Dextrin hydrolysis rates

Figure 9 shows Lineweaver-Burk plots of dextrin hydrolysis rates in the presence of the block copolymer. Again, fairly good straight lines are obtained. Some other kinetical investigations also were made for the catalytic activity of the block copolymer, and similar tendencies of catalytic behavior were found compared with that of the random copolymer. 

Figure 8. Dependence of dextrin hydrolysis rates (v) on the substrate concentration in the presence of the block copolymer at 70°C. [Catalyst] = 1.00 X 10 2N. Catalyst (mole ratio of vinyl alcohol to styrenesulfonic acid units in the copolymer) (O) sulfuric acid (%) block copolymer No. 1 (1-4) (A) block copolymer No. 2 (9.8) (A) block copolymer No. 3 (22.1).

The effect of salt addition on the hydrolysis rate of dextrin in the presence of the random copolymer catalyst were investigated. The results are summarized in Table I. The catalytic activity of the copolymer is... 

Figure 3. Change in the relative hydrolysis rates (based on sulfuric acid) of dextrin with the mole ratio of vinyl alcohol to vinylsulfonic acid repeating units at 80°C, keeping the concentration of vinulsulfonic acid unit constant at 5.00 X I0"3N. (O) In the presence of the random copoly (vinyl alcohol-vinylsulfonic acid) (%) in the presence of poly (vinyl alcohol)-poly(vinylsulfonic acid) mixture. [Substrate] = 2.00 X 10"2M.

The hydrolysis of dextrin over a 60-80 °C temperature range in the presence of cross-linked copolymers of vinyl alcohol (VA) and styrene-sulfoacid (SSA) of different composition and of the industrial styrene-sulfoacid type resin, Amberlite 120B, was investigated [23]. The hydrolysis rate was proportional to substrate and resin concentrations. This differed from the results of homogeneous hydrolysis in the presence of soluble copolymers VA-SSA, by which the reaction rate is described by Michaelis-Menten kinetics. The hydrolysis rate hereby increased with an increase in the VA concentration of the cross-linked copolymer, whereby the rate was always higher than for Amberlite 120B. 

Fig. 10. Plots of the relative rate constants of the hydrolysis of dextrin vs. the mole ratio of vinylalcohol unit to vinylsulfonic acid unit, o PVS VA, Polyvinylalcohol + HPVS (Ref.

Upon extensive hydrolysis of starch by either of these enzymes, only small differences were observed in the concentrations of the products or in the average degrees of polymerization of the dextrins. These comparisons were made for equivalent stages of hydrolyses and are not necessarily related to the rates of the hydrolysis of starch by these two amylases. 

Studies of the rate of the hydrolysis of dextrins isolated from a reaction mixture after the extensive hydrolysis of starch by maltase-free malted barley alpha amylase, led Myrback11 to conclude that the flattening of the reaction curves with this amylase is not due to equilibrium between the amylase and the products of the hydrolysis. As indicated above, similar conclusions have been reached for pancreatic amylase and for the amylase of Aspergillus oryzae.41,7a... 

The importance of time, temperature and acid concentration in the hydrolysis of cellulose with dilute acid was recognized by early investigators and applied in the investigations of Simonsen in 1898. Further study was made by Kressman and reported in U. S. Department of Agriculture Bulletin No. 983. Reviews of the quantitative aspects have been made by Doree. Liiers pointed out that the conversion of cellulose dextrin to D-glucose by dilute sulfuric acid was a monomolecular reaction. The constants of the hydrolysis of wood cellulose have been determined by Saeman. The reaction rate (A ) was found to be expressed by the following equation ... 

The catalytic activities of the block copolymer on the hydrolysis of dextrin also were investigated. Figure 8 shows the plots of reaction rate against the substrate concentration. Similar tendency, but larger rate enhancement of the reaction are found compared with that in the presence of the random copolymer catalyst (Figure 4). 

The rate of hydrolysis of the dextrin fractions in mineral acid was determined. All fractions have a rate of hydrolysis lower than that of the starch and the reaction coefficient falls gradually. Surely this is due to the occurrence of the 1,6-D-glucosidic linkages. 

The difference in structure between amylose and amyiopectin is important when selecting the appropriate starch substrate for amylase determinations (see Chapter 21). The rate of hydrolysis is affected by structural differences in the starch. a-Amylase from the pancreas hydrolyzes internal a-l,4 glycosidic linkages. This hydrolysis results initially in the production of some maltose and a mixture of dextrins, which are subsequently hydrolyzed to maltose. The -1,6-... 

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