bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of airlift bioreactors in the cultivation of some antibiotic producing microorganisms
Authors: Gavrilescu M. , Roman R. V. 
Published: December 2004

AbstractThe specific aspects of airlift reactors emphasizing their function relevance to particular application as bioreactors are presented.The two main groups of airlift reactors – external‐loop and concentric‐tube reactors – were investigated on a pilot‐plant scale with regard to their performance during the cultivation of unicellular and filamentous microorganisms which produce Bacitracin, Cephalosporin C and Nystatin. Some results were compared to those obtained in conventional stirred tank bioreactors. The comparison was carried out based on physical properties (oxygen transfer rate (OTR), volumetric mass transfer coefficient (kLa) and efficiency of oxygen transfer (E)), cell mass, productivity and substrate consumption, secondary metabolite production, and efficiency of the product formation with regard to the specific power input.It was shown that B. licheniformis, C. acremonium and S. noursei fermentations occurred similarly to those performed in stirred vessels, proving that the capacity of the airlift bioreactors surpassed the problems which arise from the morphology and rheology of the broths. From the chemical engineering point of view, it was obvious that the primary tasks of a bioreactor (uniform distribution of microorganisms and nutrients over the entire fermenter volume, appropriate supply of biomass with nutrients and oxygen) were fulfilled by the airlift bioreactors tested. In addition, the efficiency of oxygen transfer (OTR referred to power input) in the airlift fermenters proved to be about 38% higher than in the stirred tank bioreactors (expressed as average values), while the sorption efficiency (OTR referred to antibiotic production) was found to be 22% greater in the airlift system than in an STR.Therefore, the biosyntheses were performed with about a 30–40% increase in energy efficiency and energy savings compared to the conventional system.Moreover, the lack of mechanical devices in the airlift system provides greater safety and a gentler environment for the cultivation of microorganisms.
The influence of LBG addition to carrageenan on the mechanical stability of the gel and the fermentative activity of immobilized propionic acid bacteria
Authors: Czaczyk K. , Olejnik A. , Trojanowska K. 
Published: December 2004

AbstractIn the first part of the experiments, the mechanical properties of 1%, 2% and 3% carrageenan and 1%, 2% and 3% carrageenan/locust bean gum (LBG) gels stored in various concentrations of propionic and acetic acids and their mixtures were examined. The stability of these materials was measured by uniaxial compression between two parallel plates using the Instron Universal Testing Machine. A mathematical model explaining the dependence of the destroying force on the storage time was chosen for data analysis. Using this model, the average rate of gel deterioration was calculated. The structural properties of the examined gels were most influenced by the highest concentration of propionic and acetic acids and their mixtures (1% acetic acid and 2% propionic acid). The addition of LBG to carrageenan decreased the gel destroying force and increased its resistance to acids.In the second part of the experiments, the Propionibacterium freudenreichii subsp. shermanii NCFB 1081 and NCFB 566 were immobilized in a living state in 1%, 2% and 3% carrageenan and 1%, 2% and 3% carrageenan/LBG gels. The ammonia consumption, glucose utilization, production of propionic and acetic acids and the biosynthesis of vitamin B12 were examined. An increase in the productivity of propionic acid and a significant decrease in the vitamin B12 produced in the biosynthesis were observed when immobilized cells were used. The immobilization of cells enhanced the productivity of propionic acid by up to 40% compared to free cells. The best results were obtained for the second and third applications of immobilized cells in all concentrations of carrageenan gels and 2% and 3% carrageenan/LBG gels The results showed that carrageenan/LBG is a better support material for the immobilization of propionic acid bacteria than the pure carrageenan.
Optimization of the production of bacterial cellulose using multivariable linear regression analysis
Authors: Galas E. , Krystynowicz A. , Tarabasz‐Szymanska L. , Pankiewicz T. , Rzyska M. 
Published: December 2004

AbstractThe biosynthesis of bacterial cellulose by Acetobacter xylinum was optimized by numerically finding the maximum of an arbitrarily chosen second order polynomial model function of several variables (describing the dependence of the cellulose production on the concentrations of the medium components), using multivariable linear regression analysis. The chosen function appeared to describe the analyzed correlation sufficiently well. Consequently, three to six stages of optimization made the determination of the optimum medium compositions possible for 16 days of fermentation at 30°C in a medium based on fructose (wt%: fructose, 3.68; yeast extract, 5.02; (NH4)2NO3, 0.001; KH2PO4, 0.3; MgSO4 × 7 H2O, 0.05; resulting in a cellulose production equal to 0.505 wt.% – namely 5.6 times higher than before the optimization) and for 7 days fermentations at 30°C in a medium based on sucrose and ethanol (wt.%: sucrose, 5.0; ethanol, 1.36; yeast extract, 1.27; (NH4)2SO4, 0.5; KH2PO4, 0.3; MgSO4 × 7 H2O, 0.05; resulting in a cellulose production equal to 0.251 wt.% – namely 1.5 times higher than before the optimization).
Flame‐burned stainless steel wire spheres as carriers of Zymomonas mobilis cells and extracellular levansucrase
Authors: Bekers M. , Laukevics J. , Upite D. , Kaminska E. , Linde R. 
Published: December 2004

AbstractIn the present work, the use of flame‐burned WS as carriers of Z. mobilis and extracellular levansucrase and the effect of the cell fixation method by dehydration on system productivity were investigated. Lyophilization and convective drying of Z. mobilis biomass at 30°C to a moisture content of 10–14% gave the best results for the repeated batch fermentations of a sucrose medium to obtain levan and ethanol. Significant correlation between the product formation and the concentration of free cells in the fermentation medium was established. Clearly, the cells were weakly bound to the newly generated WS and were washed out into the medium during fermentation. Here the hypothesis is presented that components excreted from damaged cells during dehydration can intensify the reactivation of damaged living cells and influence the interactions between the cells and the wire surface.The passive immobilization of extracellular levansucrase in oxidized WS was also observed. The superiority of oxidized WS in comparison with non‐treated WS is related to an increase in the number of OH groups. The potential regeneration of WS by burning after the termination of fermentation cycles was also considered.
Production of L‐malate from fumarate by the yeast Dipodascus magnusii
Authors: Miková H. , Rosenberg M. , Krištofíková L. , Sulo P. 
Published: December 2004

AbstractAn alternative microbiological method for the production of malate from fumarate is presented. The yeast Dipodascus magnusii was used for this bioconversion.The optimum cell growth temperature was 28°C and the working volume 120 ml. The highest level of fumarase activity during bioconversion was achieved at a pH of 7.5 and a temperature of 37°C. These conditions were determined as optimal. Using sodium fumarate (1M), the maximum specific productivity of malic acid obtained was 1.72 g/(gDCW × h) for intact cells. In the case of ammonium fumarate, it was 2.25 g/(gDCW × h).
Continuous preparative liquid chromatography in the downstrem processing of biotechnological products
Authors: Schulte M. , Britsch L. , Strube J. 
Published: December 2004

AbstractContinuous counter‐current chromatographic processes have been successfully used in the petrochemical and sugar industry over the last 30 years. Only recently has simulated moving bed (SMB)‐technology attracted widespread interest in the pharmaceutical industry, mainly as a very efficient system for chromatographic enantioseparation. The application of this technique to the downstream processing of biotechnological products requires some specific changes to meet the special demands of bioproduct isolation. Production processes are set up on an multi‐ton scale, for example, for the purification of fructose with both yield and purity higher than 90%. Examples for other mono‐ and oligosaccharides are reported. In the purification of fatty acids or fat soluble vitamins, SMB technology under supercritical fluid conditions gives additional benefits and increases the productivity by a factor of four when a pressure gradient is applied. Another field of operation is the isolation of drug compounds from natural sources where different batch‐ and SMB‐chromatographic steps could be successfully combined. First examples are reported for cyclosporine A and paclitaxel isolation. Finally, step‐gradient elution modes can be used continuously, as demonstrated for the isolation of monoclonal antibodies.
Advanced primary treatment of waste water using a bio‐flocculation‐adsorption sedimentation process
Authors: Zhao W. , Ting Y. P. , Chen J. P. , Xing C. H. , Shi S. Q. 
Published: December 2004

AbstractAn advanced primary treatment process for a municipal waste water was systematically studied, using a bio‐flocculation‐adsorption, sedimentation and stabilzation process (BSS). It was shown that the organic removal efficiency was higher than that of the traditional primary treatment processes but lower than that of the traditional secondary treatment processes. Both adsorption and bio‐flocculation played an important role in the removal of pollutants. The activated sludge within the bio‐flocculation‐adsorption tank could be considered a bio‐flocculent which improved the quality of the effluent from the primary treatment process. As the effluent of the BSS process did not meet the requirements for a typical secondary effluent, the process may be regarded as an advanced (or enhanced) primary treatment process, suitable for waste water containing a high concentration of suspended solids and colloidal particles.
Scientific methodology for complex systems: Macroscopic patterns in eco‐ and anthropo‐sphere
Authors: Moser A. 
Published: December 2004

AbstractA quite unconventional, innovative scientific methodology called “macroscopic pattern analysis” is presented in this paper. This approach is more adequate in the case of complex systems than the well‐known microscopic, mechanistic approach. Complex systems are not only attracting more engineering interest, but their scientific treatment is increasingly wanted by society due to the manifold problems in Earth's ecosphere. The macroscopic pattern approach will be explained in depth and illustrated in some case studies from the ecosphere (sustainability, hurricanes and avalanches), where nature serves as a teacher for the solution of the sustainability problem. Then, a series of case studies on macropatterns are described showing the problem‐solving capacity for anthropo‐ and technosphere: sustainability in society with an index of sustainability, the eco‐social market economy with eco‐tech as an instrument, biokinetics, bioreactor mixing and integrated bioprocessing with models, design of cars and houses and even quality of life as an attempt to quantify macropatterns.The innovations are briefly compared in their problem‐solving capacity with known approaches such as the microscopic method in science, technology and society (free market economy), including the evaluation of other indices and cleaner production, industrial ecology and zero emission initiative. Finally, a deeper integration of sciences, ethics, arts and nature will be introduced based on the vision with macroscopic pattern analysis, where the different domains of human life are integratable to effect a reconciliation.
Aerospace materials research opportunities
Authors: Salkind Michael 
Published: December 2004

AbstractAs we approach the second century of aerospace, increased emphasis is being placed on endurance, reliability, ease of manufacture, and lower cost, in addition to weight saving. This change in emphasis will have a major effect on not only the selection of materials, but on how materials are integrated into the total system design process. Subsonic aircraft will continue to play a major role in our future with emphasis on increased durability and lower cost. Non‐metals that do not corrode are attractive; however, the issues of reliable fracture resistance to ensure safety and durability as well as ease of manufacture and inspection will be key. Higher performance engines and hypersonic aircraft will require higher temperature materials (including a substantial amount of non‐metals) along with reliable toughness and ease of manufacture. In space, weight will continue to be a major driving force along with the need for long term vacuum and radiation stability. Ease of assembly and multifunctional use (e.g. electrically or thermally conducting structure) will be additional needs for spacecraft materials. We have reached a point in the evolution of structural materials where we are moving away from processing naturally occurring materials toward synthesizing designed microstructures to perform specific functions. The mathematical modeling of microstructure–property relationships and new chemical and biotechnical synthesis techniques appear to be critical technologies for the future. In addition, the future materials developer will need a broader understanding of the total structural life cycle so that the impact of utilization, maintenance, and training requirements in the design of new materials can be considered.
Surface analysis II. Surface‐plasmon enhanced resolution in optical microscopy
Authors: Rabe Jürgen P. 
Published: December 2004

Methods of improving the resolution of optical microscopes which involve, for example, forcing the light through an aperture which is smaller than the wavelength of the light (see Figure) or the coupling of the light to a plasmon to form a surface‐plasmon polariton are described. The latter method is particularly suitable for determining, for example, the optical thickness of an ultrathin transparent film with high precision on a micron scale.
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Semiconductor wafer bonding
Authors: Lehmann V. , Ong I. W. K. , Gösele U. , Stengl R. , Mitani K. 
Published: December 2004

High‐voltage pn‐diodes, and silicon on insulator (SOI) materials are two applications that could benefit from a new method of wafer bonding which can be carried out in a normal laboratory environment. The procedure, which involves spinning the wafers at high speed (see figure) thus creating a “micro‐cleanroom” between them, could also have applications in micro‐mechanical work and wafer protection.
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Laser‐induced polymerization of siloxanes without photoinitiators
Authors: Roth Wolfgang , Henkel Hans‐J. , Hoffmann Klaus W. , Markert Helmut 
Published: December 2004

High‐purity polymers even os the chemically inert dimethylsiloxane (see figure) can be produced by initiating the polymerization of the monomers using laser light rather than chemical initiators which are usually one of the main sources of impurities in the polymers. Polysiloxanes are used in electronics due to their excellent thermal and dielectric properties.magnified image
Polymer‐salt intercalation complexes in layer silicates
Authors: Ruiz‐Hitzky Eduardo , Aranda Pilar 
Published: December 2004

Composite ionic conductors based on homoionic montmorillonites (2:1 charged layers silicates containing metal ions in their interlayer space) cinteracted with poly(ethylene oxide) exhibit enhanced condcutivity between silicate layers (see figure). The presence of tunnels in the intercalated polymer–salt complex is thought to facilitate intracrystalline ion mobility.magnified image
Biomaterials highlights VII. Implants in ear nose and throat (ENT) surgery
Authors: Heimke Ganther 
Published: December 2004

AbstractImplants are used in all three major fields of ENT surgery with, however, widely varying materials requirements. In contrast to most other fields of implantology, the transmission of functional loads is only of minor importance and, thus, neither the mechanical properties of the implant materials nor the interfacial stress and strain fields demand major consideration.
Cluster formation during desorption of multilayers of fatty acid salts
Authors: Tippmann‐Krayer Petra , Meisel Werner , Mölnwald Helmut 
Published: December 2004

The thermo desorption mechanism of Cd‐arachidate langmuir–Blodgett films has been shown to involve the lateral rupture of the film to give droplets (see Figure). On further heating, these droplets lose the aliphatic molecular part resulting in a uniform lateral distribution of three‐dimensional inorganic clusters on the substrate surface.
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Characterization and modification of conducting substrates for ultrathin organic films by scanning tunneling microscopy
Authors: Buchholz Stefan , Fuchs Harald , Rabe Jürgen P. 
Published: December 2004

Communication: The structure of an organic film of molecular thickness depends strongly on the surface properties of the underlying substrate. STM is a method which enables a substrate surface to be characterized and controlled as demonstrated in the figure, where the letter “U” etched with an STM tip into a highly oriented pyrolytic graphite (HOPG) surface is shown. The holes, which are around 5 nm in diameter, could serve as nucleation sites for an organic adsorbate phase.magnified image
The Synthesis of Polymer Supports
Authors: Arshady Reza 
Published: December 2004

AbstractConventional polymer supports (polymeric reagents, functional polymers) such as polyacrylamides and polystyrene are based on either strongly polar or nonpolar chemical structures. As a result, these polymers may show low reactivity and poor performance due to their relatively limited ranges of solvent and substrate compatibility. More‐recently introduced products are designed on the basis of copolymer structures, which incorporate both polar and nonpolar (hydrophilic and hydrophobic) residues and possess general solvent and substrate compatibility. Due to their ease of production, general solvent and substrate compatibility and improved performance, these new “amphiphilic” copolymers provide new impetus in the study and applications of polymer supports and functional polymers.
Solid‐state NMR of Heterogeneous Materials
Authors: Blümich Bernhard 
Published: December 2004

AbstractMost solid matrials are hetorogeneous on a microscopic or a microscopic scale, or both. Examoles of hetrogeneties are the phase structure of incompatible polymers, pores in ceramics, distributions in mechanical stress, variations in molecular order and mobility of extruded polymers, and chemical composition in composite materials. Nuclear magnetic resonance (NMR) spectroscopy has unique capabilities for detailed characterization of such hetrogeneities: Microscopic structures between 1 nm and 200 nm can be investigated in spin‐diffusion studies, whereas macroscopic structures above 10 μm can be analyzed in imaging experiments.
Metal injection molding: Shaping sintered metal parts
Authors: Michaeli Walter , Bielzer Raffael 
Published: December 2004

Reserch News: Rapid production of high‐tolerance metal parts with complex shapes through combining the sintering process with injection molding, a technique usually used for plastics, is described. Injection of a mixture of metal powder and binder is followed by removal of the binder (right) and then sintering to the final density (left).magnified image
The detection of halogenated hydrocarbons via host–guest chemistry—a mass‐sensitive sensor study with QMB‐ and SAW‐devices
Authors: Dickert Franz L. , Bauer Petra A. 
Published: December 2004

Communication: Ring‐like structures composed of different numbers of glucose molecules, the cyclodextrins, in which the central cavity (see Figure) can be varied in diameter from 4.7–8.5 Å have been shown to act as specific host materials for a number of halogenated hydrocarbons. The effect, and potential applications as solvent sensors based on quartz‐microbalence‐ and surface‐accoustic‐wave oscillator devices are discussed.
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High‐Performance Polymers
Authors: Herold Friedrich , Schneller Arnold 
Published: December 2004

The various applications of high‐performance polymers, for example in hollow‐fiber membranes (see figure) or as gears in chemical pumps, require materials with widely differing properties. An overview of the different classes of high‐performance polymers available, including polyetherketones, polysulfones, and polyamides, is provided and the various combinations of mechanical strength, thermal stability, chemical resistance, and electrical properties are discussed. magnified image
Covalent High‐Performance Ceramics
Authors: Böcker Wolfgang D. G. , Hamminger Rainer , Heinrich Jürgen , Huber Jürgen , Roosen Andreas 
Published: December 2004

Non‐oxide ceramics, for example aluminum nitride, silicon carbide, and silicon nitride, are ideal materials for applications under high thermal and mechanical stress. The synthetic methods including liquid‐phase sintering processes, the microstructures of the resulting materials (figure shows Si3N4 from powder produced using the diimide route), and some aspects of the characteization and application of the materials are discussed. magnified image
Ferroelectric liquid crystals in high information content displays
Authors: Escher Claus , Wingen Rainer 
Published: December 2004

Rugged, light, high‐resolution flat panel displays are now being developed using liquid‐crystal (LC) technology with the aim of replacing cathode ray tubes in for example computer monitors and televisions. The basic concepts of the displays are described, the advantages and drawbacks of the most important technologies are compared, and some recent work on ferroelectric LC displays which promise high contrast and brightness (see figure) is reviewed. magnified image
Miscible Polymer Blends: Local interaction energy theories and simulations
Authors: Jacobson Solomon H. , Gordon Douglas J. , Nelson Gregory V. , Balazs Anna 
Published: December 2004

AbstractPolymer blends of two components, in general, are not miscible. However, according to Karasz‐MacKnight theory, intramolecular repulsion may outweigh intermolecular repulsion and cause two polymers to have a net interaction. Using a simple short chain molecular model incorporating both interand intramolecular interactions, estimates of net interaction energies for a series of polymeric imides, benzimidazoles and related high‐performance polymers can be calculated and used to predict miscibility in excellent agreement with experimental results, thus providing a useful confirmation of theory and a focus for the direction of further experimental work.