2-Cellulases

Cellulases show higher affinity to molecules of fines fraction than to long fibers. It protects them from significant damage in biocatalysis process. The enzymes hydrolyze partially fines contained in the pulp, improving their drainability on paper machine. This 

Additionally, some authors emphasize possible drop in the pulp viscosity and its partial weight loss resulting from decreased polymerization of cellulose chains [30], 

Many fungi are capable of producing extracellular enzymes that can degrade cellulose. They are Trichoderma (T) reesei, T. viride, T. koningii, T. lignorum, Penicillium funiculosum, Fusarium solani, Sclerotium rolfsii, and so on. Bacterial species such as Cellulomonas along with Clostridium thermocellum can also produce cellulases (Marsden and Gray, 1986). 

Various enzymes have been reported to be susceptible to deactivation upon shearing due possibly to the disturbance of their tertiary structure. Several investigators have studied the interfacial deactivation of T. reesei enzymes (Kim et al., 1982 Reese and Mandels, 1980). The addition of a surfactant has been found to substantially reduce enzyme deactivation. The surfactant impedes the migration of enzyme to the air-liquid interface. 

Consequently, less enzyme reaches the interface, where it will deactivate by unfolding when subjected to surface tension forces. The cellulase deactivation due to this interfacial effect combined with the shear effect was found to be far more severe and extensive than that due to the shear effect alone (Kirn et al., 1982). 

As shown in Table 4.29, the Ci and Cx factors, which were found to be endo- and exo-l,4-P-glucanases respectively, hydrolyze cellulose to cellobiose. Since the Ci factor is increasingly inhibited by its product, a cellobiase is needed so that cellulose breakdown is not rapidly brought to a standstill. However, cellobiase is also subject to product inhibition. Therefore, complete cellulose degradation is possible only if cellobiase is present in large excess or the glucose formed is quickly eliminated. 

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L. O. Asferg and T. Videbaek, Softening and Polishing of Cotton Fabrics by Cellulase Treatment, ITB Dyeing/Printing/Finishing, 2/90 (1990). 

Figure 18.16 One-dlmenslonal NMR spectra, (a) H-NMR spectrum of ethanol. The NMR signals (chemical shifts) for all the hydrogen atoms In this small molecule are clearly separated from each other. In this spectrum the signal from the CH3 protons Is split Into three peaks and that from the CH2 protons Into four peaks close to each other, due to the experimental conditions, (b) H-NMR spectrum of a small protein, the C-terminal domain of a cellulase, comprising 36 amino acid residues. The NMR signals from many individual hydrogen atoms overlap and peaks are obtained that comprise signals from many hydrogen atoms. (Courtesy of Per Kraulis, Uppsala, from data published in Kraulis et al.. Biochemistry 28 7241-7257, 1989.)...

Figure 18.17 Two-dimensional NMR spectnim of the C-terminal domain of a cellulase. The peaks along the diagonal correspond to the spectrum shown in Figure 18.16b. The off-diagonal peaks in this NOE spectrum represent interactions between hydrogen atoms that are closer than 5 A to each other in space. From such a spectrum one can obtain information on both the secondary and tertiary structures of the protein. (Courtesy of Per Kraulis, Uppsala.)...

Figure 18.20 The two-dimensional NMR spectrum shown in Figure 18.17 was used to derive a number of distance constraints for different hydrogen atoms along the polypeptide chain of the C-terminal domain of a cellulase. The diagram shows 10 superimposed structures that all satisfy the distance constraints equally well. These structures are all quite similar since a large number of constraints were experimentally obtained. (Courtesy of P. Kraulis, Uppsala, from data published in P. Kraulis et ah. Biochemistry 28 7241-7257, 1989, by copyright permission of the American Chemical Society.)...

Cellulase The enzyme that cuts the linear chain of cellulose, a glucose polymer at 1-4-p-linkages into cellodextrins and glucose. 

By enzymatic means, chitosan can be easily depolymerized by a variety of hydrolases including lysozyme, pectinase, cellulases, hemicellulases, lipases and amylases, among others, thus showing a peculiar vulnerability to enzymes other than chitosanases [71-76]. While pectinase is of particular... 

Functional screening of a soil metagenomic library for cellulases revealed a total of eight cellulolytic clones, one of which was purified and characterized [58]. Despite the fact that this library had been generated from a soil sample collected from a... 

Figure 3.10 Typical screening plate for cellulase and amylase positive clones from enrichment cultures. Clear halos indicate the presence of positive clones and the halos diameters give a first idea about the overall activities of the respective enzymes.

Cellulase and all chemicals used in this work were obtained from Sigma. Hydrolysis experiments were conducted by adding a fixed amount of 2 x 2 mm oflSce paper to flasks containing cellulase in 0.05 M acetate buffer (pH = 4.8). The flasks were placed in an incubator-shaker maintained at 50 °C and 100 rpm. A Box-Behnken design was used to assess the influence of four factors on the extent of sugar production. The four factors examined were (i) reaction time (h), (ii) enzyme to paper mass ratio (%), (iii) amount of surfactant added (Tween 80, g/L), and (iv) paper pretreatment condition (phosphoric add concentration, g/L), as shown in Table 1. Each factor is coded according to the equation... 

Cellulase enzyme complexes consist of three major types of proteins that synergistically catalyze the breakdown of a cellulosic substrate. Because the enzymes are strictly substrate-specific in their action, any change in the structure or accessibility of the substrate can have a considerable influence on the course of the hydrolysis reaction. A pretreatment method based on exposing cellulosic substrate to phosphoric acid solution [9] and addition of the nonionic... 

Dry bean curd refuse was used as the substrate in the lactic acid fermentation with simultaneous saccharification (SSF). The dry bean curd refuse was preliminarily sieved under a mesh size of 250 II m. It contained 12.3% water, 4.0% ash, 0.8% lipid, 29.3% protein, 53.6% carbohydrate, respectively, in weight basis. The cellulase derived from Aspergilltis niger with an enzymatic activity of 25,000 units/g (Tokyo Kasei Industry Inc.) was employed as the saccharification enzyme. 

Table 1 shows the dry weight of substrate, and amounts of HCl aqueous solution for pretreatment, cellulase and suspension broth for the lactic acid fermentation with ESS. The initially supplied amount of bean curd refuse in dry weight basis was changed from 10 to 150 g to examine the influence of substrate loading. The amount of cellulase was increased against initial substrate loading. And also, the amoimt of 0.1 mol/1 HCl was increased against... 

Fig. 1 Time couise of lactic acid yield and its concentration in SSF with or without pretreatment using 0.1 mol/l FICI with heating at 121 1 for 30 min. Famentation conditions 3TC, pH=5.0, initial load of bean curd refiise(BCR) 10 g, cellulase amount=l gin ILsuspension.

Marigold petals are rich sources of xanthophyUs, mainly lutein esters. To increase the coloring power, chemical extraction of the colorant from flower meal is performed or a new enzymatic procedure is applied. It was shown that treatment with cellulases or mixed saprophyte microorganisms or solid state fermentation improved the xanthophyll extraction yield. ... 

Enzymatic liquefaction is a relatively new process for the production of juices from fruits and vegetables [1]. Essentially the process is as follows the material is crushed to obtun a pulp which is treated with a combination of pectinases and cellulases. After a certain incubation time, the material becomes a liquid and the Juice can be recovered by decantation. 

Irwin, D. C., Spezio, M., Walker, L P. and Wilson, D. B. (1993). Activity studies of eight purified cellulases specificity, synergism, and binding domain effects. Blotechnol Bioeng 42,1002-1013. 

Three regulators were identified by genetic analysis. The main repressor, KdgR, controls the transcription of pectinase genes, the intracellular catabolic pathway and the secretion machinery. The PecS repressor controls the production of pectate lyases and cellulases, the secretion machinery and the biosynthesis of a blue pigment. PecT acts as a repressor of the production of some pectate lyases. Other proteins are involved in the regulation of pectinase s5mthesis but their role is not well characterized. 

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