排序方式: 共有53条查询结果,搜索用时 46 毫秒
31.
Desislava Jivkova Ganesan Sathiyanarayanan Mourad Harir Norbert Hertkorn Philippe Schmitt-Kopplin Ghislain Sanhaji Sylvain Fochesato Catherine Berthomieu Alain Heyraud Wafa Achouak Catherine Santaella Thierry Heulin 《Molecules (Basel, Switzerland)》2022,27(21)
The current study examines the desiccation-resistant Ramlibacter tataouinensis TTB310T as a model organism for the production of novel exopolysaccharides and their structural features. This bacterium is able to produce dividing forms of cysts which synthesize cell-bound exopolysaccharide. Initial experiments were conducted on the enrichment of cyst biomass for exopolysaccharide production under batch-fed conditions in a pilot-scale bioreactor, with lactate as the source of carbon and energy. The optimized medium produced significant quantities of exopolysaccharide in a single growth phase, since the production of exopolysaccharide took place during the division of the cysts. The exopolysaccharide layer was extracted from the cysts using a modified trichloroacetic acid method. The biochemical characterization of purified exopolysaccharide was performed by gas chromatography, ultrahigh-resolution mass spectrometry, nuclear magnetic resonance, and Fourier-transform infrared spectrometry. The repeating unit of exopolysaccharide was a decasaccharide consisting of ribose, glucose, rhamnose, galactose, mannose, and glucuronic acid with the ratio 3:2:2:1:1:1, and additional substituents such as acetyl, succinyl, and methyl moieties were also observed as a part of the exopolysaccharide structure. This study contributes to a fundamental understanding of the novel structural features of exopolysaccharide from a dividing form of cysts, and, further, results can be used to study its rheological properties for various industrial applications. 相似文献
32.
Midouni Adnene Houchati Mohamed Ikbel Selmi Wafa Jaouadi Mouna Yahya Mondher Hamzaoui Ahmed Hichem 《Journal of Solid State Electrochemistry》2019,23(8):2465-2475
Journal of Solid State Electrochemistry - Pr0.2Ce0.8O2-δ@Li2CO3 (PDC-LC) nanocomposite electrolytes were prepared through the co-precipitation of Pr-doped cerium/lithium complex carbonate and... 相似文献
33.
Shona Duncan Qing Jing Adrian Katona Romas J. Kazlauskas Jonathan Schilling Ulrike Tschirner Waleed Wafa AlDajani 《Applied biochemistry and biotechnology》2010,160(6):1637-1652
The recalcitrance of lignocellulosic biomass to enzymatic release of sugars (saccharification) currently limits its use as
feedstock for biofuels. Enzymatic hydrolysis of untreated aspen wood releases only 21.8% of the available sugars due primarily
to the lignin barrier. Nature uses oxidative enzymes to selectively degrade lignin in lignocellulosic biomass, but thus far,
natural enzymes have been too slow for industrial use. In this study, oxidative pretreatment with commercial peracetic acid
(470 mM) removed 40% of the lignin (from 19.9 to 12.0 wt.% lignin) from aspen and enhanced the sugar yields in subsequent
enzymatic hydrolysis to about 90%. Increasing the amount of lignin removed correlated with increasing yields of sugar release.
Unfortunately, peracetic acid is expensive, and concentrated forms can be hazardous. To reduce costs and hazards associated
with using commercial peracetic acid, we used a hydrolase to catalyze the perhydrolysis of ethyl acetate generating 60–70 mM
peracetic acid in situ as a pretreatment to remove lignin from aspen wood. A single pretreatment was insufficient, but multiple
cycles (up to eight) removed up to 61.7% of the lignin enabling release of >90% of the sugars during saccharification. This
value corresponds to a predicted 581 g of fermentable sugars from 1 kg of aspen wood. Improvements in the enzyme stability
are needed before the enzymatically generated peracetic acid is a commercially viable alternative. 相似文献
34.
35.
Wafa Arsalane Bernard Rousseau Jean-Claude Duval 《Photochemistry and photobiology》1994,60(3):237-243
Abstract In a study of the relationship between nonphotochemical quenching of fluorescence and the xanthophyll cycle, we show that the diatom Phaeodactylum tricornutum exhibits several interesting characteristics. This xanthophyll cycle consists of only one reversible epoxidating/deepoxidating step (diadinoxanthiddiatoxanthin). Diadinoxan-thin, which increases from 8 to 17 molecules/100 chlorophyll a (Chl a ) during the ageing of the culture, was present as two separate pools, with a portion (of about 5 molecules/100 Chl a) which was never deepoxidated. Under a defined irradiance, the time necessary to abolish net photosynthesis increases with the pool size of diadinoxanthin available for deepoxidation. A close correlation is found between nonphotochemical quenching and the relative ratio of diatoxanthin until the photosytem II center is inactivated. The photoprotective effect of diadinoxanthin deepoxidation is limited to the phase during which quenching of the minimum fluorescence (F0 ) develops. 相似文献
36.
Ricerche di Matematica - Let D be an integral domain. We associate to a semistar operation $$\star $$ on D, a semistar operation $$*$$ on D[[X]]. We prove that if D satisfies the $$\star _f$$... 相似文献
37.
Wafa I. Abdel-Fattah M.SH. Fayed SH.R. Gooda W.F.F. Mekky 《Journal of Sol-Gel Science and Technology》1998,13(1-3):981-985
-Eucryptite solid solution (LAS) Li2O : Al 2O3 : 3SiO2(113) was prepared via a sol-gel route. Complex solutions of lithium or aluminum salts in ethanol/water mixtures were catalysed by inorganic acids (catalyst/alkoxide ratio 0.1). Different ratios of H2SO4 catalyst were also used.TGA showed that the maximum % yield of LAS 113 occurred using H2SO4 catalyst. Above 400°C exothermic peaks occurred in DSC followed by the glass transition. XRD and IR showed a high crystallinity of -eucryptite solid solution using all acids at the 0.1 ratio with the highest crystallinity for the 0.05 H2SO4 ratio. SEM revealed similar grain sizes in spite of higher acid concentrations. XRD data indicated a change to a tetragonal modification with higher catalyst ratio. 相似文献
38.
Saida Belarbi Martin Vivier Wafa Zaghouani Aude De Sloovere Valerie Agasse Pascal Cardinael 《Molecules (Basel, Switzerland)》2021,26(21)
Pesticide extraction in rapeseed samples remains a great analytical challenge due to the complexity of the matrix, which contains proteins, fatty acids, high amounts of triglycerides and cellulosic fibers. An HPLC-MS/MS method was developed for the quantification of 179 pesticides in rapeseeds. The performances of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method were evaluated using different dispersive solid-phase extraction (d-SPE) sorbents containing common octadecylsilane silica/primary–secondary amine adsorbent (PSA/C18) and new commercialized d-SPE materials dedicated to fatty matrices (Z-Sep, Z-Sep+, and EMR-Lipid). The analytical performances of these different sorbents were compared according to the SANTE/12682/2019 document. The best results were obtained using EMR-Lipid in terms of pesticide average recoveries (103 and 70 of the 179 targeted pesticides exhibited recoveries within 70–120% and 30–70%, respectively, with low RSD values). Moreover, the limits of quantification (LOQ) range from 1.72 µg/kg to 6.39 µg/kg for 173 of the pesticides. Only the recovery for tralkoxydim at 10 μg/kg level was not satisfactory (29%). The matrix effect was evaluated and proved to be limited between −50% and 50% for 169 pesticides with this EMR-Lipid and freezing. GC-Orbitrap analyses confirmed the best efficiency of the EMR-Lipid sorbent for the purification of rapeseeds. 相似文献
39.
Nonlinear Dynamics - The compass-gait biped robot is a two-DoF legged mechanical system that has been known by its passive dynamic walking. This kind of passive biped robot is modeled by an... 相似文献
40.
Ksila Wafa Younes Mohamed Kadri Ghorbel Abdelhamid Rives Alain 《Journal of Sol-Gel Science and Technology》2021,99(2):376-390
Journal of Sol-Gel Science and Technology - Our work is focused on the research of new zirconia doped telluric acid catalysts prepared with sol–gel method. Optimization of different... 相似文献