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81.
Yinglai Teng Elinor L. Scott Johan P. M. Sanders 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(10):1458-1465
BACKGROUND: Amino acids are promising feedstocks for the chemical industry due to their chemical functionality. They can be obtained by the hydrolysis of potentially inexpensive protein streams such as the byproduct of biofuel production. However, individual amino acids are required before they can be used for the further production of chemicals. Here, the separation of L‐aspartic acid (Asp) and L‐glutamic acid (Glu) mixture, which can be isolated from protein hydrolysis solutions at low pH or from electrodialysis of complex amino acid mixtures, was studied. RESULTS: Glu was converted into L‐pyroglutamic acid (pGlu) which can be separated from the mixture of Asp and Glu due to its higher solubility in water. The conversion was carried out under aqueous or melt conditions. Under aqueous conditions, the conversion was studied as a factor of time, temperature and the amount of Glu. The conversion was specific with high yield and not effected by Asp. After pGlu was separated from Asp and residual Glu by solubility difference, it can be transferred back to Glu through hydrolysis. CONCLUSION: The conversion of Glu to pGlu is specific and can be applied to separation Asp and Glu for their use in the production of bio‐based chemicals. Copyright © 2012 Society of Chemical Industry 相似文献
82.
Synthesis of C‐Glucosylated Octaketide Anthraquinones in Nicotiana benthamiana by Using a Multispecies‐Based Biosynthetic Pathway 下载免费PDF全文
Dr. Johan Andersen‐Ranberg Dr. Kenneth Thermann Kongstad Dr. Majse Nafisi Prof. Dan Staerk Finn Thyge Okkels Prof. Uffe Hasbro Mortensen Prof. Birger Lindberg Møller Dr. Rasmus John Normand Frandsen Dr. Rubini Kannangara 《Chembiochem : a European journal of chemical biology》2017,18(19):1893-1897
Carminic acid is a C‐glucosylated octaketide anthraquinone and the main constituent of the natural dye carmine (E120), possessing unique coloring, stability, and solubility properties. Despite being used since ancient times, longstanding efforts to elucidate its route of biosynthesis have been unsuccessful. Herein, a novel combination of enzymes derived from a plant (Aloe arborescens, Aa), a bacterium (Streptomyces sp. R1128, St), and an insect (Dactylopius coccus, Dc) that allows for the biosynthesis of the C‐glucosylated anthraquinone, dcII, a precursor for carminic acid, is reported. The pathway, which consists of AaOKS, StZhuI, StZhuJ, and DcUGT2, presents an alternative biosynthetic approach for the production of polyketides by using a type III polyketide synthase (PKS) and tailoring enzymes originating from a type II PKS system. The current study showcases the power of using transient expression in Nicotiana benthamiana for efficient and rapid identification of functional biosynthetic pathways, including both soluble and membrane‐bound enzymes. 相似文献
83.
Tomislav Hengl Johan G. B. Leenaars Keith D. Shepherd Markus G. Walsh Gerard B. M. Heuvelink Tekalign Mamo Helina Tilahun Ezra Berkhout Matthew Cooper Eric Fegraus Ichsani Wheeler Nketia A. Kwabena 《Nutrient Cycling in Agroecosystems》2017,109(1):77-102
Spatial predictions of soil macro and micro-nutrient content across Sub-Saharan Africa at 250 m spatial resolution and for 0–30 cm depth interval are presented. Predictions were produced for 15 target nutrients: organic carbon (C) and total (organic) nitrogen (N), total phosphorus (P), and extractable—phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), aluminum (Al) and boron (B). Model training was performed using soil samples from ca. 59,000 locations (a compilation of soil samples from the AfSIS, EthioSIS, One Acre Fund, VitalSigns and legacy soil data) and an extensive stack of remote sensing covariates in addition to landform, lithologic and land cover maps. An ensemble model was then created for each nutrient from two machine learning algorithms—random forest and gradient boosting, as implemented in R packages ranger and xgboost—and then used to generate predictions in a fully-optimized computing system. Cross-validation revealed that apart from S, P and B, significant models can be produced for most targeted nutrients (R-square between 40–85%). Further comparison with OFRA field trial database shows that soil nutrients are indeed critical for agricultural development, with Mn, Zn, Al, B and Na, appearing as the most important nutrients for predicting crop yield. A limiting factor for mapping nutrients using the existing point data in Africa appears to be (1) the high spatial clustering of sampling locations, and (2) missing more detailed parent material/geological maps. Logical steps towards improving prediction accuracies include: further collection of input (training) point samples, further harmonization of measurement methods, addition of more detailed covariates specific to Africa, and implementation of a full spatio-temporal statistical modeling framework. 相似文献
84.
Sven van der Gijp Johan E. ten Elshof Oliver Steigelmann Henk Verweij 《Journal of the American Ceramic Society》2000,83(10):2610-2612
The influence of mechanical stress and chemical homogeneity on the permittivity of BaTi0.9 Zr0.1 O3 ceramics prepared from mixed-oxide and hydrothermal powders was studied. To reduce stress, liquid-phase sintering was applied in conjunction with a low heating rate to stimulate the formation of large grains. The influence of chemical homogeneity was studied by variations in sintering temperatures and times. For both types of ceramics, the dielectric constant at the Curie temperature was influenced by both factors, but to a different extent. In the mixed oxide ceramic, chemical homogeneity played a more prominent role, while internal stress appeared to exert a larger influence in the hydrothermal ceramics. The dielectric constant at the Curie temperature could be increased by 5%–10% by an annealing treatment at 200°C, followed by slow cooling. 相似文献
85.
Toon Verstraelen Bartłomiej M. Szyja David Lesthaeghe Reinout Declerck Veronique Van Speybroeck Michel Waroquier Antonius P. J. Jansen Alexander Aerts Lana R. A. Follens Johan A. Martens Christine E. A. Kirschhock Rutger A. van Santen 《Topics in Catalysis》2009,52(9):1261-1271
Zeolite synthesis is driven by structure-directing agents, such as tetrapropyl ammonium ions (TPA+) for Silicalite-1 and ZSM-5. However, the guiding role of these organic templates in the complex assembly to highly ordered
frameworks remains unclear, limiting the prospects for advanced material synthesis. In this work, both static ab initio and
dynamic classical modeling techniques are employed to provide insight into the interactions between TPA+ and Silicalite-1 precursors. We find that as soon as the typical straight 10-ring channel of Silicalite-1 or ZSM-5 is formed
from smaller oligomers, the TPA+ template is partially squeezed out of the resulting cavity. Partial retention of the template in the cavity is, however,
indispensable to prevent collapse of the channel and subsequent hydrolysis.
相似文献
Rutger A. van Santen (Corresponding author)Email: |
86.
N‐Hydroxyethylcarbazole (EtOHCz) was electropolymerized on carbon fiber microelectrodes (CFMEs). The polyEtOHCz‐modified CFME was characterized with FTIR‐ATR, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The polymer/CFME electrode exhibited the capacitive behavior and also good stability up to 2.0 V. The presence of hydoxylic group of the monomer seems to be an advantage on polymerization because of the unpaired electrons of oxygen, which would make ease at first stage for the adsorbtion on carbon fiber. The estimated value of the low‐frequency redox capacitance (CLF) was found to increase with increasing dc potential. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
87.
88.
Richard Lakerveld Herman J.M. Kramer Andrzej I. Stankiewicz Johan Grievink 《Chemical Engineering and Processing: Process Intensification》2010
The design of current industrial crystallizers is strongly focussed on optimization of known types of crystallization equipment. These crystallizers harbour various physical phenomena, which are strongly entangled. The application of generic principles of process intensification (PI) to crystallization processes requires individual control over physical phenomena. A new design method is applied that exploits elementary processing functions as building blocks for design instead of existing equipment, which enables the application of generic principles of PI. Innovations in the field of crystallization to manipulate shear forces, manipulate nucleation rates with external fields, and improve control over solvent removal with membranes are key technologies. A case study demonstrates the application of task-based design for solution crystallization. The results show how task-based design leads to high modularization of the process representation and model architecture. In addition, task-based design enables the application of generic PI principles, which results in a large flexibility to manipulate final product quality. Future needs include generalization of task-based design for crystallization and development of novel technologies for single task manipulation. 相似文献
89.
Ron Zevenhoven Anders Wiklund Johan Fagerlund Sanni Eloneva Ben In’t Veen Hans Geerlings Gert Van Mossel Harold Boerrigter 《Frontiers of Chemical Engineering in China》2010,4(2):110-119
The use of carbon dioxide (CO2) and calcium-containing by-products from industrial activities is receiving increasing interest as a route to valuable carbonate
materials while reducing CO2 emissions and saving natural resources. In this work, wet-chemical experimental data was assessed, which involved the carbonation
of three types of materials in aqueous solutions, namely, 1) wollastonite, a calcium silicate mineral, 2) steelmaking slag,
a by-product of steel production, and 3) paper bottom ash (PBA) from waste paper incineration. Aims were to achieve either
a high carbonation degree and/or a pure carbonate product with potential commercial value. Producing a pure precipitated calcium
carbonate (PCC) material that may find use in paper industry products puts strong requirements on purity and brightness. The
parameters investigated were particle size, CO2 pressure, temperature, solid/liquid ratio, and the use of additives that affect the solubilities of CO2 and/or calcium carbonate. Temperatures and pressures were varied up to 180°C and 4 MPa. Data obtained with the wollastinite
mineral allowed for a comparison between natural resources and the industrial by-product materials, the latter typically being
more reactive. With respect to temperature and pressure trends reported by others were largely confirmed, with temperatures
above 150°C introducing thermodynamic limitations depending on CO2 pressure. The influence of additives showed some promise, although costs may make recycling and reuse of additives a necessity
for a large-scale process. When using steelmaking slag, magnetic separation may remove some iron-containing material from
the process (although this is far from perfect), while the addition of bicarbonate supported the removal of phosphorous, aside
from improving calcium extraction. The experiments with paper bottom ash (PBA) gave new data, showing that its reactivity
resembles that of steelmaking slag, while its composition results in relatively pure carbonate product. Also, with PBA no
additives were needed to achieve this. 相似文献
90.
Emma Söderhjelm Matthew P. House Neil Cruise Johan Holmberg Michael Bowker Jan-Olov Bovin Arne Andersson 《Topics in Catalysis》2008,50(1-4):145-155
Methanol oxidation to formaldehyde was studied over a series of Fe–Mo–O catalysts with various Mo/Fe atomic ratio and the end compositions Fe2O3 and MoO3. The activity data show that the specific activity passes through a maximum with increase of the Mo content and is the highest for Fe2(MoO4)3. The selectivity to formaldehyde, on the other hand, increases with the Mo content in the catalyst. A synergy effect is observed in that a catalyst with the Mo/Fe ratio 2.2 is almost as active as Fe2(MoO4)3 and as selective as MoO3. Imaging of a MoO3/Fe2(MoO4)3 catalyst by SEM and TEM shows that the two phases form separate crystals, and HRTEM reveals the presence of an amorphous overlayer on the Fe2(MoO4)3 crystals. EDS line-scan analysis in STEM mode demonstrates that the Mo/Fe ratio in the amorphous layer is ~2.1 in the fresh catalyst and ~1.7 in the aged catalyst. The enrichment of Mo at the catalyst surface is confirmed by XPS data. Raman spectra give evidence for the Mo in the amorphous material being in octahedral coordination, which is in contrast to the crystalline Fe2(MoO4)3 bulk structure where Mo has tetrahedral coordination. X-ray diffraction (XRD) analysis gives no support for the formation of a defective molybdate bulk structure. The results presented give strong support for the Mo rich amorphous structure being observed on the Fe2(MoO4)3 crystal surfaces being the active phase for methanol oxidation to formaldehyde. 相似文献