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Cellulose samples were derivatized in dimethylacetamide/LiCl (DMAc/LiCl) to give 4‐phenyl‐benzoylcelluloses (PBCs). The process is quantitative and leads to an highly substituted product, as verified by elemental analysis, IR and 13C‐NMR spectroscopy. PBC samples were characterized by viscometric and light scattering measurements in DMAc. The persistance length q is used to evaluate the theoretical critical volume fraction for mesophase formation (v′ th, which has been found higher than the experimental critical one (v′ exp)

Broom fibers have been used as reinforcement for the conventional polypro- pylene (iPP) and a maleate modified one (iPPMA). A conventional alkaline treatment and a steam explosion extraction process were applied to obtain the cellulosic material from broom branches. Composites were prepared by melt mixing materials with differ- ent weight percentages of broom fibers. Also ternary blends (iPPMA/iPP/broom fibers 5/45/50 wt) were obtained to examine the possibility of utilizing the maleate polypro- pylene as a compatibilizing agent. The fibers and the composites were thermally, mor- phologically, and mechanically characterized. Water absorption tests, to examine the behavior of these materials in wet conditions, were also performed. Particular attention was addressed to the study of the fiber/matrix interfacial adhesion. The results showed that the iPPMA-based composites, reinforced with alkaline extracted broom fibers, present specific mechanical properties competitive with those of the homologous poly- propylene-based materials reinforced with short glass fibers. The ternary blends gave similar properties to those of the corresponding whole iPPMA-based composites. It is considered that the esteric linkage between the cellulose {OH, and the maleic anhy- dride groups grafted on the polypropylene backbone is greatly responsible for the simi- larity in the properties. In spite of better adhesion observed in the samples reinforced by the steam-exploded fibers, less improvement of the mechanical properties was observed, owing to significant damage of the structure of the fibers during the steam explosion process. A general decrease of mechanical properties is observed in normal polypropyl- ene-based composites. The results are also supported by the water absorption tests: whereby the iPPMA-based composites showed good capability to return their dry prop- erties when kept in an oven after wetting for many days. q 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1077-1089, 1998

Lignocellulosic materials treated by the steam explosion technique alone, or in the presence of chemical reagents, undergo remarkable modifications at the level of both the chemical composition and supramolecular structure, developing features suitable for the production of conventional and advanced materials with improved properties. Experience in the production of high yield pulps, composite materials with microbial (PHB) and synthetic (polypropylene) thermoplastic matrices and high modulus lignocellulosic fibers is reported.

Steam explosion treatment has been proven to effectively induce such marked modifications to the chemical and supramolecular structure of wheat straw cellulose as to make this cellulose a suitable raw for dissolving processes. Regenerated and poly(acrylonitrile) (PAN) and poly(methyl methacrylate) (PMMA) grafted wheat straw fibers obtained on the laboratory scale were characterized by various techniques (X-ray diffraction, cross polarization-magic angle spinning (CP-MAS) 13C nuclear mag-netic resonance and vibrational spectroscopy, scanning electron microscopy, differential scanning calorimetry), and the relationships between the morphological–structural features and physicomechanical and end-use properties have been evidenced. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:961–974, 1998

Cellulose organo gels with liquid crystalline (LC) order have been prepared by crosslinking cellulose chains with a difunctional unit, adipoylchloride, or a monofunctional molecule containing a reactive double bond, 4-pentenoil chloride. Both gels display a reversible change from LC order to isotropic phase by changing the amount of solvent. The relation between the critical concentration at which the LC phase is stable, and the degree of crosslinking depends on the crosslinking agent. Both gels swell in dimethylacetamide and acetone: however the degree of swelling decreases with the degree of crosslinking in dimethylacetamide, while an increase is observed in acetone. This particular behavior can be explained by taking into account the different composition of the networks. © 1997 John Wiley & Sons, Ltd.

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. Aus Weizenstrohfasern und Polypropylen (iPP) bzw. mit Maleinsaureanhydrid modifiziertem Polypropylen (iPPMA) wurden Composite hergestellt. Die Weizenstrohfasern wurden vor dem Einmischen in die Polypropylenmatrix einem Dampfexplosionsprozes unterworfen, der bei Lignocellulosematerialien morphologische und strukturelle Veranderungen bewirkt, die zu einer Verbesserung der Wechselwirkungen mit der thermoplastischen Matrix fuhren konnen. 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 Grenzflachenhaftung in den iPPMA-Compositen kann mit den beim Mischen der Fasern mit der Polymerschmelze gebildeten kovalenten Esterbindungen zwischen den Maleinsaureanhydrid-Segmenten und den dampfbehandelten Fasern erklart werden.

The thermal behaviour of lignin blended with triglycidyl isocyanurate (TGI) was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) over a range of lignin contents from 0 to 85 wt.-%. DSC thermograms of lignin/TGI blends show two exothermic peaks at about 250 and 355°C while TG analysis in nitrogen bears evidence of a single loss of weight at about 360°C. The first exotherm is suggested to correspond to the heat of bulk reaction between epoxy groups of TGI with phenolic hydroxy groups of lignin, and the second one to the heat of char formation of lignin. TG and infrared analyses suport this conclusion. Mittels DSC und TG wurde die Reaktion zwischen Lignin und Triglycidylisocyanurat (TGI) mit Lignin-Gehalten von 0 bis 85 Gew.-% untersucht. Die DSC-Thermogramme der Lignin/TGI-Mischungen zeigen zwei Exotherme bei etwa 250 und 355°C, wahrend die TG-Analysen im Stickstoffstrom einen einzigen Gewichtsverlust bei etwa 360°C zeigen. Wir schlagen vor, das das erste exotherme Signal der Reaktionswarme zwischen den TGI-Epoxygruppen und den phenolischen Wasserstoffatomen des Lignins und das zweite Signal der Reaktionswarme der Verkohlung des Lignins entspricht. TG und IR-Spektroskopie unterstutzen diese Folgerung.

We report a study of the compatibility of a system involving a flexible polymer, hyaluronic acid (HA), and a semirigid polymer, (hydroxypropyl)cellulose (HPC). The phase diagram of ternary mixtures composed of HA, HPC, and H 2 O showed a homogeneous solution at an overall polymer concentration lower than C p ≃ 15%, but when the concentration was increased, two demixing areas were evidenced: the first (range C p 15-21%) corresponds to an equilibrium between two isotropic phases, while the second (over C p =21%) represents the coexistence of a HPC mesophase with an isotropic phase of both polymers. In contrast, optical and electron microscopy observations as well as X-ray, FT-Raman, DSC, and DMTA experiments carried out on blended films showed complete HPC/HA compatibility in all the compositions. DMTA experiments revealed a single glass transition temperature (T g ); its dependence as a function of composition was analyzed by Kwei's equation. Different values were found for dry and 65% relative humidity (RH) conditioned samples, suggesting the important role of water as a plasticizer in HPC/HA blends

A number of cellulose samples was submitted to homogeneous phase carbanilation in dimethylacetamide/LiCl. The process is quantitative and leads to a completely substituted product, as verified by elemental analysis and UV spectroscopy. Tricarbanilated samples were characterized by viscometric and light-scattering measurements in tetrahydrofuran. Our results are in good agreement with those reported in the literature, concerning products obtained in the heterogeneous phase. Gel permeation chromatography was performed for evaluating the molecular weight distribution of the parent cellulose, using both universal and linear calibration. The chromatographic technique is not adequate for samples exhibiting a high degree of polymerization. © 1995 John Wiley & Sons, Inc.

The syntheses of octyl β-D-glucopyranoside-GABA and GABOB conjugates are presented. The selectively protected octyl-β-D-glucopyranoside and γ-aminobutyric acids were coupled with N, N'-dicyclohexylcarbodiimide. 1H and 13C NMR spectroscopy were used to verify the proposed structures.

Poplar wood was steam exploded under various experimental conditions (230°C, 120–360 sec) and was then dissolved in dimethylacetamide-lithium chloride (DMAc-LiCl). Solutions of different concentrations (cp 4–10%) were obtained without any activation. Mesophases were not formed in any of the conditions tested. The good spinnability of the solutions led to wood fibers that were evaluated in terms of physico-mechanical properties and morphological and supramolecular characteristics. The tensile strength and the modulus of the wood fibers, improved through delignification treatments, were comparable to those of conventional rayons. After annealing treatments at 260°C in protic solvent, X-ray and CP MAS 13C–NMR experiments revealed evidence of a marked modification of the fiber supramolecular structure. © 1994 John Wiley & Sons, Inc.

The effect of a graft copolymer based on cellulose (CE) and polyacrylonitrile (PAN) on the compatibility of the two homopolymers in solution was analysed. Samples of copolymers containing different proportions of CE and PAN were synthesized. In order to reduce the degradation of the cellulose chain we tested different synthetic routes. After extraction of PAN homopolymer, the reaction products were composed of pure CE and copolymer; the percentage of PAN with respect to the total weight varied between 13 and 32.2%. A significant increase in compatibility was obtained by using graft copolymers in mixtures with the homopolymers, as evident from ternary phase diagrams and morphology of solution-cast films. Moreover, solutions containing the graft copolymer showed a liquid crystalline phase at high concentration.

The conformational properties of chitosan, a copolymer of 2-acetamido-2-deoxy- d -glucose and 2-amino-2-deoxy- d -glucose, have been examined both in solution and in the solid state. Little has been reported previously on the determination of molecular weight using high-performance gel-permeation chromatography (HPGPC) and no attempt has been devoted to an examination of molecular weight distribution. An HPGPC method for evaluating the above-mentioned parameters for chitosan samples having different molecular weights and different degrees of acetylation was therefore developed. Calibration using sodium polystyrene sulfonate commercial standards of narrow molecular weight distribution could not be carried out in the solvent system used for chitosan. Calibration was therefore performed by means of chitosan samples obtained by depolymerization.

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.

Wheat straw was pretreated by steam explosion under various conditions. The capability of the process in inducing a high fractionation of the lignocellulosic material in its major components and the influence of the explosion conditions on the substrate susceptibility to the attack of cellulolytic enzymes have been investigated. Bioconversion was studied considering the cellulose-rich fraction obtained from product fractionation as well as the product directly obtained from the explosion treatment. Quantitative data in terms of rate and yield of hydrolysis have been obtained for the different conditions.

Structural differences between α-chitin from shrimp ( Crangon crangon ) and β-chitin from squid (Loligo), as well as between their precipitated products from N,N-dimethylacetamide-LiCl solutions, are indicated by the CP-MAS 13 C-NMR, FT-IR, FT-Raman spectra and the X-ray diffractograms. The 13 C-NMR spectra in the solid state of α-chitin consisting of eight major resonances suggest a high degree of structural homogeneity. In the spectrum of β-chitin, the C-3 and C-5 signals merged in a single resonance. The bands contour of deconvoluted and curve-fit FT-IR and FT-Raman spectra shows a more detailed structure of α-chitin in the region of OH, NH and CO stretching regions; in particular the Amide I band is split, whereas a single broad band dominates in the corresponding β-form. Precipitation treatments induce a general disorder in α-chitin, while the metastable structure of β-chitin tends toward a more ordered architecture. All the present spectroscopic data of chitin samples are consistent with the corresponding X-ray diffraction patterns.

Chitosans from Euphausia superba of different degrees of acetylation (42%, 28% and The X-ray powder patterns indicated a decrease of order with decreasing the degree of acetylation as well as after regeneration and acid treatments. Similarly, the CP-MAS 13C-NMR and FTIR spectra exhibited a general broadening of signals suggesting the occurrence of new conformations for chitosans after regeneration. Furthermore, samples treated with hydrochloric acid showed some structural modifications which accounted for their behaviour in solution as reported in the first part of this study.

A technological development of chitosan (copolymer of N -acetylglucosamine and glucosamine) is based on the knowledge of parameters such as composition. types of sequence, chain length and distribution. In addition to the sample source, these factors are related to preparation and purification methods. In this connection the authors examined chitosan samples having the same origin ( Euphausia superba ), but different degrees of acetylation, as well as materials which were subjected to regeneration and beating processes. In addition, the authors prepared chitosan samples of different degrees of polymerization by hydrolysis of commercial chitosan of high degree of acetylation under different pH and temperature conditions. The samples were characterized in 0·1 n CH 3 COOH (HAc) - 0·2 m NaCl by intrinsic viscosity ([η]) and light scattering techniques. The viscometric behaviour of the starting chitosans and of all depolymerization products follows an expected pattern. On the other hand, light scattering shows important differences among samples having identical [η], but obtained under different hydrolysis conditions. A tentative explanation is suggested for the discrepant responses.

To study the effect of selected bacterial strains on hemp water-retting and properties of retted fibre.The trials were performed in laboratory tanks. The traditional water-retting process, without inoculum addition, was compared to a process modified by inoculating water tanks with two selected pectinolytic bacteria: the anaerobic strain Clostridium sp. L1/6 and the aerobic strain Bacillus sp. ROO40B. Six different incubation times were compared. Half the fibre obtained from each tank was combed. Micromorphological analyses were performed by scanning electron microscopy on uncombed and combed fibres. Moreover, organoleptic and chemical analyses of uncombed fibres were performed.The inoculum, besides speeding up the process, significantly improved the fibre quality. The fibre was not damaged by mechanical hackling, thanks to the good retting level obtained by the addition of selected strains, differently to what happened with the traditionally retted fibre. The best fibre quality was obtained after 3-4 days of retting with the addition of the bacterial inoculum.Retting is the major limitation to an efficient production of high-quality hemp fibres. The water-retting process and fibre quality were substantially improved by simultaneously inoculating water tanks with two selected pectinolytic strains.

Bropirimine was found to form an inclusion complex with β-Cyclodextrin in aqueous solution and in the solid phase. Phase-solubility and UV spectroscopic studies revealed the formation of a 1:1 complex. The usefulness of the ultrafiltration technique for studying this interaction was proved and the stability constant of the complex was calculated using simple equations. Chemical-shift changes observed in the 1 H-NMR spectra of both the host and guest molecules clearly indicated complex formation and confirmed the penetration of part of bropirimine molecule into the β-Cyclodextrin cavity. The formation of the complex in the solid state was confirmed by differential scanning calorimetry, CP-MAS 13 C-NMR. and infrared spectroscopy.

The interaction of cyclomaltohexaose ( a -cyclodextrin, a CD) with alkyl glycosides (AG) in solution in D 2 O was investigated by n.m.r. spectroscopy. a CD induced significant shifts of 1 H and 13 C signals (especially for the alkyl chain and the anomeric center) of octyl and dodecyl a - and β- d -glucopyranoside, dodecyl β-maltoside, and octadecyl β- d -glucopyranoside. The 1 H signals of the C 12 and C 18 AG, which were tightly bound in the original micelles, also sharpened dramatically. The CD-induced 13 C shifts and changes in spin-lattice relaxation times for the octyl β-glucoside were largest for C-4/C-7 of the alkyl chain as expected for inclusion of the chain in the CD cavity. The CD disrupted the AG aggregates, with inclusion of the hydrophobic chains in their macrocycles, suggesting their use for controlling the solution properties of alkyl glycosides and glycolipids.

The synthesis of neutral and ionic α- and β- d -alkylglucopyranosides bearing hydrocarbon chains of different length (C 8 -C 16 was performed by Fischer, Koenigs-Knorr and Schmidt methods. Cationic derivatives were obtained via tosylates as intermediates. The physico-chemical properties of products were investigated both in solution and at solid state by various techniques (quasi-elastic dynamic light scattering, differential scanning calorimetry. FTIR and CP-MAS spectroscopy and X-ray diffractometry). Above the critical micellar concentration, micellar or bilayer microagregates were obtained depending on the configuration of the anomeric centre of alkylglucopyranoside. Molecular packing and hydrogen bonds between saccharide heads in the solid state also depended on the aliphatic chain length and on the anomeric configuration.

The properties of aqueous micelles and similar supramolecular assemblies can be “fine-tuned” by varying the structure of the head groups. This approach is illustrated by considering the variation of the head group in cetyl (hexadecyl) surfactants in the sequence Me 3 N + , Et 3 N + , n-Pr 3 N + , n-Bu 3 N + and quinuclidinium and its effects on the rates of decarboxylation of the 6-nitrobenzisoxazole-3-carboxylate ion and the reaction of Br − and OH − with methyl naphthalene-2-sulfonate. β-Octyl glucoside (β-C 8 G) and β-dodecyl maltoside β-C 12 M) are water soluble and form normal micelles in water and induce circular dichroism in Cresol Red. α-Octyl glucoside (α-C 8 G) is sparingly water soluble, forms very large extended structures and does not induce circular dichroism in Cresol Red.

A new method for N-deacetylation of chitin is proposed in which a polymer almost free of N-acetyl groups is obtained by flash treatment. The reaction is carried out in 40% NaOH solution for 30–270 s at 140–190°C, using saturated steam. Flash treatment was found to proceed faster and with a higher activation energy for the deacetylation reaction (Ea = 36 kcal mol−1) compared with the traditional treatment (Ea = 11 kcal mol−1). X-Ray diffractometry, CP-MAS 13C-NMR and FTIR spectroscopy show that the flash treatment induces structure modifications; in particular, higher crystallinity indexes and specific area values are observed together with changes in the local and chain conformation.

Steam explosion pulps were studied by means of CP/MAS 13C NMR spectroscopy. The steam explosion treatment of aspen chips with Na2SO3 and Na2SO3 + NaOH led to a loss in hemicellulose and an increase in cellulose crystallinity. No lignin dissolution occurred during explosion pulping, although the lignin structure might have changed to a certain extent. For comparison purposes, conventional CMP and CTMP pulps were also analyzed. The conventional treatments revealed less modification in the spectrum with regard to original wood samples.

The authors studied interaction between water and cellulose in laboratory paper prepared ad hoc in alkaline condition using H-1 NMR relaxation techniques. Since paramagnetic substances play a major role in NMR relaxation processes, EPR spectra were also studied. 1H NMR can give information on the interaction between cellulose and water coupled by a strong spin diffusion that can equalize Ti values. Measurements of the cellulose/total water molar ratio and the cellulose/bound water molar ratio result from the free induction decay. Free water content in groundwood paper is more than double for linter and kraft paper sheets. Performing a line shape analysis of the 1H resonance as a function of temperature provides information about the porosity of the system obtaining a scale of the distribution of pore diameter sizes. T-2 values of the water component depend on the amount and type of paramagnetic impurities that short T-2 values and the amount of free water. This parameter is therefore only useful for comparing paper from the same origin.

The interaction between water and cellulose was studied in papers sized with neutral alkylketene dimer and in papers prepared with acidic rosin sizing. We analyzed samples using nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). We measured molar ratios of cellulose/total water and cellulose/ bound water. For linter and kraft acid papers, bound water is lower in acidic papers than in their neutral counter-parts. The water content in ground-wood paper is almost twice that of linter and kraft papers.

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 degrees C. The activation energies of the turnover constant for inulinase and invertase activities were found to be similar (56-57 kJ x 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 degrees C, and an activation energy of 350-370 kJ x mol(-1) was evaluated.

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. Baumwollabfalle wurden einer verschieden dosierten γ-Bestrahlung unterworfen und in 10proz. NaOH-Losungen aufgelost. Die aus diesen Losungen 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 Rontgenstreuung 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 Veranderungen der kinetischen Kenngrosen des enzymatischen Prozesses, im besonderen dem als Spezifizitatskonstante bezeichneten Verhaltnis Vmax/Km festgestellt. Nur die Bestrahlung und die Auflosung gemeinsam ergaben eine bemerkenswerte Wirkungszunahme der enzymatischen Reaktion, wahrend die Behandlung mit γ-Strahlen allein keine Zunahme der Hydrolyseausbeute bewirkte.

The reaction between glycidylmethacrylate and proteins (enzymes) leads to products which were separated by gel filtration into different fractions, which were examined by means of various analytical techniques. Spectroscopic analysis gives evidence of a perturbation of the chromophore groups of the protein as a consequence of a strong interaction with the bifunctional monomer. This perturbation is caused by reaction under formation of a covalent bond as verified especially by electrophoretic and amino acid analysis and secondarily by IR and NMR spectra. The competitive reactivity of epoxy ring and double bond of the monomer can be established by the comparative reaction between monofunctional monomers, as methylacrylate and methylmethacrylate, and the protein. The effect of the reaction with glycidylmethacrylate on the stability of the enzymes is a decrease of the specific activity from 5 to 30% for reaction periods ranging from 12 to 120 h. The copolymerization of the reaction products produces materials having activities dependent on the degree of substitution of the fractions, and recoveries of activity higher than 50%. Die Reaktion von Glycidylmethacrylat mit Proteinen fuhrt zu einem Mischprodukt, aus dem durch Gel-Filtration einige Fraktionen isoliert werden konnen. Letztere wurden mit Hilfe verschiedener Methoden untersucht. Die spektroskopische Untersuchung zeigt eine Storung der chromophoren Gruppen des Proteins, die von der Wirkung des bifunktionellen Monomeren verursacht wird. Die anderen Untersuchungsmethoden zeigen, das eine Reaktion unter Bildung von kovalenten Bindungen eingetreten ist, was erstens durch die elektrophoretische Analyse der Aminosauren, und zweitens durch IR- und NMR-Untersuchungen bestatigt wird. Die Reaktionsfahigkeit des Epoxyringes und der Doppelbindung geht aus der Reaktion der monofunktionellen Verbindungen (Methylacrylat, Methylmethacrylat) mit den Proteinen hervor. Die Reaktion von Glycidylmethacrylat bewirkt eine Verminderung der spezifischen Aktivitat der Enzyme um 5-30% innerhalb einer Reaktionszeit von 12-120 h. Die Copolymerisation dcr Reaktionsproduktc liefert Matcrialien. dercn Aktivitat vom Substitutionsgrad der Fraktionen abhlngig ist. Die Wiedergewinnung der Aktivitat betragt ca. 50%.

A method for grafting enzymes on polysaccharides using a redox system as a radical initiator is reported (Fe2+-H2O2). Glycidylmethacrylate was used as a vinylating reagent and the reaction product with enzymes (HRP, GOD, Am, ChT) was copolymerized with different matrices (cellulose, Sepharose, Sephadex, starch). During the enzyme vinylation reaction, no appreciable denaturation was observed, and various products were obtained using chromatography. Various factors affect the final activity of the copolymers; these include the redox system, the type of support, and the quantity and type of vinyl monomer added. Using a fixed quantity of enzyme, recovery of activity varied 2–50%. Graft copolymers thus obtained appear to be stable in storage and present higher thermal stability than that of the free enzyme. The kinetics of these copolymers indicate that diffusion is not appreciably limited, and that the immobilization reaction does not alter the enzymatic activity.

The hydrolysis of malto-oligosaccharides G 3 -G 6 catalysed by porcine pancreatic alpha-amylase was investigated kinetically at 25°. Kinetic parameters corresponding to different positions of enzymic attack were determined and product inhibition was evaluated. The enzymic hydrolysis was compared in terms of reaction rate and pattern of action with hydrolysis in 0.1 m H 2 SO 4 at 70°. Mathematical models for the mechanism of hydrolysis were developed and a good rationalisation of the experimental results was achieved.

Textile cotton wastes were treated with ..gamma.. rays and 18% NaOH and 70% ZnCl/sub 2/ solutions and were subjected to enzymatic hydrolysis. The untreated and treated samples were characterized both before and after hydrolysis by means of parameters concerning molecular structure (degree of polymerization), supermolecular structure (x-ray diffraction), accessibility, and reactivity (moisture regain, enzyme adsorption, and solubility in FeTNa). These parameters were correlated to kinetic parameters of the hydrolysis reaction. The V/sub max/ and K/sub m/ values were evaluated from Lineweaver-Burk plots at different temperatures. The V/sub max//K/sub m/ ratio, analogous to the specificity constant, proved to be less sensitive to experimental errors and more suitable for a comparison of the kinetic behavior of the samples. The modifications of both supermolecular structure and morphology of cellulose were of primary importance to attain high yields and rates of hydrolysis. Furthermore, the structural and morphologic parameters chosen to characterize the samples can be correlated to the kinetic parameters of enzymatic hydrolysis, in particular to K/sub m/ values.

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.

Structures formed by self-assembly of α- and β-1-n-octyl-D-glucopyranoside and β-1-n-dodecyl-D-maltoside in water depend upon the configuration at the anomeric center. The β-anomers form aggregates of size comparable to normal ionic micelles, while the α-glucoside is sparingly soluble in water and forms very large, nonspherical assemblies. This contrasting behavior suggests that the head group configuration controls its orientation to the apolar residue and, consequently, the packing of monomers in self-assemblies.The β-anome the latter is evidence of its strong interaction with micellized β-maltoside.

Commercial chitosan, and highly deacetylated congeners thereof, can be selectively and extensively sulfated at the O-6 level. Either a 2:1 mixture of sulfuric and chlorosulfonic acid (Method I) or a pyridine-SO3 complex, following protection of the 2-NH2 and 3-OH groups with copper ions (Method II), can be used. The properties of sulfated chitosan with different degrees of acetylation are studied at pH conditions which promote a polyampholyte structure. Light scattering and intrinsic viscosity ([η]) measurements of chitosan 6-O-sulfate with a degree of acetylation of 20%, prepared by Method II, indicate the presence of molecular and structural heterogeneity, probably due to ordered structures in highly acetylated regions of the parent chitosan. This hypothesis is confirmed by the NMR analysis of the fragments obtained by depolymerization with nitrous acid. The heterogeneity is not observable in compounds obtained by Method I and in highly deacetylated chitosan 6-O-sulfate. The [η] increase of the polyampholyte on decreasing ionic strength can be explained in terms of a more rigid conformation stabilized by electrostatic interactions between the sulfate groups and the protonated amino groups on neighbouring residues.

Selective sulfation of the primary hydroxyl group of chitosan was performed by means of the pyridine-SO3 complex after the positions 2 and 3 of the aminoglucopyranosidic ring were protected by coordination with copper ions. The requirements for complexing copper ions were investigated as a function of the pH and Cu(II)/chitosan mole ratio of the starting solution. Cu(II)-chitosan complexes were characterized by ESR and 13C NMR CP-MAS investigations; two different paramagnetic Cu(II) species were observed, whose relative quantity changes by changing the pH of the starting solution. The g tensor values (species I: g1‖ = 2,28, g1‖ = 2,06, A2‖ = 160 G; species II; g2‖ = 2,24, g2‖ = 2,06, A2‖ = 160 G) are consistent with a CuN2O2 chromophore. The sulfation reaction was studied in the range of 25 to 75°C using 2 : 1 to 6 : 1 pyridine-SO3/Cu(II)-chitosan mole ratios. Under optimized reaction conditions, a selective 6-O sulfation was obtained in more than 90% yield.

A method of enzyme immobilization by graft copolymerization on polysaccharides is reported. Glycidylmethacrylate was used as a vinylating reagent and the reaction product with enzymes (HRP, GOD, Am, ChT) was copolymerized with different matrices (cellulose, Sepharose, Sephadex, Starch). Various factors affect the final activity of copolymers; these include the redox system, the type of support, and the quantity and type of vinyl monomer added. Using a fixed quantity of enzyme and support (3 mg enzyme, 100 mg support), the coupling efficiency varied from 2 to 50%. The most important characteristics in these immobilized systems were tested (stability in continuous washing, kinetic characteristics, storage, thermal, and lyophilization stability). Immobilized-enzyme graft copolymers have very similar kinetic behavior to that of the free enzyme. Diffusion is not seriously limited, as shown by kinetic parameters and energy activation values, and this indicates that the immobilization reaction does not alter the enzymatic activity.

Sulphopropylated hemicelluloses have been prepared and characterized by elemental analysis, 13 C-n.m.r., conductivity, intrinsic viscosity and light scattering techniques. The binding constant with acridine orange has been evaluated in essentially salt-free solution by spectroscopy measurements. Competition between dye and a monovalent salt for the polyanionic site has also been studied. Results are compared with literature data on similar complexes. Cationic polypeptides and positively charged proteins displace acridine orange from sulphopropylated hemicelluloses. Polyanion-polycation complexes have been further investigated by viscosity and circular dichroism technique.

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.

Horseradish peroxidase was immobilized onto crosslinked acrylamide beads after a pretreatment of the enzyme with glycidyl-methacrylate. The enzyme initiates the polymerization of the acrylic comonomers. The activity of the solid materials increases by increasing the amount of glycidyl-methacrylate and the time of reaction between the vinyl monomer and the enzyme, while it is not greatly influenced by the concentration of the acrylamides. The beads obtained showed little dependence on diffusion; the Km values using guaiacol and H2O2 as substrates were the same as for free peroxidase. No decrease in stability was observed after 150h storage at room temperature or after freeze-drying. By continuous flow measurements, using guaiacol or iodide as cosubstrate, a different adsorption of the reaction products was found. Das Enzym Peroxydase wurde nach Vorbehandlung mit Glycidylmethacrylat in Polyacrylamidgel immobilisiert. Das Enzym initiiert die Polymerisation von Acrylcomonomeren. Die Aktivitat des festen Materials nimmt mit zunehmender Menge an Glycidylmethacrylat und mit zunehmender Reaktionsdauer zwischen dem Vinylmonomeren und dem Enzym zu, wahrend sie in geringem Mase von der Konzentration des Acrylamids beeinflust wird. Das erhaltene Gel zeigt eine schwache Diffusionsabhangigkeit. Die Km-Werte sind bei Verwendung von H2O2 und Guajakol gleich denen, die bei freier Peroxydase festgestellt wurden. Nach 150 h Lagerung bei Raumtemperatur oder nach der Gefriertrocknung wurde keine Stabilitatsentnahme des Enzyms beobachtet. Mittels kontinuierlicher Durchflusmessungen wurde, bei Verwendung von Guajakol als Substrat, verschiedene Adsorption der Reaktionsprodukte festgestellt.

Adsorption of a crude cellulase complex from Trichoderma viride on variously pretreated cotton celluloses has been studied in the framework of the Langmuir approach, in the temperature range 2–8°C. The saturation amount of adsorbed enzyme has been related to their susceptibility to hydrolysis. In every case the adsorption process was found to be faster by 2–3 orders of magnitude than the hydrolysis step to give end products. For one substrate, the Langmuir parameters were found to be fairly well correlated with the value of the Michaelis constant Km, measured for its enzymatic hydrolysis, and the adsorptive complex (ES)ad was indistinguishable from the complex (ES) of the Michaelis–Menten model for the hydrolysis.

Die Passivitat der Zellstoffe wird verschiedenen Faktoren zugeschrieben: Der Regularitat der primaren Struktur der Celluloseketten, deren steifer Beschaffenheit sowie deren Fahigkeit, wahrend der Biosynthese die Gestalt von langen Bandern anzunehmen, welche in hohem Mase zur Bildung eines Wasserstoffbruckennetzes neigen. Das Ergebnis ist ein hochgeordnetes und dicht gepacktes Polymeres. Es wird uber die Aktivierung von Zellstoffausschus berichtet, der infolge Derivatisierungsreaktionen und biologischer Konversion als Rohstoff fur die Herstellung von Erzeugnissen mit hohem Mehrwert verwendet werden kann. Die Auflosung der Abfallstoffe in nichtwasrigen Losungsmitteln wird als mogliche Alternative gegenuber den ublichen Verfahren zur Herstellung von Kunstfasern besprochen. Zwecks Aktivierung der Zellstoffe wurden physikalische (γ- und UV-Bestrahlung), physikalisch-chemische (Quellung, Entkristallisation und Auflosung) sowie chemische Verfahren (Copolymerisation) angewendet. Die Aktivierung der Zellstoffe wurde mittels Untersuchung ihrer Struktur (Rontgenstrukturanalyse, Festkorper-NMR-Spektroskopie, Doppelbrechung) ermittelt. Auserdem wurde die Geschwindigkeit der enzymatischen Hydrolyse bestimmt. The passivation of cellulose is attributed to a variety of factors: the regular primary structure of the cellulose chains, their rigid set-up as well as their ability to take the form of long strips during biosynthesis, which to a large extent tend to form a hydrogen bonding network. These factors result in a sophisticated and densely packed strukture. The activation of cellulose waste is reported, which, due to the derivatization reactions and biological conversion, may be used for manufacturing products with high added value. The dissolution of the waste materials in non-aqueous solvents is discussed as a possible alternative with regard to the conventional methods for the production of man-made fibers. For cellulose activation physical (γ- and UV-radiation), chemico-physical (swelling, decrystallization, and dissolution) as well as chemical methods (copolymerization) were applied. Cellulose activation was evaluated by means of structural methods (X-rays, 13C-NMR solid state spectroscopy, birefringence). Moreover, the speed of enzymatic hydrolysis was determined.

Oligomers have been primarily obtained by chemical or enzymatic hydrolysis of chitin. As opposed to previous processes, the use of hydrogen fluoride for the preparation of these compounds offers an alternative and convenient approach. Whereas the use of other mineral acids may give N-deacetylated products, depolymerisation using HF preserves this linkage. Oligomers produced from the HF hydrolysis of chitin can be separated by gel permeation chromatography (GPC) on Biogel P-4 equilibrated with ammonium acetate buffer (0.05 M, pH 4.5).

A kinetic study of the enzymatic hydrolysis of two celluloses with different structural features was performed at various temperatures (26-50 degrees C). The enzymatic system consisted of three types of enzymes: E(1)-beta-1,4-glucan glucanohydrolase; E(2)-beta-1,4-glucan cellobiohydrolase; and E(3)-beta-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 E(1) and E(2), respectively, appeared to occur for both substrates. Inhibition by cellobiose was checked at 34 degrees C on one substrate. The V(max), K(m), and glucose inhibition constants were optimized and their dependence on temperature determined.