Activities cellulose degradation effects

Finally, dissolution of non-activated cellulose in LiCl/DMAc, and in ionic liquids has been accelerated by microwave irradiation [72,103,104], although the effect of microwave heating on the DP of the polymer has not been investigated. This last point is relevant in view of the fact that ILs are heated with exceptional efficiency by microwaves [105], so that care must be taken to avoid excessive localized heating that can induce chain degradation of the polymer during its dissolution. 

In an attempt to separate the domains from the cores, we used limited degradation with several proteases. CBH I (65 kda) and CBH II (58 kda) under native conditions could only be cleaved successfully with papain (15). The cores (56 and 45 kda) and terminal peptides (11 and 13 kda) were isolated by affinity chromatography (15,16) and the scission points were determined unequivocally. The effect on the activity of these enzymes was quite remarkable (Fig. 7). The cores remained perfectly active towards soluble substrates such as those described above. They exhibited, however, a considerably decreased activity towards native (microcrystalline) cellulose. These effects could be attributed to the loss of the terminal peptides, which were recognized as binding domains, whose role is to raise the relative concentration of the intact enzymes on the cellulose surface. This aspect is discussed further below. The tertiary structures of the intact CBH I and its core in solution were examined by small angle X-ray scattering (SAXS) analysis (17,18). The molecular parameters derived for the core (Rj = 2.09 mm, Dmax = 6.5 nm) and for the intact CBH I (R = 4.27 nm, Dmax = 18 nm) indicated very different shapes for both enzymes. Models constructed on the basis of these SAXS measurements showed a tadpole structure for the intact enzyme and an isotropic ellipsoid for the core (Fig. 8). The extended, flexible tail part of the tadpole should thus be identified with the C-terminal peptide of CBH I. 

The oxidative effect of the DMSO/PhNCO system on cellulose was confirmed by means of alcoholic model compounds (60, 62, 64) that were neatly oxidized into the corresponding ketones. The presence of the active species, the oxidatively acting sulfonium ylide 66, in the cellulose carbanilation mixture was proven by trapping with two reagents, a tocopherol-based compound (48) and a naphthoquinone (68) that was also used in a facile color test to estimate the degrading effect of certain carbanilation mixtures and conditions on cellulose. 

From an industrial perspective, the use of carbohydrate-active enzymes as cost effective, selective catalysts of biomass hydrolysis has been growing steadily over the last century (5). In particular, carbohydrases play key roles in the starch processing, animal feed, textile, and pulp and paper industries (5-7) (Table 1). The observation that enzymatic starch processing alone accounted for nearly 10% of the U.S. 1.4 billion enzyme market (1998 values) further underscores the importance of these catalysts (6). The use of (hemi)cellulose-degrading enzymes to saccharify biomass as a precursor to biofuels production and other bioreflnery purposes are of particular contemporary interest in the quest to reduce fossil fuel dependence (5,8,9). 

Figures 1 and 2 show positive correlation, although of varying degrees of goodness of fit, between the specific activities of endo ucanase, exoglucanase, and -glucosidase activities with the cellulose composition and degradation in digester feed, respectively. These data indicate a direct relationship between the cellulose content in the feed and cellulase enzyme complex production by the digester consortia. In this system, as in many others studied, cellulose is an effective inducer of cellulase secretion (67,68),...

Other fibers. The other major class of synthetic fibers, the polyacrylonitriles (orlon, acrilon, etc.) like the cellulosics (rayon, cotton) show no thermal activity up to 300 °C. Above these temperatures degradation of sample accompanies any characteristic transitions or curing exotherms. To minimize this effect, the samples are run in an inert environment such as N2, as seen in figure 16. Under these conditions reproducible characteristic endotherms were obtained for identifying wool, cotton and rayon. In roughly the same temperature region,... 

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