw sunflower stalks and after thermo-alkaline pretreatment at 55 °C, 24 h, and 4% NaOH and 170 °C, 1 h, and 4% NaOH, respectively. Enzymatic pretreatment alone showed an enhancement of the biohydrogen yields to 30.4 mL of H 2 g-1 of initial VS, whereas it led to 49 and 59.5 mL of H2 g-1 of initial VS when combined with alkaline pretreatment at 55 and 170 °C, respectively. Interestingly, a diauxic effect was observed with sequential consumption of sugars by the mixed cultures during dark fermentation. Glucose was first consumed, and once glucose was completely exhausted, xylose was used by the microorganisms, mainly related to Clostridium species. © 2013 American Chemical Society. Source

El Miri N.,Hassan II University | Abdelouahdi K.,French National Center for Scientific Research | Zahouily M.,Hassan II University | Fihri A.,MAScIR Foundation | And 3 more authors.
Journal of Applied Polymer Science | Year: 2015

Bio-nanocomposite films based on polyvinyl alcohol/chitosan (PVA/CS) polymeric blend and cellulose nanocrystals (CNC) were prepared by casting a homogenous and stable aqueous mixture of the three components. CNC used as nanoreinforcing agents were extracted at the nanometric scale from sugarcane bagasse via sulfuric acid hydrolysis; then they were characterized and successfully dispersed into a PVA/CS (50/50, w/w) blend to produce PVA/CS-CNC bio-nanocomposite films at different CNC contents (0.5, 2.5, 5 wt %). Viscosity measurement of the film-forming solutions and structural and morphological characterizations of the solid films showed that the CNC are well dispersed into PVA/CS blend forming strong interfacial interactions that provide an enhanced load transfer between polymer chains and CNC, thus improving their properties. The obtained bio-nanocomposite films are mechanically strong and exhibit improved thermal properties. The addition of 5 wt % CNC within a PVA/CS blend increased the Young's modulus by 105%, the tensile strength by 77%, and the toughness by 68%. Herein, the utilization of Moroccan sugarcane bagasse as raw material to produce high quality CNC has been explored. Additionally, the ability of the as-isolated CNC to reinforce polymer blends was studied, resulting in the production of the aforementioned bio-nanocomposite films with improved properties. © 2015 Wiley Periodicals, Inc. Source

Boissou F.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources | Sayoud N.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources | De Oliveira Vigier K.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources | Barakat A.,CNRS Agropolymers Engineering and Emerging Technologies | And 3 more authors.
ChemSusChem | Year: 2015

Ball milling of cellulose in the presence of a catalytic amount of H2SO4 was found to be a promising pre-treatment process to produce butyl glycosides in high yields. Conversely to the case of water, n-butanol has only a slight effect on the recrystallization of ball-milled cellulose. As a result, thorough depolymerization of cellulose prior the glycosylation step is no longer required, which is a pivotal aspect with respect to energy consumption. This process was successfully transposed to wheat straw from which butyl glycosides and xylosides were produced in good yields. Butyl glycosides and xylosides are important chemicals as they can be used as hydrotropes but also as intermediates in the production of valuable amphiphilic alkyl glycosides. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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