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Results for “Process optimization”

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PubMed2004

An efficient new method for extraction, separation and purification of psoralen and isopsoralen from Fructus Psoraleae by supercritical fluid extraction and high-speed counter-current chromatography.

Psoralen and isopsoralen were extracted from Fructus Psoraleae (Psoralea corylitolia L.) by supercritical CO2. The effect of various parameters, i.e., pressure, temperature and sample particle size on yield was investigated with an analytical-scale supercritical fluid extraction (SFE) system to find the optimal conditions. The process was then scaled up by 50 times with a preparative SFE system under the optimized conditions of pressure (26 MPa), temperature (60 degrees C) and a sample particle size of 40-60 mesh. The yield of the preparative SFE was 9.1% and the combined yield of psoralen and isopsoralen was 2.5 mg/g of dry seeds. Psoralen and isopsoralen in the extract were separated and purified by high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:0.7:1:0.8, v/v), and the fractions were analyzed by HPLC, MS, 1HNMR and 13C NMR. The structures of the products were further confirmed by comparison with authentic samples (National Institute of the Control of Pharmaceutical and Biological Products, Beijing, China).

Chromatography, High Pressure Liquid↗

PubMed2005

Research on processing medicinal herbs with multi-steps infrared macro-fingerprint method.

How to apply rapid and effective method to research medicinal herbs, the representative of complicated mixture system, is the current study focus for analysts. The functions of non-processed and processed medicinal herbs are greatly different, so controlling the processing procedure is highly important for guarantee of the curative effect. Almost, the conventional criteria of processing are based on personal sensory experience. There is no scientific and impersonal benchmark. In this article, we take Rehmannia for example, conducting a systematic study on the process of braising Rehmannia with yellow wine by using the multi-steps infrared (IR) macro-fingerprint method. The method combines three steps: conventional Fourier transform infrared spectroscopy (FT-IR), second derivative spectroscopy, and two-dimensional infrared (2D-IR) correlation spectroscopy. Based on the changes in different types of IR spectra during the process, we can infer the optimal end-point of processing Rehmannia and the main transformations during the process. The result provides a scientific explanation to the traditional sensory experience based recipe: the end-point product is "dark as night and sweet as malt sugar". In conclusion, the multi-steps IR macro-fingerprint method, which is rapid and reasonable, can play an important role in controlling the processing of medicinal herbs.

Carbohydrate Conformation↗

PubMed2002

Retention of arsenic on hydrous ferric oxides generated by electrochemical peroxidation.

Electrochemical peroxidation (ECP), an emerging remediation technology, with direct electric current applied to steel electrode and small addition of H2O2, was used to remove As(III) from contaminated aqueous solutions. Bench scale experiments were conducted to evaluate the sorption and distribution of arsenic between the soluble and solid state hydrous ferric oxides (HFO) formed as part of the ECP process. ECP was effective in removing arsenic from the aqueous solution, with >98% of the applied As(III) adsorbed on HFO. Removal was complete within 3 min of ECP treatment and apparently independent of the initial pH of the water (3.5-9.5). In the absence of H2O2 more As(III) was adsorbed by solid state iron at pH 9.5 than at 3.5 (2600 vs. 1750 microg l(-1)). Thus H2O2 was crucial to oxidize As(III) to As(V) which is more strongly retained by HFO. Removal of As was not significantly affected by the concentration of H2O2 or by current processing time. The optimal operating conditions were pH < 6.5, H2O2 concentration of 10 mg l(-1) and current process time not exceeding 3 min. X-ray diffraction (XRD), diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy and transmission electron microscopy (TEM) were applied to study the HFO deposits. The XRD data indicated the prevalence of poorly ordered Fe minerals in the suspended ECP solids with a dominance of 5 line ferrihydrite in the absence of H2O2. At pH 3.5 and with 100 mg H2O2 l(-1), akaganeite was formed, whereas an incipient hematitic phase, reflection at 0.39 nm, occurred at pH 6.5. DRIFT data indicate that both As(III) and As(V) were specifically adsorbed onto HFO at acid and neutral pH. TEM observations indicated the presence of spherical shape ferrihydrite and provided evidence for possible formation of subrounded hematite and acicular shape goethite.

Adsorption↗

PubMed2004

ProteinShop: a tool for interactive protein manipulation and steering.

We describe ProteinShop, a new visualization tool that streamlines and simplifies the process of determining optimal protein folds. ProteinShop may be used at different stages of a protein structure prediction process. First, it can create protein configurations containing secondary structures specified by the user. Second, it can interactively manipulate protein fragments to achieve desired folds by adjusting the dihedral angles of selected coil regions using an Inverse Kinematics method. Last, it serves as a visual framework to monitor and steer a protein structure prediction process that may be running on a remote machine. ProteinShop was used to create initial configurations for a protein structure prediction method developed by a team that competed in CASP5. ProteinShop's use accelerated the process of generating initial configurations, reducing the time required from days to hours. This paper describes the structure of ProteinShop and discusses its main features.

Computational Biology↗

PubMed2005

Design and analysis of orthogonally compliant features for local contact pressure relief in transtibial prostheses.

A very attractive advantage of manufacturing prosthetic sockets using solid freeform fabrication is the freedom to introduce design solutions that would be difficult to implement using traditional manufacturing techniques. Such is the case with compliant features embedded in amputee prosthetic sockets to relieve contact pressure at the residual limb-socket interface. The purpose of this study was to present a framework for designing compliant features to be incorporated into transtibial sockets and manufacturing prototypes using selective laser sintering (SLS) and Duraform material. The design process included identifying optimal compliant features using topology optimization algorithms and integrating these features within the geometry of the socket model. Using this process, a compliant feature consisting of spiral beams and a supporting external structure was identified. To assess its effectiveness in reducing residual limb-socket interface pressure, a case study was conducted using SLS manufactured prototypes to quantify the difference in interface pressure while a patient walked at his self-selected pace with one noncompliant and two different compliant sockets. The pressure measurements were performed using thin pressure transducers located at the distal tibia and fibula head. The measurements revealed that the socket with the greatest compliance reduced the average and peak pressure by 22% and 45% at the anterior side distal tibia, respectively, and 19% and 23% at the lateral side of the fibula head, respectively. These results indicate that the integration of compliant features within the socket structure is an effective way to reduce potentially harmful contact pressure and increase patient comfort.

Amputees↗

PubMed2006

Modeling for gellan gum production by Sphingomonas paucimobilis ATCC 31461 in a simplified medium.

Gellan gum production was carried out by Sphingomonas paucimobilis ATCC 31461 in a simplified medium with a short incubation time, and a kinetic model for understanding, controlling, and optimizing the fermentation process was proposed. The results revealed that glucose was the best carbon source and that the optimal concentration was 30 g liter(-1). As for the fermenting parameters, considerably large amounts of gellan gum were yielded by an 8-h-old culture and a 4% inoculum at 200 rpm on a rotary shaker. Under the optimized conditions, the maximum level of gellan gum (14.75 g liter(-1)) and the highest conversion efficiency (49.17%) were obtained in a 30-liter fermentor in batch fermentation. Logistic and Luedeking-Piret models were confirmed to provide a good description of gellan gum fermentation, which gave some support for the study of gellan gum fermentation kinetics. Additionally, this study is the first demonstration that gellan gum production is largely growth associated by analysis of kinetics in its batch fermentation process. Based on model prediction, higher gellan gum production (17.71 g liter(-1)) and higher conversion efficiency (57.12%) were obtained in fed-batch fermentation at the same total glucose concentration (30 g liter(-1)).

Biotechnology↗

PubMed2002

[Study on enrichment process of total flavonoids from Euphorbia himifusa with macroporous resin].

OBJECTIVE: To study the optimal technology parameters of the enrichment process for total flavonoids of Euphorbia himifusa with macroporous resin. METHODS: The enrichment process was studied by orthogonal experiment design using orthogonal form L9(3(4)) with the content of total flavonoids from Euphorbia himifusa as indexes, and three factors were chosen in this experiment, including the saturation of the extract sicca from Euphorbia himifusa, duration of absortion and the consistence of alcohol as eluent. RESULTS: The results showed that the optimal enrichment process was that 10 ml of the extract of Euphorbia himifusa (i.e. lml 75% alcohol contains 0.5 g the extract sicca from Herba Euphorbiae Humifusae) was absorbed 30 min with a column of macroporous resin(r 15 mm x H160 mm) and the total flavonoids was eluted from the macroporous resin with 95% alcohol. CONCLUSION: The elutive rate of total flavonoids was above 93% by means of the macroporous resin. So this process enriching the total flavonoids of Euphorbia himifusa is feasible.

Drugs, Chinese Herbal↗

PubMed1998

An efficient method for small field treatment dose calculation for stereotactic radiosurgery using a LINAC.

The normal procedure for a physician-physicist team designing a treatment plan for multiarc stereotactic radiosurgery is the trial-and-error approach of changing the collimator size and the location of the isocenter of radiation and viewing the isodose curves on two-dimensional computed tomography (CT) or magnetic resonance imaging (MRI) image planes. Automatic optimization procedures have also been used to optimize beam weight or beam size. However, either process is very time consuming. To improve the speed of the dose calculation, a random sampling method has been proposed. Unfortunately, the sampled values of an objective function are different from one sample to another. Such a sampling method cannot be used in automatic optimization because the next move in an optimization process is based on the current and past objective function values. To this end, an adaptive method based on the size of the collimators is proposed and used to determine a small volume in the shape of a hollow sphere for which the dose is calculated. With an appropriate choice of an adaptive hollow sphere, the objective function calculated based on such a hollow sphere is the same as that calculated with the traditional three-dimensional (3-D) cube matrix. However, with the new adaptive method, the speed of calculating a dose can be improved by a factor of 4 to a factor of 100. Because of the improvement in the speed of calculating a treatment dose, the new adaptive hollow sphere method for calculating a treatment dose can be used routinely in designing a treatment plan.

Automation↗

PubMed1985

The role of visual experience in the development of cat striate cortex.

By the third postnatal week, intrinsic developmental programs have established a framework within the cat visual system; this will be used to guide the course of subsequent experience-dependent development. Key elements in this framework are precociously mature cells in visual cortex area 17. These orientation-selective cells are predominantly first-order neurons, they are concentrated in layers IV and VI of area 17, most of them are activated monocularly, many may receive their direct excitatory input from lateral geniculate nucleus X cells, and the distribution of their preferred orientations is biased toward horizontal and vertical. Between the third and the sixth postnatal week, most of the remaining cells in area 17 develop orientation selectivity; this extension of orientation selectivity is blocked or delayed if kittens are deprived of normal patterned visual stimulation. Furthermore, exposure to a limited range of stimulus orientations can lead to an increase in the proportion of orientation-selective cells, and the range of orientation preferences that the cells acquire is restricted by the range of orientations to which the animal is exposed. This occurs with no apparent change in the physiology or morphology of intrinsically selective area 17 cells. Thus selective exposure may have its effect by influencing the connections between the intrinsically selective cells and higher-order neurons in area 17. Experience-dependent changes in the visual system may function to "fine-tune" sensory processing and thus optimize the system's response to the dominant features of the environment. This experience-dependent process could help the young animal to focus its "attention" on those features of its environment that are critical to its survival.

Animals↗

PubMed1997

Role of high-performance liquid chromatographic protein analysis in developing fermentation processes for recombinant human growth hormone, relaxin, antibody fragments and lymphotoxin.

Development of efficient and reliable fermentation processes for protein pharmaceuticals is aided by the availability of accurate quantitative and qualitative product analyses. We have developed a variety of single and dual column chromatographic separations that meet the needs of process development and examples will be provided of how the resulting data has been used to optimize the culture process. For single column methods, reversed-phase chromatography has been the most versatile, permitting the reliable quantitation of many yeast, Chinese hamster ovary (CHO) cell and Escherichia coli-expressed products in the matrix of culture broth or cell extract. Analysis of secreted human growth hormone synthesized in E. coli, along with clipped and unprocessed forms, will be discussed. Another reversed-phase assay for direct analysis of a peptide product (B-chain relaxin) and its degradation products secreted into E. coli fermentation medium has allowed the purification of the responsible protease. Cation-exchange has proven extremely useful for the direct analysis of antibody fragment synthesized in E. coli, allowing the separation and quantitation of the desired Fab' and Fab'2, as well as the unwanted products of glutathione addition and translational read-through. Assay development is often complicated by the presence of host proteins with chromatographic behavior that is similar to that of the product. Commercial instrumentation now permits the facile development of multidimensional chromatographic assays. We show examples of coupled receptor affinity-reversed-phase assays for a mistranslation product and for covalent multimers of E. coli-synthesized lymphotoxin.

Amino Acid Sequence↗

PubMed1997

Long-term health care outcomes in diabetes. Economic and political implications.

With building pressure for cost-containment of medical expenditures, the medical community is finding it increasingly necessary to justify its procedures and systems of care. The analysis of health care outcomes has been extensively applied to diabetes care as a means of determining the process by which optimal outcomes may be achieved. This article reviews basic concepts of outcomes analysis, with differentiation between process measures and outcome measures. A review of the available outcome literature as it pertains to diabetes also is provided.

Behavior↗

PubMed2003

Kramers problem in evolutionary strategies.

We calculate the escape rates of different dynamical processes for the case of a one-dimensional symmetric double-well potential. In particular, we compare the escape rates of a Smoluchowski process, i.e., a corresponding overdamped Brownian motion dynamics in a metastable potential landscape, with the escape rates obtained for a biologically motivated model known as the Fisher-Eigen process. The main difference between the two models is that the dynamics of the Smoluchowski process is determined by local quantities, whereas the Fisher-Eigen process is based on a global coupling (nonlocal interaction). If considered in the context of numerical optimization algorithms, both processes can be interpreted as archetypes of physically or biologically inspired evolutionary strategies. In this sense, the results discussed in this work are utile in order to evaluate the efficiency of such strategies with regard to the problem of surmounting various barriers. We find that a combination of both scenarios, starting with the Fisher-Eigen strategy, provides a most effective evolutionary strategy.

Journal Article↗

PubMedDate not supplied

The influence of semantic and syntactic context constraints on lexical selection and integration in spoken-word comprehension as revealed by ERPs.

An event-related brain potential experiment was carried out to investigate the influence of semantic and syntactic context constraints on lexical selection and integration in spoken-word comprehension. Subjects were presented with constraining spoken sentences that contained a critical word that was either (a) congruent, (b) semantically and syntactically incongruent, but beginning with the same initial phonemes as the congruent critical word, or (c) semantically and syntactically incongruent, beginning with phonemes that differed from the congruent critical word. Relative to the congruent condition, an N200 effect reflecting difficulty in the lexical selection process was obtained in the semantically and syntactically incongruent condition where word onset differed from that of the congruent critical word. Both incongruent conditions elicited a large N400 followed by a left anterior negativity (LAN) time-locked to the moment of word category violation and a P600 effect. These results would best fit within a cascaded model of spoken-word processing, proclaiming an optimal use of contextual information during spoken-word identification by allowing for semantic and syntactic processing to take place in parallel after bottom-up activation of a set of candidates, and lexical integration to proceed with a limited number of candidates that still match the acoustic input.

Acoustic Stimulation↗

PubMed2005

Heterologous protein production using the Pichia pastoris expression system.

The Pichia pastoris expression system is being used successfully for the production of various recombinant heterologous proteins. Recent developments with respect to the Pichia expression system have had an impact on not only the expression levels that can be achieved, but also the bioactivity of various heterologous proteins. We review here some of these recent developments, as well as strategies for reducing proteolytic degradation of the expressed recombinant protein at cultivation, cellular and protein levels. The problems associated with post-translational modifications performed on recombinant proteins by P. pastoris are discussed, including the effects on bioactivity and function of these proteins, and some engineering strategies for minimizing unwanted glycosylations. We pay particular attention to the importance of optimizing the physicochemical environment for efficient and maximal recombinant protein production in bioreactors and the role of process control in optimizing protein production is reviewed. Finally, future aspects of the use of the P. pastoris expression system are discussed with regard to the production of complex membrane proteins, such as G protein-coupled receptors, and the industrial and clinical importance of these proteins.

Bioreactors↗

PubMed2006

Toward more efficient protein expression: keep the message simple.

Optimization of gene coding-sequence, including preferred codon usage and removal of cryptic splice sites and mRNA-destabilizing motifs, has been shown to improve recombinant protein production of different proteins. Here, we present data to show that gene optimization can also be used to improve the production of a complex macromolecule, namely an antibody. When applied to the heavy and light chain genes of our model antibody, we found that greater numbers of high-producing transfectants as well as increased levels of protein production were observed (approximately 1.5-fold). In this test model, production was improved even though the antibody has previously been demonstrated to give high expression in stably transfected cells (up to 5 g/L in bioreactors). Because the parental heavy chain sequence contained introns, and the process of gene optimization is most efficiently performed on sequences without introns, we demonstrated that removal of introns in the coding sequence had no effect on the quantity of antibody produced. All constructs were evaluated using Lonza's glutamine synthetase gene expression vectors in Chinese hamster ovary cells. Our findings suggest that significant improvements in product yields can be achieved by gene optimization, which may facilitate the processing and translation of gene transcripts.

Animals↗

PubMed2004

Optimization of phase feeding of starter, grower, and finisher diets for male broilers by mixture experimental design: forty-eight-day production period.

A mixture experiment, a variant of response surface methodology, was designed to determine the proportion of time to feed broiler starter (23% protein), grower (20% protein), and finisher (18% protein) diets to optimize production and processing variables based on a total production time of 48 d. Mixture designs are useful for proportion problems where the components of the experiment (i.e., length of time the diets were fed) add up to a unity (48 d). The experiment was conducted with day-old male Ross x Ross broiler chicks. The birds were placed 50 birds per pen in each of 60 pens. The experimental design was a 10-point augmented simplex-centroid (ASC) design with 6 replicates of each point. Each design point represented the portion(s) of the 48 d that each of the diets was fed. Formulation of the diets was based on NRC standards. At 49 d, each pen of birds was evaluated for production data including BW, feed conversion, and cost of feed consumed. Then, 6 birds were randomly selected from each pen for processing data. Processing variables included live weight, hot carcass weight, dressing percentage, fat pad percentage, and breast yield (pectoralis major and pectoralis minor weights). Production and processing data were fit to simplex regression models. Model terms determined not to be significant (P > 0.05) were removed. The models were found to be statistically adequate for analysis of the response surfaces. A compromise solution was calculated based on optimal constraints designated for the production and processing data. The results indicated that broilers fed a starter and finisher diet for 30 and 18 d, respectively, would meet the production and processing constraints. Trace plots showed that the production and processing variables were not very sensitive to the grower diet.

Animal Feed↗

PubMed1998

Investigation of protein patterns in mammalian cells and culture supernatants by matrix-assisted laser desorption/ionization mass spectrometry.

The direct protein profiling of mammalian cells and bacteria has a growing influence in biotechnology as a high information bearing method for characterization of cells and cell states. Monitoring of proteins excreted in culture media not only serves to produce data on product yield and quality but provides important information on cell viability and nutrient supply that forms the basis for future process and expression optimization. Fast and simple MALDI mass spectrometry approaches were developed to efficiently characterize such complex biological systems. Several mammalian cell lines including CHO DXB11, CHOSSF3, and hybridomas were investigated; the lysis process, the sample pretreatment, and the matrix preparation were optimized for MALDI conditions. Initial experiments to observe the success of protein translation in gene expression experiments were performed. Using MALDI-compatible detergents, it was possible to extend the mass range detectable by MALDI mass spectrometry from the current range of 16,000 to 75,000 Da. In this mass range, the data are complementary (offering a better mass accuracy) to those obtained by SDS-PAGE electrophoresis experiments. These new methods were used to monitor a large-scale cultivation of hybridoma cells expressing an antibody of the IgG type. The increase in whole antibody and antibody light-chain protein, 8650 Da, and the decrease of insulin were followed during the monitoring period. Quantitative measurements of the IgG level during the cultivation compared favorably with those obtained by affinity HPLC.

Animals↗

PubMed2007

Influence of bioreactor scale and complex medium on probing control of glucose feeding in cultivations of recombinant strains of Escherichia coli.

The objective of this work was to evaluate the performance of a feedback glucose control strategy (the probing strategy) in production relevant bioreactors with complex and mineral media. Experimental results from fed-batch cultivations with two recombinant Escherichia coli constructs expressing two different human therapeutic proteins were used to assess the performance and limitations of the glucose probing technique. Even though the performance of the probing strategy was affected by scale and complex media, this methodology rapidly identified a glucose feed protocol similar to an experimentally derived feed regime. This methodology may serve as a powerful tool for industrial process development and in optimization of glucose feed regimes when transferring process technology from one bioreactor system to another.

Bioreactors↗