1,720,982 research outputs found
HIGH-MOLECULAR-WEIGHT CHITOSAN 6-O-SULFATE - SYNTHESIS, ELECTRON-SPIN-RESONANCE AND NMR CHARACTERIZATION
No full textCellulosic Materials: Structure and Enzymatic Hydrolysis Relationships
No full textStructural and morphological features of four different cellulosic materials have been studied 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 mathematical 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
Fractionation and Bioconversion of Steam-Exploded Wheat Straw
No full textWheat 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
Enzymatic Hydrolysis of Cellulosic Materials: A Kinetic Studycarniti
No full textBiotechnology and Bioengineering, 26, 1233 (1984)
Structural Features of Cellulose and Cellulose Derivatives, and Their Effects on Enzymatic Hydrolysis
No full textEffects of structural features of cotton cellulose on enzymatic hydrolysis
No full textIn the reported experiment, textile cotton wastes were treated with gamma rays and 18% NaOH and 70% ZnCl//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(max) and K//m values were evaluated from Lineweaver-Burk plots at different temperatures. 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//m values
HYDROLYSIS OF INULIN - A KINETIC-STUDY OF THE REACTION CATALYZED BY AN INULINASE FROM ASPERGILLUS-FICUUM
No full textA 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
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