Enzymes cellulose, effect

Work in several laboratories (22, 27, 55, 56) has shown a pattern of cellulase action in cellulolytic organisms which requires at least one of a set of three closely related enzymes in order to hydrolyze crystalline cellulose effectively. These enzymes often possess little ability to degrade either CM-cellulose (as measured viscosimetrically) or crystalline cellulose. Nevertheless they are characterized by the capacity to cleave swollen cellulose or cellooligosaccharides almost entirely to cellobiose by virtue of their / -( - 4)glucan cellobiohydrolase activity. Recognition of this pattern has been difficult because prior to this report the three enzymes had not been purified and characterized apart from contaminating enzyme activity. 

As noted earlier in this chapter, the apparent Km values of immobilized enzymes vary with the thickness of the diffusion layer surrounding the particles. In packed-bed enzyme reactors, the thickness of this layer varies with the mobile phase flow rate. Faster flow rates produce smaller diffusion layers and therefore K m values that more closely approximate the true Km of the enzyme. This effect has also been observed with the ficin-CM-cellulose reactor, and plots of K m against flow rate Q obtained at different mobile phase flow rates are shown in Figure 4.14. 

Ghosh P, Pamment NB, Martin WRB. (1982). Simultaneous saccharification and fermentation of cellulose—effect of beta-d-glucosidase activity and ethanol inhibition of ceUulases. Enzyme Microb Technol, 4(6), 425 30. 

An important chemical finishing process for cotton fabrics is that of mercerization, which improves strength, luster, and dye receptivity. Mercerization iavolves brief exposure of the fabric under tension to concentrated (20—25 wt %) NaOH solution (14). In this treatment, the cotton fibers become more circular ia cross-section and smoother ia surface appearance, which iacreases their luster. At the molecular level, mercerization causes a decrease ia the degree of crystallinity and a transformation of the cellulose crystal form. These fine stmctural changes iacrease the moisture and dye absorption properties of the fiber. Biopolishing is a relatively new treatment of cotton fabrics, involving ceUulase enzymes, to produce special surface effects (15). 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

Biofinishing, or biopolishing as it is more popularly known, is similar to denim washing in its use of cellulase enzymes, although the effects intended are quite different. The process is designed to eliminate, by dissolution, the cellulosic fibrils projecting from the surface of the fabric. This treatment results in [76] ... 

Oral pancreatic enzyme supplements are available as powders, uncoated or coated tablets, capsules, enteric-coated spheres and microspheres, or enteric-coated microtablets encased in a cellulose or gelatin capsule (Table 28-2). Microencapsulated enteric-coated products are not superior to recommended doses of conventional non-enteric-coated enzyme preparations. The quantity of active lipase delivered to the duodenum appears to be a more important determinant in pancreatic enzyme replacement therapy than the dosage form. GI side effects appear to be dose related but occur less frequently with enteric-coated products. 

Humans lack enzymes to hydrolyse cellulose, and some odier carbohydrates in food. However, bacteria in the intestine can hydrolyse and ferment some of this carbohydrate to produce short-chain fatty acids, which are used by the colon and the liver. It is estimated that for each gram of unavailable carbohydrate in the diet, 8.4 kJ of energy is made available in this way, although this is influenced by factors such as ripeness of fruit or the way leguminous seeds are cooked. Nonetheless, these effects will be small and can be ignored unless the amount of such carbohydrate is high or very accurate results are required. (The subject of unavailable carbohydrate and fibre in the diet is discussed in Chapters 4, 6 and 15). 

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),...

The effects of feedstock cellulose content on cellulase enzyme activities in the digester system were examined in multiple laboratory-scale CSTR digesters operated under similar conditions with identical levels of feedstock organic loading (g VS/reactor d) but different levels of cellulose (Solka Floe). In general, all celli se enzyme... 

Figure 1. Comparison of the effects of feedstock cellulose content on specific ceUulase enzyme activities in sludge from 4 CSTR reactors operated under similar conditions. Although the cellulose content of the feedstock was varied, the total volatile solids content for all reactors was equivalent.

Wheat straw. Wheat straw ground to 20 mesh was treated with 2% NaOH solution (wt/vol) in 1 2 (solidiliquid) ratio at 121 C for 0.5 h (i.e., 4 g NaOH/100 g wheat straw). Trichoderma reesei QMY-1 was grown on pretreated wheat straw in SSF as well as in LSF under otherwise identical culture conditions. The SSF was carried out with full nutrient concentrations in one set and with one-half nutrient concentrations in the other set to evaluate the possible deleterious effects of elevated osmotic pressure. T reesei QMY-1 produced FP cellulase of 8.6 lU/ml (430 lU/g cellulose or 172 lU/g substrate) in 22 days. This showed that the organism was able to tolerate the high salt concentrations required in the SSF. In contrast, when the nutrients were supplied in one-half concentration, FP cellulase activity dropped to 6.7 lU/ml (335 lU/g cellulose or 134 lU/g substrate). However, the maximum enzyme activity was obtained one week earlier (14 days) than that obtained with full salt concentrations (Table I). 

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