bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of Fructose and Ethanol from Cane Molasses Using Saccharomyces cerevisiae ATCC 36858
Authors: Atiyeh H. , Duvnjak Z.
Published: February 2003

The purpose of this research was to study the possibility of the production of ethanol and enriched fructose syrups from sugar cane molasses using the yeast Saccharomyces cerevisiae ATCC 36858. In batch experiments with a total sugar concentration of between 96.7 g/l and 323.5 g/l, the fructose yield was above 90% of the theoretical value. The ethanol yield and volumetric productivity were in the range of 66% and 77% of the theoretical value, and between 0.53 g ethanol/l × h and 3.15 g ethanol/l × h, respectively. The fructose fraction in the carbohydrates content of the produced syrups was more than 95% when the total initial sugar concentration in the medium was below 273.8 g/l. Some oligosaccharides and glycerol were also produced in all tested media. The maximum amount of produced oligosaccharides including raffinose accounted for 13.4 g/l in the cane molasses medium with 323.5 g/l sugars in the initial phase of the fermentation process. The oligosaccharides produced and raffinose were completely consumed by the end of the fermentation process when the total initial sugar concentration was less than 191.3 g/l. The glycerol concentration was below 9.9 g/l. These findings are useful in the production of ethanol and high fructose syrups using sugar cane molasses.
Biodegradation of Grape Cluster Stems and Ligninolytic Enzyme Production by Phanerochaete chrysosporium during Semi‐Solid‐State Cultivation
Authors: Rodríguez Couto S. , Rodríguez R. , Gallego P. P. , Sanromán A.
Published: February 2003

The degradation undergone by grape cluster stems (woody component of vine bagasse), an agroindustrial waste, was investigated during the semi‐solid‐state cultivation of Phanerochaete chrysosporium BKM‐F‐1767 (ATCC 24725). For this, the content of lignin, cellulose and hemicellulose in grape cluster stems was determined before and after the enzymatic process. It was found that about 20% of Klason lignin, 48% of hemicellulose and 5% of cellulose were degraded during the process, being the ligninolytic enzymes (manganese‐dependent peroxidase and lignin peroxidase) produced by such cultures responsible for the degradation of grape cluster stems. In parallel, semi‐solid‐state cultures of P. chrysosporium grown on an inert support (cubes of nylon sponge), which is not susceptible to undergoing degradation during the enzymatic process, were used as reference cultures.

In addition, the in vivo decolourisation of a model dye, the polymeric dye Poly R‐478, by both grape cluster stem and nylon cultures was studied in order to assess their degradative ability. A percentage of biological decolourisation higher than 90% after four days of dye addition was obtained using nylon sponge cultures, whereas grape cluster stem cultures led to a decolourisation of around 70% after eight days of dye incubation. The lower percentage of dye degradation achieved by the cultures grown on grape cluster stems was due to the enzymes produced, which were not only employed in the decolourisation of the dye but also in the degradation of the support, as indicated by the data mentioned above.
Fructan Biosynthesis by Intra‐ and Extracellular Zymomonas mobilis Levansucrase after Simultaneous Production of Ethanol and Levan
Authors: Bekers M. , Upite D. , Kaminska E. , Grube M. , Laukevics J. , Vina I. , Vigants A. , Zikmanis P.
Published: February 2003

The chemical composition of the Zymomonas mobilis biomass and the culture liquid after ethanol and levan synthesis were studied. The activities of intra‐ and extracellular levansucrase produced by the Z. mobilis strain 113 “S” under optimum conditions both for levan and fructooligosaccharide (FOS) synthesis were also determined. It was shown that levan production relates to the reduction of the carbohydrate and lipid content in the biomass by increasing the nucleic acid and protein content. The levan producing activity of cellular levansucrase after ethanol and levan synthesis was approximately 30–40% of the total activity in the second fermentation stage. It was established that the cell free culture liquid, containing ethanol, levan, gluconic acid and sucrose (15%) at 25 °C, did not show any additional levan synthesising activity. At optimum FOS synthesis conditions (45 °C and 70% sucrose), the cell‐free culture liquid exhibited a high FOS synthesising activity (31% from total carbohydrates), with slightly reduced biomass activity. It was concluded that as a result of the simultaneous ethanol and levan production, the remaining biomass as well as the cell‐free culture liquid could be used for FOS production.
Tunneling Current in Polycrystalline Organic Thin‐Film Transistors
Authors: Horowitz G.
Published: February 2003

Several recent papers have demonstrated that charge‐carrier mobility in organic field‐effect transistors made of vacuum‐evaporated films may become temperature‐independent at low temperature. To account for this behavior, we developed a model based on the polycrystalline nature of these films, where charge transport is mostly limited by grain boundaries. The free‐carrier density in the intergrain regions is controlled by traps, which leads to the formation of back‐to‐back Schottky barriers at each side of the grain boundaries. The height and width of these barriers is estimated from solving Poisson’s equation using the graded‐channel approximation. It is shown that in most cases the barrier width is negligibly small as compared to the physical size of the grain boundaries. In the high‐temperature regime, the conducting channel can be simply described by grains and grain boundaries connected in series, so that the overall resistance reduces to that of the grain boundaries. At low temperatures, tunneling through the barrier becomes predominant, leading to temperature‐independent mobility. A complete two‐dimensional model for charge tunneling through the barriers is developed. A quantitative check of the model is made by least‐squares fitting of the gate voltage‐dependent current measured on an octithiophene transistor at low temperature, which gives a reasonable determination of the trap density and size of the grain boundaries.
Surfactant‐Assisted Synthesis of Alumina with Hierarchical Nanopores
Authors: Deng W. , Toepke M.W. , Shanks B.H.
Published: February 2003

Using surfactant‐assisted synthesis, aluminas with hierarchical nanopores are produced. The hierarchical structures are composed of mesopores of 4 nm diameter, and macropores with diameters of about 300 nm. The structures were found to be stable to the thermal removal of the surfactant. Synthesis factors affecting the appearance of the hierarchically structured alumina material are presented. A potential mechanism for the formation of the uniquely structured aluminas is proposed.
Controlling the Morphology of Nanocrystal–Polymer Composites for Solar Cells
Authors: Huynh W.U. , Dittmer J.J. , Libby W.C. , Whiting G.L. , Alivisatos A.P.
Published: February 2003

We have shown recently that the use of high‐aspect‐ratio inorganic nanorods in conjunction with conjugated polymers is a route to obtaining efficient solar cells processed from solution. Here, we demonstrate that the use of binary solvent mixtures in which one of the components is a ligand for the nanocrystals is effective in controlling the dispersion of nanocrystals in a polymer. By varying the concentration of the solvent mixture, phase separation between the nanocrystal and polymer could be tuned from micrometer scale to nanometer scale. In addition, we can achieve nanocrystal surfaces that are free of surfactant through the use of weak binding ligands that can be removed through heating. When combined, the control of film morphology together with surfactant removal result in nanorod–polymer blend photovoltaic cells with a high external quantum efficiency of 59 % under 0.1 mW cm–2 illumination at 450 nm.
Selective Growth of Carbon Nanotubes for Nanoscale Transistors
Authors: Choi W.B. , Cheong B.‐H. , Kim J.J. , Chu J. , Bae E.
Published: February 2003

The selective growth of vertically aligned carbon nanotubes (CNTs) and their application as field‐effect transistors (FETs) are demonstrated. Vertically aligned carbon nanotubes were selectively grown in nanoholes formed in an anodized aluminum oxide (AAO) template. Each device element is formed on a vertical carbon nanotube attached to bottom (source) and upper (drain) electrodes and a gate electrode, which can be integrated in large arrays with the potential for tera‐level density (1012 cm–2). Simulation of the potential distribution shows that the direction of potential formation would depend on the polarity of the gate bias, which is consistent with an experimental result of CNT‐FET operation.
Novel Nanostructures of Functional Oxides Synthesized by Thermal Evaporation
Authors: Dai Z.R. , Pan Z.W. , Wang Z.L.
Published: February 2003

Functional oxides are the fundamentals of smart devices. This article reviews novel nanostructures of functional oxides, including nanobelts, nanowires, nanosheets, and nanodiskettes, that have been synthesized in the authors’ laboratory. Among the group of ZnO, SnO2, In2O3, Ga2O3, CdO, and PbO2, which belong to different crystallographic systems and structures, a generic nanobelt structure has been synthesized. The nanobelts are single crystalline and dislocation‐free, and their surfaces are atomically flat. The oxides are semiconductors, and have been used for fabrication of nanodevices such as field‐effect transistors and gas sensors. Taking SnO2 and SnO as examples, other types of novel nanostructures are illustrated. Their growth, phase transformation, and stability are discussed. The nanobelts and related nanostructures are a unique group that is likely to have important applications in electronic, optical, sensor, and optoelectronic nanodevices.
“(Hot‐)Water‐Proof”, Semiconducting, Platinum‐Based Chain Structures: Processing, Products, and Properties
Authors: Caseri W.R. , Chanzy H.D. , Feldman K. , Fontana M. , Smith P. , Tervoort T.A. , Goossens J.G.P. , Meijer E.W. , Schenning A.P.H.J. , Dolbnya I.P. , Debije M.G. , de Haas M.P. , Warman J.M. , van de Craats A.M. , Friend R.H. , Sirringhaus H. , Stutzmann N.
Published: February 2003

A promising solution to the environmental instability of semiconducting organic materials is presented. Thin, highly ordered films (see Figure, a scanning probe microscopy image), fibers, and field‐effect transistors (FETs), comprising chain‐structures based on the so‐called Magnus’ green salt, [Pt(NH3)4]‐[PtCl4], were synthesized in aqueous media (see Cover). FETs were manufactured under ambient conditions from common organic solvents, and exposed—without significant loss of performance—to white light and air for periods of time in excess of 6 months, and to water of 90 °C for more than 12 h.
Electrodeposition of Metallic Nanowire Thin Films Using Mesoporous Silica Templates
Authors: Wang D. , Zhou W.L. , McCaughy B.F. , Hampsey J.E. , Ji X. , Jiang Y.‐B. , Xu H. , Tang J. , Schmehl R.H. , O’Connor C. , Brinker C.J. , Lu Y.
Published: February 2003

Metal nanowire thin films have been obtained by electrodeposition into mesoporous silica thin‐film templates, resulting in nanowire arrays that reflect the pore structure of the template. Removal of silica is achieved via annealing followed by etching to leave mechanically strong freestanding metal nanowire films (see Figure). These metal films have many potential applications, such as electrodes, optical hosts, catalysts, magnetic materials, photovoltaic devices, and sensors.
Polyaniline Nanotubes Doped with Sulfonated Carbon Nanotubes Made Via a Self‐Assembly Process
Authors: Wei Z. , Wan M. , Lin T. , Dai L.
Published: February 2003

Sulfonated multiwalled carbon nanotubes (MWNT‐(OSO3H)n) can act simultaneously as a dopant and template for the formation of conducting polyaniline(PANI) nanostructures. By controlling the aniline/MWNT‐(OSO3H)n ratio, two kinds of nanotubes—PANI‐coated MWNT‐(OSO3H)n nanotubes and PANI nanotubes doped with MWNT‐(OSO3H)n (see Figure)—can be obtained.
Controlling Dielectric and Optical Properties of Ordered Mesoporous Organosilicate Films
Authors: Balkenende A.R. , de Theije F.K. , Kriege J.C.K.
Published: February 2003

Mesoporous hybrid inorganic–organic silicate films with pendant methyl groups are prepared. With a high organic fraction, these films are hydrophobic, which is important in the fabrication of low‐k dielectrics. The refractive index of layers with smaller organic fraction can be switched reversibly over a large refractive index interval by varying the relative humidity (see Figure).
Diameter‐Controlled Growth of Single‐Crystalline In2O3 Nanowires and Their Electronic Properties
Authors: Li C. , Zhang D. , Han S. , Liu X. , Tang T. , Zhou C.
Published: February 2003

Single‐crystalline In2O3 nanowires have been synthesized using a laser ablation approach. Precise control over the nanowire diameter was achieved by using monodispersed gold clusters as the catalyst. Extensive material characterization has been carried out to determine the lattice structure (see Figure) and dimensions of these nanowires. Individual In2O3 nanowires have been utilized to construct field‐effect transistors with on/off ratios up to 1000.
An Unusual Electrochromic Device Based on a New Low‐Bandgap Conjugated Polymer
Authors: Meng H. , Tucker D. , Chaffins S. , Chen Y. , Helgeson R. , Dunn B. , Wudl F.
Published: February 2003

A new low‐bandgap conjugated polymer is synthesized (see Figure for structure). It is transparent, easily processed, and exhibits electrochromic behavior specific to the near‐infrared region of the spectrum. The absence of electrochromic behavior in the visible range may permit this polymer to be used in near‐infrared device applications.
Patterned Microstructures of Porous Silicon by Dry‐Removal Soft Lithography
Authors: Sirbuly D.J. , Lowman G.M. , Scott B. , Stucky G.D. , Buratto S.K.
Published: February 2003

A new procedure to directly pattern a luminescent porous silicon substrate by dry‐removal soft lithography is outlined. The ability to transfer a removed microstructure of porous silicon to a free‐standing flexible polymer film is also demonstrated, and by removing strips in orthogonal directions, an array of PSi pillars is produced (see Figure).
Sonochemical Synthesis of CdSe Hollow Spherical Assemblies Via an In‐Situ Template Route
Authors: Zhu J.J. , Xu S. , Wang H. , Zhu J.M. , Chen H.‐Y.
Published: February 2003

CdSe hollow spherical assemblies composed of 5 nm nanoparticles have been synthesized sonochemically. During the process, amorphous Cd(OH)2, which acts as the in‐situ template, directs the growth of primary CdSe nanoparticles on its surface and their assembly into hollow spherical structures. The Figure is a schematic of the proposed mechanism for the formation of the hollow chalcogenide spheres.
Ordered Arrays of Nanopillars Formed by Photoelectrochemical Etching on Directly Imprinted TiO2 Single Crystals
Authors: Masuda H. , Kanezawa K. , Nakao M. , Yokoo A. , Tamamura T. , Sugiura T. , Minoura H. , Nishio K.
Published: February 2003

Arrays of TiO2 nanopillars have been prepared by photochemically etching a TiO2 single crystal that had been previously imprinted with a corresponding array of dimples using SiC molds. The pillars have a high aspect ratio (see scanning electron microscopy (SEM) image in Figure) and the method is simple and suitable for high‐throughput production.
Titelbild: Angew. Chem. 4/2003
Authors: Kitaura Ryo , Seki Kenji , Akiyama George , Kitagawa Susumu
Published: February 2003

Flexibel und dynamisch sind die Kanäle im verzahnten Netzwerk eines Koordinationspolymers, dessen Struktur (ein Ausschnitt) das Titelbild zeigt. Bei dieser Verbindung ist eine Kristall‐zu‐Kristall‐Umwandlung von einer nichtporösen Struktur (geschlossene Form) zu einer mikroporösen (offene Form) möglich, die durch Adsorption überkritischer Gase ausgelöst wird und reversibel ist. Die links unten gezeigte Isotherme weist eine Hysterese auf und lässt abrupte Adsorption und ebenso scharfe Desorption bei bestimmten Drücken erkennen. Mehr über dieses Koordinationspolymer berichten S. Kitagawa et al. in der Zuschrift auf S. 444 ff.
Grundzüge der Sensorik Höherer Pflanzen
Authors: Weiler Elmar W.
Published: February 2003

Pflanzen reagieren auf eine Vielzahl unterschiedlicher Reize aus ihrem Körperinneren und ihrer Umgebung. Unser Wissen um die sensorischen Fähigkeiten von Pflanzen hat gerade in den letzten zehn Jahren enorm zugenommen. Dies liegt einerseits an dem konsequenten Einsatz molekulargenetischer Verfahren, andererseits daran, daß weltweit viele Kräfte auf eine einzige, repräsentative Höhere Pflanze konzentriert werden, auf Arabidopsis thaliana, die Acker‐Schmalwand. Dieser Aufsatz konzentriert sich eher auf die Prinzipien als auf Details und beschränkt sich auf solche Systeme, die funktional eindeutig identifiziert sind. Höhere Pflanzen sind hinsichtlich ihrer sensorischen Fähigkeiten um nichts weniger faszinierend, nicht weniger komplex, nicht weniger empfindlich als Tiere oder sogar der Mensch. Pflanzen überwachen dauernd ihre Umgebung und den Zustand in ihrem Inneren mit Hilfe eines erstaunlichen Aufgebots sensorischer Systeme, die sich von denen der Tiere oder des Menschen unterscheiden.
Cover Picture: Angew. Chem. Int. Ed. 4/2003
Authors: Kitaura Ryo , Seki Kenji , Akiyama George , Kitagawa Susumu
Published: February 2003

Flexible and dynamic channels created by an interdigitated framework of microporous coordination polymers are shown on the cover picture. The compound undergoes reversible crystal‐to‐crystal transformation from a nonporous (closed‐form) to a microporous (open‐form) structure, which is triggered by adsorption of supercritical gases. A hysteretic isotherm, shown bottom left, displays abrupt adsorption at a gate‐opening pressure and equally sharp desorption at a gate‐closing pressure. More about this coordination polymer is reported in the Communication by S. Kitagawa et al. on page 428 ff.
Recent Developments in Protein Microarray Technology
Authors: Wilson David S. , Nock Steffen
Published: February 2003

The sequencing of the human genome and the advent of DNA chips and sophisticated bioinformatics platforms have enabled molecular biologists to take a more global view of biological systems and to analyze naturally occurring genetic variation. Microarrays of antibodies can measure the concentrations of many proteins quickly and simultaneously. Microarrays of genomically encoded proteins allow scientists to screen entire genomes for proteins that interact with particular factors, catalyze particular reactions, or act as substrates for protein‐modifying enzymes or as targets of autoimmune responses. The new protein microarray platforms will prove invaluable to basic biological research, and will dramatically accelerate the pace of discovery of drug targets and diagnostic biomarkers.
One Century of Aryne Chemistry
Authors: Wenk Hans Henning , Winkler Michael , Sander Wolfram
Published: February 2003

Arynes, which are formally derived from aromatic rings by abstraction of two hydrogen atoms, have been a focus of organic chemistry for 100 years. In contrast to ortho‐benzyne, which is mentioned in almost every introductory textbook on organic reaction mechanisms as a reactive intermediate of nucleophilic aromatic substitution, the meta and para isomers were regarded as rather exotic until recently. This situation has changed dramatically with the discovery of the enediyne antibiotics, a promising new class of antitumor drugs, and has aroused the interest of research groups from all branches of chemistry. Nowadays, arynes and related compounds are among the most intensively studied systems in chemistry. However, many aspects of the chemistry of these reactive intermediates are not well understood yet. In this review we outline the historical developement with an emphasis on recent progress in this challenging field of research.
Development of a novel process for the biological conversion of H2S and methanethiol to elemental sulfur
Authors: Sipma Jan , Janssen Albert J. H. , Hulshoff Pol Look W. , Lettinga Gatze
Published: February 2003

The feasibility of anaerobic treatment of wastewater containing methanethiol (MT), an extremely volatile and malodorous sulfur compound, was investigated in lab‐scale bioreactors. Inoculum biomass originating from full‐scale anaerobic wastewater treatment facilities was used. Several sludges, tested for their ability to degrade MT, revealed the presence of organisms capable of metabolizing MT as their sole source of energy. Furthermore, batch tests were executed to gain a better understanding of the inhibition potential of MT. It was found that increasing MT concentrations affected acetotrophic organisms more dramatically than methylotrophic organisms. Continuous reactor experiments, using two lab‐scale upflow anaerobic sludge bed (UASB) reactors (R1 and R2), aimed to determine the maximal MT load and the effect of elevated sulfide concentrations on MT conversion. Both reactors were operated at a hydraulic retention time (HRT) of about 7 hours, a temperature of 30°C, and a pH of between 7.3 and 7.6. At the highest influent MT concentration applied, 14 mM in R1, corresponding to a volumetric loading rate of about 50 mM MT per day, 87% of the organic sulfur was recovered as hydrogen sulfide (12.2 mM) and the remainder as volatile organic sulfur compounds (VOSCs). Upon decreasing the HRT to 3.5 to 4.0 h at a constant MT loading rate, the sulfide concentration in the reactor decreased to 8 mM and MT conversion efficiency increased to values near 100%. MT conversion was apparently inhibited by the high sulfide concentrations in the reactor. The specific MT degradation rate, as determined after 120 days of operation in R1, was 2.83 ± 0.27 mmol MT g VSS−1 day−1. During biological desulfurization of liquid hydrocarbon phases, such as with liquefied petroleum gas (LPG), the combined removal of hydrogen sulfide and MT is desired. In R2, the simultaneous addition of sodium sulfide and MT was therefore studied and the effect of elevated sulfide concentrations was investigated. The addition of sodium sulfide resulted in enhanced disintegration of sludge granules, causing significant washout of biomass. Additional acetate, added to stimulate growth of methanogenic bacteria to promote granulation, was hardly converted at the termination of the experimental period. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 1–11, 2003.
A reversible hydrogel membrane for controlling the delivery of macromolecules
Authors: Tang M. , Zhang R. , Bowyer A. , Eisenthal R. , Hubble J.
Published: February 2003

Glucose‐sensitive hydrogel membranes have been synthesized and characterized for their rate‐of‐delivery of macromolecules. The mechanism for changing this rate is based on variable displacement of the affinity interaction between dextran and concanavalin A (con A). Our main objective was to characterize the diffusion of model proteins (insulin, lysozyme, and BSA) through the membrane, in response to changes in environmental glucose concentrations. Membranes were constructed from crosslinked dextrans to which con A was coupled via a spacer arm. Changes in the porosity of the resulting hydrogel in the presence of glucose led to changes in the diffusion rate observed for a range of proteins. Gels of specified thickness were cast around to nylon gauze support (pore size, 0.1 mm) to improve mechanical strength. Diffusion of proteins through the gel membrane was determined using a twin‐chamber diffusion cell with the concentrations being continuously monitored using a UV‐spectrophotometer. Changes in the transport properties of the membranes in response to glucose were explored and it was found that, while 0.1M D‐glucose caused a substantial, but saturateable, increase in the rates of diffusion of both insulin and lysozyme, controls using glycerol or L‐glucose (0.1M) had no significant effect. Sequential addition and removal of external glucose in a stepwise manner showed that permeability changes were reversible. As expected, diffusion rates were inversely proportional to membrane thickness. A maximum increase in permeability was observed at pH 7.4 and at 37°C. The results demonstrate that this hydrogel membrane functions as a smart material allowing control of solute delivery in response to specific changes in its external environment. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 47–53, 2003.
Theory of pH‐stat titration
Authors: Ficara Elena , Rozzi Alberto , Cortelezzi Paola
Published: February 2003

Innovative techniques are being studied to assess the activity of bioreactors and to improve the performance and operational stability of biological processes. Among these techniques, the pH‐stat titration is applicable to any bioreaction involving pH variations. Up to now, the main application of the pH‐stat titration has been for nitrification monitoring. In this article, we present a theoretical model of pH‐stat titration, which predicts the response to any reaction involving the production or consumption of protons, hydroxyl ions, or inorganic carbon chemical species (CO2, HCO3−, CO3=). This model is a useful tool to understand pH‐stat titrations, to define their applicability and limits, and to select the best experimental conditions for specific applications. Tests have been performed to compare experimental pH‐stat titration rates in the presence of carbon dioxide and HCO3− producing reactions to the values predicted by the model and a very satisfying correspondence was found. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 28–37, 2003.
Outdoor helical tubular photobioreactors for microalgal production: Modeling of fluid‐dynamics and mass transfer and assessment of biomass productivity
Authors: Hall David O. , Acién Fernández F. G. , Guerrero E. Cañizares , Rao K. Krishna , Grima E. Molina
Published: February 2003

The production of the microalga Phaeodactylum tricornutum in an outdoor helical reactor was analyzed. First, fluid dynamics, mass‐transfer capability, and mixing of the reactor was evaluated at different superficial gas velocities. Performance of the reactor was controlled by power input per culture volume. A maximum liquid velocity of 0.32 m s−1 and mass transfer coefficient of 0.006 s−1 were measured at 3200 W m−3. A model of the influence of superficial gas velocity on the following reactor parameters was proposed: gas hold‐up, induced liquid velocity, and mass transfer coefficient, with the accuracy of the model being demonstrated. Second, the influence of superficial gas velocity on the yield of the culture was evaluated in discontinuous and continuous cultures. Mean daily values of culture parameters, including dissolved oxygen, biomass concentration, chlorophyll fluorescence (Fv/Fm ratio), growth rate, biomass productivity, and photosynthetic efficiency, were determined. Different growth curves were measured when the superficial gas velocity was modified—the higher the superficial gas velocity, the higher the yield of the system. In continuous mode, biomass productivity increased by 35%, from 1.02 to 1.38 g L−1 d−1, when the superficial gas velocity increased from 0.27 to 0.41 m s−1. Maximal growth rates of 0.068 h−1, biomass productivities up to 1.4 g L−1 d−1, and photosynthetic efficiency of up to 15% were obtained at the higher superficial gas velocity of 0.41 m s−1. The fluorescence parameter, Fv/Fm, which reflects the maximal efficiency of PSII photochemistry, showed that the cultures were stressed at average irradiances within the culture higher than 280 μE m−2 s−1 at every superficial gas velocity. For nonstressed cultures, the yield of the system was a function of average irradiance inside the culture, with the superficial gas velocity determining this relationship. When superficial gas velocity was increased, higher growth rates, biomass productivities, and photosynthetic efficiencies were obtained for similar average irradiance values. The higher the superficial gas velocity, the higher the liquid velocity, with this increase enhancing the movement of the cells inside the culture. In this way the efficiency of the cells increased and higher biomass concentrations and productivities were reached for the same solar irradiance. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 62–73, 2003.
Enhancement of 2‐phenylethanol productivity by Saccharomyces cerevisiae in two‐phase fed‐batch fermentations using solvent immobilization
Authors: Serp D. , von Stockar U. , Marison I. W.
Published: February 2003

The bioconversion of L‐phenylalanine to 2‐phenylethanol by Saccharomyces cerevisiae in fed‐batch experiments has shown that concentrations of 2‐phenylethanol of >2.9 g/L have a negative impact on the oxidative capacity of the yeast. Without tight control on ethanol production, and hence on the feed rate, ethanol rapidly accumulates in the culture media, resulting in complete inhibition of cell growth before the maximal 2‐phenylethanol concentration of 3.8 g/L, obtained in the absence of ethanol production, could be achieved. This effect was attributed to a cumulative effect of ethanol and 2‐phenylethanol, which reduced the tolerance of the cells for these two products. To enhance the productivity of the bioconversion, a novel in situ product recovery strategy, based on the entrapment of an organic solvent (dibutylsebacate) into a polymeric matrix of polyethylene to form a highly absorbent and chemically and mechanically stable composite resin, was developed. Immobilization of the organic solvent successfully prevented phase toxicity of the solvent and allowed for an efficient removal of 2‐phenylethanol from the bioreactor without the need for prior cell separation. The use of the composite resin increased the volumetric productivity of 2‐phenylethanol by a factor 2 and significantly facilitated downstream processing, because no stable emulsion was formed. The 2‐phenylethanol could be backextracted from the composite resin, yielding a concentrated and almost cell‐free solution. In comparison to two‐phase extractive fermentations with cells immobilized in alginate‐reinforced chitosan beads, the use of a composite resin was extremely inexpensive and simple. In addition, the composite resin was found to be insensitive to abrasion and chemically stable, such that sterilization with 2 M NaOH or heat was possible. Finally, the composite resin could be produced on a large scale using commercially available equipment. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 103–110, 2003.
Quantification of a novel h‐shaped ultrasonic resonator for separation of biomaterials under terrestrial gravity and microgravity conditions
Authors: Böhm Hannes , Briarty Lewis G. , Lowe Kenneth C. , Power J. Brian , Benes Ewald , Davey Michael R.
Published: February 2003

A novel, h‐shaped ultrasonic resonator was used to separate biological particulates. The effectiveness of the resonator was demonstrated using suspensions of the cyanobacterium,Spirulina platensis. The key advantages of this approach were improved acoustic field homogeneity, flow characteristics, and overall separation efficiency (σ = 1 − ratio of concentration in cleared phase to input), monitored using a turbidity sensor. The novel separation concept was also effective under microgravity conditions; gravitational forces influenced overall efficiency. Separation ofSpirulinaat cleared flow rates of 14 to 58 L/day, as assessed by remote video recording, was evaluated under both microgravity (≤0.05g) and terrestrial gravity conditions. The latter involved a comparison with 5‐ and 24‐μm‐diameter polystyrene microspheres. Influences of gravity on σ were evaluated by varying the relative inclination angle (within a range of 120°) between the resonator and the gravitational vector. Cells ofSpirulinabehaved in a manner comparable to that of the 5‐μm‐diameter polystyrene microspheres, with a significant decrease in mean (±SE, n = 3) σ from 0.97 ± 0.03 and 0.91 ± 0.02 at a flow rate of 14 L/day, to corresponding values of 0.53 ± 0.05 and 0.57 ± 0.03 (P< 0.05) at 58 L/day, respectively. During a typical microgravity period of ca. 22 s, achieved during the 29th ESA Parabolic Flight Campaign, σ was unchanged at a flow rate of 14 L/day, compared with terrestrial gravity conditions; with increased flow rates, σ was significantly reduced. Overall, these results demonstrate that, for optimum resonator performance under the relatively short microgravity period utilized in this study, flow rates of ca. 14 L/day were preferred. These data provide a baseline for exploiting noninvasive, compact, ultrasonic separation systems for manipulating biological particulates under microgravity conditions. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 74–85, 2003.
Inactivation of bacteria and spores by pulse electric field and high pressure CO2 at low temperature
Authors: Spilimbergo Sara , Dehghani Fariba , Bertucco Alberto , Foster Neil R.
Published: February 2003

The common methods for inactivation of bacteria involve heating or exposure to toxic chemicals. These methods are not suitable for heat‐sensitive materials, food, and pharmaceutical products. Recently, a complete inactivation of many microorganisms was achieved with high‐pressure carbon dioxide at ambient temperature and in the absence of organic solvent and irradiation. The inactivation of spores with CO2 required long residence time and high temperatures, such as 60°C. In this study the synergistic effect of pulsed electric field (PEF) in combination with high‐pressure CO2 for inactivation was investigated. The bacteria Escherichia coli, Staphylococcus aureus, and Bacillus cereus were suspended in glycerol solution and treated in the first step with PEF (up to 25 KV/cm) and then with high‐pressure CO2 not higher than 40°C and 200 bar. The inactivation efficiency was determined by counting the colony formation units of control and sample. Samples of the cells subjected to PEF treatment alone and in combination with CO2 treatment were examined by scanning electron microscopy to determine the effect of the processes on the cell wall. Experimental results indicate that the viability decreased with increasing electrical field strength and number of pulses. A further batch treatment with supercritical CO2 lead to complete inactivation of bacterial species and decreased the count of the spores by at least three orders of magnitude, the inactivation being enhanced by an increase of contact time between CO2 and the sample. A synergistic effect between the pulsed electric field and the high‐pressure CO2 was evident in all the species treated. The new low temperature process is an alternative for pasteurization of thermally labile compounds such as protein and plasma and minimizes denaturation of important nutrient compounds in the liquid media. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 118–125, 2003.
Numerical Simulations of the Direct Shear Test
Authors: Thornton C. , Zhang L.
Published: February 2003

Numerical simulations of the direct shear test have been performed under constant normal stress conditions, using the Discrete Element Method. Results are presented to show how the average shear to normal stress ratio acting on the shear band compares with the force data at the boundaries. From the calculations of the stress tensor inside the shear band the corresponding Mohr’s circles are obtained and the principal stress directions identified. The principal directions of stress and strain‐rate are shown to be coaxial under steady‐state conditions. Using the state of stress and strain in the shear band, the interpretation of direct shear test data is discussed in the context of traditional experimental measurements.
Applying the Discrete Element Method in Process Engineering
Authors: Theuerkauf J. , Dhodapkar S. , Manjunath K. , Jacob K. , Steinmetz T.
Published: February 2003

This paper provides insight into the application of discrete element modeling in the field of bulk solids handling. This is shown with examples starting with the calibration of a virtual numerical material used in the simulation to mimic the actual material’s behavior. Based on the calibration of the material, solid handling problems such as the flow patterns and the stress distribution in silos are discussed.
Uniaxial Testing and the Performance of a Pallet Press
Authors: Enstad G.G. , Ose S.
Published: February 2003

It is a common problem that powders become aerated during filling into sacks, causing increased volumes, low mechanical stability, bursting of sacks, dusting as air escapes, difficulties in palletizing, and stacking of the pallets. In order to overcome such problems, a pallet press was developed several years ago. The press is used to obtain a more uniform geometry and to get rid of excess air from palletized sacks by simply pressing the pallets into a rectangular shape. How a powder will behave during filling into sacks will depend on its properties. By testing the powders to be stored in this way, one can predict what advantages can be obtained by using the pallet press for specific powders. The applicability of a uniaxial tester, developed for testing flow properties of powders, has been investigated for this purpose by Tel‐Tek, POSTEC dept.
A Stressing Model for the Description and Optimization of Grinding Processes
Authors: Kwade A.
Published: February 2003

The comminution behavior of a mill is characterized by the frequency of stress events, and the stress energy, acting at each stress event. Based on this, a comminution result is determined by the number of stress events, and the stress intensity. The product of stress number and stress energy is proportional to the specific energy input. The proportionality factor is the energy transfer factor, which describes the percentage of energy that is used for stressing the product particles. Using the characteriztic numbers based on a few tests, the operating parameters can be optimized and different mills can be compared. The application of the stressing model is shown for stirred media mills.
Investigation and Modeling of Growth, Structure and Oxygen Penetration in Particle Supported Biofilms
Authors: Boessmann M. , Staudt C. , Neu T.R. , Horn H. , Hempel D.C.
Published: February 2003

Particle supported biofilms have been investigated with respect to biofilm formation, substrate transport and utilization. The investigated autotrophic and heterotrophic biofilms were cultivated in airlift suspension reactors. CLSM was used to describe the biofilm structure by recording volumes of bacteria and EPS glycoconjugates. Additionally, the microelectrode technique was used to measure transport and substrate utilization in the biofilm system. The experimental results on the microscopic scale were used to improve a mathematical model for biofilm growth. The oxygen profiles measured in the particle supported biofilms and the data from CLSM were used to optimize the model parameters.
X‐ray Diffraction Studies on Mesophases of Cetyl‐ and Dodecyltrimethylammoniumbromide in Liquid Ammonia
Authors: Bzik Stefan , Jansen Martin
Published: February 2003

We have studied solutions of the surfactants cetyltrimethylammoniumbromide (CTAB) and dodecyltrimethylammoniumbromide (DTAB) in liquid ammonia with respect to the formation of lyotropic phases. For this purpose, a set‐up for performing X‐ray scattering experiments at temperatures up to 120 °C on samples containing liquid ammonia has been developed. Both systems form hexagonal and monoclinic lyotropic phases above the dissolving temperature of the surfactant, thus representing the first examples for lyotropic phases in liquid ammonia, and for monoclinic phases in nonaqueous solvents. The phase diagrams of CTAB/liquid NH3 and DTAB/liquid NH3 show similarities to their respective aqueous systems. However, the regions of existence of monoclinic phases are much larger in the ammonia system, while the cubic phases, as observed in the water based systems, do not seem to exist. The liquid‐crystalline phases found provide potentiality for preparing mesoporous, nitride‐based solids.
Determining the Strengths of Hydrogen Bonds in Solid‐State Ammonia and Urea: Insight from Periodic DFT Calculations
Authors: Morrison Carole A. , Siddick Muhammad M.
Published: February 2003

Plane‐wave density functional theory has been applied to determine the strengths of hydrogen bonds in the phase I crystal structures of ammonia and urea. For ammonia, each component of the trifurcated hydrogen bond has been found to be almost as strong as a standard N‐H⋅⋅⋅N interaction, and for urea the strengths of the two different N‐H⋅⋅⋅O interactions have been determined by a quantum mechanical technique for the first time.
Cover Picture: Chem. Eur. J. 3/2003
Authors: Klapötke Thomas M. , Krumm Burkhard , Piotrowski Holger , Polborn Kurt , Holl Gerhard
Published: February 2003

The cover picture shows the molecular structure of an azido‐substituted hexabenzylhexaazaisowurtzitane (carbon: red, nitrogen: blue). The hexaazaisowurtzitane cage system, a 2,4,6,8,10,12‐hexaazatetracyclo[5.5.0.05,9.03,11]dodecane, consists, just as this shown derivative, entirely of carbon, nitrogen and hydrogen (omitted in this image). The synthesis of hexaazaisowurtzitanes is limited solely to the condensation of certain benzylamines with glyoxal. Further derived hexaazaisowurtzitanes exhibit properties that are useful for the possible application as energetic materials and/or propellants (see background). An investigation of the influence of azido‐ and fluoro‐substituted benzyl amines on the formation of this cage system is described by T. M. Klapötke, B. Krumm et al. on p. 687 ff.
Early–Late Heterobimetallic Alkoxides as Model Systems for Late‐Transition‐Metal Catalysts Supported on Titania
Authors: Fandos Rosa , Hernández Carolina , Otero Antonio , Rodríguez Ana , Ruiz María José , Terreros Pilar
Published: February 2003

Titanium complexes with chelating alkoxide ligands [TiCp*(O2Bz)(OBzOH)] (1) and [TiCp*(Me){(OCH2)2Py}] (2) were synthesised by reaction of [TiCp*Me3] (Cp*=η5‐C5Me5) with 2‐hydroxybenzyl alcohol ((HO)2Bz) and 2,6‐pyridinedimethanol ((HOCH2)2Py), respectively. Complex 1 reacts with [{M(μ‐OH)(cod)}2] (M=Rh, Ir) to yield the early–late heterobimetallic complexes [TiCp*(O2Bz)2M(cod)] [M=Rh (3), Ir (4)]. Carbon monoxide readily replaces the COD ligand in 3 to give the rhodium dicarbonyl derivative [TiCp*(O2Bz)2Rh(CO)2] (5). Compound 2 reacts with [{M(μ‐OH)(cod)}2] (M=Rh, Ir) with protonolysis of a TiMe bond to give [TiCp*{(OCH2)2Py}(μ‐O)M(cod)] [M=Rh (6), Ir (7)]. The molecular structures of complexes 3, 5 and 7 were established by single‐crystal X‐ray diffraction studies.
New Mechanistic Insight into the Coupling Reactions of CO2 and Epoxides in the Presence of Zinc Complexes
Authors: Kim Hoon Sik , Kim Jai Jun , Lee Sang Deuk , Lah Myoung Soo , Moon Dohyun , Jang Ho Gyeom
Published: February 2003

Coupling reactions of CO2 and epoxide to produce cyclic carbonates were performed in the presence of a catalyst [L2ZnX2] (L=pyridine or substituted pyridine; X=Cl, Br, I), and the effects of pyridine and halide ligands on the catalytic activity were investigated. The catalysts with electron‐donating substituents on pyridine ligands exhibit higher activity than those with unsubstituted pyridine ligands. On the other hand, the catalysts with electron‐withdrawing substituents at the 2‐position of the pyridine ligands show no activity; this demonstrates the importance of the basicity of the pyridine ligands. The catalytic activity of [L2ZnX2] was found to decrease with increasing electronegativity of the halide ligands. A series of highly active zinc complexes bridged by pyridinium alkoxy ions of the general formula [{(μ‐OCHRCH2L)ZnBr2}n] (n=2 for R=CH3; n=3 for R=H; L=pyridine or substituted pyridine) were synthesized and characterized by X‐ray crystallography. The dinuclear zinc complexes obtained from propylene oxide adopt a square‐planar geometry for the Zn2O2 core with two bridging pyridinium propoxy ion ligands. Trinuclear zinc complexes prepared from ethylene oxide adopt a boat geometry for the Zn3O3 core, in which three zinc and three oxygen atoms are arranged in an alternate fashion. These zinc complexes bridged by pyridinium alkoxy ions were also isolated from the coupling reactions of CO2 and epoxides performed in the presence of [L2ZnBr2]. Rapid CO2 insertion into the zincoxygen bond of the zinc complexes bridged by pyridinium alkoxy ions leads to the formation of zinc carbonate species; these which yield cyclic carbonates and zinc complexes bridged by pyridinium alkoxy ions upon interaction with epoxides. The mechanistic pathways for the formation of active species and cyclic carbonates are discussed on the basis of results from structural and spectroscopic analyses.
Synthesis and Structures of Trifluoromethyl‐, Fluoro‐, and Azido‐Substituted Hexabenzylhexaazaisowurtzitanes and Isolation of a Novel Hexaazaisowurtzitane‐Based Polycycle
Authors: Klapötke Thomas M. , Krumm Burkhard , Piotrowski Holger , Polborn Kurt , Holl Gerhard
Published: February 2003

The first hexabenzylhexaazaisowurtzitane cage compounds with trifluoromethyl and azide groups, as well as those with fluorine atoms in the 3‐ and 4‐positions, have been prepared and fully characterized. A study of the substituent influence on the benzene ring regarding the formation of the hexaazaisowurtzitane polycycle in either the 2‐ or 4‐position with CF3, F, and N3 revealed an interesting difference. In all cases with CF3, F, and N3 substituents in the 4‐position, the corresponding hexabenzylhexaazaisowurtzitanes were isolated. The corresponding hexabenzylhexaazaisowurtzitanes were also formed when these substituents were in the 2‐position; however, in addition with azide in 2‐position a novel type of polycycle was isolated and identified. 15N NMR data and crystal structures of hexabenzylhexaazaisowurtzitane derivatives were obtained and are discussed in detail.
Competitive Reactions of Interstrand and Intrastrand DNA‐Pt Adducts: A Dinuclear‐Platinum Complex Preferentially Forms a 1,4‐Interstrand Cross‐Link Rather than a 1,2 Intrastrand Cross‐link on Binding to a GG 14‐Mer Duplex
Authors: Berners‐Price Susan J. , Davies Murray S. , Cox John W. , Thomas Donald S. , Farrell Nicholas
Published: February 2003

A study of the kinetics and mechanism of the reaction between the dinuclear Pt complex [{trans‐PtCl(NH3)2}2(μ‐NH2(CH2)6NH2)]2+ (1) and the 14‐mer duplex 5′‐d(ATACATG(7)G(8)TACATA)‐3′⋅5′‐d(TATG(25)TACCATG(18)TAT)‐3′ is reported. [1H,15N]‐HSQC NMR was used to follow the reaction at 298 K, pH 5.4. The product is primarily the 5′–5′ 1,4‐interstrand cross‐link between G(8) and G(18) bases and exists in two conformational forms. No evidence for the possible 1,2‐intrastrand G(7)G(8) adduct was seen, confirming the preferential formation of interstrand cross‐links by these dinuclear complexes. An initial electrostatic association of 15N‐1 with the duplex is indicated by changes in its 1H/15N chemical shifts, followed by aquation of 1 to form the monoaqua monochloro species 2, with a rate constant of 4.00±0.03×10−5 s−1. Monofunctional binding to the duplex occurs primarily at G(8), the 3′ base of the nucleophilic GG grouping, with a rate constant of 1.5±0.7 M−1 s−1. Changes in the 1H/15N shifts indicate there is an electrostatic interaction between the unbound {PtN3Cl} group of the monofunctional adduct and the duplex. No peaks for a transient aquated monofunctional species are seen and closure of 3 to form the 1,4‐G(8)G(18) interstrand cross‐link (5) was treated as direct, with a rate constant of 4.47±0.06×10−5 s−1. The G(8)G(18) cross‐link was confirmed from analysis of the NOESY NMR spectrum of the final product. Structural perturbations for the 1,4‐interstrand cross‐link extend over approximately four base‐pairs and are similar to those found for a 1,4‐interstrand cross‐link with a shorter 8‐mer ‐GTAC‐ sequence. A major distortion was evident for the 5′T (T(17)) adjacent to the platinated G(18), consistent with the findings from the use of chemical probes to investigate the conformation of 1,4‐interstrand cross‐links.