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PubMed1990

High-performance liquid chromatography.

Gas chromatography has developed over the past 25 years or so into one of the most extensively used on-line analytical techniques in industrial process control and optimization. Liquid chromatography, and its several individual techniques, is firmly established in the laboratory, but its on-line process use has not developed as rapidly as GC. At the present time, only three companies (Applied Automation Inc., Dionex Corp., and Millipore Corp.) are active in this area. Nevertheless, substantial growth in on-line process LC is predicted for the next few years. The techniques of HPLC (normal-phase and reversed-phase), IEC, and SEC have great potential in industry as on-line analytical techniques, including the new field of biotechnology. Computer-based, multistream, multicomponent systems should find extensive use in pilot-plant investigations, where their ability to gather large amounts of data (on-line rather than by laboratory testing) could have important implications. In bioprocess control, undoubtedly the greatest challenge will come in the area of sample-handling technique. On-line chromatography has traditionally involved the sampling and conditioning of fairly conventional process gases and liquids. One exception is in the plastics and elastomers areas, where on-line SEC has been used for polymer MWD measurement. Here the sample is more difficult to handle, and some specialized techniques have been used. In biotechnology, we are treading new ground; nevertheless, it is hoped that some of the experience in sample handling gained in industry over the past 25 years will be of use in this new field.

Chromatography, High Pressure Liquid↗

PubMed1990

[Determination of the rate of utilization of glucose in a suspension of erythrocytes].

The authors suggest a new method for measuring the rate of glucose utilization in a cell (red cell) suspension, making use of interferometry. This method allows an easy examination of glucose utilization kinetics in time with but 1000 cells. Thermostatic control of the sample in the cuvette of the device permits detecting the temperature effects on glucose metabolism kinetics and thus define the temperature optimal for the process. A correlation was revealed between the point of structure phase transition in the red cell membrane and the optimal temperature for glucose utilization within the range of physiologic temperatures. This method may be useful in medical, biochemical, physiologic, and hematologic studies. The relative error of the technique is 3 percent.

Blood Glucose↗

PubMed2001

Cyclic activated sludge technology--recent operating experience with a 90,000 p.e. plant in Germany.

Cyclic activated sludge technology was selected for the Potsdam Wastewater Treatment Plant (90,000 p.e.). The cyclic activated sludge facility comprises four modules integrated into two circular basins. Construction was commenced in February 1998 with seeding of the plant for start up taking place in October 1998. Process performance has been met since Spring 1999 at 80-90% of design load. In order to optimize start-up procedures, respiration rates were used as a guidance for process stabilization and online process optimization during normal operation. Operation for co-current nitrification denitrification provided an ammonia removal of 1.1 mg NH4-N/g MLSS.h (15 degrees C) and a corresponding nitrate respiration rate of 0.85 mg NO3-N/g MLSS.h under aerated conditions. Enhanced biological phosphorus removal generated an effluent mean total phosphorus concentration of 0.38 mg/L without precipitant addition.

Bioreactors↗

PubMedDate not supplied

Pharmacokinetic data processed by microcomputer for the formulation of optimal drug dosage form.

Microcomputers have been used in pharmacokinetics for several years, but their use in the area of formulation is a new application. By using appropriate data on the drug, the dosage form required and its mechanism of absorption and clearance, microcomputers can systematize and speed-up formulation, simplify manufacturing processes and, through simulated models and plasma level predictions, reduce the number of bioavailability studies needed.

Biological Transport↗

PubMed1992

Optimal medium use for continuous high density perfusion processes.

For maintenance of high cell density in continuous perfusion processes not only feeding with substrates but also removal of inhibitors and toxic waste products are of special interest. High perfusion rates cause large volumes of product containing medium which have to be processed in product isolation. In order to minimize these volumes concentrated feed solutions of optimized medium are used. On the other hand, such media may cause high concentrations of toxic or inhibitory metabolites which can negatively influence cell growth and product formation. Especially, if the spent medium (or special parts of it) is used again after product isolation, the removal or even better the control of inhibitor production is of highest importance. We have developed a continuous fermentation concept and system (continuous medium cycle bioreactor, cMCB) in which both limitation and inhibition effects can be generated to identify special substances as limiting or inhibitory components. With the results from those experiments it was possible to lower the total perfusion rate during serum-free perfusion cultures of hybridoma cells and to obtain an optimal substrate utilization. The advantages for decreasing the production costs (for media, special supplements and product isolation) are obvious. The other aim of this study was to identify secreted metabolic waste products as inhibitor or toxic metabolite.

Animals↗

PubMed1993

Clinical application of three-dimensional sonography in internal medicine.

Three-dimensional sonography represents a development of non-invasive diagnostic imaging by real-time two-dimensional sonography. The use of transparent rotating scans, comparable to a block of glass, generates a three-dimensional effect. The first clinical application of this technique was in the field of gynecology and obstetrics, namely in prenatal diagnostics. In this study we describe its first application in internal medicine. In preliminary examinations on healthy volunteers we obtained specific processing data for optimal imaging results. This was followed by secondary examinations on 123 patients who had previously undergone conventional sonography with pathological findings. In more than 75% of the cases examined we found an optimal reproduction of sonographic findings with respect to the evaluation criteria developed by us for the three dimensional imaging of processed data. With the inclusion of measurement parameters such as distance determination and volume measurements the data gathered will allow the generation of reproducible results. Future studies will confirm the value of this method in diagnostic imaging.

Adult↗

PubMed2005

Comparison of phytase production on wheat bran and oilcakes in solid-state fermentation by Mucor racemosus.

Comparisons were made for phytase production using wheat bran (WB) and oilcakes as substrates in solid-state fermentation (SSF) by Mucor racemosus NRRL 1994. WB was also used as mixed substrate with oil cakes. Sesame oil cake (SOC) served as the best carbon source for phytase synthesis by the fungal strain as it gave the highest enzyme titres (30.6 U/gds). Groundnut oil cake (GOC) also produced a reasonably good quantity of enzyme (24.3 U/gds). Enzyme production on WB was surprisingly much less (almost 3.5 times less in comparison to SOC). Mixing WB with SOC (1:1 ratio) resulted in better phytase activity (32.2 U/gds). Optimization of various process parameters such as incubation time, initial moisture content and inoculum concentration was carried out using the single variable mode optimization technique. Under optimized conditions, the production of phytase reached 44.5 U/gds, which was almost 1.5-fold higher than the highest yield obtained with any individual substrate used in this study and was more than 4-fold higher than that obtained from WB.

6-Phytase↗

PubMed2001

The meaning of death: some simulations of a model of healthy and unhealthy consumption.

Simulations of a model of healthy and unhealthy consumption are used to investigate the impact of various terminal conditions on life-span, pathways of health-related consumption and health. A model in which life-span and the 'death' stock of health are fixed is compared to versions in which (i) the 'death' stock of health is freely chosen; (ii) life-span is freely chosen; (iii) both the 'death' stock of health and life-span are freely chosen. The choice of terminal conditions has a striking impact on optimal plans. Results are discussed with reference to the existing demand for health literature and illustrate the application of iterative processes to determine optimal life-span, the role played by the marginal value of health capital in determining optimal plans, and the importance of checking the second-order conditions for the optimal choice of life-span.

Attitude to Death↗

PubMed2001

Extraction kinetics of phenol with N, N-di (1-methyl-heptyl) acetamide-kerosene using hollow fiber membrane extractor.

Extraction kinetics of phenol with N,N-di(1-methyl-heptyl) acetamide-kerosene using hollow fiber membrane extractor has been studied. The rate regularities and kinetic types of forward and backward extraction were obtained respectively by determining the forward and backward extraction rate under various experimental conditions. The mass transfer mechanism was discussed. Both the forward and backward extraction of phenol might be controlled by diffusion processes, and the diffusion resistance for both forward and backward extraction mainly exists in aqueous phase. In addition, ways to optimize the extraction process of phenol were discussed as well.

Acetamides↗

PubMed1991

[Selection of the optimal conditions for the procurement and regeneration of protoplasts of the industrial strain of Streptomyces rimosus, the producer of oxytetracycline, and the effect of the protoplasting process on the antibiotic activity].

Optimal conditions for protoplasting of the Streptomyces rimosus industrial strain No. 1 producing oxytetracycline were developed. Observation of the early stages of the protoplast regeneration in microchambers showed that there were two regeneration types: normal and anomalous. The latter was likely defined by the glycine effect on cell wall synthesis. It was accompanied by the stage in which the protoplasts had the form of multiplying protoplast-like cells. The protoplasting of the S. rimosus culture producing oxytetracycline resulted in an increase in the variability of an antibiotic producing property and the frequency of low active variants.

Bacteriological Techniques↗

PubMed2006

Effect of molecular weight on the morphological modifications induced by UV laser ablation of doped polymers.

This work investigates the effect of polymer molecular weight (M(W)) on the surface morphology of poly(methyl methacrylate) (PMMA) and polystyrene (PS) films doped with iodonaphthalene (NapI) and iodophenanthrene (PhenI) following irradiation in air at 248 nm. In agreement with previous studies, irradiation of PMMA at 248 nm results in surface swelling and bubble formation within the irradiated bulk. Most importantly, the size of bubbles varies sensitively for the different M(W) values, with larger bubbles being formed for the low M(W) systems. Nevertheless, the maximum swelling attains higher values for the high M(W) values (when compared at the corresponding ablation threshold of the systems). Real-time monitoring of transmission of a probing beam shows that morphological changes last longer in the low M(W) polymer. Melting, consistent with a thermal mechanism, occurs, and enough evidence is gathered to provide direct support for the bulk photothermal model, according to which ejection requires that a critical number of bonds is broken. In particular, the observed different morphological effects can be ascribed to the interplay of two factors, namely, of the much more efficient decomposition of the low M(W) polymer to gaseous products and of the dependence of the mechanical polymer properties on M(W). For PS at 308 nm, the changes parallel the ones for PMMA at 248 nm. In contrast, at the strongly absorbed 248 nm, the morphological processes in PS show a less dramatic dependence on M(W). In all, these results are of direct importance for the optimization of laser processing schemes and applications (e.g., tissue processing, laser deposition, laser restoration, etc.).

Journal Article↗

PubMed1993

Processivity of mitochondrial DNA polymerase from Drosophila embryos. Effects of reaction conditions and enzyme purity.

Mitochondrial DNA polymerase from Drosophila embryos has been characterized with regard to its mechanism of DNA synthesis under the influence of a variety of compounds in moderate salt (120 mM KCl), where the enzyme is most highly active and only moderately processive, and in low salt (30 mM KCl), where it is less active yet most highly processive. Disparate activity and processivity optima were obtained in low salt in the presence of varying pH or MgCl2 and ATP concentrations; in moderate salt, optimal activity and processivity were achieved coincidentally. Whereas no correlation between processivity and activity optima was observed upon addition of polyethylene glycol in either low or moderate salt, the optima were coincident at both salt levels on addition of glycerol. None of the reaction conditions examined allowed DNA polymerase gamma to exhibit maximal activity and processivity concurrently; maximal activity was always achieved in moderate salt and the highest processivity in low salt. However, while limiting the availability of primer termini had no effect on the mechanism of DNA synthesis, we found that the ability of mitochondrial DNA polymerase to copy singly primed M13 DNA was enhanced then diminished during the course of purification, suggesting loss of an accessory factor.

Adenosine Triphosphate↗

PubMed2006

Biodegradable polylactide/chitosan blend membranes.

Biodegradable blend membranes based on polylactide and chitosan with various compositions were prepared via a two-step processing pathway. In the first step, solutions of each component were properly mixed and cast into a gelatinous membrane, and in the second step, the obtained membrane was immersed into a mixed solution for the solvent extraction followed by a drying procedure to finally generate a well-blended membrane. An acetic acid-acetone solvent system was selected for poly(DL-lactide)/chitosan membranes, and another solvent system for poly(L-lactide)/chitosan membranes consisted of acetic acid and dimethyl sulfoxide. Some processing parameters, such as the concentration of component solutions and the composition ratio of mixed solvents and extraction solvents, were optimized by primarily considering whether the directly visible phase separation occurred during the processing procedures. Morphologies of these blend membranes were viewed using SEM. It was found that the processing parameters exerted quite notable impacts on the morphology of the membranes. The hydrophilicity of membranes was examined by measuring their water contact angle and swelling index. These blend membranes were also investigated for their miscibility using IR spectra, X-ray diffractograms, TG, DSC, and dynamic mechanical analysis methods. Although the presence of phase separation at a microscopic level was detected for these membranes, pronounced interactions between components were confirmed. The obtained results shown that some membranes prepared under optimized processing conditions had a partially miscible structure.

Acetic Acid↗

PubMed2006

The REFOLD database: a tool for the optimization of protein expression and refolding.

A large proportion of proteins expressed in Escherichia coli form inclusion bodies and thus require renaturation to attain a functional conformation for analysis. In this process, identifying and optimizing the refolding conditions and methodology is often rate limiting. In order to address this problem, we have developed REFOLD, a web-accessible relational database containing the published methods employed in the refolding of recombinant proteins. Currently, REFOLD contains >300 entries, which are heavily annotated such that the database can be searched via multiple parameters. We anticipate that REFOLD will continue to grow and eventually become a powerful tool for the optimization of protein renaturation. REFOLD is freely available at http://refold.med.monash.edu.au.

Databases, Protein↗

PubMed2002

Optimal design of batch and simulated moving bed chromatographic separation processes.

Preparative chromatography, especially simulated moving bed (SMB) chromatography, is a key technology for the separation of fine chemicals on a production scale. Most of the design methods for batch and SMB processes proposed in the open literature deal with the optimisation of the operating conditions for a given chromatographic unit only. Therefore, a comparison of the process economy may lead to incorrect results. In this contribution, an effective strategy for the optimal choice of all process parameters (operation and design parameters) is proposed. The main idea of this strategy is to apply a detailed and experimentally validated process model and to reduce the number of influencing parameters by introducing and optimising dimensionless process parameters. It is shown that there is an infinite choice of design and operating parameters to achieve maximum productivity or minimum separation costs and not at the maximum pressure drop only. The detailed design of the chromatographic unit and the selection of the operating conditions can be adjusted by considering the availability of columns and packing materials. As the model system, the separation of a racemic mixture (EMD53986) on Chiralpak AD was investigated. After complete optimisation of a batch and a SMB unit, a real comparison of the process economy can be achieved. Finally, the influences of two different objective functions, productivity and specific separation cost, are analysed.

Chromatography, Liquid↗

PubMed2004

An evaluation of surfactant foam technology in remediation of contaminated soil.

Soil contamination is notoriously difficult to treat because the contaminants are often tightly bound to the soil particles. Conventional remediation technologies are becoming less popular due to the high treatment costs. This paper gives a comprehensive overview and evaluation of an emerging promising alternative, surfactant foam technology. Different from other approaches, surfactant foam technology may be designed either to remove contaminants or/and simultaneously act as an augmentation for the existing technologies such as pump-and-treat systems and bioremediation processes to improve the contaminant removal efficiency and cost effectiveness. Encouraging results were achieved from laboratory and field demonstrations. However, as an innovative technology, there are many factors to be investigated with the future development. Special attention is paid to the selection of the most appropriate foaming surfactant and surfactant concentration, which are critical to the success of the implementation of the remediation process and have significant effects on the treatment costs. Moreover, development of predictive mathematical models in for future research is helpful to optimize the remediation process.

Bacteria↗

PubMed2000

Techniques for the optimization of proteomic strategies based on head column stacking capillary electrophoresis.

Proteomics is the large-scale study of the proteins related to a genome. Presently, proteomic procedures have relied on mass spectrometry as a tool of choice to perform analysis of proteins. Optimization and understanding of the different steps involved in proteomics using mass spectrometry is expensive and time-consuming and, for this reason, have been typically paid insufficient attention. However, optimization becomes a critical issue as we try to analyze ever shrinking amounts of proteins. We present here the development of a technique that allows the rapid, sensitive, semiquantitative, and automated optimization of the processes involved in proteomics. Furthermore, it allows the rapid testing of new methodologies without having to rely on expensive mass spectrometric techniques. The technique, based on head column stacking capillary zone electrophoresis, allows the concentration, separation, and analysis of protein digests at concentrations from high picomoles to subfemtomoles per microliter and sample volumes from a few microliters to a few hundred microliters produced by proteomic processes. Furthermore, the incorporation of UV detection in the system allows the tracking of the relative changes in peptide levels observed during optimization. In addition, all the buffers and solvents used in this technique are compatible with its future coupling to electrospray ionization mass spectrometry. The potential of this technique for the analysis of low-abundance proteins is demonstrated using peptide standards and tryptic digests of standard proteins. Moreover, we exemplify the application of this technique in proteomic prototyping for the rapid and automated study of the procedure of enzymatic digestion of proteins.

Electrophoresis, Capillary↗

PubMed2000

Cyanobacterial-bacterial mat consortia: examining the functional unit of microbial survival and growth in extreme environments.

Cyanobacterial-bacterial consortial associations are taxonomically complex, metabolically interactive, self-sustaining prokaryotic communities representing pioneer and often the only biota inhabiting extreme aquatic and terrestrial environments. Laminated mats and aggregates exemplify such communities. The fossil record indicates that these associations represent the earliest extant inhabitants and modifiers (i.e. anoxic to oxic conditions) of the Earth's biosphere. Present-day consortia flourish in physically and chemically stressed environments, including nutrient-deplete, hypersaline, calcified, desiccated and high-irradiance ecosystems ranging from the tropics to polar regions. Consortial members exhibit extensive metabolic diversification, but have remained structurally simple. Structural simplicity, while advantageous in countering environmental extremes, presents a 'packaging problem' with regard to compartmentalizing potentially cross-inhibitory aerobic versus anaerobic growth processes. To circumvent these metabolic constraints, phototrophic cyanobacteria and microheterotrophs orient along microscale chemical (i.e. O2, pH, Eh) gradients to meet and optimize the biogeochemical processes (C, N, S cycling) essential for survival, growth and the maintenance of genetic diversity, needed to sustain life. Microscale ecophysiological, analytical, molecular (immunological and nucleic acid) techniques have helped to develop a mechanistic basis for understanding consortial growth and survival under extreme environmental conditions on Earth. Consortia are ideal model systems for developing a process-based understanding of the structural and functional requirements for life in extreme environments representative of the Earth's earliest biosphere and possibly other planets.

Adaptation, Physiological↗

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