bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic analysis of enzymatic chiral resolution by progress curve evaluation
Authors: Rakels J. L. L. , Romein B. , Straathof A. J. J. , Heijnen J. J. 
Published: December 2004

AbstractThe present study deals with kinetic modeling of enzyme‐catalyzed reactions by integral progress curve analysis, and shows how to apply this technique to kinetic resolution of enantiomers. It is shown that kinetic parameters for both enantiomers and the enantioselectivity of the enzyme may be obtained from the progress curve measurement of a racemate only.A parameter estimation procedure has been established and it is shown that the covariance matrix of the obtained parameters is a useful statistical tool in the selection and verification of the model structure. Standard deviations calculated from this matrix have shown that progress curve analysis yields parameter values with high accuracies.Potential sources of systematic errors in (multiple) progress curve analysis are addressed in this article. Amongst these, the following needed to be dealt with: (1) the true initial substrate concentrations were obtained from the final amount of product experimentally measured (mass balancing); (2) systematic errors in the initial enzyme concentration were corrected by incorporating this variable in the fitting procedure as an extra parameter per curve; and (3) enzyme inactivation is included in the model and a first‐order inactivation constant is determined.Experimental verification was carried out by continuous monitoring of the hydrolysis of ethyl 2‐chloropropionate by carboxylesterase NP and the α‐chymotrypsin‐catalyzed hydrolysis of benzoylalanine mathyl ester in a pH‐stat system. Kinetic parameter values were obtained with high accuracies and model predictions were in good agreement with independent measurements of enantiomeric excess values or literature data. © 1994 John Wiley & Sons, Inc.
Glycosidase activities of the 293 and NS0 cell lines, and of an antibody‐producing hybridoma cell line
Authors: Gramer Michael J. , Goochee Charles F. 
Published: December 2004

AbstractWe have previously demonstrated that Chinese hamster ovary (CHO) cell lysates harbor sialidase, β‐galactosidase, β‐hexosaminidase, and fucosidase activities that can accumulate extracellularly in CHO cell culture, thereby potentially leading to extracellular modification of glycoprotein oligosaccharides. The sialidase activity in CHO cell lysates was surprisingly active and stable at pH 7.5, with a half‐life of 57 h at 37°C.We have extended this work to determine whether 293, NS0, or hybridoma cell lysates contain similar glycosidase activities. The pH‐activity profiles of β‐galactosidase and β‐hexosaminidase in lysates of these three cell lines resemble the pH‐activity profiles for these enzymes in CHO cell lysate, whereas the pH‐activity profiles of sialidase and fucosidase appear to be cell‐type dependent. Sialidase activities were relatively stable at pH 4.5 in 293, NS0, and hybridoma cell lysates. However, the activities in 293 and NS0 cell lysates were unstable at pH 7.5, with no activity remaining after a 2‐h incubation at 37°C. The sialidase activity in hybridoma cell lysate was moderately stable at pH 7.5 with 30% of the activity remaining after a 2‐h incubation at 37°C. We conclude that the sialidase activites from 293, NS0, and hybridoma cells have characteristics similar to the vast majority of reported mammalian sialidase activities, and that these activities are markedly differant from the CHO cell sialidase activity.Finally, sialidase, β‐galactosidase, β‐hexosaminidase, and fucosidase activities were measured at pH 7 in cell‐free bioreactor supernatants of the hybridoma cell line. As previously observed in CHO cell culture, all four glycosidase activities were present in the hybridoma supernatants. However, the sialidase activity in hybridoma supernatant was an order of magnitude lower than in CHO cell culture supernatant despite the fact that the hybridoma cell lysis rate was an order of magnitude higher. © 1994 John Wiley & Sons, Inc.
Extraction of cephalosporin C from whole broth and separation of desacetyl cephalosporin C by aqueous two‐phase partition
Authors: Yang Wu‐Yung , Lin Chun‐Der , Chu I‐Ming , Lee Chau‐Jen 
Published: December 2004

AbstractCephalosporin C was extracted from diluted or whole broth by PEG/salt aqueous two‐phase systems. Parameters such as PEG molecular weight, salt type, pH, and salt concentration were investigated for finding a suitable extraction system. In PEG 600/ammonium sulfate or phosphate systems, Kc (partition coefficienct of cephalosporin C) was observed to be larger than 1, with Kd (partition coefficient of desacetyl cephalosporin C) being smaller than 1. The particular values of these coefficients would imply that the difficult separation of cephalosporin C and desacetyl cephalosporin C could possibly be achieved via the aqueous two‐phase extraction. The addition of surfactants, water‐miscible solvents, and neutral salts for enhancement of the separation efficiency was also investigated. The addition of surfactants to the system did not affect the separation efficiency substantially. Kc would increase whereas Kd decreased as a result of the addition of acetone, MeOH, EtOH, IPA, and n‐BuOH. Meanwhile both Kc and Kd would decrease whenever neutral salts, NaCl, KCl, Kl, or KSCN, were added. The partitioning behavior of cephalosporin C and desacetyl cephalosporin C in filtered, whole, and different batches of broth was notably quite similar to that of diluted broth. The recovery yield of cephalosporin C in whole broth extraction was observed to be a function of centrifugal force used in phase separation. © 1994 John Wiley & Sons, Inc.
Whole skeletal muscle transplantation: Mechanisms responsible for functional deficits
Authors: Faulkner John A. , Carlson Bruce M. , Kadhiresan Veerichetty A. 
Published: December 2004

AbstractOne aspect of tissue engineering of skeletal muscle involves the transposition and transplantation of whole muscles to treat muscles damaged by injury or disease. The transposition of whole muscles has been used for many decades, but since 1970, the development of techniques for microneurovascular repair has allowed the transplantation of muscles invariably result in structural and functional deficits. The deficits are of the greatest magnitude during the first month, and then a gradual recovery results in the stabilization of structural and functional variables between 90 and 120 days. In stabilized vascularized grafts ranging from 1 to 3 g in rats to 90 g in dogs, the major deficits are ∼25% decrease in muscle mass and in most grafts ∼40% decrease in maximum force. The decrease in power is more complex because it depends on both the average shortening force and the velocity of shortening. As a consequence, the deficit in maximum power may be either greater or less than the deficit in maximum force. Tenotomy and repair are the major factors responsible for the deficits.Although the data are limited, skeletal muscle grafts appear to respond to training stimuli in a manner no different from that of control muscles. The training stimuli include traditional methods of endurance and strength training, as well as chronic electrical stimulation. Transposed and transplanted muscles develop sufficient force and power to function effectively to: maintain posture; move limbs; sustain the patency of sphincters; partially restore symmetry in the face; or serve as, or drive, assist devices in parallel or in series with the heart.
Effects of substratum morphology on cell physiology
Authors: Singhvi Rahul , Stephanopoulos Gregory , Wang Daniel I. C. 
Published: December 2004

AbstractAmong the host of substratum properties that affect animal cell behavior, surface morphology has received relatively little attention. The earliest effect of surface morphology on animal cells was discovered almost a century ago when it was found that cells became oriented in response to the underlying topography. This phenomenon is now commonly known as contact guidance. From then until very recentrly, little progress has been made in understanding the role of surface morphology on cell behavior, primarily due to a lack of defined surfaces with uniform morphologies. This problem has been solved recently with the development of photolithographic techniques to prepare substrata with well defined and uniform surface morphologies. Availability of such surfaces has facilitated systematic in vitro experiments to study influence of surface morphology on diverse cell physiological aspects such as adhesion, growth, and function. For example, these studies have shown that surfaces with uniform multipls parallel grooves can enhance cell adhesion by confining cells in grooves and by mechanically interlocking them. Several independent studies have demosterated that cell shape is a major determinant of cell growth and function. Because surface morphology has been shown to modulate the extent of cell spreading and cell shape, its effects on cell growth and function appear to be mediated via this biological coupling between cell shape and function. New evidence in the cell biology literature is emerging to suggest that surface morphology could affect other cell behavioral properties such as post‐translational modifications. Further elucidation of such effects will enable better designs for implant and cell culture substrata.
N‐acetylglucosamine and adenosine derivatized surfaces for cell culture: 3T3 fibroblast and chicken hepatocyte response
Authors: Gutsche A. T. , Parsons‐Wingerter P. , Chand D. , Saltzman W. M. , Saltzman W. M. , Leong K. W. 
Published: December 2004

Abstract3T3 fibroblasts and primary chicken hepatocytes were cultured on derivatized polystyrene surfaces to examine the effect of cell‐specific ligands on cellular morphology and growth. Surfaces were prepared by derivatizing chloromethylated polystyrene with N‐acetylglucosamine (GlcNAc; recognized by the chicken asialoglycoprotein receptor) and adenosine (not recognized by adult hepatocytes). These surfaces were compared with tissue culture polystyrene (TCPS), acid‐cleaned glass, and the unmodified chloromethylated polystyrene. The spreading, cytoskeletal structure and growth of the fibroblasts following attachment to these surfaces were examined. The extent of attachment, total protein levels, and DNA contents for surfaces‐attached chicken hepatocytes were also measured. Fibroblast spreading was greatest on polymer surfaces derivatized with GlcNAc, whereas cytoskeletal structure and growth rate were independent of surface chemistry. Although chicken hepatocytes attached most efficiently to the GlcNAc derivatized polymer, the total protein and DNA levels of the surface‐attached cells were not affected. In anticipation of the application of these polymers for cell culture and hybrid artificial organ design, the GlcNAc‐derivatized polystryrene was fabricated into porous microcarriers. Fibroblasts grew avidly on the microcarriers, whereas chicken hepactocytes adhered well to the formed large aggregates arounds the microcarriers.
Filtration‐based perfusion of hybridoma cultures in protein‐free medium: Reduction of membrane fouling by medium supplementation with DNase I
Authors: Mercille Sylvain , Johnson Mark , Lemieux Réal , Massie Bernard 
Published: December 2004

AbstractIn this study, a filtration‐based perfusion process was developed for the production of monoclonal antibodies (IgM) by suspended hybridoma cells grown in protein‐free medium. It was found that the use of protein‐free medium for perfusion culture generated the formation of numerous visible suspended particles consisting of dead cells and cellular debris aggregated into fibrous material. Surprisingly high apparent viabilities were observed in such protein‐free cultures. In addition, membrane fouling occurred more rapidly in protein‐free medium than in conventional serum‐supplemented medium. By the addition of deoxyribonuclease I (DNase I) to the protein‐free medium, it was possible to prevent the formation of aggregates and to follow the evolution of the total cell population more accurately. Moreover, DNase I significantly reduced the fouling of filtration membranes, and that, for two different types of separation systems (cross‐flow and vortex‐flow filtration) and two different types of membranes (polycarbonate and hydrophilized polysultone). From these results, it is clear that the presence of DNA fragments liberated following cellular death is playing an important role in membrane fouling. Longevity of filtration membranes was found to be considerably greater using a vortex‐flow filtration module than with a static plate‐and‐frame cross‐flow filtration module. The use of vortex‐flow filtration of conjuction with DNase I allowed maintenance of perfusion cultures for more than 1 month without membrane fouling or antibody retention and with a constant permeate IgM concentration of 250 mg/L. Hybridomacells appeared to gradually adapt to increasing rotational speed in the vortex‐flow filtration module.
A metabolic model of cellular energetics and carbon flux during aerobic Escherichia coli fermentation
Authors: Ko Yun‐Fei , Bentley William E. , Weigand William A. 
Published: December 2004

AbstractAn integrated metabolic model for the production of acetate by Escherichia coli growing on glucose under aerobic conditions was presented previously (Ko et al., 1993). The resulting model equations can be used to explain phenomena often observed with industrial fermentations, i.e., increased acetate production which follows from high glucose uptake rate, a low dissolved oxygen concentration, a high specific growth rate, or a combination of these conditions. However, several questions still need to be addressed. First, cell composition is growth rate and media dependent. Second, the macromolecular composition varied between E. coli strains. And finally, a model that represents the carbon fluxes between the Embden–Meyerhof–Parnas (EMP) and the hexose monophosphate (HMP) pathways when cells are subject to internal and/or external stresses is still not well defined. In the present work, we have made an effort to account for these effects, and the resulting model equations show good agreement for wild‐type and recombinant E. coli experimental data for the acetate concentration, the onset of acetate secretion, and cell yield based on glucose. These results are useful for optimizing aerobic E. coli fermentation processes. More specifically, we have determined the EMP pathway carbon flux profiles required by the integrated metabolic model for an accurate fit of the acetic acid profile data from a wild‐type E. coli strain ML308. These EMP carbon flux profiles were correlated with a dimensionless measurement of biomass and then used to predict the acetic acid profiles for E. coli strain F‐122 expressing human immunodeficiency virus‐(HIV528) β‐galactosidase fusion protein. The effect of different macromolecular compositions and growth rates between these two E. coli strains required a constant scaling factor for improved quantitative predictions.
Mammalian cell damage in a novel membrane bioreactor
Authors: Millward H. R. , Bellhouse B. J. , Nicholson A. M. , Beeton S. , Jenkins N. , Knowles C. J. 
Published: December 2004

AbstractThe experimental study has assessed a novel membrane bioreactor for mammalian cell culture. In the absence of a gas phase, the key features of cell damage associated with laminar and turbulent flow have been identified. The bioreactor employs a dimpled membrane in order to enhance transverse mixing in a narrow channel, but a fall in viable cell density has been observed at Reynolds numbers above Re = 83. In the laminar flow regime wall shear is the critical mechanism and an accurate calculation of shear rate in a complex channel has been achieved using the Reynolds analogy. Flow generating a wall shear rate in excess of 3000 s−1 has been shown to cause damage. Power dissipation measurements have been used to distinguish between laminar and turbulent flow and also to predict Kolmogorov eddy lengths. An additional turbulent bulk stress damage mechanism at higher Reynolds numbers (Re > 250) results in a very rapid fall in viable cell density.
Enzymatic catalysis in heterogenous mixtures of substrates: The role of the liquid phase and the effects of “Adjuvants”
Authors: López‐Fandiño Rosina , Gill Iqbal , Vulfson Evgeny N. 
Published: December 2004

AbstractThe physicochemical mechanism of protease‐catalyzed peptide synthesis in heterogenous etuectic mixtures of substrates has been examined by a combination of microscopic techniques. Using a number of model reactions of dipeptide amide synthesis, it was determined that liquid phase catalysis was mostly, if not exclusively, responsible for the observed conversion of substrates. Furthermore, the formation of liquid or semiliquid eutectics was an important requirement for the occurrence of those reactions where both substrates were solids in the pure state. The addition of small quantities of hydrophilic solvents (adjuvants) often resulted in significat improvements in the rates and yields of the reactions. This was due to the ability of these adjuvants to promote the formation of eutectics, thereby increasing the proportion, as well as affecting the composition the properties, as well as affecting the composition and properties of the liquid phase. © 1994 John Wiley & Sons, Inc.
Cybernetic model for synthesis of poly‐β‐hydroxybutyric acid in Alcaligenes eutrophus
Authors: yoo Seung , Kim Woo‐Sik 
Published: December 2004

AbstractThe pathway of poly‐β‐hydroxybutyric acid (PHB) exhibits a mode of transcriptional control induced by environmental stress. A new cybernetic model for coordinated regulation of stress‐induced metabolism was developed to predict the growth and the synthesis of PHB in Alcaligenes eutrophus. A plausible objective for this control is optimization of acetyl‐CoA utilization so that the cells have a high degree of flexibility in their catabolism. The state equation for key protein synthesis was assumed to have a dependence on the nonlinear control variable. The proposed model can demonstrate the mixed‐growth‐associated synythesis of PHB. Reported unstructured models were compared statistically with the result of the simulation derived from the proposed model using the experimental data of this study and the literature. The proposed model appeared to provide an excellent description for the overall fermentation range. © 1994 John Wiley & Sons, Inc.
The effects of pH and ionic strength on the partitioning of four proteins in reverse micelle systems
Authors: Andrews B. A. , Pyle D. L. , Asenjo J. A. 
Published: December 2004

AbstractFour proteins with different physicochemical properties have been partitioned in reversed micelle systems: thaumatin, ribonuclease A, soybean trypsin inhibitor, and α‐lactalbumin. The organic phase was formed by sodium salt (AOT) in isooctane, and the aqueous phase contained KCl, KBr, MgCl2, or NaCl. Aqueous phase pH was varied between 2 and 13 and ionic strength from 0.1 to 1.0 M. Small changes in pH [around the isoelecric point (pl)] were found to influence the solubilization of ribonuclease A and trypsin inhibitor, but for thaumatin the pH change necessary to affect partition was much greater as a consequence of the difference in net charge (titration curves) of these protein molecules as pH changes. The type of ions present in the system was also a determining factor for partition; the larger ions (K+) produced more electrostatic screening and hence less protein solubilization than the smaller ions (Na+). With changes in ionic strength surface hydrophobicity was a dominant factor affecting solubilization of thaumatin in NaCl‐containing systems at high pH. Charge distribution and hydrophobicity are thought to be important parameters when partitioning the protein α‐lactalbumin. © 1994 John Wiley & Sons, Inc.
Stabilizing effect of amphiphilic excipients on the freeze‐thawing and freeze‐drying of lactate dehydrogenase
Authors: Izutsu Ken‐ichi , Yoshioka Sumie , Terao Tadao 
Published: December 2004

AbstractThe effects of amphiphilic excipients on the inactivation of lactate dehydrogenase (LDH) during freeze‐thawing and freeze‐drying were studied. Some amphiphilic excipients such as hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), CHAPS, polyethylene glycol (PEG) 3350, and sucrose fatty acid monoester prevented LDH inactivation during freeze‐thawing and freeze‐drying at a lower concentration than sugars and amino acids. Polyoxyethylene 9 lauryl ether and PEG 400 protected LDH during freeze‐thawing but not during freeze‐drying. The buffer concentration of the solution to be freeze‐dried (10, 50, and 200 mM) affected the stabilizing effect of trehalose, but not that of HP‐β‐CD. © 1994 John Wiley & Sons, Inc.
Anaerobic acidogenesis of primary sludge: The role of solids retention time
Authors: Elefsiniotis Panagiotis , Oldham William K. 
Published: December 2004

AbstractThis research investigates the effect of solids retention time (SRT) on the acid‐phase anaerobic digestion of primary sludge. A series of experiments were conducted using two continuous‐flow 3‐L units with the following configuration: a completely mixed reactor (CMR) with clarifier and solids recycle and an upflow anaerobic sludge blanket (UASB) reactor. Results show that C2 to C5 volatile fatty acids (VFA) were the predominant compounds formed. At a constant hydraulic retention time (HRT) of 12 h, variation in SRT from 10 to 20 days resulted in a slight increase in VFA production in both systems, but at a shorter SRT (5 days) a drastic drop in acid production was observed. In addition, the percent distribution of VFA was to some extent affected by the change in SRT. On the other hand, organic matter degradation [measured by the chemical oxygen demand (COD) specific solubilization rate or the percent volatile suspended solids (VSS) reduction] appeared to be independent of SRT, at least in the range investigated. The percent soluble COD in the form of VFA, however, increased steadily with increasing SRT, approaching the 90% level at 20 days. The remaining soluble COD in the effluent from these systems may be mainly attributed to metabolic intermediates and unused soluble substrate. © 1994 John Wiley & Sons, Inc.
Two‐phase airlift fermentor operation with elicitation for the enhanced production of enzophenanthridine alkaloids in cell suspensions of Escherichia californica
Authors: Byun Sang Yo , Pedersen Henrik 
Published: December 2004

AbstractApproaches to increasing the productivity of benzophenanthridine alkaloids in suspension cultures in Escherichia californica were made in an airlift fermentor under different culture conditions. Elicitation with yeast extract elicitor reduced the time required to obtain a certain amount of alkaloid production. In a two‐phase airlift fermentor with compounded silicone fluid, total alkaloid concentration in silicone fluid was 153.1 mg/L and that in the aqueous cellular phase was 8.2 mg/L at day 21 from inoculation. The large accumulation capacity of silicone fluid made it possible to store correspondingly large amounts of total alkaloid and increased the alkaloid production. Act day 21 from inoculation, the volumetric alkaloid productivity and the netproduction in a two‐phase airlift fermentor were 1.4 and 1.5 times higher than those of normal airlift fermentor operation. This performance was furthermore enhanced by elicitation. Elicitation in two‐phase airlift fermentor operation increased the volumetric productivity and the new production 3.3‐ and 3.5‐fold compared to those of normal airlift fermentor operation. © 1994 John Wiley & Sons, Inc.