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  • 1
    Electronic Resource
    Electronic Resource
    The Influence of “Slip” on Rheological Measurements on a Mycelial Broth of Aspergillus niger (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 506 (1987), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1987.tb23853.x
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  • 2
    Electronic Resource
    Electronic Resource
    A model of insulin delivery by a controlled release micropump (1986)
    Springer
    Annals of biomedical engineering 14 (1986), S. 257-276 
    Details
    ISSN: 1573-9686
    Keywords: Insulin ; Controlled release micropump ; Basal delivery ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A model has been developed to describe the delivery of insulin from a controlled release micropump (CRM). Basal delivery was provided by diffusion due to a concentration difference driving force across the CRM. This was modelled by considering the CRM to be a series of one-dimensional steady-state diffusion resistances. This delivery model was used to size prototypes and identify the piston, foam and the pump outlet as the controlling resistances to basal insulin transport. Augmented delivery by the CRM was achieved by repeated compression of a foam disk by a mild steel piston which was driven by a solenoid (tested voltage range 0–173 V DC; 5 msec “on” time; frequency 20–40 min−1). The increased delivery was attributed to the combination of mixing inside the pump barrel and displacement of barrel contents into the downstream reservoir. This action was approximated by a three-compartment model, which considered the CRM to consist of a well-mixed upstream reservoir and pump barrel (with a downstream reservoir) separated by two resistances: a constant upstream membrane resistance, (KmAm)−1, and a variable downstream mixing rate resistance, (Qd)−1. A least squares fit of the model to experimental data showed Qd to increase with the cube of the force on the piston and linearly with the compression frequency. In agreement with experimental results, the model predicted the upstream membrane to be rate controlling only at augmented pump resistances close to the value (KmAm)−1. These models were used to design an improved prototype (VIII) which is now being evaluated in vivo in pancreatectomized dogs for its efficacy in restoring and sustaining normoglycemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000004
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrodynamics and mass transfer in Aspergillus niger fermentations in bubble column and loop bioreactors (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 731-740 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of Aspergillus niger broth rheology, bioreactor geometry, and superficial gas velocity on the volumetric liquid phase oxygen transfer coefficient (kLaL), riser gas holdup (εGR), and circulating liquid velocity (uLR) was studied in a bubble column (BC) and two external-circulation-loop airlift (ECLAL) bioreactors. The results are compared to those of previous studies on homogeneous fluids and in particular with a recent study on non-Newtonian carboxymethylcellulose (CMC) solutions conducted in the same contactors used for the A. niger fermentations. As expected from the CMC-based studies, in the heterogeneous broths of A. niger εGR, kLaL, and uLR decreased with increasing broth apparent viscosity; εGR and kLaL decreased with increasing downcomer-to-riser cross-sectional area ratio, Ad/Ar, whereas uLR increased with increasing Ad/Ar. Gas holdup data in the airlift fermentations of A. niger were well predicted by the CMC-based correlation. However, the CMC-based correlations produced conservative estimations of kLaL and overestimates of uLR compared to the observed values in the A. niger broths.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340602
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  • 4
    Electronic Resource
    Electronic Resource
    Oxygen transfer to mycelial fermentation broths in an airlift fermentor (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 746-753 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxygen transfer rates and gas holdups were measured in mycelial fermentation broths of Chaetomium cellulolyticum and Neurospora sitophila, each cultured in a 1300-L pilot-plant-scale airlift fermentor. These cultures exhibited highly non-Newtonian flow behavior coupled with a substantial decrease in oxygen transfer rates. The volumetric mass transfer coefficients in these cultures were found to be 65-70% lower than those in water. The data were compared with the available correlations obtained for simulated fermentation broths. In general, the data for C. cellulolyticum are in satisfactory agreement with the correlations for the model media but the data for N. sitophila are higher than that predicted by the correlations. Model media based correlations are found to be applicable to the fermentation processes if the culture medium does not possess a high yield stress.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260300607
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  • 5
    Electronic Resource
    Electronic Resource
    Comments on the communication: On the calculation of shear rate and apparent viscosity in airlift and bubble column bioreactors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 212-216 
    Details
    ISSN: 0006-3592
    Keywords: airlift bioreactor ; shera rates in reactors ; hydrodynamics ; non-Newtonian fluids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The determination of the shear rate in bubble column and airlift bioreactors is an important question from both the perspective of cell damage and the correlation of hydrodynamic parameters in non-Newtonian fluids in these contractors. In the context of correlating hydrodynamic parameters in non-Newtonian fluids, a common approach involves assuming that there exists an average shear rate in the column that is proportional to the superficial gas velocity. This average shear rate is then used to evaluate an effective viscosity of the non-Newtonian fluid that is subsequently used to quantify the fluid's rheological behavior in correlation. Contrary to a recent communication, this report illustrates that this approach, which has mainly been applied to bubble columns, can also be applied to external loop airlift contractors, replacing the superficial gas velocity by the superficial gas velocity by the superficial gas velocity supplied to the riser of the contractor. This extension is based upon consideration of the relevant characteristic velocity in the active zone (i.e., the riser section) of the reactor.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380214
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  • 6
    Electronic Resource
    Electronic Resource
    Direct measurement of the yield stress of filamentous fermentation broths with the rotating vane technique (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 403-412 
    Details
    ISSN: 0006-3592
    Keywords: filamentous fermentation broths ; rheology ; yield stress ; non-Newtonian ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The existence of a yield stress in filamentous fermentation broths has important transport phenomena implications in the design and operation of bioreactors. In this study, the constant shear rate vane method was assessed for directly measuring the yield stress of filamentous Aspergillus niger fermentation broths, as well as model fluids (ketchup, yogurt, and pulp suspensions). The method involved rotating 4-, 6-, and 8-bladed vanes (7.2 cm ≤ height ≤ 15 cm; 4.0 cm ≤ dia. ≤ 6 cm) at speeds of 0.01 to 0.64 rpm in the fluid and plotting the torque as a function of time. Based on visual observations, the consistency of the results with vane type and speed and comparison with previous work on nonbiological samples, it was concluded that the method is an effective and consistent technique for yield stress measurements on filamentous fermentation broths. Based on comparisons with concentric cylinder viscometer results, it was also concluded that the value determined via the vane method was a “static” yield stress (values of up to 28 Pa) which was much greater than the extrapolated (or “dynamic”) yield stress determined via the concentric cylinder viscometer. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400310
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