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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Analytical Biochemistry 150 (1985), S. 421-428 
    ISSN: 0003-2697
    Keywords: computer methods ; organic acids ; pH determination ; polyacids
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0003-2697
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 38 (1992), S. 39-45 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Small diameter alginate beads (microspheres) were formed via internal gelation of alginate solution emulsified within vegetable oil. Gelation was initiated by addition of an oil-soluble acid thereby reducing the pH of the alginate solution and releasing soluble Ca2+ from the citrate complex. Smooth, spherical, micron-sized beads were formed. The mean diameter ranged from 200 to 1000 μm, controlled by the reactor impeller design and rotational speed. The technique has potential for large-scale and continuous applications in immobilization.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 251-255 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Polymer microbead production by parallel plate electrostatic extrusion is presented. Factors affecting microbead size such as needle gauge, electrostatic potential, distance between needle and collecting solution, and polymer solution concentration and flow rate were evaluated. Smaller microbeads resulted from reduced needle diameter, reduced needle to collecting solution distance, increased electrostatic potential, and reduced polymer solution concentration and flow rate. In terms of process scale-up, it was shown that a multi-needle (20) device could continuously produce relatively uniform beads via electrostatics. The technology was demonstrated to be feasible for cell encapsulation or immobilization as there was no detectable effect of applied potential on Spodoptera frugiperda viability.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Alginate microspheres were produced by emulsification/internal gelation of alginate sol dispersed within vegetable oil. Gelification was initiated within the alginate sol by a reduction in pH (7.5 to 6.5), releasing calcium from an insoluble complex. Smooth, spherical beads with the narrowest size dispersion were obtained when using low-guluronic-acid and low-viscosity alginate and a carbonate complex as the calcium vector. A more finely dispersed form of the complexed calcium within the alginate sol promotes a more homogeneous gelification. Microsphere mean diameters ranging from 50 μm to 1000 μm were obtained with standard deviations ranging from 35% to 45% of the mean.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 644-650 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Alginate microspheres were produced by emulsification/internal gelation of alginate sol dispersed within vegetable oil. Gelification was initiated within the alginate sol by a reduction in pH (7.5 to 6.5), releasing calcium from an insoluble complex. Smooth, spherical beads with the narrowest size dispersion were obtained when using low-guluronic-acid and low-viscosity alginate and a carbonate complex as the calcium vector. A more finely dispersed form of the complexed calcium within the alginate sol promotes a more homogeneous gelification. Microsphere mean diameters ranging from 50 μm to 1000 μm were obtained with standard deviations ranging from 35% to 45% of the mean.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1994), S. 251-255 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Polymer microbead production by parallel plate electrostatic extrusion is presented. Factors affecting microbead size such as needle gauge, electrostatic potential, distance between needle and collecting solution, and polymer solution concentration and flow rate were evaluated. Smaller microbeads resulted from reduced needle diameter, reduced needle to collecting solution distance, increased electrostatic potential, and reduced polymer solution concentration and flow rate. In terms of process scale-up, it was shown that a multi-needle (20) device could continuously produce relatively uniform beads via electrostatics. The technology was demonstrated to be feasible for cell encapsulation or immobilization as there was no detectable effect of applied potential onSpodoptera frugiperda viability.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1157-1163 
    ISSN: 0006-3592
    Keywords: chitosan microcapsules ; lactic acid bacteria ; microencapsulation ; interfacial cross-linking ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lactic acid bacteria were microencapsulated within cross-linked chitosan membranes formed by emulsification/interfacial polymerization. The technique was modified and optimized to provide biocompatible conditions during encapsulation involving the use of mineral oils as the continuous phase and chitosan as the membrane material. Chitosan cross-linked with hexamethylene diisocyanate or glutaraldehyde resulted in strong membranes, with a narrow size distribution about a mean diameter of 150 μm. Cell viability and activity was demonstrated by the acidification of milk. Loss of acidification activity during microencapsulation was recovered in subsequent fermentations to levels similar to that of free cell fermentations. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 438-446 
    ISSN: 0006-3592
    Keywords: DNA ; alginate ; encapsulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alginate gels produced by an external or internal gelation technique were studied so as to determine the optimal bead matrix within which DNA can be immobilized for in vivo application. Alginates were characterized for guluronic/mannuronic acid (G/M) content and average molecular weight using 1H-NMR and LALLS analysis, respectively. Nonhomogeneous calcium, alginate, and DNA distributions were found within gels made by the external gelation method because of the external calcium source used. In contrast, the internal gelation method produces more uniform gels. Sodium was determined to exchange for calcium ions at a ratio of 2:1 and the levels of calcium complexation with alginate appears related to bead strength and integrity. The encapsulation yield of double-stranded DNA was over 97% and 80%, respectively, for beads formed using external and internal calcium gelation methods, regardless of the composition of alginate. Homogeneous gels formed by internal gelation absorbed half as much DNAse as compared with heterogeneous gels formed by external gelation. Testing of bead weight changes during formation, storage, and simulated gastrointestinal (GI) conditions (pH 1.2 and 7.0) showed that high alginate concentration, high G content, and homogeneous gels (internal gelation) result in the lowest bead shrinkage and alginate leakage. These characteristics appear best suited for stabilizing DNA during GI transit. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 438-446, 1998.
    Additional Material: 7 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1427-1432 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mild chitosan/calcium alginate encapsulation process, as applied to encapsulation of hemoglobin, was investigated. The first procedure consisted of adding dropwise a hemoglobin-containing sodium alginate mixture in a chitosan solution, then hardening the interior of capsules thus formed, in the presence of CaCl2. In the second method, the droplets were directly pulled off in a chitosan-CaCl2 mixture. Both procedures led to beads containing a high concentration in entrapped hemoglobin as more than 90% of the initial concentration (150 g/L) were retained inside the beads provided that the chitosan concentration was great enough. The molecular weight of chitosan (M̄u 245,000 or 390,000) and the pH of its solution (2, 4, or 5.4) had only a slight effect, the best retention being obtained with beads prepared at pH 5.4. The hemoglobin release during the bead storage in water was found to depend on the conditions of their formation and especially on the chitosan molecular weight. The best retention during storage in water was obtained with beads prepared with the high M̄u chitosan solution at pH 2. Considering the total loss in hemoglobin during the bead formation and after 1 month of storage in water, the best results were obtained by preparing the beads in an 8 g/L solution of a 390,000 chitosan at pH 4 (less than 7% of loss with regard to the 150 mg/L initial concentration). © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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