Hydrolysis, of cellobiose

Proceeding on the same line, Hagerdal et al. reported that perfluorinated resin supported sulfonic sites (NATION 501) can hydrolyze disaccharides [25]. In particular, these authors studied the effect of the addition of sodium chloride in the hydrolysis of cellobiose, a subunit of cellulose much more resistant to hydrolysis than sucrose. They observed that the presence of sodium chloride in water dramatically increased the conversion of cellobiose. Indeed, in the presence of 10 wt% of sodium chloride, 80% of cellobiose was converted at 95°C after 6 h. For comparison, when 1% of sodium chloride was added, only 50% of cellobiose was hydrolyzed. It should be noted that without addition of sodium chloride only 15% conversion was achieved, thus pushing forward the key role of sodium chloride on the reaction rate. Effect of salt on the reaction rate was attributed to a change of the pH caused by the release of proton in the reaction medium (due to an exchange of the supported proton by sodium). 

As expected, mesoporous silica-supported sulfonic sites were able to catalyze the hydrolysis of cellobiose. Indeed, at 448 K, 90% of cellobiose was hydrolyzed within 30 min of reaction with an apparent activation energy ( = 130 kJ moF ) similar to that of reactions promoted by homogeneous organic acid catalysts [33]. The hydrolysis reaction rate is proportional to the concentration of hydrated... 

Maltose is hydrolyzed by the enzyme maltase (specific for a-glycosidic linkage) to two units of glucose, but for the hydrolysis of cellobiose the enzyme emulsin (specific for (3-glycosidic linkage) is necessary. While maltose is the building block of the polysaccharide starch, cellobiose is the building block of another polysaccharide, cellulose. 

Fig. 5. Lineweaver-Burk plot of the Orpinomyces BglA on hydrolysis of cellobiose (0.04-16 mM). The release of glucose was measured. Reciprocal initial velocities (mg/U) are plotted against the reciprocal concentrations of substrates (1 mM). The inset is a plot of initial velocities (U/mg) against the log cellobiose concentrations (mM).

Fig. 2. Degree of Inhibition on (3-glucosidase activity caused by addition of glucose during hydrolysis of cellobiose and pNPG.

Problem 35.5 Why is alkaline hydrolysis of cellobiose octaacetate (better named octa-O-acetylcellobiose) to (+)-ccllobiosc preferred over acidic hydrolysis ... 

Perhaps, the best support for the theory of restriction to rotation, propounded by Feather and Harris, was provided by an investigation of the hydrolysis of cellobiose (30), cellobiouronic acid (31), and pseudo-cellobiouronic acid (4-0-i8-D-glucopyranosyl-D-glucuronic acid) (32). 

Rate Constants and Activation Energies for the Hydrolysis of Cellobiose, Cellobiouronic Acid, and Pseudocellobiouronic Acid"... 

Shimizu K-I, Furukawa H, Kobayashi N, Itaya Y, Satsuma A (2009) Effects of Bronsted and Lewis acidities on activity and selectivity of heteropolyacid-based catalysts for hydrolysis of cellobiose and cellulose. Green Chem 11(10) 1627-1632... 

Hydrolysis of disaccharides — cellobiose, maltose and lactose — was investigated over A, X, and Y type zeolites. The conversion profiles of the hydrolysis of cellobiose over NaX are shown in Fig. 4.19. The reaction was carried out at 373 K and initial reactant concentration of 1.0 wt%, and a catalyst loading of 0.1 gcm . Total conversion is based on the amount of cellobiose consumed by the reaction. A very large fraction of the reaction occurs within the first 0.5 h and the entire reaction terminates after 1 h. The pH profile of the reaction broth is also shown in Fig. 4.19. Upon addition... 

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