bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biodegradable polymers from organic acids by using activated sludge enriched by aerobic periodic feeding
Authors: Dionisi Davide , Majone Mauro , Papa Viviana , Beccari Mario 
Published: February 2004

AbstractThis article describes a new process for the production of biopolymers (polyhydroxyalkanoates, PHAs) based on the aerobic enrichment of activated sludge to obtain mixed cultures able to store PHAs at high rates and yields. Enrichment was obtained through the selective pressure established by feeding the carbon source in a periodic mode (feast and famine regime) in a sequencing batch reactor. A concentrated mixture of acetic, lactic, and propionic acids (overall concentration of 8.5 gCOD L−1) was fed every 2 h at 1 day−1 overall dilution rate. Even at such high organic load (8.5 gCOD L−1 day−1), the selective pressure due to periodic feeding was effective in obtaining a biomass with a storage ability much higher than activated sludges. The immediate biomass response to substrate excess (as determined thorough short‐term batch tests) was characterized by a storage rate and yield of 649 mgPHA (as COD) g biomass (as COD)−1 h−1 and 0.45 mgPHA (as COD) mg removed substrates (as COD−1), respectively. When the substrate excess was present for more than 2 h (long‐term batch tests), the storage rate and yield decreased, whereas growth rate and yield significantly increased due to biomass adaptation. A maximum polymer fraction in the biomass was therefore obtained at about 50% (on COD basis). As for the PHA composition, the copolymer poly(β‐hydroxybutyrate/β‐hydroxyvalerate) with 31% of hydroxyvalerate monomer was produced from the substrate mixture. Comparison of the tests with individual and mixed substrates seemed to indicate that, on removing the substrate mixture for copolymer production, propionic acid was fully utilized to produce propionylCoA, whereas the acetylCoA was fully provided by acetic and lactic acid. © 2004 Wiley Periodicals, Inc.
Aven and Bcl‐xL enhance protection against apoptosis for mammalian cells exposed to various culture conditions
Authors: Figueroa Bruno , Chen Sulin , Oyler George A. , Hardwick J. Marie , Betenbaugh Michael J. 
Published: February 2004

AbstractA balance between proliferation and cell death is critical for achieving desirable high cell densities in mammalian cell culture. In this study, we evaluate a recently discovered anti‐apoptotic gene, aven, and examine its effectiveness alone and in combination with a member of the Bcl‐2 family, bcl‐xL. The commercially popular cell line, Chinese hamster ovary (CHO), was genetically modified to constitutively express aven, bcl‐xL, and the two genes in combination. Cells were exposed to several model insults that simulate severe bioreactor environments, including serum deprivation, spent medium, and Sindbis virus infection, as well as staurosporine, a known chemical inducer of apoptosis. CHO cells exhibited DNA fragmentation, a hallmark of apoptosis, after exposure to these model insults. After exposure to serum deprivation, 4‐ and 5‐day spent medium, and staurosporine, cells expressing Aven provided limited protection against cell death when compared with the protection afforded by cells expressing Bcl‐xL alone. However, the highest survival levels for all insults were achieved when Aven was expressed in combination with Bcl‐xL. In fact, Aven appeared to act synergistically to enhance the protective function of Bcl‐xL for several insults, because the protective function of the two genes expressed together in one cell line often exceeded the additive protective levels of each anti‐apoptosis gene expressed alone. Surprisingly, Aven expression provided a mildly pro‐apoptotic response in CHO isolates infected with Sindbis virus. However, CHO cells expressing both Bcl‐xL and Aven showed protection against Sindbis virus infection due to the inhibitory properties of the bcl‐xL anti‐apoptosis gene. This study shows that combinatorial anti‐apoptosis cell engineering strategies may be the most effective mechanisms for providing extended protection against cell death in mammalian cell culture. © 2004 Wiley Periodicals, Inc.
High‐level secretion of functional green fluorescent protein from transgenic tobacco cell cultures: Characterization and sensing
Authors: Su Wei Wen , Guan Peizhu , Bugos Robert C. 
Published: February 2004

AbstractGreen fluorescent protein (GFP) is useful for studying protein trafficking in plant cells. This utility could potentially be extended to develop an efficient secretory reporter system or to enable on‐line monitoring of secretory recombinant protein production in plant cell cultures. Toward this end, the aim of the present study was to: (1) demonstrate and characterize high levels of secretion of fluorescent GFP from transgenic plant cell culture; and (2) examine the utility of GFP fluorescence for monitoring secreted recombinant protein production. In this study we expressed in tobacco cell cultures a secretory GFP construct made by splicing an Arabidopsis basic chitinase signal sequence to GFP. Typical extracellular GFP accumulation was 12 mg/L after 10 to 12 days of culture. The secreted GFP is functional and it accounts for up to 55% of the total GFP expressed. Findings from culture treatments with brefeldin A suggest that GFP is secreted by the cultured tobacco cells via the classical endoplasmic reticulum–Golgi pathway. Over the course of flask cultures, medium fluorescence increased with the secreted GFP concentrations that were determined using either Western blot or enzyme‐linked immunoassay. Real‐time monitoring of secreted GFP in plant cell cultures by on‐line fluorescence detection was verified in bioreactor cultures in which the on‐line culture fluorescence signals showed a linear dependency on the secreted GFP concentrations. © 2004 Wiley Periodicals, Inc.
Biodegradation kinetics of volatile hydrophobic organic compounds in cultures with variable fractional volumes
Authors: Hong Tien Truong , Katayama Arata 
Published: February 2004

AbstractAn extension of the models developed by Guha and Jaffé (Biotechnol Bioeng [1996] 50:693–699) to describe the phenanthrene biodegradation kinetics for the cultures with variable fractional volumes is presented. Batch experiments were conducted with a culture capable of degrading the phenanthrene using a single culture vessel from which samples were withdrawn over time to monitor the disappearance of phenanthrene. For accurate measurement of phenanthrene concentrations, a sampling procedure designed for quantifying the sorption of phenanthrene onto glassware was also introduced. The Monod parameters were estimated by nonlinear regression analyses of simultaneous solutions to the substrate utilization/volatilization and Monod equations for growth of the cell mass. The results demonstrate that the models were able to be extended to phenanthrene‐degrading cultures with variable fractional volumes. When the ratio between sampling volume and volume of the culture medium was relatively small, the parameters obtained were similar to those which would be obtained using constant fractional volumes of culture medium. It was also found that the model's fit to the phenanthrene disappearance data in this study were better than those obtained by Guha and Jaffé, implying that the sorption process of phenanthrene during the sampling period could significantly affect the measurement of phenanthrene concentrations. Failing to account for these losses led to less accurate measurements of substrate concentrations, which in turn resulted in a poor estimation of the parameters. The findings of this study reduce considerably the experimental work necessary in the estimation of Monod kinetic parameters for the purpose of modeling. © 2004 Wiley Periodicals, Inc.
High‐rate ferric sulfate generation by a Leptospirillum ferriphilum‐dominated biofilm and the role of jarosite in biomass retainment in a fluidized‐bed reactor
Authors: Kinnunen Päivi H.‐M. , Puhakka Jaakko A. 
Published: February 2004

AbstractThe aims of this work were to develop a high‐rate fluidized‐bed bioprocess for ferric sulfate production, to characterize biomass retainment, and to determine the phylogeny of the enrichment culture. After 7 months of continuous enrichment and air aeration at 37°C, the iron oxidation rate of 8.2 g Fe2+ L−1h−1 (4.5·10−12 g Fe2+ cell−1 h−1) was obtained at a hydraulic retention time (HRT) of 0.6 h. However, oxygen supply became the rate‐limiting factor. With gas mixture (99.5% O2 /0.5% CO2 (vol/vol)) aeration and HRT of 0.2 h, the iron oxidation rate was 26.4 g Fe2+ L−1h−1 (1.0·10−11 g Fe2+ cell−1 h−1). Leptospirillum sp. was predominant in the mesophilic fluidized‐bed reactor (FBR) enrichment culture as determined by fluorescent in situ hybridization, while Acidithiobacillus ferrooxidans was not detected. Denaturing gradient gel electrophoresis (DGGE) of the amplified partial 16S rDNA showed only three bands, indicating a simple microbial community. DGGE fragment excision and sequencing showed that the populations were related to L. ferriphilum (100% similarity in sequence) and possibly to the genus Ferroplasma (96% similarity to F. acidiphilum). Jarosite precipitates accumulated on the top of the activated carbon biomass carrier material, increasing the rate of iron oxidation. The activated carbon carrier material, jarosite precipitates, and reactor liquid contained 59% (or 3.71·109 cells g−1), 31% (or 3.12·1010 cells g−1) and 10% (or 1.24·108 cells mL−1) of the total FBR microbes, respectively, demonstrating that the jarosite precipitates played an important role in the FBR biomass retainment. © 2004 Wiley Periodicals, Inc.
Hyperactivation of Rhizomucor miehei lipase by hydrophobic xerogels
Authors: Aucoin Marc G. , Erhardt Frank A. , Legge Raymond L. 
Published: February 2004

AbstractAlthough a variety of approaches exist for the immobilization of enzymes, the “science” of enzyme immobilization is still in its infancy. In recent years, considerable interest has developed regarding the use of xerogels for enzyme immobilization. There are several advantages to xerogels for enzyme immobilization, including the opportunity to produce them in defined shapes or thin films and the ability to manipulate their physical characteristics (e.g., porosity, hydrophobicity, and optical properties). In this study we examined the effect of xerogel hydrophobicity on the activity of lipase (EC 3.2.2.3) from Rhizomucor miehei. The hydrophobicity of the xerogels was manipulated by generating xerogels with various molar ratios of propyltrimethoxysilane (PTMS) to tetramethoxysilane (TMOS), from 1:1 to 10:1. The belief was that, by increasing the proportion of propyl groups, the hydrophobicity of the resulting xerogel would be increased. Differences in the hydrophobicity of the resulting xerogels were confirmed using water‐affinity studies. Two approaches were taken for water‐affinity determinations by examining the ability of the xerogels to remove water from air (controlled humidity) and from water‐saturated isopropyl ether. Xerogels with higher propyl content showed a reduced affinity for water. A crude lipase preparation from Rhizomucor miehei was then contacted with sized xerogel particulates and the effect of the xerogel on lipase activity was determined. The presence of the xerogel resulted in hyperactivation of the lipase. Analysis of the protein adsorption revealed changes in the profile of proteins adsorbed to the xerogel based on the hydrophobicity of the xerogel. Based on estimations of the specific activity of the hyperactivated lipase, a minimum hyperactivation of 207% was observed. Part of the hyperactivation may be attributable to xerogel–lipase interactions, but also to the adsorption of a component from the crude lipase preparation that may complex with the lipase and the xerogel producing a stabilizing effect. Further improvements in hyperactivation and selectivity of the xerogels is likely possible by working at lower PTMS:TMOS ratios than those investigated in this study. © 2004 Wiley Periodicals, Inc.
Hollow fiber bioreactor: New development for the study of contrast agent transport into hepatocytes by magnetic resonance imaging
Authors: Planchamp Corinne , Ivancevic Marko K. , Pastor Catherine M. , Vallée Jean‐Paul , Pochon Sibylle , Terrier François , Mayer Joachim M. , Reist Marianne 
Published: February 2004

AbstractThe aim of our study was to develop a magnetic resonance (MR)‐compatible in vitro model containing freshly isolated rat hepatocytes to study the transport of hepatobiliary contrast agents (CA) by MR imaging (MRI). We set up a perfusion system including a perfusion circuit, a heating device, an oxygenator, and a hollow fiber bioreactor (HFB). The role of the porosity and surface of the hollow fiber (HF) as well as the perfusate flow rate applied on the diffusion of CAs and O2 was determined. Hepatocytes were isolated and injected in the extracapillary space of the HFB (4 × 107 cells/mL). The hepatocyte HFB was perfused with an extracellular CA, gadopentetate dimeglumine (Gd‐DTPA), and gadobenate dimeglumine (Gd‐BOPTA), which also enters into hepatocytes. The HFB was imaged in the MR room using a dynamic T1‐weighed sequence. No adsorption of CAs was detected in the perfusion system without hepatocytes. The use of a membrane with a high porosity (0.5 μm) and surface (420 cm2), and a high flow rate perfusion (100 mL/min) resulted in a rapid filling of the HFB with CAs. The cellular viability of hepatocytes in the HFB was greater than 85% and the O2 consumption was maintained over the experimental period. The kinetics of MR signal intensity (SI) clearly showed the different behavior of Gd‐BOPTA that enters into hepatocytes and Gd‐DTPA that remains extracellular. Thus, these results show that our newly developed in vitro model is an interesting tool to investigate the transport kinetics of hepatobiliary CAs by measuring the MR SI over time. © 2004 Wiley Periodicals, Inc.
Pediocin production by Pediococcus acidilactici in solid state culture on a waste medium: Process simulation and experimental results
Authors: Vázquez J.A. , González M.P. , Murado M.A. 
Published: February 2004

AbstractThe production of pediocin by Pediococcus acidilactici was comparatively studied in submerged and solid‐state culture, using polyurethane foam particles soaked in commercial (MRS) and waste media with various supplements, where product concentrations were 15 times higher in MRS medium. For the solid state analysis, cultures were treated by successive compression and refilling of tubular minireactors equipped with a piston, without the need for reinoculation. This method was found to be simple, reproducible, and easily controllable, allowing culture productivity to be maintained for long periods of time without alterations in the basic properties of the system. In addition, yields were found to be superior compared to those from submerged culture. The system kinetics were modeled on the basis of widely accepted assumptions with a good fit to the experimental results and observed biomass fluctuations less evident than those predicted by the kinetic model. © 2004 Wiley Periodicals, Inc.
Computational aspects of protein functionality
Authors: Paton R. C. , Toh C.‐H. 
Published: February 2004

AbstractThe purpose of this short article is to examine certain aspects of protein functionality with relation to some key organizing ideas. This is important from a computational viewpoint in order to take account of modelling both biological systems and knowledge of these systems. We look at some of the lexical dimensions of the function and how certain constructs can be related to underlying ideas. The pervasive computational metaphor is then discussed in relation to protein multifunctionality, and the specific case of von Willebrand factor as a ‘smart’ multifunctional protein is briefly considered. Some diagrammatic techniques are then introduced to better articulate protein function. Copyright © 2004 John Wiley & Sons, Ltd.
MicroCore: mapping genome expression to cell pathways and networks
Authors: Patel Manish , Nagl Sylvia 
Published: February 2004

AbstractThe MicroCore toolkit is a suite of analysis programs for microarray and proteomics data that is open source and programmed exclusively in Java. MicroCore provides a flexible and extensible environment for the interpretation of functional genomics data through visualization. The first version of the application (downloadable from the MicroCore website: http://www.ucl.ac.uk/oncology/MicroCore/microcore.htm), implements two programs—PIMs (protein interaction maps) and MicroExpress—and is soon to be followed by an extended version which will also feature a fuzzy k‐means clustering application and a Java‐based R plug‐in for microarray analysis. PIMs and MicroExpress provide a simple yet powerful way of graphically relating large quantities of expression data from multiple experiments to cellular pathways and biological processes in a statistically meaningful way. Copyright © 2004 John Wiley & Sons, Ltd.
Development of a grounded‐trench MOS‐assisted bipolar‐mode FET
Authors: Murakami Yoshinori , Asada Kunihiro 
Published: February 2004

AbstractThe grounded‐trench MOS‐assisted bipolar‐mode FET, or GTBT, is made by introducing an insulated trench electrode into a bipolar‐mode JFET. This resulting device has normally‐off characteristics which are retained until avalanche breakdown, a high current gain, high rate switching, and so on. This paper summarizes GTBT's structure, mechanism, our design approach to enhance its functionality, and the various characteristics of the chips we fabricated. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 62–73, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10105
An 85‐Mbit/s DQPSK MODEM‐LSI using a ROM storage capacity reducing technique based on phase plane symmetry
Authors: Yamagishi Akihiro , Tsukahara Tsuneo , Muraguchi Masahiro 
Published: February 2004

AbstractAs a configuration for a baseband delayed detection circuit for the phase modulation scheme widely used in wireless communication systems, a technique is proposed for reducing the capacity of the ROM used for phase detection by means of symmetry in the phase plane. With this technique, the capacity of the ROM needed can be reduced to 1/5. A MODEM‐LSI is fabricated in a one‐chip format for trial by the present technique with 0.5‐µm CMOS. A bandwidth of more than 85 Mbit/s and a low power consumption of 23 mA in 80 Mbit/s operation are achieved. Also, by means of the present LSI, a DQPSK modulator and demodulator are configured and a fixed deterioration of 2 dB at BER = 1e−5 is obtained by folding measurement. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(3): 12–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10194
Period formulas of shear wall buildings with flexible bases
Authors: Ghrib Faouzi , Mamedov Haji 
Published: February 2004

AbstractThe evaluation of the fundamental period of shear wall buildings considering the flexibility of the base is investigated in this paper. This research is motivated by the discrepancy reported between the formulas used in different building codes and the measurement of real buildings. Both experimental and analytical approaches are used to assess the effect of the base flexibility on the fundamental period of shear wall structures. In total, twenty buildings built on different types of soil are tested under ambient vibration. The fundamental period is identified using a non‐parametric linear model in the frequency domain. The results show that fundamental period formulas used by UBC‐97 and NBCC‐95 are inadequate since they do not include the effect of the foundation stiffness. To improve the estimation of the fundamental period of shear wall buildings, an analytical approach is presented. The structure and the foundation are represented by a continuous‐discrete system. The stiffnesses of the base are represented by translational and rotational discrete springs. The rigidities of these springs are evaluated from the elastic uniform compression of the soil mass and the size of the foundation. The analytical predictions improve the estimation of the fundamental period and keep the computation simple. The error between the measured period and the analytical results is, on average, less than 10%. Copyright © 2003 John Wiley & Sons, Ltd.
Solution of the shallow‐water equations using an adaptive moving mesh method
Authors: Tang Huazhong 
Published: February 2004

AbstractThis paper extends an adaptive moving mesh method to multi‐dimensional shallow water equations (SWE) with source terms. The algorithm is composed of two independent parts: the SWEs evolution and the mesh redistribution. The first part is a high‐resolution kinetic flux‐vector splitting (KFVS) method combined with the surface gradient method for initial data reconstruction, and the second part is based on an iteration procedure. In each iteration, meshes are first redistributed by a variational principle and then the underlying numerical solutions are updated by a conservative‐interpolation formula on the resulting new mesh. Several test problems in one‐ and two‐dimensions with a general geometry are computed using the proposed moving mesh algorithm. The computations demonstrate that the algorithm is efficient for solving problems with bore waves and their interactions. The solutions with higher resolution can be obtained by using a KFVS scheme for the SWEs with a much smaller number of grid points than the uniform mesh approach, although we do not treat technically the bed slope source terms in order to balance the source terms and flux gradients. Copyright © 2004 John Wiley & Sons, Ltd.
Gardening at the edge: Documenting the limits of tropical Polynesian kumara horticulture in southern New Zealand
Authors: Bassett Kari N. , Gordon Hamish W. , Nobes David C. , Jacomb Chris 
Published: February 2004

Abstract An Erratum has been published for this article in Geoarchaeology 19(6) 2004, 613. Kumara (Ipomoea batatus), a major food source for Maori, was brought to New Zealand from tropical Eastern Polynesia ∼700 years ago. Maori successfully adapted their cultivation techniques to grow kumara in New Zealand's cooler, seasonal climate, although most kumara cultivation was limited to the warmer North Island, with cultivation becoming more marginal southward. Banks Peninsula area is considered to be the southernmost limit for kumara gardening. The Okuora Farm archeological site on the southern side of Banks Peninsula has five pits that appear to be of the raised‐rim type used for over winter storage of kumara tubers. We conducted a preliminary investigation into the nature of the pits and surrounding 1 km2 area using nondestructive techniques in accordance with Maori designation of food storage sites as tapu. Ground penetrating radar (GPR) investigation of two of the pits revealed subsurface disturbances consistent with postholes and drains, typical of raised rim kumara storage pits. Soil modification typical of kumara gardening was identified on a 1 ha area on a warm north‐northwest facing hillside. Several large borrow pits were identified as the likely source of the gravel added to the modified soil, possibly to retain heat and moisture. A plant phytolith study of soil samples identified several that appear to be from kumara. The combination of results strongly suggests this site was one of the southernmost Maori kumara gardening sites yet identified in New Zealand. © 2004 Wiley Periodicals, Inc.