Cellobiose, solubility

SONG w o, BEECHER G R and eitenmiller R R (2000), Modern Analytical Methodologies In Fat- and Water-soluble Vitamins. Chichester, Wiley. sprenger c, galensa r and jensen d (1999), Simultaneous determination of cellobiose, maltose and maltotriose in fruit juices by high-performance liquid chromatography with biosensor detection , Dtsch Lebensm Rundsch, 95, 499-504. 

The active center of CBH I (or Core I) did not seem to be implicated in the adsorption on Avicel since no influence of small, soluble ligands (e.g., cellobiose) was observed (16). The importance of an adjacent site for the binding was, however, suspected because of inhibition of adsorption by large molecular weight ligands such as xylan (DP =... 

All of the likely conformations of cellobiose, cellulose, and xylan are explored systematically assuming the ring conformations and IC-D-O-IC-4 ) angle for each pair of residues to be fixed and derivable from known crystal structures. The absolute van der Waals energies, but not the relative energies of different conformations, are sensitive to the choice of energy functions and atomic coordinates. The results lead to possible explanations of the known conformational stiffness of cellulose and Its solubility properties in alkali. The characteristics of xylan conformations are compared with cellulose. 

In 1896, Fischer developed the phenylhydrazine test" for the detection of hydrolytic scission of disaccharides, especially by enzymes this depends on the fact that the phenylosazones of disaccharides are soluble in hot water, whereas those of the monosaccharides are not. Lactose is hydrolyzed by emulsin (1894) and by lactase it is not fermentable by yeast, and is unaffected by invertase (1894). An extract of the small intestine of horses and cattle, especially from young animals, hydrolyzes lactose (1896). The action of enzymes on lactose allowed it to be classified, along with cellobiose and maltose, with the normal (and not the y-type of) methyl glucoside (1914). In the discussion of maltose, the relationship of lactose to the /9-series will be mentioned later. 

Treatment of an alkali-soluble xyloglucan from the seed of Annona muricata with cellulase liberated tetra- and penta-saccharides, together with D-glucose, cellobiose, and a small proportion of a D-xylosylcellobiose.25 From the molar amounts of these products, it may be postulated that the... 

The major soluble components of acid hydrolysates are sugars, such as xylose, glucose, and cellobiose furfurals, such as furfuraldehyde and hydroxymethyl furfural and organic acids, such as levulinic acid, formic acid, and acetic acid (13). When natural sources of cellulose are acid-hydrolized, numerous products can result, largely because of the hemicellulose materials. These make it difficult to produce a relatively pure sugar product and limit the utility of the acid hydrolysis process. 

Cellobiose produced from swollen cellulose (wt °/o of soluble products after 30 min incubation at 40°C)... 

The CBH I (D) is identical in composition and activity to the CBH I (D) previously described (2) from T. reesei QM 9123. The close correspondence of their amino acid contents (Table VI), the nearly identical content of neutral carbohydrate 6.8% by weight for the CBH I (D) produced in the presence of sophorose and 6.7% for T. reesei QM 9123 CBH I (D) grown on cellulose (2), and identical electrophoretic properties clearly argue for a common molecular structure for these CBH s I (D). The CBH II is clearly different from all other CBH s in electrophoretic mobility (Figure 12) and amino acid composition (41), but is devoid of endoglucanase activity and produces predominantly cellobiose (>90% by weight of soluble products) from cellulose. It has a sedimentation coefficient of 3.71 in comparison to CBH I (D), for which a value of 3.66 was obtained. 

The combined data provide a ready means by which to compare and select appropriate assays for application in cellulase-catalyzed cellulose saccharification experiments. Products in such experiments are expected to include glucose cellobiose and, potentially, some cellooligosaccharides. Optimum reducing sugar assays would have equivalent molar color yields for these soluble products. As shown in Table 3, this optimum situation only applies to the two copper-based assays (Nelson, BCA). Because of their importance with respect to the analysis of insoluble cellulose (discussed next), calibration curves reflecting the molar color yields for the DNS and BCA assays are presented in Fig. 1. 

Fig. 1. Absorbance response of equimolar amounts of soluble cellulose saccharification products glucose (G), cellobiose (G2), and cellotriose (G3) by (A) DNS assay and (B) BCA assay.

The colorimetric assays discussed herein are most commonly used in cellulose/cellulase studies to quantify the number of reducing sugars associated with the soluble phase (glucose, cellobiose, low-DP cellooli-... 

With mixed results, correlations have been attempted between polysaccharide composition and function. Beginning with simple sugars, sucrose (an a-D-glucopyranosyl-p-D-fructofuranoside) and maltose (an a-D-glucopyrano-syl-a-D-glucopyranose) are truly soluble cellobiose (a 1,4-(3-n-glucopyrano-... 

Various authors have shown that non-ionic surfactants have a beneficial effect on the hydrolysis of cellulosic and lignocellulosic substrates, whereas anionic and cationic surfactants alone interfere negatively (Castanon and Wilke, 1981 Helle et al, 1993 Park et al, 1992 Ooshima et al., 1986 Traore and Buschle-Diller, 1999 Ueda el al., 1994 Eriksson el al., 2002). Increases in the amount of reducing soluble sugars and substrate conversion were reported. The effect depends on the substrate and is not observed for soluble substrates, such as carboxymethylcellulose or cellobiose. Nonionic surfactants increased the initial rate of hydrolysis of Sigmacell 100, and when they were added later in the process they were less effective (Helle et al, 1993). They same authors found also that the addition of cellulose increases the critical micelle concentration of the surfactant, which indicates that the surfactant adsorbs to the substrate. Surfactants are more effective at lower enzyme loads and reduce the amount of adsorbed protein (Castanon and Wilke, 1981 Ooshima et al, 1986 Helle et al, 1993 Eriksson et al., 2002) which can be used to increase desorption of cellulase from the cellulosic substrate (Otter et al., 1989). Anyhow, the use of surfactants to enhance desorption of cellulases from textile substrates in order to recover and recycle cellulases was not successful (Azevedo et al., 2002b). 

The activity of cellulases is inhibited by various natural products (40), the most important of which is the product cellobiose. By preventing overproduction of extracellular soluble sugars, this feedback inhibition is of competitive advantage to the organism. 

The solubility of the trityl ethers is of advantage in experimental work. For example, during the conversion of methyl 2,3,4-triacetyl-/3-D-glucopyranoside to the 2,3,6-triacetate (see page 95) there is formed an equilibrium mixture of these two substances from which the compound with the free 4-hydroxyl group can be separated only in poor yield by simple crystallization. Separation is more complete when the mixture is tritylated in the ordinary way with trityl chloride in pyridine. Tritylation occtirs almost exclusively at the 6-hydroxyl of the 2,3,4-triacetate, the 6-trityl ether thus formed being insoluble in water. The untritylated 2,3,6-triacetate can then be extracted and is obtained in good yield. It is of interest as an intermediate in the synthesis of cellobiose. 

---