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  • 1
    Electronic Resource
    Electronic Resource
    Enzymatic hydrolysis of cellulosic materials: A kinetic study (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 1233-1238 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic study of the enzymatic hydrolysis of two celluloses with different structural features was performed at various temperatures (26-50°C). The enzymatic system consisted of three types of enzymes: E1 - β-1,4-glucan glucanohydrolase; E2 - β-1,4-glucan cellobiohydrolase; and E3 - β-glucosidase. A mathematical model for the mechanism of the hydrolysis of cellulosic materials catalyzed by a multienzymatic system was checked and a good rationalization of the experimental results was achieved. Uncompetitive and competitive glucose inhibition on E1 and E2, respectively, appeared to occur for both substrates. Inhibition by cellobiose was checked at 34°C on one substrate. The Vmax, Km, and glucose inhibition constants were optimized and their dependence on temperature determined.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260261013
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrolysis of inulin: A kinetic study of the reaction catalyzed by an inulinase from Aspergillus ficuum (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 575-579 
    Details
    ISSN: 0006-3592
    Keywords: inulin ; inulinase ; fructose ; enzymic hydrolysis ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic study of the hydrolysis of inulin was performed by using as catalyst a commercial inulinase from Aspergillus ficuum. The reaction was studied carrying out initial rate as well as time course measurements. Both inulinase and invertase activities of the enzyme were taken into account, and the corresponding kinetic parameters were determined in the temperature range 30-50°C. The activation energies of the turnover constant for inulinase and invertase activities were found to be similar (56-57 kJ · mol-1). The ratio S/I of invertase to inulinase activity was 1.6 regardless of temperature. The thermal degradation of the enzyme was also investigated up to 70°C, and an activation energy of 350-370 kJ · mol-1 was evaluated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370612
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  • 3
    Electronic Resource
    Electronic Resource
    Enzymatic hydrolysis of cotton wastes. Effect of γ-ray pretreatments (1982)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 102 (1982), S. 187-197 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Baumwollabfälle wurden einer verschieden dosierten γ-Bestrahlung unterworfen und in 10proz. NaOH-Lösungen aufgelöst. Die aus diesen Lösungen regenerierten Cellulosen wurden einer enzymatischen Hydrolyse unterzogen und der Verlauf der hydrolytischen Reaktion mit demjenigen an unbehandelten oder nur mit γ-Strahlen behandelten Cellulosen verglichen.Die einzelnen Muster wurden mittels Röntgenstreuung sowie Messungen des Polymerisationsgrades, der Feuchtigkeitsaufnahme und der Wasserretention charakterisiert. Es wurde eine wechselseitige Beziehung zwischen den durch die Vorbehandlungen hervorgerufenen strukturellen und morphologischen Modifizierungen und den Veränderungen der kinetischen Kenngrößen des enzymatischen Prozesses, im besonderen dem als Spezifizitätskonstante bezeichneten Verhältnis Vmax/Km festgestellt. Nur die Bestrahlung und die Auflösung gemeinsam ergaben eine bemerkenswerte Wirkungszunahme der enzymatischen Reaktion, während die Behandlung mit γ-Strahlen allein keine Zunahme der Hydrolyseausbeute bewirkte.
    Notes: Textile cotton wastes were irradiated with γ-rays at different doses and solubilized with 10% NaOH solutions. The regenerated products underwent enzymatic hydrolysis and their degradation pattern was compared with that of the cotton celluloses untreated or treated only with γ-rays. The different samples were characterized by measurements of X-ray diffraction, degree of polymerization, moisture regain and water retention. The structural and morphological modifications induced by the pretreatments were correlated with the variations of kinetic parameters, particularly the Vmax/Km ratio, defined as specificity constant. Only the combination of irradiation with dissolution pretreatments gave a considerable increase of hydrolysis reaction effectiveness.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1982.051020118
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  • 4
    Electronic Resource
    Electronic Resource
    Steam-exploded wheat straw fibers as reinforcing material for polypropylene-based composites. Characterization and properties (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 149-166 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aus Weizenstrohfasern und Polypropylen (iPP) bzw. mit Maleinsäureanhydrid modifiziertem Polypropylen (iPPMA) wurden Composite hergestellt. Die Weizenstrohfasern wurden vor dem Einmischen in die Polypropylenmatrix einem Dampfexplosionsprozeß unterworfen, der bei Lignocellulosematerialien morphologische und strukturelle Veränderungen bewirkt, die zu einer Verbesserung der Wechselwirkungen mit der thermoplastischen Matrix führen können. Die modifizierte iPPMA-Matrix weist im Vergleich zur iPP-Matrix bessere mechanische Eigenschaften (Zug- und Schlagverhalten) und eine bemerkenswerte Verringerung der Wasseraufnahme, einer der Hauptnachteile von Compositen mit Naturfasern, auf. Die gute Grenzflächenhaftung in den iPPMA-Compositen kann mit den beim Mischen der Fasern mit der Polymerschmelze gebildeten kovalenten Esterbindungen zwischen den Maleinsäureanhydrid-Segmenten und den dampfbehandelten Fasern erklärt werden.
    Notes: Composites of wheat straw fibers with polypropylene (iPP) and maleic anhydride modified polypropylene (iPPMA) were prepared.Before being mixed with polypropylene matrices, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosic materials. Such changes are able to enhance the interactions with the thermoplastic matrix.Compared with iPP, the modified matrix (iPPMA) has shown higher mechanical performances (tensile and impact behavior) and a remarkable decrease of water absorption, that is one of the main drawbacks of natural fiber composites.Finally, the presence of covalent bonds between maleic anhydride and steam-exploded (STEX) fibers, by means of an esterification reaction, produced during the melt-mixing process, can explain the resulting good interfacial adhesion found in iPPMA-based composities.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052330113
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  • 5
    Electronic Resource
    Electronic Resource
    Cellulosic materials: Structure and enzymatic hydrolysis relationships (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 3329-3338 
    Details
    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: Structural and morphological features of four different cellulosic materials have been deeped by X-ray, CP-MAS NMR, water retention, and specific surface area analysis. Hydrolysis time courses of two of these celluloses were followed by employing an enzymatic system consisting of a cellulase from Trichoderma viride and a cellobiase from Aspergillus niger. Experimental results were rationalized on the basis of a methematical model previously verified on the other two substrates. All the celluloses presented the same mechanistic framework involving product inhibitions. The most efficient pretreatment was found to be the dissolution of cellulosic material in the dimethyl sulfoxide-paraformaldehyde system and regeneration with ammonia. This treatment cancelled the memory of the initial structural order.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070291110
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  • 6
    Electronic Resource
    Electronic Resource
    Sulfopropylated hemicellulose: Synthesis and NMR characterization (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 129-138 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Sulfopropylation of hemicelluloses was achieved in dimethyl sulfoxide solution. The progress of sulfopropylation reaction was studied as a function of the dimsyl/hemicellulose ratio, reaction time with dimsyl (dimethylsulfinyl carbanion), propanesultone/hemicellulose ratio, and reaction time with propanesultone. The degree of substitution of sulfopropylhemicelluloses ranged between 0,5 and 1,1 as a function of experimental conditions. Intrinsic viscosity (0,1 - 0,3 dl/g) and molecular weight measurements (15000 g.mol - 1) showed a controllable degradation of hemicellulose chains during the reaction. The NMR characterization of enzymatically degradated sulfopropylhemicelluloses indicated a homogeneous substitution along the polysaccharide chains. A significant regioselectivity for the OH-2 hydroxyl groups was observed only for DS ≤ 0,5.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900114
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  • 7
    Electronic Resource
    Electronic Resource
    A new class of biodegradable materials: Poly-3-hydroxy-butyrate/steam exploded straw fiber composites. I. Thermal and impact behavior (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 2091-2103 
    Details
    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: Biodegradable thermoplastic composites reinforced with wheat straw fibers were prepared. The matrix was an expensive polyester, poly-3-hydroxy-butyrate (PHB), produced by bacterial fermentation. Before being mixed with the PHB, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosics. Such changes enhance the interaction with the thermoplastic matrix. The two components were melt mixed and the composite molded under hot compression. Compared with neat PHB, not only does the composite material show better mechanical properties but, moreover, production costs are dramatically reduced because wheat straw is a very inexpensive product. Finally, FTIR measurements revealed some PHB/straw fiber molecular interactions that interfere with the PHB crystallization. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070491205
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