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Michael M Meagher - One of the best experts on this subject based on the ideXlab platform.
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modeling pichia pastoris growth on Methanol and optimizing the production of a recombinant protein the heavy chain fragment c of botulinum neurotoxin serotype a
Biotechnology and Bioengineering, 2000Co-Authors: Wenhui Zhang, Mark A Bevins, Bradley A Plantz, Leonard A Smith, Michael M MeagherAbstract:An unstructured growth model for the recombinant methylotrophic yeast P. pastoris Mut+ expressing the heavy-chain fragment C of botulinum neurotoxin serotype A [BoNT/A(Hc)], was successfully established in quasi-steady state fed-batch fermentations with varying cell densities. The model describes the relationships between specific growth rate and Methanol Concentration, and the relationships between specific Methanol and ammonium consumption rates and specific growth rate under Methanol-limited growth conditions. The maximum specific growth rate (μ) determined from the model was 0.08 h−1 at a Methanol Concentration of 3.65 g/L, while the actual maximum μ was 0.0709 h−1. The maximum specific Methanol consumption rate was 0.0682 g/g WCW/h. From the model, growth can be defined as either Methanol-limited or Methanol-inhibited and is delineated at a Methanol Concentration of 3.65 g/L. Under inhibited conditions, the observed biomass yield (YX/MeOH) was lower and the maintenance coefficient (mMeOH) was higher than compared to limited Methanol conditions. The YX/MeOH decreased and mMeOH increased with increasing Methanol Concentration under Methanol-inhibited conditions. BoNT/A(Hc) content in cells (α) under inhibited growth was lower than that under limited growth, and decreased with increasing Methanol Concentration. A maximum α of 1.72 mg/g WCW was achieved at a μ of 0.0267 h−1 and induction time of 12 h. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 70: 1–8, 2000.
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modeling pichia pastoris growth on Methanol and optimizing the production of a recombinant protein the heavy chain fragment c of botulinum neurotoxin serotype a
Biotechnology and Bioengineering, 2000Co-Authors: Wenhui Zhang, Mark A Bevins, Bradley A Plantz, Leonard A Smith, Michael M MeagherAbstract:An unstructured growth model for the recombinant methylotrophic yeast P. pastoris Mut(+) expressing the heavy-chain fragment C of botulinum neurotoxin serotype A [BoNT/A(H(c))], was successfully established in quasi-steady state fed-batch fermentations with varying cell densities. The model describes the relationships between specific growth rate and Methanol Concentration, and the relationships between specific Methanol and ammonium consumption rates and specific growth rate under Methanol-limited growth conditions. The maximum specific growth rate (mu) determined from the model was 0.08 h(-1) at a Methanol Concentration of 3.65 g/L, while the actual maximum mu was 0.0709 h(-1). The maximum specific Methanol consumption rate was 0.0682 g/g WCW/h. From the model, growth can be defined as either Methanol-limited or Methanol-inhibited and is delineated at a Methanol Concentration of 3.65 g/L. Under inhibited conditions, the observed biomass yield (Y(X/MeOH)) was lower and the maintenance coefficient (m(MeOH)) was higher than compared to limited Methanol conditions. The Y(X/MeOH) decreased and m(MeOH) increased with increasing Methanol Concentration under Methanol-inhibited conditions. BoNT/A(H(c)) content in cells (alpha) under inhibited growth was lower than that under limited growth, and decreased with increasing Methanol Concentration. A maximum alpha of 1.72 mg/g WCW was achieved at a mu of 0.0267 h(-1) and induction time of 12 h.
Zhongyi Jiang - One of the best experts on this subject based on the ideXlab platform.
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Chitosan membranes filled by GPTMS-modified zeolite beta particles with low Methanol permeability for DMFC
Chemical Engineering and Processing: Process Intensification, 2010Co-Authors: Yabo Wang, Zhongyi Jiang, Dong YangAbstract:Abstract Uniform zeolite beta particles about 800 nm in diameter were synthesized by a hydrothermal method, and functionalized by γ-glycidoxypropyltrimethoxysilane (GPTMS). Subsequently, chitosan (CS) membranes filled by GPTMS-modified zeolite beta particles were prepared, and characterized by SEM, FT-IR, XRD and TGA. Compared with the pure CS and Nafion®117 membrane, these CS/zeolite beta hybrid membranes show apparently the lower Methanol permeability, which could be assigned to the better interfacial morphology and compatibility between the GPTMS-modified zeolite beta particles and chitosan matrix. In all the prepared CS/zeolite beta hybrid membranes, the CS membrane filled by 10 wt.% GPTMS-modified zeolite beta particles exhibits the lowest Methanol permeability, which is 4.4 × 10−7 and 2.2 × 10−7 cm2 s−1 at 2 and 12 M Methanol Concentration, respectively. The proton conductivity of this hybrid membrane is 1.31 × 10−2 S cm−1, which is slightly lower than that of the pure CS membrane. The selectivity of CS/GPTMS-zeolite beta membranes is comparable with Nafion® 117 at 2 M Methanol Concentration, and much higher at 12 M Methanol Concentration.
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zeolite beta filled chitosan membrane with low Methanol permeability for direct Methanol fuel cell
Journal of Power Sources, 2008Co-Authors: Yabo Wang, Dong Yang, Xiaohong Zheng, Zhongyi JiangAbstract:Abstract Zeolite beta particles with different sizes and narrow size distribution were hydrothermally synthesized and incorporated into chitosan (CS) matrix to prepare CS/zeolite beta hybrid membranes for direct Methanol fuel cell (DMFC). It was found that the chitosan membrane filled by zeolite beta particles about 800 nm in size exhibited the lowest Methanol permeability, which can be ascribed to their optimum free volume and Methanol diffusion characteristics. To further improve the performances of CS/zeolite beta hybrid membranes, zeolite beta particles about 800 nm in size were sulfonated via three different approaches. The results indicated that the introduction of sulfonic groups could reduce the Methanol permeability further as a result of the enhanced interfacial interaction between zeolite beta and chitosan matrix. Furthermore, in terms of the overall selectivity index, CS/zeolite beta hybrid membranes were comparable to Nafion ® 117 membrane at low Methanol Concentration (2 mol L −1 ) and much better at high Methanol Concentration (12 mol L −1 ).
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surface modified y zeolite filled chitosan membrane for direct Methanol fuel cell
Journal of Power Sources, 2007Co-Authors: Bin Zheng, Xiaohong Zheng, Jingtao Wang, Weikang Yuan, Zhongyi JiangAbstract:Abstract Hybrid membranes composed of chitosan (CS) as organic matrix and surface-modified Y zeolite as inorganic filler are prepared and their applicability for DMFC is demonstrated by Methanol permeability, proton conductivity and swelling property. Y zeolite is modified using silane coupling agents, 3-aminopropyl-triethoxysilane (APTES) and 3-mercaptopropyl-trimethoxysilane (MPTMS), to improve the organic–inorganic interfacial morphology. The mercapto group on MPTMS-modified Y zeolite is further oxidized into sulfonic group. Then, the resultant surface-modified Y zeolites with either aminopropyl groups or sulfonicpropyl groups are mixed with chitosan in acetic acid solution and cast into membranes. The transitional phase generated between chitosan matrix and zeolite filler reduces or even eliminates the nonselective voids commonly exist at the interface. The hybrid membranes exhibit a significant reduction in Methanol permeability compared with pure chitosan and Nafion117 membranes, and this reduction extent becomes more pronounced with the increase of Methanol Concentration. By introducing –SO 3 H groups onto zeolite surface, the conductivity of hybrid membranes is increased up to 2.58 × 10 −2 S cm −1 . In terms of the overall selectivity index ( β = σ / P ), the hybrid membrane is comparable with Nafion117 at low Methanol Concentration (2 mol L −1 ) and much better (three times) at high Methanol Concentration (12 mol L −1 ).
Mohammad Ali Abdelkareem - One of the best experts on this subject based on the ideXlab platform.
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comparative analysis of liquid versus vapor feed passive direct Methanol fuel cells
Renewable Energy, 2019Co-Authors: Mohammad Ali Abdelkareem, Anis Allagui, Enas Taha Sayed, El Haj M Assad, Zafar Said, Khaled ElsaidAbstract:Abstract Passive direct Methanol fuel cells (pDMFCs) have several advantages such as high theoretical energy density, quick refueling and environmentally safe. However, Methanol crossover (MCO) is one of the major challenges to the commercialization of pDMFCs. Significant progress has been achieved over the last few years in controlling MCO through different approaches, such as applying porous plate, pervaporative membranes, and so forth. These methods are mainly based on supplying Methanol to the anode surface in vapor phase. Thus, two types of pDMFCs are available: low Methanol Concentration (liquid-feed pDMFC) and high Methanol Concentration (vapor-feed pDMFC). The Methanol and water transports are different in these two types of cells. Moreover, under low operating temperature and at high Methanol Concentration (i.e., above 50 mol%) in the vapor-feed pDMFC, the possibility for chemical intermediate to form increases. Such intermediates not only decrease the efficiency of the cell but are also harmful for the health and the environment. The aim of this review is to highlight and clarify the differences between liquid and vapor-feed pDMFCs. Moreover, the mechanism of intermediates formation in vapor-feed pDMFC and the different approaches to controlling it are presented. Finally, we present recommendations for designing safe and high performance pDMFCs.
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development of a passive direct Methanol fuel cell stack for high Methanol Concentration
Journal of Power Sources, 2010Co-Authors: Takuya Tsujiguchi, Mohammad Ali Abdelkareem, Takuya Kudo, Nobuyoshi Nakagawa, Tatehiro Shimizu, Michio MatsudaAbstract:Abstract In order to develop a vertically arranged passive DMFC with a porous carbon plate, PCP, the effect of the head height of the Methanol solution in contact with the porous carbon plate on the power generation was investigated for a 55 mm height using a single cell. The single cell was operated at several Methanol Concentrations greater than 70 wt%. By filling the reservoir with 90 and 100 wt% Methanol solutions, power densities greater than 30 mW cm −2 for over 10 h were demonstrated. Based on the result of the single cell study, a passive DMFC stack consisting of 8 unit cells with the PCP was designed and fabricated. The power generation characteristics were then experimentally measured. The maximum power output of 1.8 W, which was almost 10% lower than that expected from the single cell performance, was obtained with 100% Methanol. At the same time, a nonuniform cell voltage among the 8 unit cells was found as a reason for the decreasing power output with the increasing current.
Rong Chen - One of the best experts on this subject based on the ideXlab platform.
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effects of anode microporous layers made of carbon powder and nanotubes on water transport in direct Methanol fuel cells
Journal of Power Sources, 2009Co-Authors: Tianshou Zhao, Rong Chen, Weiwei YangAbstract:The effects of the design parameters of the anode diffusion layer (DL), including the PTFE loading in the backing layer (BL), and the carbon and PTFE loading in the microporous layer (MPL), on water transport through the membrane and the performance of a liquid-feed direct Methanol fuel cell (DMFC) are experimentally investigated. The results indicate that increasing the PTFE loading in the BL and introducing a MPL could decrease water crossover through the membrane without sacrificing cell performance when the feed Methanol Concentration is increased. It is also found that changing the PTFE loading in the MPL has little effect on water crossover, whereas increasing the carbon loading in the MPL could noticeably decrease the water-crossover flux. Nevertheless, the ability of the MPL to reduce water crossover is limited by the presence of a number of mud cracks. To reduce further the water-crossover flux, a crack-free MPL made of multi-walled carbon nanotubes (MWCNTs) and PTFE is proposed. Tests indicate that the DMFC with the nanotube MPL results in a much lower water-crossover flux than a conventional carbon-powder MPL. More importantly, the use of the nanotube MPL allows the DMFC to be operated with a higher Methanol Concentration, and thereby increases the fuel cell system energy density.
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effect of membrane thickness on the performance and efficiency of passive direct Methanol fuel cells
Journal of Power Sources, 2006Co-Authors: Jianguo Liu, Zhenxing Liang, Rong ChenAbstract:The use of various Nafion membranes, including Nafion 117, 115 and 112 with respective thicknesses of 175 μm, 125 μm and 50 μm, in a passive direct Methanol fuel cell (DMFC) was investigated experimentally. The results show that when the passive DMFC operated with a lower Methanol Concentration (2.0 M), a thicker membrane led to better performance at lower current densities, but exhibited lower performance at higher current densities. When the Methanol Concentration was increased to 4.0 M, however, the three membranes exhibited similar cell voltages over a wide range of current densities. In contrast, this work also shows the polarization behaviors in an active DMFC when the three membranes were substantially different. Finally, the test of fuel utilization indicates that the passive DMFC with a thicker membrane exhibited higher efficiency.
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the effect of Methanol Concentration on the performance of a passive dmfc
Electrochemistry Communications, 2005Co-Authors: Tianshou Zhao, Rong Chen, Chungwai WongAbstract:Abstract A passive, air-breathing liquid feed direct Methanol fuel cell (DMFC), with no external pumps or other auxiliary devices, was designed, fabricated and tested with different Methanol Concentrations. It was found that the cell performance was improved substantially with an increase in Methanol Concentration; a maximum of power density of 20 mW/cm 2 was achieved with 5.0 M Methanol solution. The measurements indicated that the better performance with higher Methanol Concentrations was mainly attributed to the increase in the cell operating temperature caused by the exothermic reaction between permeated Methanol and oxygen on the cathode. This finding was subsequently confirmed by the fact that the cell performance was degraded, when the cell running with higher Methanol Concentrations was cooled down to room temperature.
Ulrike Krewer - One of the best experts on this subject based on the ideXlab platform.
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sensing Methanol Concentration in direct Methanol fuel cell with total harmonic distortion theory and application
Electrochimica Acta, 2012Co-Authors: Ulrike KrewerAbstract:Abstract The nonlinear frequency response of a direct Methanol fuel cell (DMFC) is studied by analyzing the total harmonic distortion (THD) spectra. The dependence of the THD spectra on Methanol Concentration and Methanol oxidation kinetics is investigated by means of both simulation and experiment. Simulation using a continuous stirred tank reactor network model suggests that the Methanol Concentration profile in the anode has a strong impact on the THD spectra. The experimentally observed nonlinear behavior of the DMFC anode can be qualitatively reproduced with a model containing a three-step Methanol oxidation mechanism with Kauranen–Frumkin/Temkin kinetics. Both experiment and simulation results show that THD value has a monotonic correlation with Methanol Concentration at certain frequencies and its sensitivity to Concentration is improved with increased current amplitude. The monotonic relationship enables the THD to sense the Methanol Concentration level by the DMFC itself, which is of mayor interest for the portable application as an external sensor for the system can be omitted.
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simple and reliable model for estimation of Methanol cross over in direct Methanol fuel cells and its application on Methanol Concentration control
Energy and Environmental Science, 2011Co-Authors: Ulrike Krewer, Federico ZenithAbstract:A simplified model of mass-transport phenomena on the anodic side of direct Methanol fuel cells (DMFCs) is presented, with the objective of estimating the cross-over flux in order to enable feedforward (sensorless) control of anodic Concentration in DMFC systems. The effect of parameter uncertainty on the tracking error of the control system is analysed and several models for temperature dependence are proposed. Experimental data on Methanol cross-over was gathered in a DMFC system, and the models were discriminated by means of nonlinear regression. The regression results and an initial test run indicate that feedforward control of anodic Methanol Concentration in DMFC systems is feasible.