Cellulase application

The example of cellulase application given above is dealing with their ability to aggressive destruction of different renewable feedstock and with the craiversion of insoluble cellulose-containing substrates to soluble C6 and C5 sugars (which could be defined as saccharolytic activity). 

Figure 2.19 Cross section of fiber ceii showing effects of cellulase application on its structure.

Lenting, HBM Warmoeskerken, MMCG. Guidelines to come to minimized tensile strength loss upon cellulase application. Journal of Biotechnology, 2001, 89(2-3), 227-32. 

The precise effects obtained are dependent on the fabric quality, the type of cellulase enzyme and the application conditions, but no mechanical forces are involved in removal of the fibrils. The process has attracted considerable attention and is now one of the main methods of defibrillating lyocell fabrics [94,101-114]. Simultaneous treatment with cellulase and protease enzymes has been applied to the biofinishing of wool/cotton blends [115]. 

Application of a mixture of cellulases, pectinases and lignases, again without damage to the wool. 

In the treatment of cellulose pulps one essential criterion for a suitable enzyme preparation is that its cellulase activity should be as low as possible, or preferably absent completely. As even extremely low cellulase activities may ruin pulp quality, Trichoderma enzyme preparations are unlikely to be suitable for these applications. Many bacterial and fungal enzymes with low cellulase activity have been shown to be suitable for treatment of pulps 14, 15, 16,17), Regulation of the often synchronous production of cellulolytic and hemicellulolytic enzymes in micro-organisms is not well understood, and is further complicated by substrate cross-specificity of these enzymes. Enzymes with both endoglucanase and xylanase activity have been reported for bacteria 18, 19) and fungi 20, 21, 22), In addition to selection of strain and... 

A literature survey indicated that very little work has been done to produce an optimal cellulase system as described above. Here, we used solid-state fermentation (SSF) to achieve this objective. SSF processes, such as the "koji" process, have been used extensively for amylase production on wheat bran in Japan its application was extended to cellulase production on wheat bran and Ugnocellulosic materials by Toyama (13), Since then, wheat bran has become an important substrate for producing various products by SSF (14-20), In this study, we tested various lignocellulosic substrates for the production of cellulase and )3-glucosidase from T, reesei QMY-1 by SSF. 

Cost sensitivity studies have shown that the successful commercialization of cellulase-based processes, such as the conversion of cellulose to fermentable sugars, is highly dependent on the cost of enzyme production (i). Because fungal -D-glucosidase (EC 3.2.1.21) is the most labile enzyme in this system under process conditions (2), and k to efficient saccharification of cellulose, this enzyme was targeted for application of stabilization technology, both through chemical modification and immobilization to solid supports. 

Since protein adsorption to an anion exchange resin is reversible and does not constitute a classical immobilization, the ability of the resins to retain activity under various conditions must be determined. Macrosorb KAX DEAE bound -D-glucosidase was tested with solutions of primary interest for their final application. Several batch washes of a 1% w/v slurry were required to ensure complete equilibrium elution for a given concentration, as determined from the absence of pNPG units in subsequent washes. Several salt solutions of typical fermentation media components were tested. These included 3 mM to 50 mM solutions of MgSO, KHgPO, NaQ, and sodium acetate. Also, incubations with cellulase solutions were tested to determine if the proteins present in a cellulose hydrolysis would displace the -D-glucosidase. Both of these displacement studies were carried out at 22°C and 40 C. 

The construction of hybrid proteins containing bacterial CBDs may provide a cheap generic method for enzyme immobilization and/or purification using cellulosic matrices. The CBD can be fused at the amino or carboxyl terminus, as in the parent cellulase, to suit individual applications. We have constructed model fusion proteins using the C. fimi CBDs to demonstrate this potential. 

Selective inhibition of cellulases by Hg in a mixture of cellulases and xylanases of Sporotrichum dimorphosporum used in a laboratory experiments (22) cannot be considered for industrial application for obvious reasons. 

Similar results were obtained with crude cellulase preparations from Penicillium pinophilum (12). The general applicability of this biospecific chromatography is illustrated by the isolation of the EGD from C. t., cloned in E. c. (Fig. 6). 

The second area of application involves the use of cellulase-free xylanases for removal of hemicellulose from pulps (10-20) and plant fibres (21). It is essential that these xylanase preparations are free of contaminating cellulase activity or damage to the cellulose fibres and consequently the product quality will result. 

For xylanase applications which require xylanases of high selectivity (e.g., biopulping), any contaminating cellulases can be detrimental to the treatments. The constitutive levels of cellulases in yeasts is generally very low in relation to xylanase levels thus indicating yeast xylanase preparations are promising for the selective hydrolysis of xylans. However, extracellular yeast xylanases are typically produced in the order of 1 unit per millilitre... 

Several methods to prepare high-purity xylanases for potential industrial applications have focused on eliminating the cellulase contamination instead of purifying the xylanase components. This appears to be a very effective approach as it precludes the need for very expensive biochemical procedures and focuses, rather, on a limited number of simple steps to eliminate cellulase activity. Since the remaining materials in the enzyme preparation are essentially inert with respect to the cellulose, their presence may often be ignored. 

Novo Nordisk has also introduced another application of the laccase formulation, namely for stonewashing in combination with cellulase. It enhances the abrasion effect. In this case, a lower dose of the enzyme/mediator slurry is sufficient. Low doses have a mild bleaching effect though the end-result doesn t look like bleaching. Instead the denim looks as if it has been subject to more abrasion. Cellulases can give a stonewashed look to jeans but they have certain limitations when used on their own. If denim finishers want a highly abraded effect, they usually prefer a combination of cellulases and stones to obtain the desired level of abrasion. With the laccase slurry stones are no longer needed. 

The observation47 that the stability of the secondary-ordered structure of xanthan (and as a consequence, its susceptibility to hydrolysis by cellulase) is a function of temperature, pH, and ionic strength has allowed the application of enzymic techniques to structural analysis. Xanthan is hydrolyzed in salt-free, aqueous solutions at elevated temperatures that is, hydrolysis occurs if the chain is unordered. It was proposed that, at lower temperatures and in the presence of salt, the small side-chains organize around the (1 ->4)-/3-D-glucan backbone and protect it from hydrolysis. 

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