bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new approach for modeling cellulase–cellulose adsorption and the kinetics of the enzymatic hydrolysis of microcrystalline cellulose
Authors: Nidetzky Bernd , Steiner Walter 
Published: December 2004

AbstractTwo fractions of substrate in microcrystalline cellulose which differ in their adsorption capacities for the cellulases and their susceptibility to enzymatic attack have been identified. On the basis of a two‐substrate hypothesis, mathematical models to describe enzyme adsorption and the kinetics of hydrolysis have been derived. A new nonequilibrium approach was chosen to predict cellulase–cellulose adsorption. A maximum binding capacity of 76 mg protein per gram substrate and a half‐maximum saturation constant of 26 filter paper units (FPU) per gram substrate have been calculated, and a linear relationship of hydrolysis rate vs. adsorbed protein has been found. The fraction of substrate more easily hydrolyzed, as calculated from hydrolysis data, represents 19% of the total effective substrate concentration. This fraction is only slightly different from that of other celluloses and has been estimated to be 27% and 30% for NaOH‐ and H3PO4‐swollen cellulose, respectively. The effective substrate concentration is equal to the maximum amount of the substrate which can be converted during exhaustive hydrolysis. This in turn is determined by the overall degradability of the substrate by the cellulases (85–90% for microcrystalline cellulose) and by the cellobiose concentration during hydrolysis. The kinetic model is based on a summation of two integrated first‐order reactions with respect to the effective substrate concentration. Furthermore, it includes the principal factors influencing the reaction rates: the ratio of filter paper and β‐glucosidase units per gram substrate and the initial substrate concentration. © 1993 John Wiley & Sons, Inc.
Development of a recovery and recycle process for a pseudomonas lipase used for large‐scale enzymatic synthesis
Authors: Junker B. H. , Bhupathy M. , Buckland B. C. 
Published: December 2004

AbstractEnzymes are potential catalysts for a wide range of large‐scale chemical synthesis steps, particularly when the creation of a specific chiral center is desired. The efficient recycling of the enzyme catalyst and the removal of carryover impurities were crucial factors in the improvement of a stereoselective ester hydrolysis step used in the synthesis of a selective leukotriene antagonist. In this enzymatic reaction step, the substrate and product were both largely insoluble, while the enzyme was soluble in the aqueous reaction mixture. Microfiltration and ultrafiltration of the slurry reaction mother liquor indicated near 100% enzyme protein recovery, while activity recovery was about 70% to 80%. These activity losses might be accounted for by enzyme degradation (1 to 2 mg/L · h) during the 40‐hour reaction period. Dissolved impurities, principally a diacid byproduct, in the enzyme recycling stream were reduced 60% to 70% by either lowering the solution pH to 4.0 or raising the solution ionic strength to 1 M. © 1993 John Wiley & Sons, Inc.
Plant cell suspension culture rheology
Authors: Curtis Wayne R. , Emery Alden H. 
Published: December 2004

AbstractThe results of rheological measurements on 10 different plant cell suspension cultures are presented. Nicotiana tabacum (tobacco) suspension cultures grown in serial batch subculture display high viscosity and power law rheology. This “undesirable” rheology is shown to be a result of elongated cell morphology. The rheology of Papaver somniferum (poppy) cell suspensions is quite different; poppy suspensions behave as Newtonian fluids and have relatively low viscosity (less than 15 cP) at fresh cell densities up to 250 g/L. This flow behavior can be attributed to a lack of elongation in batch‐grown poppy cells. A simple correlation for the viscosity as a function of cell density is developed for poppy suspensions up to 300 g fresh weight (FW)/L. It is shown that tobacco cells do not elongate when grown in semicontinuous culture (daily media replacement). These semicontinuously cultured cells have rheological behavior that is indistinguishable from that of poppy, further confirming the dependence of rheology on plant cell morphology. The rheology of a wide variety of other plant suspensions at 200 g FW/L is presented. Most cell suspensions, including soybean, cotton, bindweed, and potato, display low viscosities similar to poppy suspensions. Only carrot and atriplex exhibit slight pseudoplastic behavior which corresponded to a slight degree of cellular elongation for these cultures. This demonstrates that complex rheology associated with elongated cell morphology is much less common than low‐viscosity Newtonian behavior. High viscosity in plant cell culture is therefore not an intrinsic characteristic of plant cells but, instead, is a result of the ability to grow cultures to extremely high cell densities due to low biological oxygen demand. © 1993 John Wiley & Sons, Inc.
The yield equations in the modeling and control of bioprocesses
Authors: Andrews G. F. 
Published: December 2004

AbstractTwo basic questions in bioprocess modeling are how many rate equations must be specified and which processes (substrate uptake, product formation, etc.) they should describe. The number of rate equations is constrained by the yield equations, which represent the balances of reducing power, energy in the form of ATP, and the various elements involved in microbial metabolism. These balances are derived from a simplified picture that divides metabolism into catabolic, anabolic, respiratory, and product formation pathways. The linear growth equation for aerobic metabolism and the Ludeking–Piret equation for product formation by fermentation are derived from these balances, and the yield coefficients are related to the metabolic parameters, YATP (P/O), etc. The use of oxygen for purposes other than respiration is included in the analysis and extends the idea of a constant “yield on available electrons” to very reduced substrates. These balances specify the number of degrees of freedom, i.e., the number of pieces of information required to complete the description of the system. This information may be in the form of measurements, knowledge of the biochemical pathways, or rate equations. The number of rate measurements available (usually two, the consumption rates of O2 and CO2) versus the number needed defines the state estimation problem in bioprocess control. Rate equations usually specify the biomass growth rate, but it may be preferable to specify the specific consumption rate of the limiting nutrient. © 1993 John Wiley & Sons, Inc.
Microbial degradation of quinoline: Kinetic studies with Comamonas acidovorans DSM 6426
Authors: Miethling R. , Hecht V. , Deckwer W.‐D. 
Published: December 2004

AbstractThe microbial degradation of quinoline by Comamonas acidovorans was studied in a laboratory scale stirred tank reactor. In continuous culture experiments using quinoline as a sole source of carbon and nitrogen, it was shown by means of mass balances that quinoline was converted completely to biomass, carbon dioxide, and ammonia. Degradation rates up to 0.7 g/L h were obtained. Measured yield coefficients Yx/s for quinoline were about 0.7 g/g, which is in agreement with the theoretical value for complete mineralization. Kinetic constants based on Haldane substrate inhibition were evaluated. The values were μmax = 0.48 h−1, Ki = 69 mg/L, and Ks < 1.45 mg/L. © 1993 John Wiley & Sons, Inc.
Fatty acid production characteristics of fungi with particular emphasis on gamma linolenic acid production
Authors: Kennedy Max J. , Reader Sarah L. , Davies R. Julian 
Published: December 2004

AbstractThe fatty acid production characteristics of fungi are described. These characteristics are the relationship between the oil content of the cell and the fatty acid content of the oil. For example, for polyunsaturated fatty acid (PUFA) production by Mucor hiemalis IPD 51, the oil content of the cell and the GLA content of the oil are coupled. For fungal production of some PUFA, synthesized after the rate‐limiting step in the fatty acid anabolic chain, a maximum fatty acid production model was developed to link the fatty acid content of the oil and the oil content of the cell. Maximum volumetric productivity of gamma linolenic acid (GLA) by molds was found to occur at a specific GLA content of the oil. For example, for M. hiemalis IPD 51, a maximum volumetric of 4.7 mg GLA/L · h was produced at a GLA content of the oil of 8% to 10%. Similarly for Mucor circinelloides v. Tieghem IPD 155 a maximum volumetric productivity of 4.8 mg GLA/L · h was produced at a GLA content of the oil of 14% to 16%. These results imply that, when screening microorganisms for GLA or other fatty acid production, a number of medium compositions need to be evaluated to determine the tradeoff between oil content of the cell and fatty acid content of the oil. © 1993 John Wiley & Sons, Inc.
Growth rate effects on fundamental transport properties of bacterial populations
Authors: Mercer James R. , Ford Roseanne M. , Stitz Jill L. , Bradbeer Clive 
Published: December 2004

AbstractIn many natural environments, bacterial populations experience suboptimal growth due to the competition with other microorganisms for limited resources. The chemotactic response provides a mechanism by which bacterial populations can improve their situation by migrating toward more favorable growth conditions. For bacteria cultured under suboptimal growth conditions, evidence for an enhanced chemotactic response has been observed previously. In this article, for the first time, we have quantitatively characterized this behavior in terms of two macroscopic transport coefficients, the random motility and chemotactic sensitivity coefficients, measured in the stopped‐flow diffusion chamber assay. Escherichia coli cultured over a range of growth rates in a chemostat exhibits a dramatic increase in the chemotactic sensitivity coefficient for D‐fucose at low growth rates, while the random motility coefficient remains relatively constant by comparison. The change in the chemotactic sensitivity coefficient is accounted for by an independently measured increase in the number of galactose‐binding proteins which mediate the chemotactic signal. This result is consistent with the relationship between macroscopic and microscopic parameters for chemotaxis, which was proposed in the mathematical model of Rivero and co‐workers. © 1993 John Wiley & Sons, Inc.
Multigradient method for optimization of slow biotechnological processes
Authors: Tammisola Jussi , Ojamo Heikki , Kauppinen Veli 
Published: December 2004

AbstractA new method (named a “jumping spider”) is introduced for the optimization of slow biotechnological processes. The more traditional sequential experimentation (i.e., gradient search, simplex, etc.) is not well suited for slow dynamic processes, e.g., plant cell culture and differentiation. Therefore, a more simultaneous approach is proposed. A large number of initial experiments are performed, on the basis of which several of the initial experiments are selected as starting points. A search is then performed simultaneously from several gradient directions and the optimum is estimated by a quadratic approximation. In simulations, the spider generally climbs up the slopes quickly and the final estimator yields good maximum point estimates even on a complex topography. The spider may even approach more than one local maximum point simultaneously. As a model application, the average xylitol conversion rate ofCandida guilliermondiiwas optimized in relation to cultivation volume (oxygen availability) and the concentration of nitrogen and phosphorus in the medium. A threefold increase in xylitol production was obtained with three experimental steps. © 1993 John Wiley & Sons, Inc.
Growth and production modeling in hybridoma continuous cultures
Authors: Cazzador Lorenzo , Mariani Luigi 
Published: December 2004

AbstractSeveral experimental data on continuous cultures of hybridoma cells show that monoclonal antibody productivity is a decreasing function of dilution rate. It has been suggested that this unusual behavior may be due to the arrest of a fraction of cycling cells at a critical point of Phase G1. Although this hypothesis has been recently investigated by using population balance models, mathematical analysis has been performed without accounting for the dynamics of the arrested cells properly. In this article, a more general and accurate approach is presented and new specific assumptions are introduced to characterize the arrest and the later progress through the cycle. Two different models (stochastic and deterministic) and two different critical points for the arrest (at the beginning and at the end of G1) are considered. The cell cycle parameters are estimated so that data predicted by the model fit those reported in the literature. In particular, the fraction of arrested cells, the cell arrest probability, and the mean cell generation time are computed as functions of the dilution rate. Results so far obtained predict that there is an optimal value of dilution rate for maximizing specific production rate of monoclonal antibody. © 1993 John Wiley & Sons, Inc.
Screening of concanavalin A‐bead cellulose conjugates using an enzyme thermistor with immobilized invertase as the reporter catalyst
Authors: Dočolomanský Peter , Gemeiner Peter , Mislovičová Danica , Štefuca Vladimír , Danielsson Bengt 
Published: December 2004

AbstractScreening and design of immobilized biocatalysts (IMBs) is a time‐consuming process. An ideal process should be universal, fast, convenient, precise, and reproducible. Many of these requirements are met by enzymic flow microcalorimeters, also known as enzyme thermistors (ETs) or thermal assay probes (TAPs). Adaptation of ETs to real measurements of reaction rates requires coupling of the mathematical description of the reaction‐diffusion phenomena in the ET column with heat balance and, subsequently, experimental verification of the mathematical model. This article presents such a process developed as an adaptation of ETs for the characterization of the microkinetic properties of IMBs and their further application for screening of IMBs. The IMBs characterized were the preparations of invertase, biospecificaly adsorbed on concanavalin A conjugated to activated bead cellulose. © 1994 John Wiley & Sons, Inc.
Surfactant pretreatment of a polysulfone ultrafilter for reduction of antifoam fouling
Authors: Yamagiwa Kazuaki , Kobayashi Hiroe , Onodera Masayuki , Ohkawa Akira , Kamiyama Yoshiyasu , Tasaka Kentaro 
Published: December 2004

AbstractEffectiveness of surfactant precoat treatment of the polysulfone ultrafilter was first investigated for reduction of membrane fouling in ultrafiltration of antifoam. Fifteen different surfactants, including alcohols and synthetic nonionic surfactants, were tested. In general, pretreatment with nonionic surfactant gave a larger flux than that with alcohol did. The flux increase by pretreatment with nonionic surfactant depended on a hydrophile lipophile balance (HLB) value and type of hydrophobic tail. The most effective surfactant for reducing antifoam fouling among the 15 surfactants was Brij‐58 which has an HLB value of 16 and a straight alkyl hydrophobic chain. The ultrafiltration flux of the membrane treated with Brij‐58 was almost three times larger than that of untreated membrane. The precoat treatment with Brij‐58 was the most effective for reducing antifoam fouling in terms of rejection properties.Furthermore, flux was also improved by the surfactant pretreatment in ultrafiltration of model process streams, such as fermentation media, broth, and yeast suspension with or without antifoam. The surfactant Brij‐58 was found to be more effective for reducing membrane fouling in ultrafiltration of model stream YG compared with ethanol or Brij‐35. The mean flux increase by the pretreatment with Brij‐58 was about 80% in ultrafiltration of the model stream without antifoam. When antifoam was added to the model stream, flux was almost doubled by the pretreatment with Brij‐58. The effectiveness of surfactant precoat treatment for reducing membrane fouling was also confirmed in terms of rejection properties. © 1994 John Wiley & Sons, Inc.
A mathematical model for the bacterial oxidation of a sulfide ore concentrate
Authors: Nagpal Soumitro , Dahlstrom Donald , Oolman Timothy 
Published: December 2004

AbstractThe effect of dilution rate and feed solids concentration on the bacterial leaching of a pyrite/arsenopyrite ore concentrate was studied. A mathematical model was developed for the process based on the steady‐state data collected over the range of dilution rates (20 to 110 h) and feed solids concentrations (6 to 18% w/v) studied. A modified Monod model with inhibition by arsenic was used to model bacterial ferrous ion oxidation rates. The model assumes that (i) pyrite and arsenopyrite leaching occurs solely by the action of ferric iron produced from the bacterial oxidation of ferrous iron and (ii) bacterial growth rates are proportional to ferrous ion oxidation rate. The equilibrium among the various ionic species present in the leach solution that are likely to have a significant effect on the bioleach process were included in the model. © 1994 John Wiley & Sons, Inc.
Multifactorial experimental design for optimizing transformation: Electroporation of Streptococcus thermophilus
Authors: Marciset Olivier , Mollet Beat 
Published: December 2004

AbstractA multifactorial process was used to optimize transformation of Streptococcus thermophilus by electroporation. Simple experimental designs were applied to study three, four, or five factors in eight experiments. Four qualitative factors, growth and recovering media, and plasmid and bacterial strains, were studied empirically. Eight quantitative factors, including electrical, physiological, and chemical parameters, were studied by fractional factorial designs. Effects of individual parameters as well as interactions between them were investigated and optimized. Optimization was performed for one S. thermophilus strain, ST11, and proved to work for all other tested strains of the same species. Transformation efficiencies of 9 × 102 to 6 × 105 transformants per microgram DNA were achieved, depending on the strains and vectors used. © 1994 John Wiley & Sons, Inc.
A 3‐year experience of quality control and quality assurance in the multisite delivery of a lymphocyte‐based cellular therapy for renal cell carcinoma
Authors: du Moulin Gary C. , Stack Jessica , Pitkin Zorina , Chew‐Darke Judy , Cyr Carolyn , White Adrienne , Ho Letinh , Shen Yuan‐Jin , Hamilton Dylan , Davies Brian , Charles Carla , Conti Evelyn , Liu Victor 
Published: December 2004

AbstractAutolymphocyte therapy (ALT) is outpatient‐based adoptive immunotherapy using ex vivo–activated memory T‐cells. To support the safe and reproducible delivery of ALT at three cell processing facilities (Boston, MA; Atlanta, GA; Orange, CA) we created a comprehensive quality assurance/quality control program compliant with recent FDA guidance relevant to activated lymphocytes and somatic cell therapies. Each facility performed extensive QC testing to ensure sterility, viability, and proper cell yield. Additonally, several QC tests were performed at Cellocr′s centralized reference laboratory to monitor cell potency and identity of the ex vivo‐processed lymphocytes. We report here the successful implementation of this QA/QC program for ALT which has resulted in the safe preparation and delivery of cell infusion products amounting to over 3600 treatments at seven clinical sites nationwide. We believe this program will serve as a model for other cellular therapies.
Preliminary validation of an activation assay for ex vivo activated T cells utilized in cancer immunotherapy
Authors: Hamilton Dylan , Goodwin Joseph , Clarke Mary Beth , du Moulin Gary C. , Liu Victor , Caplan Barry , Babbitt Bruce 
Published: December 2004

AbstractAn in vitro assay that measures the activation level of ex vivo activated (EVA) T cells currently being used in the adoptive immunotherapy of metastatic renal cell carcinoma has been developed. This assay is based on the ability of activated, but not resting. T cells to proliferate in response to the protein kinase C activator, phorbol myristate (PMA). To utilize this assay for in‐process monitoring and control, we have begun an initial validation of the overall reproducibility of this assay. The proliferation of activated T cells in response to PMA, as measured by the mean cpm values of 3H‐thymidine incorporated, was demonstrated to have intra‐assay coefficients of variation (cv′s) for individual analysts that were typically less than 10% and rarely exceeded 20%. Activated T cells could be frozen and stored for at least 6 weeks with little or no deterioration in their ability to proliferate in response to PMA. Using these cells, inter‐assay cv′s that were typically less than 15% were obtained by individual analysts, and overall cv′s of 10% to 25% were obtained for different samples assayed by different analysts at different times. This level of variability is very reasonable for a cellular assay. Furhter validation of this assay will address the issues of sensitivity, linearity and selectivity. To date, this assay has been used to analyze over 90 patient EVA cell samples and has revealed a broad range of proliferative responses to PMA. Taken together, these results suggest that this assay may be useful in defining the potency of the activated T cell used therapeutically.
Collagen fabrics as biomaterials
Authors: Cavallaro John F. , Kemp Paul D. , Kraus Karl H. 
Published: December 2004

AbstractTissue‐engineered implants require appropriate biomaterials to serve the required physical function of the tissue being repaired or replaced while facilitating remodeling of the implant. We report on the development of implantable fabrics manufactured from continuous collagen threads. The collagen threads are formed by extrusion of native, acid‐extracted bovine colagen into a buffered solution of polyethylene glycol, followed by rinsing and air drying. The high manufacturing rate of such threads permits the production of colagen fabrics of various configurations. The fiber diameter can be controlled, and threads with dry diameters as low as 25 μm have been produced. Braids and bundles of collagen threads implanted as a replacement of the anterior cruciate ligament in a dog model were completely remodeled into host tissue by 12 weeks. Knitted collagen fabrics implanted in a rat abdominal repair model prevented herniation, and connective tissue ingrowth was observed within the fabric by 12 weeks.