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  • Wiley-Blackwell  (106)
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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 321-333 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model has been developed to predict the coupled hydrodynamics and high-molecular-weight protein transport in mammalian-cell hollow-fiber bioreactors (HFBRs). The analysis applies to reactors with isotropic ultrafiltration membranes under startup conditions when the extracapillary space (ECS) is essentially unobstructed by cells. The model confirms the experimental finding that secondary ECS flows, engendered by the primary flow in the fiber lumens, can cause significant downstream polarization of ECS proteins at typical mammalian-cell HFBR operating conditions. It also reveals that the osmotic activity of the proteins, by curtailing transmembrane fluid fluxes, can influence strongly the outcome of the polarization process. In fact, at order-of-magnitude higher protein concentrations and/or lower recycle flow rates, the secondary flow velocities can be reduced by as much as six orders-of-magnitude throughout the ECS, thereby virtually eliminating the polarization problem. This result has important implications for improved reactor startup procedures.
    Additional Material: 10 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 415-425 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A 1-D model, which neglects radial variations, describes the hydrodynamics of cell-free ultrafiltration hollow-fiber bioreactors (HFBRs) and the transport of highmolecular-weight proteins trapped in the extracapillary space (ECS). The profiles of radially-averaged protein concentrations predicted by this model are identical to those obtained using a model with radial variations. The model predictions agree well with axial profiles of bovine serum albumin (BSA) and human transferrin concentrations measured in transient and steady-state experiments. The validated model explores the influence of cell culture operating conditions on HFBR protein transport. Increasing protein loading decreases BSA and transferrin polarization in HFBRs operated with unidirectional lumen flow. A relationship developed predicts the protein loading needed to ensure a nonzero steady-state protein concentration throughout the ECS. This critical protein loading depends only on the lumen pressure drop and the ECS protein osmotic pressure. Periodic reversal of the lumen flow direction also decreases protein polarization. The influence of the flow-direction switching time and membrane permeability on the ECS protein distribution is investigated.
    Additional Material: 11 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1575-1582 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 4
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1309-1318 
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; fermentation ; cell wall ; surface electrochemistry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cell-wall properties of three strains of the yeast Sacharomyces cerevisiae have been experimentally studied at various times during fermentation. The cell walls have been characterized by electrophoretic mobility measurements, from which zeta potentials may be calculated. They have also been characterized by computerized pH titration, which gives direct information on the number and nature of groups in the yeast cell wall. The data have been quantitatively analyzed in three ways. First, a simplified analysis of the electrokinetic data of a type used by previous workers has been applied. Second, such a simplified analysis of the electrokinetic data has been developed more rigorously by means of a two-dimensional site-dissociation model of the outer cell wall-solution interface. Third, a description of the yeast cell-wall electrochemical properties in terms of a three-dimensional gel model incorporating site dissociation has been developed. The advantages and disadvantages of the three analyses are discussed. Only the three-dimensional gel model can account simultaneously for both the electrokinetic and pH surface titration data. It provides new insights into the changes that occur to the yeast cell wall during fermentation. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 580-586 
    ISSN: 0006-3592
    Keywords: tissue engineering ; N1E-115 neuroblastoma cells ; electrophysiological differentiation ; retinoid cytotoxicity ; teratogenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cytotoxic effects of retinoids on neuroblastoma cells at various times during electrophysiological differentiation were evaluated. We used N1E-115, a clone of the murine neuroblastoma C1300 derived from the neural crest, and three retinoids: vitamin A (retinol), all-trans retinoic acid (tretinoin), and 13-cis-retinoic acid (isotretinoin). Differentiating N1E-115 cells exposed to retinoids at an isotretinoin EC50 of 16 μM exhibited the greatest vulnerability in terms of cell death during a period (8 to 10 days) that was previously found to be the most sensitive for induction of gross malformations in rodents. This finding suggested possible similarities between the in vivo and in vitro retinoid mechanism(s) of action. The greatest period of vulnerability to retinoid cytotoxicity was also found to coincide with the rapid resting membrane potential (Vm) development period, suggesting a linkage between neuronal Vm and/or electrical excitability development and vulnerability to retinoid cytotoxicity. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1099-1106 
    ISSN: 0006-3592
    Keywords: protein adsorption ; hollow fiber bioreactor ; transferrin ; serum-free medium ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The recovery of serum-free medium proteins from poly-sulfone hollow fiber bioreactors (HFBRs) was investigated. More than 99% of the initial transferrin was adsorbed to the hydrophobic hollow fibers within 2 h of HFBR operation. A methodology to minimize transferrin adsorption by pre-adsorption of bovine serum albumin (BSA) was developed. BSA adsorption on suspended cut fibers was virtually complete within 1 h. BSA-coated fibers adsorbed only 5% of the transferrin within 10 days, whereas uncoated cut fibers adsorbed more than 99% of the transferrin within 1 h. An improved HFBR startup procedure, using a BSA-coating step before inoculation, resulted in substantially higher transferrin recovery. Additional factors influenced extracapillary space (ECS) transferrin concentrations. Pronounced downstream polarization of transferrin was observed in the ECS. In addition, the 30-kDa nominal molecular weight cutoff ultrafiltration membranes rapidly leaked transferrin from the ECS to the lumen. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 125-135 
    ISSN: 0006-3592
    Keywords: ultrafiltration ; proteins ; colloidal interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A rigorous dynamic mathematical model for predicting the rate of ultrafiltration of proteins has been developed. The model is based on sophisticated descriptions of the protein-protein interactions within the layer close to the membrane surface which are responsible for controlling permeation rate. Electrostatic interactions are accounted for by a Wigner-Seitz cell approach, including a numerical solution of the nonlinear Poisson-Boltzmann equation. London-van der Waals forces are calculated using a computationally efficient means of approximating screened, retarded Lifshitz-Hamaker constants. Configurational entropy effects are calculated using an equation of state giving excellent agreement with molecular dynamic data. Electroviscous effects are also taken into account. These descriptions of protein-protein interactions are used to develop an a priori model, with no adjustable parameters, that allows quantitative prediction of the rate of filtration of proteins as a function of zeta potential (and hence pH), ionic strength, applied pressure, protein size, and membrane resistance. A comparison with experimental data for the filtration of bovine serum albumin (BSA) shows that the model is in excellent agreement with such data. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 491-497 
    ISSN: 0006-3592
    Keywords: membrane ; microfiltration ; enzyme ; activity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental study of the interaction of the enzyme yeast alcohol dehydrogenase (YADH) with microfiltration membranes has been carried out. Most measurements were made with capillary pore inorganic membranes (Anopore) with some comparative measurements being made with polymeric membranes of low protein affinity (Durapore). It has been shown that the prolonged exposure of the enzyme to the inorganic membrane under low-shear conditions (slow recycle) resulted in a loss of enzyme activity. Under filtration conditions, the membrane permeation rate decreased continuously with time. This decrease could be quantified using the standard blocking filtration law, which describes a decrease in pore volume due to deposition of enzyme on the walls of the pore. No significant loss in activity of permeating enzyme occurred under solution conditions where the enzyme was stable. However, a significant loss of such activity occurred under solution conditions where the enzyme was slightly unstable. The experiments indicate that the likely mechanism for activity loss is a membrane/enzyme interaction resulting from a shear induced deformation of the enzyme structure. Two conclusions of practical importance are drawn from the work. © 1992 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 130-138 
    ISSN: 0006-3592
    Keywords: recombinant baculovirus ; virus-like particles ; parvovirus B19 ; multiplicity of infection ; co-infection ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant human parvovirus B19 virus-like particles (VLPs), a candidate vaccine, were produced using the insect cell (Sf-9)-baculovirus (AcNPV) expression system. The synthesis and assembly of the particles in Sf-9 cells are directed by double infections with one recombinant virus (bacVP1) expressing the parvovirus minor viral protein VP1 and a second virus (bacVP2) expressing the major viral protein VP2. Previous animal studies demonstrated that the polypeptide composition of the VLPs strongly affects the elicitation of virus neutralizing antibodies. The key factor controlling the production of an immunologically potent product in bioreactors was identified to be the multiplicity of infection (MOI) of bacVP1 and bacVP2 used for infection. A probabilistic model, which correlates well with the experimental results, was employed to facilitate the selection of MOIs and to provide a better understanding of the baculovirus co-infection process. A novel production process based on secondary infections was developed to ensure product consistency and to simplify large-scale logistics. The effects of other critical process parameters, such as temperature, dissolved oxygen concentration, lactate concentration, cell concentration at infection, and harvest time, were also investigated. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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