bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extractive fermentation for butyric acid production from glucose by Clostridium tyrobutyricum
Authors: Wu Zetang , Yang Shang‐Tian 
Published: February 2003

AbstractA novel extractive fermentation for butyric acid production from glucose, using immobilized cells of Clostridium tyrobutyricum in a fibrous bed bioreactor, was developed by using 10% (v/v) Alamine 336 in oleyl alcohol as the extractant contained in a hollow‐fiber membrane extractor for selective removal of butyric acid from the fermentation broth. The extractant was simultaneously regenerated by stripping with NaOH in a second membrane extractor. The fermentation pH was self‐regulated by a balance between acid production and removal by extraction, and was kept at ∼pH 5.5 throughout the study. Compared with conventional fermentation, extractive fermentation resulted in a much higher product concentration (>300 g/L) and product purity (91%). It also resulted in higher reactor productivity (7.37 g/L · h) and butyric acid yield (0.45 g/g). Without on‐line extraction to remove the acid products, at the optimal pH of 6.0, the final butyric acid concentration was only ∼43.4 g/L, butyric acid yield was 0.423 g/g, and reactor productivity was 6.77 g/L · h. These values were much lower at pH 5.5: 20.4 g/L, 0.38 g/g, and 5.11 g/L · h, respectively. The improved performance for extractive fermentation can be attributed to the reduced product inhibition by selective removal of butyric acid from the fermentation broth. The solvent was found to be toxic to free cells in suspension, but not harmful to cells immobilized in the fibrous bed. The process was stable and provided consistent long‐term performance for the entire 2‐week period of study. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 93–102, 2003.
Surface functionalization of porous polypropylene membranes with polyaniline for protein immobilization
Authors: Piletsky Sergey , Piletska Elena , Bossi Alessandra , Turner Nicholas , Turner Anthony 
Published: February 2003

AbstractCommercial porous polypropylene membranes were chemically modified with polyaniline (PANI) using ammonium persulfate as the oxidizer. The influence of polymerization conditions on the membrane properties was studied by adsorption analysis and membrane permeability. The PANI‐coated polypropylene (PANI/PP) membranes possessed high affinity toward the proteins, which can be immobilized onto the membrane surface through physical adsorption or covalent immobilization. The quantity of immobilized horseradish peroxidase (HRP) and its activity depended on the quantity and quality (oxidation level) of PANI. The storage conditions for PANI/PP membranes containing immobilized HRP were studied. HRP immobilized on the PANI/PP membrane was shown to retain 70% of its activity after 3‐month storage at +5°C, suggesting that this material can be used for practical application, such as in bioreactors as enzyme membranes. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 86–92, 2003.
Pulsed addition of limiting‐carbon during Aspergillus oryzae fermentation leads to improved productivity of a recombinant enzyme
Authors: Bhargava Swapnil , Wenger Kevin S. , Marten Mark R. 
Published: February 2003

AbstractFungal morphology in many filamentous fungal fermentations leads to high broth viscosity which limits oxygen mass transfer, and often results in reduced productivity. The objective in this study was to determine if a simple, fed‐batch, process strategy—pulsed addition of limiting‐carbon source—could be used to reduce fungal broth viscosity, and increase productivity of an industrially relevant recombinant enzyme (glucoamylase). As a control, three Aspergillus oryzae fed‐batch fermentations were carried out with continuous addition of limiting‐carbon. To determine the effect of pulse‐feeding, three additional fermentations were carried out with limiting‐carbon added in 90‐second pulses, during repeated five‐minute cycles. In both cases, overall carbon feed‐rate was used to control dissolved oxygen concentration, such that increased oxygen availability led to increased addition of limiting‐carbon. Pulse‐fed fermentations were found to have smaller fungal mycelia, lower broth viscosity, and improved oxygen mass transfer. As a result, more carbon was added to pulse‐fed fermentations that led to increased enzyme productivity by as much as 75%. This finding has significant implications for the bioprocessing industry, as a simple process modification which is likely to cost very little to implement in most production facilities, has the potential to substantially increase productivity. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 111–117, 2003.
The Evolution of Bulk Solids Technology Since 1982
Authors: Feise H.J. , Carson J.W. 
Published: February 2003

AbstractSince 1982 when Schwedes published his review paper on the “Evolution of Bulk Solids Technology since 1974” the field of bulk solids handling has experienced many advances. This paper attempts to review five major areas of technological development in this field. Three of these have been areas of constant interest since the days of Jenike’s pioneering work and were already part of Schwedes’ review: bulk solids characterization, modeling of the mechanical behavior of bulk solids, and standards for testing and silo loads. The two new areas of development are numerical simulations, namely FEM and DEM methods, and the technology of silo inserts. Developments in all these areas are indicative of the many significant accomplishments in the field of silo technology during the last twenty years. However, there are still many problems that need to be addressed and questions that need to be answered.
Flow Properties of Highly Dispersed Powders at Very Small Consolidation Stresses
Authors: Schulze D. , Wittmaier A. 
Published: February 2003

AbstractWith a modified standard ring shear tester yield loci of highly dispersed, dry powders were measured at preshear normal stresses down to 32 Pa and shear stresses down to 10 Pa. At small consolidation stresses stress, σ1, (< 500 Pa) the values obtained for the unconfined yield strength, σc, are proportional to the consolidation stress, σ1.
The Influence of Air Permeation on the Flow Properties of Bulk Solids
Authors: Klein J. , Höhne D. , Husemann K. 
Published: February 2003

AbstractThis paper considers the influence of low air permeation on the flow properties of slightly consolidated bulk solids in steady state flow. A ring shear device was built that enables the powder sample to be permeated during the shear test from below, upwards with flow velocities below the onset of fluidization. Furthermore, a mathematical model predicting the dependence of both the shear stress as well as the location of the shear zone in the shear cell on the aeration degree was developed. This model predicts a reduction of the shear stress with increasing air feed pressure and a sudden displacement of the shear zone from the cover to the bottom of the shear cell for a high degree of aeration. The good agreement between the measured results and the model predictions proves that the influence of the permeation on the flow properties of bulk solids can be traced back to the change of the normal stresses in the shear zone.
Measurements on Cohesive Powder with two Biaxial Shear Testers
Authors: Janssen R.J.M. , Zetzener H. 
Published: February 2003

AbstractAt the Technical University of Braunschweig (Germany) and the Delft University of Technology (The Netherlands) two True Biaxial Shear Testers were used to perform comparative measurements. The Braunschweig Biaxial Tester (BBT) and the Flexible Wall Biaxial Tester (FWBT) are part of a new generation of advanced powder testers whose goal is to fundamentally investigate powder flow based on the same principles. The general aim of these investigations is to compare the results obtained with both testers and gain new experience in handling powders.
Chute Performance and Design for Rapid Flow Conditions
Authors: Roberts A.W. 
Published: February 2003

AbstractMany industrial chute applications are characterised by rapid flow conditions in which the bulk solid stream thickness or depth is less than the chute width. Under these conditions, it is possible to describe the stream flow by means of a lumped parameter model which takes into account the frictional drag around the chute boundaries as well as making allowance for inter‐particle friction. Equations of motion to describe the chute flow are presented and their application to the determination of chute profiles to achieve optimum flow is illustrated. By means of design examples, the problems associated with the feeding of bulk solids onto belt conveyors and conveyor transfers are discussed. Criteria for the selection of the most appropriate chute geometry to minimise chute wear and belt wear at the feed point are presented. The determination of optimum chute profiles to achieve specified performance criteria is outlined.
The Effects of Operating Conditions on the Milling of Microcrystalline Cellulose
Authors: Kwan C.C. , Ghadiri M. , Papadopoulos D.G. , Bentham A.C. 
Published: February 2003

AbstractThere is little detailed work relating the physical process that occurs during milling to the mechanical properties and mechanism of particle breakage. Very often, the selection of an appropriate mill and subsequently the determination of its optimum operating conditions are by trial and error. This paper look into optimizing the operating conditions of a ball mill through statistical analysis and the effect of temperature on the milling behavior of a common pharmaceutical excipient, microcrystalline cellulose (MCC). In addition, the bulk milling behavior of MCC is compared to its single particle breakage behavior. In this work, milling is conducted in a Retsch single ball mill where a bed of powder is subjected to impact by a steel ball in a horizontal cylindrical container. The container is vibrated horizontally at a set frequency, causing the ball to impact on the bed of particles. It is found that the finest MCC product can be achieved by milling a 2 g batch of material using a 12 mm ball size and at a frequency of 18 Hz. Temperature is found to have insignificant effect on the extent of breakage of MCC in both bulk milling and single particle impact testing. Milling and single particle impact experiments have both shown that MCC is more susceptible to breakage with increasing strain rate. In conclusion, the single impact tests could be used successfully for predicting the bulk milling behavior of the material, as shown in the case of MCC.
Comminution of Organic Material
Authors: Müller J.A. 
Published: February 2003

AbstractThe comminution of materials of bioorganic origin such as organic solids, biological agglomerates or micro‐organisms is described in this work. The intent of this disintegration process is to release products, to improve the product quality or to enhance biological degradation processes. Special analytical techniques based on biochemical parameters are required in order to characterize the result of the comminution of organic materials. These techniques supplement techniques that are known from the comminution of brittle inorganic materials. The defined stressing of single particles can be used to characterize the comminution properties of solid bioorganic materials. The disintegration of micro‐organisms has been investigated in the fields of biotechnological product release and biodegradability of wastewater sludges. It is possible to optimize the operational parameters of stirred ball mills based on stress intensity and stress number in order to reduce the energy input and to improve product release.
New Objectives of Sludge Treatment Considering a Safe Sludge Removal
Authors: Dichtl N. 
Published: February 2003

AbstractSewage sludge consists of valuable components such as nutrients as well as harmful substances, e.g. heavy metals. For sludge with a low concentration of pollutants, its utilization in agriculture is the best way of sludge reuse. Carbon recycling is also possible by using disintegration in combination with anaerobic degradation processes. The other important compound in sludge is phosphorus, which is a limited resource on earth. Recycling options for phosphorus are also described in the paper. A safe disposal of the residues can be achieved by using incineration.
Halide Anion Capture and Recognition by a Tetrahedral Tetraammonium Receptor in Water: A Molecular Dynamics Investigation
Authors: Chaumont Alain , Engler Etienne , Wipff Georges 
Published: February 2003

AbstractWe report molecular dynamics potential of mean force (PMF) simulations on the capture of halide anions X− (F−, Cl−, Br−) by a tetrahedral receptor L4+ built from four quaternary ammonium sites connected by six (CH2)n chains, leading to the formation of inclusion complexes X−⊂L4+. Simulations performed with a reaction field correction of the electrostatics and with PME‐Ewald summation gave very similar energy profiles. In aqueous solution, an energy barrier of 12‐17 kcal mol−1 was found for the three anions, mainly due to their dehydration when they enter through the largest triangular face of L4+. In the inclusion complexes, the anion is anchored near the center of the cavity due to the electrostatic field of the four positively charged ammonium sites, shielded from the surrounding water molecules. It was predicted that L4+ is selective for Cl− over Br− which both form stable inclusion complexes, while the F− complex should dissociate. The comparison of PMFs in aqueous solution and in the gas phase and the energy component analysis demonstrates the importance of solvent on the nature of these complexes and on the complexation energy profiles. The Cl−/Br− selectivity obtained from the dissociation pathways in water was in good agreement with the results of free energy perturbation simulations based on the “alchemical route” of a thermodynamic cycle, and consistent with experimental observations.
Topological Rotational Strengths as Chirality Descriptors for Fullerenes
Authors: Rassat André , Làszló Istvàn , Fowler Patrick W. 
Published: February 2003

AbstractA graph‐theoretical procedure is proposed for assigning a chirality descriptor (the topological signτ(+) orτ(−)) to each enantiomer of a chiral polyhedron, polyhedral molecule or graph, independently of any vertex labelling scheme. Model Cartesian coordinates and rotational strengths are obtained using only adjacency information; a generalised HOMO–LUMO rotational strength is used to associate a sign with a Schlegel diagram and the corresponding three‐dimensional structure, polyhedron or molecule. The topological sign gives an unambiguous way of communicating the identity of an enantiomer. The mean‐square topological rotational strength is a possible measure of thechirality contentof a polyhedral graph or structure.
Synthesis of Enantiomerically‐Pure [13C]Aristeromycylcobalamin and Its Reactivity in Dioldehydratase, Glyceroldehydratase, Ethanolamine Ammonia‐Lyase and Methylmalonyl‐CoA Mutase Reactions
Authors: Weigl Ulrich , Heimberger Martin , Pierik Antonio J. , Rétey János 
Published: February 2003

AbstractWe describe a novel enantioselective synthesis of aristeromycin, the carbocyclic analogue of adenosine. The seven‐step synthesis is also suitable for the preparation of specifically‐labelled [6′‐13C]aristeromycin. Both the unlabelled and 13C‐labelled product was coupled to vitamin B12 to form aristeromycylcobalamin. This carbocyclic analogue of coenzyme B12 was examined for its coenzymic activity with several adenosylcobalamin‐dependent enzymes. For glyceroldehydratase and dioldehydratase, the reaction rate (kcat) was 38 and 44 % of that measured with adenosylcobalamin as coenzyme. In contrast, aristeromycylcobalamin showed no detectable activity with methylmalonyl‐CoA mutase and ethanolamine ammonia‐lyase. Instead, it was a weak inhibitor of the former and a strong inhibitor of the latter enzyme. The slower turnover rate with glyceroldehydratase raised the hope of detecting the 6′‐deoxyaristeromycyl radical intermediate. Comparison of the EPR spectra of the intermediates in the glyceroldehydratase reaction, which used adenosyl‐ and aristeromycylcobalamines, respectively, as coenzyme, revealed a significant shift and this suggests a different geometric position of these cofactors at the binding site during the cleavage of the carbon‐cobalt bond. However, we found no evidence for the existence of a 6′‐deoxyaristeromycyl radical during the reaction with [6′‐13C]aristeromycylcobalamin. We conclude that the lifetime of this radical is still too short to be observed.
A New Class of Ferromagnetically‐Coupled Mixed Valence Vanadium(IV/V) Polyoxometalates
Authors: Manos Manolis J. , Tasiopoulos Anastasios J. , Tolis Evangelos J. , Lalioti Nicolia , Woollins J. Derek , Slawin Alexandra M. Z. , Sigalas Michael P. , Kabanos Themistoklis A. 
Published: February 2003

AbstractReaction of [VVIOCl2(thf)2] with a bidentate nitrogen‐donor ligand (L: phen=1,10‐phenanthroline, 5‐mephen=5‐methyl‐1,10‐phenanthroline, bipy=2,2′‐bipyridine, 5,5′‐me2bipy=5,5′‐dimethyl‐2,2′‐bipy) in methyl alcohol, in the presence of triethylamine, leads to the formation of hexameric [V2IVV4V] oxo‐alkoxo‐vanadates of the general formula [V6O12(μ2‐OCH3)4(L)4]⋅x H2O [L=phen (1⋅4 H2O), 5‐mephen (2⋅6 H2O), bipy (3⋅4 H2O), 5,5′‐me2bipy (4⋅H2O)]. X‐ray structure analysis of 1⋅2 H2O and 4⋅8 CH3OH revealed a pair of V3O13N4 trimeric units sharing two corners, with a centrosymmetric planar V6‐core. In addition, a fully oxidized VV species [VV4O8(OCH3)2(μ3‐OCH3)2(5,5′‐me2bipy)2]⋅3 CH3OH (5⋅3 CH3OH) was isolated from the reaction mixture used for the synthesis of 4⋅H2O. The crystal structure of 5⋅3 CH3OH revealed a dicubane‐like framework with two missing vertices. Electron paramagnetic resonance (EPR) and variable temperature magnetic susceptibility studies for the hexamers 1⋅4 H2O and 3⋅4 H2O showed the complete localization of the single 3d electrons on the VIV ions and unusual ferromagnetic interaction between the two paramagnetic vanadium(IV) ions separated by a distance of about 5.1 Å. Furthermore, intermolecular antiferromagnetic interactions through π‐contacts of phenyl rings were observed for these species below 8 K. The ferromagnetic exchange coupling observed in the hexanuclear compounds 1⋅4 H2O and 3⋅4 H2O is also discussed using ab initio UHF calculations on a model compound. The value of the exchange coupling constant (3.7 cm−1) for this model compound, calculated using the broken symmetry approach, is in good agreement, both in sign and magnitude, with the experimental J values (6.00 cm−1 for 1⋅4 H2O and 8.54 cm−1 for 3⋅4 H2O).
Template Synthesis of Benzannulated N‐Heterocyclic Carbene Ligands
Authors: Hahn F. Ekkehardt , Langenhahn Volker , Meier Nicole , Lügger Thomas , Fehlhammer Wolf Peter 
Published: February 2003

AbstractThe reaction of 2‐azidophenyl isocyanide (7) with [M(CO)5(thf)] (M=Cr, W) yields the isocyanide complexes [M(CO)5(7)] (M=Cr 8, M=W 9). Complexes 8 and 9 react with tertiary phosphines such as triphenylphosphane at the azido function of the isocyanide ligand to give the 2‐triphenylphosphiniminophenyl isocyanide complexes 10 (M=Cr) and 11 (M=W). The polar triphenylphosphiniminophenyl function in complexes 10 and 11 can be hydrolyzed with H2O/HBr to afford triphenylphosphane oxide and the complexes containing the unstable 2‐aminophenyl isocyanide ligand. This ligand spontaneously cyclizes by intramolecular nucleophilic attack of the primary amine at the isocyanide carbon atom to yield the 2,3‐dihydro‐1H‐benzimidazol‐2‐ylidene complexes 12 (M=Cr) and 13 (M=W). Double deprotonation of the cyclic NH,NH‐carbene ligands in 12 and 13 with KOtBu and reaction with two equivalents of allyl bromide yields the N,N′‐dialkylated benzannulated N‐heterocyclic carbene complexes 14 (M=Cr) and 15 (M=W). The molecular structures of complexes 9 and 11–15 were confirmed by X‐ray diffraction studies.
An ab Initio/RRKM Study of Product Branching Ratios in the Photodissociation of Buta‐1,2‐ and ‐1,3‐dienes and But‐2‐yne at 193 nm
Authors: Lee Hwa‐Yu , Kislov Vadim V. , Lin Sheng‐Hsien , Mebel Alexander M. , Neumark Daniel M. 
Published: February 2003

AbstractAb initio G2M(MP2)//B3LYP/6‐311G** calculations have been performed to investigate the reaction mechanism of photodissociation of buta‐1,2‐ and ‐1,3‐dienes and but‐2‐yne after their internal conversion into the vibrationally hot ground electronic state. The detailed study of the potential‐energy surface was followed by microcanonical RRKM calculations of energy‐dependent rate constants for individual reaction steps (at 193 nm photoexcitation and under collision‐free conditions) and by solution of kinetic equations aimed at predicting the product branching ratios. For buta‐1,2‐diene, the major dissociation channels are found to be the single CC bond cleavage to form the methyl and propargyl radicals and loss of hydrogen atoms from various positions to produce the but‐2‐yn‐1‐yl (p1), buta‐1,2‐dien‐4‐yl (p2), and but‐1‐yn‐3‐yl (p3) isomers of C4H5. The calculated branching ratio of the CH3 + C3H3/C4H5 + H products, 87.9:5.9, is in a good agreement with the recent experimental value of 96:4 (ref. 21) taking into account that a significant amount of the C4H5 product undergoes secondary dissociation to C4H4 + H. The isomerization of buta‐1,2‐diene to buta‐1,3‐diene or but‐2‐yne appears to be slower than its one‐step decomposition and plays only a minor role. On the other hand, the buta‐1,3‐diene→buta‐1,2‐diene, buta‐1,3‐diene→but‐2‐yne, and buta‐1,3‐diene→cyclobutene rearrangements are significant in the dissociation of buta‐1,3‐diene, which is shown to be a more complex process. The major reaction products are still CH3 + C3H3, formed after the isomerization of buta‐1,3‐diene to buta‐1,2‐diene, but the contribution of the other radical channels, C4H5 + H and C2H3 + C2H3, as well as two molecular channels, C2H2 + C2H4 and C4H4 + H2, significantly increases. The overall calculated C4H5 + H/CH3 + C3H3/C2H3 + C2H3/C4H4 + H2/C2H2 + C2H4 branching ratio is 24.0:49.6:4.6:6.1:15.2, which agrees with the experimental value of 20:50:8:2:2022 within 5 % margins. For but‐2‐yne, the one‐step decomposition pathways, which include mostly H atom loss to produce p1 and, to a minor extent, molecular hydrogen elimination to yield methylethynylcarbene, play an approximately even role with that of the channels that involve the isomerization of but‐2‐yne to buta‐1,2‐ or ‐1,3‐dienes. p1 + H are the most important reaction products, with a branching ratio of 56.6 %, followed by CH3 + C3H3 (23.8 %). The overall C4H5 + H/CH3 + C3H3/C2H3 + C2H3/C4H4 + H2/C2H2 + C2H4 branching ratio is predicted as 62.0:23.8:2.5:5.7:5.6. Contrary to buta‐1,2‐ and ‐1,3‐dienes, photodissociation of but‐2‐yne is expected to produce more hydrogen atoms than methyl radicals. The isomerization mechanisms between various isomers of the C4H6 molecule including buta‐1,2‐ and ‐1,3‐dienes, but‐2‐yne, 1‐methylcyclopropene, dimethylvinylidene, and cyclobutene have been also characterized in detail.