bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a biosensor for assaying postmortem nucleotide degradation in fish tissues
Authors: Mulchandani A. , Male K. B. , Luong J. H. T. 
Published: May 2005

AbstractAn enzyme sensor system has been developed to assess the freshness level in fish tissue. The system was designed to measure the K value, the concentration ratio of [Hx + HxR] and [Hx + HxR + IMP], where Hx, HxR, and IMP are hypoxanthine, inosine and inosine‐5′‐monophosphate, respectively. The [Hx + HxR] concentration in tissue extract was measured by nucleoside phosphorylase and xanthine oxidase immobilized on a preactivated nylon membrane and attached to the tip of a polarographic electrode. The electrode amperometrically detected the products of degradation, hydrogen peroxide and uric acid. For determination of [IMP + HxR + Hx], IMP was first converted to HxR by nucleotidase immobilized on the wall of a polystyrene tube. The enzyme electrode consisting of nucleoside phosphorylase and xanthine oxidase provided excellent reproducible results for at least 40 repeated assays and immobilized nucleotidase was good for at least 40 assays as well. The K value for each sample could be determined in ca. 10 min. When applied to K value measurements in several fish meats, the results obtained agreed well with those obtained by the conventional enzymatic method.
Use of regulated secretion in protein production from animal cells: An evaluation with the AtT‐20 model cell line
Authors: Sambanis A. , Stephanopoulos Gregory , Sinskey A. J. , Lodish H. F. 
Published: May 2005

AbstractRegulated secretion, i.e., the ability of certain specialized animal cells to store secretory proteins intracellularly and release them upon stimulation, may be used to realize production schemes that facilitate downstream processing of protein products. Mouse AtT‐20 cells expressing recombinant human insulin and human growth hormone (hGH) were found to secrete the proteins at relatively low and constant rates when exposed to media with no secretion agonists: basal rates were 1.0–1.6 μU insulin‐reiated peptides and 0.38 ng hGH/105 cells‐h. When induced with 8 brorno‐cyclic AMP (BrcAMP), the cells secreted recombinant proteins at initial rates 3.5–9‐fold higher. A cycling secretion experiment was conducted with the insulin‐producing cells in which the cells were exposed alternately to complete growth medium and to secretion medium with BrcAMP. During the first three cycles, the cells secreted immunoreactive insulin at the foregoing high induced rates when they were exposed to BrcAMP. The cells then started to detach from the culture surface, leading to a reduction of BrcAMP‐induced secretion. Operational modifications that may result in improved system performance are discussed.
Kinetics of carrot somatic embryo development in suspension culture
Authors: Cazzulino Dana L. , Pedersen Henrik , Chin Chee‐Kok , Styer Donald 
Published: May 2005

AbstractSomatic embryos in liquid culture can serve as a mass cloning system in a plant propagation program. A quantitative formulation of embryo development obtained from cell suspension cultures is used to develop a segregated kinetic model. The model is based on standard classification schemes as previously developed by plant physiologists. Dependent variables include carbohydrate concentrations (sucrose, fructose, and glucose) and biomass apportioned among the inoculum (free single cells, cell clusters), normal developmental stages, and aberrant cell and embryo types. Good agreement between the model and experimental results is indicated and allows for a rigorous approach to media optimization and reactor scaleup for embryo formation.
Detection of microbial contamination in fermentation processes: Mass spectrometric determination of gram‐negative bacteria in Leuconostoc mesenteroides cultures
Authors: Elmroth Ingrid , Valeur Anders , Odham Göran , Larsson Lennart 
Published: May 2005

AbstractGas chromatography/mass spectrometry was used to detect the presence of Enterobacter cloacae in cultures of Leuconostoc mesenteroides, an organism used in an industrial process for production of dextrane. The penta‐fluorobenzoyl‐methyl ester derivative of 3‐hydroxy‐myristic acid, a characteristic compound of gram‐negative bacteria, was used as the analyte. By using gas chromatography/mass spectrometry with selected ion monitoring, E. cloacae was determined over the range of 1 ppm to 1% in cultures of L. mesenteroides. The proposed analytical approach represents a useful alternative to conventional methods for determining contaminating organisms in industrial fermentation processes.
The pH‐auxostat as a tool for studying microbial dynamics in continuous fermentation
Authors: Larsson G. , Enfors S.‐O. , Pham H. 
Published: May 2005

AbstractIf a microorganism has a growth coupled production or consumption of acid or alkali, it is possible to use the pH‐auxostat as a means of control in continuous fermentation. In using the pH‐auxostat, it is possible to separate the inlet substrate flow in two different streams. These will both be pH controlled, with one main flow, consisting of nutrients and a second minor but concentrated flow, of acid or alkali. Hereby, it is possible to vary the difference in pH between the fermentor and the inlet medium. This pH difference is proportional to the steady‐state cell mass concentration.1,2 It is shown that by separating the inlet flow in two different streams and cultivating without any substrate limitation, the maximum growth rate may be obtained while the cell mass concentration will be controlled. This will also give the possibility to reach high cell mass concentrations at μmax without the risk of wash‐out. A modified expression, based on hydrogen, of the steady‐state bio‐mass concentration, X, is developed as

where YX/H is the yield coefficient of cell mass per acid produced. The indexes Hin and Min refer to the inflows of alkali and medium, respectively; CHin is the inlet concentration of hydrogen ions. The boundary condition for the cell mass shows that Sin > X/YX/S, where Sin is the medium substrate concentration and YX/S is the yield of biomass per consumed substrate. It is shown that when the cell mass concentration exceeds this value, the flow stops. The applicability of the pH‐auxostat method is then verified from different experiments. It is hereby used to detect a deviation from the maximal growth rate showing effects on the microbial physiology. With Escherichia coli used as the model organism, the effect on the growth rate of temperature and high concentration of ammonia were investigated.
Effect of β‐cyclodextrin on production of L‐phenylacetyl carbinol by immobilized cells of Saccharomyces cerevisiae
Authors: Mahmoud Wafaa M. , El‐Sayed Abdel‐Halim M. M. , Coughlin Robert W. 
Published: May 2005

AbstractThe rate and extent of microbial transformation of higher concentrations of benzaldehyde substrate to L‐phenylacetyl carbinol (L‐PAC) by immobilized cells of Saccharomyces cerevisiae ATCC 834 was markedly stimulated by addition of different concentrations of β‐cyclodextrin (BCD) to the fermentation medium. With 0.5, 1.0, and 1.5% BCD in the fermentation medium and cumulative doses of benzaldehyde of 12 and 14 g/L, significantly higher yields of L‐PAC were obtained, about one‐ to twofold that of the yields of the control experiments. The favorable effects of BCD were evident in spite of its presence in stoichiometric concentrations significantly lower than those of benzaldehyde. The presence of BCD also appeared to stimulate microbial growth slightly. Enhanced cellular activity was reflected by faster D‐glucose consumption and faster benzaldehyde utilization in the presence of BCD.
Use of novel immobilized β‐galactosidase reactor to hydrolyze the lactose constituent of skim milk
Authors: Bakken Andrew P. , Hill Charles G. , Amundson Clyde H. 
Published: May 2005

Abstractβ‐galactosidase from Aspergillus oryzae immobilized in an axial‐annular flow reactor was used to effect the hydrolysis of the lactose component of skim milk. Nonlinear regression methods were employed to determine the kinetic parameters of four rate expressions derived from a proposed enzymatic mechanism. Data taken at three different temperatures (30°C, 40°C, and 50°C) were fit via nonlinear regression methods assuming an Arrhenius temperature model for each of the parameters. For the reaction conditions used in this research, a three‐parameter rate expression which includes the separate competitive inhibition effects of α‐ and β‐galactose (and the associated mutarotation reaction) is sufficient to model the hydrolysis of lactose in skim milk. The effects of temperature on the individual kinetic parameters are small. The most significant effect appears in the term for inhibition by the β anomer of galactose (EA = 10.3 kcal/mol). At 40°C and a space time of 10 min, 70% of the lactose present in skim milk can be hydrolyzed with the axial‐annular flow reactor. This reactor can be used to hydrolyze the lactose in skim milk without the problems observed with other reactor configurations, namely, plugging due to particulates, microbial contamination, and large pressure drop.
Recovery of a charged‐fusion protein from cell extracts by polyelectrolyte precipitation
Authors: Parker Diane E. , Glatz Charles E. , Ford Clark F. , Gendel Steven M. , Suominen Ilari , Rougvie Malcolm A. 
Published: May 2005

Abstractβ‐Galactosidase served as a model system to explore the feasibility of enhancing the selectivity of a low‐cost, easily scaled separation method—precipitation. Enhanced selectivity was sought by fusing the enzyme with polypeptide tails including 5 and 11 aspartaies. The unfused protein could not be selectively removed from the Escherichia coli cell extract by precipitation with polyethylenimine (PEI), but the longest fusion could be selectively removed. The presence of nucleic acids limited the purification attainable. Pretreatment with nuclease followed by diafiltration resulted in an extract from which the same fusion could be precipitated with greater than fivefold enrichment, while the untailed enzyme remained unenriched by the same precipitation step. Selectivitiy is attributed to the binding strength of the polyanionic tails to the polycationic PEI.
Damage mechanisms of suspended animal cells in agitated bioreactors with and without bubble entrainment
Authors: Kunas Kurt T. , Papoutsakis Eleftherios T. 
Published: May 2005

AbstractWe show that when freely suspended hybridoma cells are cultured in an agitated bioreactor, two fluid‐mechanical mechanisms can cause cell damage and growth retardation. The first is present only when there is a gas phase, and is associated with vortex formation accompanied by bubble entrainment and breakup. In the absence of a vortex and bubble entrainment, cells can be damaged only at very high agitation rates, above approximately 700 rpm, by stresses in the bulk turbulent liquid. Cell damage then correlates with Kolmogorov eddy sizes similar to or smaller than the cell size. In the absence of a vortex, the entrainment and motion of very fine bubbles cause no growth retardation even at agitation rates as high as 600 rpm.
Some comments on respiratory quotient (RQ) determination from the analysis of exit gas from a fermentor
Authors: Aiba Shuichi , Furuse Hisamoto 
Published: May 2005

AbstractRecently, the respiratory quotient (RQ) of microbes measured in situ in a fermentor by exit‐gas analysis has been used successfully, for instance, in a fed‐batch culture of baker's yeast as a criterion to control the feeding rate.1–3 It is significant here to keep RQ values close to unity throughout; any deviations of RQ from unity give rise to deterioration of the cell growth yield.However easy it might be to keep RQ values around unity by controlling the feeding rate, the question of whether or not RQ values determined by gas analysis at the fermentor exit could generally represent those in vivo deserves attention. Indeed, for a fermentation carried out at an alkaline side, gas analysis would give RQ values that differ remarkably from true values because of the medium's “storage” of CO2 released from microbes. The purpose of this communication is to make clear those factors that would affect true RQ values in the analysis of exit gas from a fermentor.
A structured, segregated model for genetically modified Escherichia coli cells and its use for prediction of plasmid stability
Authors: Kim Byung Gee , Shuler M. L. 
Published: May 2005

AbstractA structured, segregated model is presented for an asynchronously growing population of genetically modified Escherichia coli cells. A finite representation method was modified so that 272 cells could be used to represent a microbial population. The concept of a “limbo” compartment was introduced to allow random plasmid distribution to daughter cells upon cell division while restricting the number of computer cells included in the calculation. This scheme enabled us to predict plasmid instability and distribution of plasmid‐originated properties in a population without a priori determination of growth rates or probability of forming plasmid‐free cells from plasmid‐containing cells. Predictions of population behavior using a single‐cell model requires no adjustable parameters. The results comparing different induction strategies suggest that in continuous culture, there exists an optimum efficiency of partial induction that maximizes the long‐term productivity of the gene product due to plasmid stability. With the optimum efficiency of partial induction, constant induction appears to prove more stable than cycling induction.
Lipoprotein lipase immobilization onto polyacrolein microspheres
Authors: Hayashi Toshio , Ikada Yoshito 
Published: May 2005

AbstractA lipoprotein lipase (LPL) was made water insoluble by immobilizing onto the surface of polyacrolein (PAA) microspheres with and without oligoglycines as spacer. The activity of the immobilized LPL was found to remain high toward a small ester substrate, p‐nitrophenyl laurate (pNPL). The relative activity of the immobilized LPL without spacer decreased gradually with the decreasing surface concentration of the immobilized LPL on the PAA microsphere. On the contrary, the immobilized LPL with oligoglycine spacers gave an almost constant activity for the substrate hydrolysis within the surface concentration region studied and gave a much higher relative activity than that without any spacer. The Michaelis constant Km and the maximum reaction velocity Vm were estimated for the free and the immobilized LPL. The apparent Km was larger for the immobilized LPL than for the free one, while Vm was smaller for the immobilized LPL. The pH, thermal, and storage stabilities of the immobilized LPL were higher than those of the free one. The initial enzymatic activity of the immobilized LPL maintained almost unchanged without any leakage and inactivation of LPL when the batch enzyme reaction was performed repeatedly, indicating the excellent durability of the immobilized LPL.
Protein–protein interaction in low water organic media
Authors: Gaertner Hubert F. , Puigserver Antoine J. 
Published: May 2005

AbstractTrypsin either modified with polyethylene glycol or as a suspended powder was used to catalyze digestion of protein substrates in benzene in order to get insight into protein–protein interactions in water‐immiscible organic media. Depending on whether suspended or soluble trypsin was used, catalysis was found to proceed differently. In the first case, the amount of water in the reaction mixture (up to 1% v/v) appeared to be critical, and adsorption of water from the reaction medium by the protein substrate allowed it to behave as a hydrophilic support material comparable to that involved in immobilized enzymes. In the latter case, the presence of an additional nucleophile was a prerequisite for catalysis to proceed, and thus both water and nucleophile concentrations had some influence on trypsin activity. Phe–NH2 was the most potent nucleophile for proteolysis catalyzed by polyethylene glycol‐modified trypsin in organic media containing 1–2% water (v/v). The organic solvent‐soluble enzyme was found to bind reversibly to the protein substrate as a function of both extent of hydration of the reaction medium and time of incubation. The overall results strongly suggested that modified trypsin catalyzed peptide bond hydrolysis at the protein substrate‐organic solvent interface. Peptide mapping of bovine insulin digest by reversed‐phase high‐performance liquid chromatography definitely showed that enzyme‐catalyzed proteolysis did occur in organic solvents with a concomitant and significant transpeptidation reaction.
The large‐scale immobilization of Penicillium chrysogenum: Batch and continuous operation in an air‐lift reactor
Authors: Keshavarz T. , Eglin R. , Walker E. , Bucke C. , Holt G. , Bull A. T. , Lilly M. D. 
Published: May 2005

AbstractA temperature‐sensitive cell division cycle mutant of Penicillium chrysogenum P2 has been immobilized on Celite and grown in a 250–320‐L working volume air‐lift fermenter. The ability to uncouple growth and penicillin synthesis by raising the temperature to 30 °C also overcame the problem of the free cell mass which appeared after 300 h operation with the parent organism. After 500 h operation, penicillin and ACV dimer were still being synthesized.
A viscous pump bioreactor
Authors: Kleis S. J. , Schreck S. , Nerem R. M. 
Published: May 2005

AbstractThe fluid dynamic design and characterization of a low mechanical stress agitator and bioreactor vessel for large‐scale bioprocessing using anchorage dependent mammalian cells is considered. The complex and fragile nature of mammalian cells puts stringent constraints on the design of agitators for stirred tank bioreactors. Traditional agitators have difficulty meeting the competing requirements of fluidization and mixing while maintaining low enough mechanical stress levels to avoid cell damage. A rotating disc agitator design is proposed. Flow visualization and laser Doppler velocimeter measurements reveal fluidization of microcarriers with a gentle (low turbulence level), highly three‐dimensional flow characterized by good mixing at low hydrodynamic shear stress levels.
Kinetic studies and unstructured models of lymphocyte metabolism in fed‐batch culture
Authors: Truskey George A. , Nicolakis Dimitri P. , DiMasi Don , Haberman Allan , Swartz Randall W. 
Published: May 2005

AbstractThe growth of two lymphocyte cell lines, a hybridoma cell line and a human cutaneous T cell lymphoma (HuT78), was studied in fed‐batch culture, and unstructured models of growth developed. A criteria was established to insure that the growth rate varied by less than a specified tolerance throughout the culture period. Glutamine and serum were growth‐limiting nutrients for both cell lines with half‐maximal growth rates at 0. 53 mM glutamine and 0. 55%(v/v) serum for the hybridoma cells and 0. 21 mM glutamine and 1. 5% serum for the HuT‐78 cells. Over the range of glucose concentrations from 5. 5 mM to 28 mM, the specific growth rate of hybridoma cells was independent of glucose concentration, whereas glucose concentrations above 5. 5 mM inhibited HuT‐78 growth. For both cell lines, the growth rate was significantly inhibited by the addition of ammonium, although the hybridoma cell line was more affected by ammonia than was the HuT‐78 cell line. Growth of HuT‐78 cells increased in the presence of interleukin‐2. Unstructured models for the hybridoma cells were similar to other models presented in the literature. Applications of these models to adoptive immunotherapy are discussed.
Changes in the activity of the general amino acid permease from Saccharomyces cerevisiae var. ellipsoideus during fermentation
Authors: Lglesias R. , Ferreras J. M. , Arias F. J. , Muñoz R. , Girbès T. 
Published: May 2005

AbstractThe evolution of the activity of the general amino acid permease and ethanol and glucose concentrations in the medium were studied in a mild fermentation process carried out by a wine strain of Saccharomyces cerevisiae var. ellipsoideus isolated from grape musts in spontaneous fermentation. The cells displayed a reduction in the activity of the general amino acid permease parallel to the increase of ethanol in the medium. This ethanol increase was not enough to promote a substantial inhibition on the total polypeptide synthesis measured as polyuridylic‐acid‐directed polyphenylalanine synthesis.
Glucose oxidase immobilized polyethylene‐g‐acrylic acid membrane for glucose oxidase sensor
Authors: Hsiue Ging‐Ho , Wang Chee‐Chang 
Published: May 2005

AbstractA polyethylene‐g‐acrylic acid (PE‐g‐AA) graft copolymer was prepared via gamma‐ray‐irradiation‐induced postirradiation procedures, and was used as support material for the immobilization of glucose oxidase. Soluble carbodiimides were used as the coupling agent. Reasonable yields were obtained with CMC but not with EDAC, EEDQ, or WRK. A number of factors were studied. (1) The use of water‐soluble carbodiimides as condensing agent was attempted and the optimum condition for coupling glucose oxidase to PE‐g‐AA was established; (2) the effect of pH and temperature on the reactivity of native and immobilized glucose oxidase was studied. When exposed to temperatures in excess of 60 °C, the immobilized glucose oxidase was less sensitive to thermal inactivation than the native enzyme. The optimum pH value for the performance of the enzyme‐immobilized membrane was 5. 6. For 200 tests, the response error of glucose sensor was less than 4% and its linear detected range was 0–1000 ppm. The obtained glucose oxidase‐immobilized PE‐g‐AA membranes were kept in pH 5. 6 acetate buffer solution at 4 °C. The glucose oxidase activity of the membrane was determined at sevenday intervals. The membranes still have 92% glucose oxidase activity even after eight weeks of storage.
Micromixing in fermentors: Metabolic changes in Saccharomyces cerevisiae and their relationship to fluid turbulence
Authors: Dunlop E. H. , Ye S. J. 
Published: May 2005

AbstractEven when microorganisms are grown in highly agitated fermentors, calculation predicts a mismatch between the microscale of the turbulence (where the smallest eddy is typically 50–300 μm diameter) and the cellular dimensions (1–5 μm). The cell thus spends substantial portions of time in an apparently stagnant eddy, depleted of nutrients. The local fluid microscales were measured in a laboratory fermenter to confirm this. Using S. cerevisiae in continuous culture, it is shown that the local microscales influence cell metabolism dramatically. The issues addressed in this study are thus micromixing and microsegregation of reactants and how they influence cell yield.
An HPLC assay for rat liver ferrochelatase activity
Authors: Li Famei , Lim Chang Kee , Peters Timothy J. 
Published: May 2005

AbstractA rapid, reliable, sensitive and reproducible HPLC method was developed for the assay of ferrochelatase activity in rat liver. The assay was carried out aerobically with Zn2+ and mesoporphyrin or protoporphyrin IX as substrates. Zn‐porphyrins formed were extracted with dimethyl sulphoxide/methanol (30:70, v/v) containing Zn‐deuteroporphyrin as the internal standard for separation and quantification by reversed‐phase chromatography. The Km for mesoporphyrin was 5.9 μM, for protoporphyrin IX 8.8 μM and for zinc 6.0 μM. The specific activities were 33.1 ± 5.0 nmol Zn‐mesoporphyrin or 13.4 ± 2.0 nmol Zn‐protoporphyrin formed per hour per mg of protein for mitochondria and 12.3 ± 2.2 nmol Zn‐mesoporphyrin or 4.6 ± 0.9 nmol Zn‐protoporphyrin per hour per mg of protein for liver homogenate.