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Efficient H2 production via Chlamydomonas reinhardtii
En savoir plusPublication year: 2011 Source: Trends in Biotechnology, In Press, Corrected Proof, Available online 25 July 2011 Maria G., Esquível , Helena M., Amaro , Teresa S., Pinto , Pedro S., Fevereiro , F. Xavier, Malcata Molecular hydrogen (H2) obtained from biological sources provides an alternative to bulk chemical processes that is moving towards large-scale, economical generation of clean fuel for automotive engines. This opinion article examines recent improvements in H2 production by wild and mutant strains of Chlamydomonas reinhardtii – the green microalga currently considered the best eukaryotic H2 producer. Here, we review various aspects of genetic and metabolic engineering of C. reinhardtii, as well as of process engineering. Additionally, we lay out possible scenarios that would lead to more efficient research approaches in the near future, as part of a consistent strategy for sustainable...
Date : 08/01/2012 - Editeur : ScienceDirect
A novel ZnO
En savoir plusPublication year: 2011 Source: Chemical Engineering Journal, In Press, Accepted Manuscript, Available online 27 July 2011 Simelys-Pris, Hernández , Martina, Chiappero , Nunzio, Russo , Debora, Fino The aim of this work, which was carried out as part of the BioH2Power project, was to identify a system for both the desulphurization and dehalogenation of landfill biogas at ambient temperature. Such a system should be capable of reducing, to less than 1 ppmv, the substances that are present in the biogas which are considered undesirable for both reforming and Molten Carbonate Fuel Cell (MCFCs) catalysts. The principal goal was to identify a multifunctional adsorption bed that would be able to purify the landfill biogas to sulphur and chlorine concentrations of below 1 ppmv, with a high removal efficiency...
Date : 08/01/2012 - Editeur : ScienceDirect
Interplay among culture parameters, light, mixing, and photobioreactor configuration during H2 production by sulfur
En savoir plusPublication year: 2011 Source: International Journal of Hydrogen Energy, In Press, Corrected Proof, Available online 31 July 2011 T., Zhang The interplay among the culture parameters, light intensity and illumination conditions, mechanical mixing conditions, and reactor configurations during O2 evolution and H2 production in sulfur-deprived Chlamydomonas reinhardtii cultures is studied in this work. The advective-diffusive reaction equation is used to describe the diffusion and the local biochemical reactions of the species involved in the biological process for H2 production. Solutions of the diffusion equation are obtained for different boundary conditions. An empirical equation is used to describe the relation between the light attenuation coefficient and the initial chlorophyll concentration, which characterizes both the culture absorption property and the mechanical mixing... Highlights: ? We model the interplay among key parameters in tubular photobioreactor during H2 production. ? We use empirical light attenuation function to characterize both culture optical property and mechanical mixing condition. ? Tubular reactor is more favorite for H2 production than flat plate reactor under the given condition. ? High light intensity is preferred for high initial cell concentration in H2 production.
Date : 08/01/2012 - Editeur : ScienceDirect
Increased H2 production in the cyanobacterium Synechocystis sp. strain PCC 6803 by redirecting the electron supply via genetic engineering of the nitrate assimilation pathway
En savoir plusPublication year: 2011 Source: Metabolic Engineering, In Press, Accepted Manuscript, Available online 2 August 2011 Wipawee, Baebprasert , Saowarath, Jantaro , Wanthanee, Khetkorn , Peter, Lindblad , Aran, Incharoensakdi The unicellular cyanobacterium Synechocystis sp. strain PCC 6803 contains a single bidirectional NiFe-Hox-hydrogenase which evolves hydrogen under certain environmental conditions. The nitrate assimilation pathway is a potential competing pathway which may reduce the electron flow to the hydrogenase and thereby limit hydrogen production. To improve H2 production, the nitrate assimilation pathway was disrupted by genetic engineering to redirect the electron flow towards the Hox-hydrogenase. Mutant strains disrupted in either nitrate reductase (?narB) or nitrite reductase (?nirA) or both nitrate reductase and nitrite reductase (?narB:?nirA) were constructed and tested for their ability to produce hydrogen. H2 production and Hox-hydrogenase activities in... Highlights: ? We create mutants of Synechocystis 6803 disrupted in the nitrate assimilation pathway.? Engineered cells show significantly higher H2 production.? Only minor changes in transcript and activity of Hox-hydrogenase in engineered cells.? High rate of H2 production by redirecting the electron flow to the Hox-hydrogenase.
Date : 08/01/2012 - Editeur : ScienceDirect
Synergy effect of MgO and ZnO in a Ni/Mg–Zn–Al catalyst during ethanol steam reforming for H2
En savoir plusPublication year: 2011 Source: Catalysis Today, In Press, Corrected Proof, Available online 27 August 2011 Guangming, Zeng , Qinghua, Liu , Ruixue, Gu , Lihong, Zhang , Yongdan, Li Nickel based mixed oxide catalysts derived from Ni–Mg–Zn–Al hydrotalcite-like precursors are prepared and evaluated for H2-rich gas production via ethanol steam reforming. It has been found that the catalyst properties (e.g. BET surface area, Ni dispersion and reducibility) and catalytic performance depend on the Mg:Zn molar ratio. MgO and ZnO have a synergetic effect. At 700°C, the quaternary catalyst with a Mg:Zn ratio of 4 exhibits the highest H2 yield and best stability, viz. no apparent variation of the product distribution over 100h operation, whereas the ternary catalyst without Mg suffers severe coke accumulation after 7h on-stream. Two types of... Graphical abstract: Long-term stability test over a catalyst with Mg:Zn ratio=4 at 700°C. Highlights: ? Ni/Mg–Zn–Al catalysts derived from hydrotalcite-like precursors are active in ethanol steam reforming. ? The quaternary catalyst with a Mg:Zn ratio of 4 is hard to reduce, has a high Ni dispersion and good catalytic performance. ? TPO and HR-TEM verify that two types of carbon deposited on the catalyst surface.
Date : 08/01/2012 - Editeur : ScienceDirect
Photoresponse and H2 production of topographically controlled PEG assisted Sol–gel WO3 nanocrystalline thin films
En savoir plusPublication year: 2011 Source: International Journal of Hydrogen Energy, In Press, Corrected Proof, Available online 27 August 2011 N., Naseri , S., Yousefzadeh , E., Daryaei , A.Z., Moshfegh WO3 thin films were fabricated by sol–gel method using polyethylene glycol (PEG) as dispersing agent. Physical and photoelectrochemical properties of the synthesized nanocrystalline films were studied by varying weight ratio of PEG to tungsten precursor (x). Based on AFM observations and statistical modeling of the WO3 surface, the thickness of the films increased by increasing the amount of x with a nearly linear fashion while the surface roughness reached to a saturated value. However, the film synthesized with x = 4 showed a chaotic surface behavior. Optical analysis revealed that by increasing the x, transmittance of the films decreased while their band... Highlights: ? WO3 thin films were synthesized containing different amount of PEG using sol–gel method. ? Thickness of the films increased linearly by increasing PEG concentration. ? Also linear increasing behavior was observed for PEC response and H2 generation of samples. ? Modeling the surface topography data showed the surface roughness saturated in 0.5 = x. ? Transport life time of the electrons in the films decreased by increasing PEG amount.
Date : 08/01/2012 - Editeur : ScienceDirect
g
En savoir plusPublication year: 2011 Source: International Journal of Hydrogen Energy, In Press, Corrected Proof, Available online 31 August 2011 Xiaoxiang, Xu , Gang, Liu , Chamnan, Randorn , John T.S., Irvine A highly active photocatalyst based on g-C3N4 coated SrTiO3 has been synthesized simply by decomposing urea in the presence of SrTiO3 at 400 °C. The catalyst demonstrates a high H2 production rate ~440 µmol h-1/g catalyst in aqueous solution under visible light irradiation, which is much higher than conventional anion doped SrTiO3 or physical mixtures of g-C3N4 and SrTiO3. The improved photocatalytic activity can be ascribed to the close interfacial connections between g-C3N4 and SrTiO3 where photo-generated electron and holes are effectively separated. The newly synthesized catalyst also exhibited a stable performance in the repeated experiments. Highlights: ? Synthesis of a photocatalyst based on g-C3N4 coated SrTiO3. ? The catalyst shows high activity for H2 production. ? The special structure is responsible for high activity.
Date : 08/01/2012 - Editeur : ScienceDirect
H2 blockers decrease gut mucus production and lead to barrier dysfunction in vitro
En savoir plusPublication year: 2011 Source: Surgery, Volume 150, Issue 4, October 2011, Pages 736-743 Lawrence N. Diebel, David M. Liberati, Lisa Hall-Zimmerman BackgroundPneumonia and other gut-related infectious complications have been associated with the use of histamine 2 (H2) receptor antagonists such as cimetidine in critically ill patients. The mechanism(s) may include acid suppression with resultant effects on the gut flora. Other possibilities include immunologic effects and perturbation of gut barrier function. Recent work has demonstrated the importance of mucus on the gastrointestinal mucosal barrier. We studied the effect of cimetidine on mucus production and mucosal barrier function in vitro.MethodsHT29–MTX, a mucus-producing intestinal epithelial cell line, was used. HT29–MTX cell monolayers were grown to confluence in the presence of cimetidine for 0, 3, or 6 days. Mucus production was quantified by Western Blot analysis and O-linked oligosaccharide chain release and mucin content by enzyme-linked immunosorbent assay. Fluorescein-labeledEscherichia coli(EC) or unlabeled EC were added to quantify bacterial adherence (60-min co-culture) and passage thru HT29–MTX cell monolayers (120-min co-culture), respectively.ResultsCimetidine treatment decreased mucus/mucin content after 3 or 6 days of treatment. The effect was more profound after 6 days. There was nearly a 2-fold increase in passage of EC across HT29–MTX monolayers after cimetidine treatment.ConclusionCimetidine seems to contribute to gut barrier dysfunction by its effect on mucus production. This study supports the increasing clinical suspicion that routine administration of H2 blockers in critically ill patients may be ill advised.
Date : 08/01/2012 - Editeur : ScienceDirect
Properties and H2 production ability of Pt photodeposited on the anatase phase transition of nitrogen
En savoir plusPublication year: 2011 Source: International Journal of Hydrogen Energy, In Press, Corrected Proof, Available online 14 June 2011 Bing-Shun, Huang , Ming-Yen, Wey The effect of calcination temperature on the properties and H2 production ability of nitrogen-doped (N-doped) titanium dioxide (TiO2) photodeposited with 0.2 wt% Pt (platinum) was studied. The increase in crystallinity of pre-calcinated N-doped TiO2 initiated at temperatures higher than 131 °C transformed the morphology from anomalous nanostructure to texture composed of nanoparticles and enhanced the specific surface areas. At 200–400 °C, the anatase peaks gradually became sharper and the visible light absorption region decreased due to the growth of crystallites and the decrease of N-doping content, respectively. Maximum H2 production was reached when N-doped TiO2 was calcined at 200 °C followed by Pt photodeposition.... Highlights: ? N-doped content decreases with increasing calcination temperature. ? Structure transformation from anomalous to texture enables growth of SBET. ? Pt/N-doped TiO2 has high SBET and excellent visible light absorption ability.
Date : 23/07/2011 - Editeur : ScienceDirect
TOWARDS H2
En savoir plusPublication year: 2011 Source: Journal of Power Sources, In Press, Accepted Manuscript, Available online 15 June 2011 Aline Lima da, Silva , Iduvirges Lourdes, Müller In this work, the Gibbs energy minimization method is applied to investigate the unmixed steam reforming (USR) of methane to generate hydrogen for fuel cell application. The USR process is an advanced reforming technology that relies on the use of separate air and fuel/steam feeds to create a cyclic process. Under air flow (first half of the cycle), a bed of Ni-based material is oxidized, providing the heat necessary for the steam reforming that occurs subsequently during fuel/steam feed stage (second half of the cycle). In the presence of CaO sorbent, high purity hydrogen can be produced in a single...
Date : 23/07/2011 - Editeur : ScienceDirect
