Starch, hydrolysis reaction with

The biocatalysts obtained were evaluated with respect to the composition, morphology, activity and stability of the immobilised enzyme in the starch hydrolysis reaction. In general, two alternative methods can be used, considering the bioartificial matrix as a substrate for the enzyme (this method is used for example to drive drug release into erosion control devices), or alternatively, as in the case of this work, after blending the enzyme with a polymer, and investigating its activity against an external substrate. The apparent kinetic parameters of the reaction catalyzed by the immobilised and native enzymes were determined and compared. 

In industrial production of acid-modified starches, a 40% slurry of normal com starch or waxy maize starch is acidified with hydrochloric or sulfuric acid at 25—55°C. Reaction time is controlled by measuring loss of viscosity and may vary from 6 to 24 hs. For product reproducibiUty, it is necessary to strictly control the type of starch, its concentration, the type of acid and its concentration, the temperature, and time of reaction. Viscosity is plotted versus time, and when the desired amount of thinning is attained the mixture is neutralized with soda ash or dilute sodium hydroxide. The acid-modified starch is then filtered and dried. If the starch is washed with a nonaqueous solvent (89), gelling time is reduced, but such drying is seldom used. Acid treatment may be used in conjunction with preparation of starch ethers (90), cationic starches, or cross-linked starches. Acid treatment of 34 different rice starches has been reported (91), as well as acidic hydrolysis of wheat and com starches followed by hydroxypropylation for the purpose of preparing thin-hoiling and nongelling adhesives (92). 

The slowing down of enzyme reactions has often been attributed to reaction with, or equilibrium between, the enzyme and its substrate or between the enzyme and the products of its action. In order to determine the influence of the products of the action of pancreatic amylase on the extent of the hydrolysis of starch, portions of its hydrolysis mixtures were subjected to efficient dialysis during hydrolysis and the results compared with aliquots of the reaction mixture which had been treated in the same way except for dialysis.41 The results of such experiments... 

There are several examples of one-pot reactions with bifunctional catalysts. Thus, using a bifunctional Ru/HY catalyst, water solutions of corn starch (25 wt.%) have been hydrolyzed on acidic sites of the Y-type zeolite, and glucose formed transiently was hydrogenated on ruthenium to a mixture of sorbitol (96%), mannitol (1%), and xylitol (2%) [68]. Similarly a one-pot process for the hydrolysis and hydrogenation of inulin to sorbitol and mannitol has been achieved with Ru/C catalysts where the carbon support was preoxidized to generate acidic sites [69]. Ribeiro and Schuchardt [70] have succeeded in converting fructose into furan-2,5-dicarboxylic acid with 99% selectivity at 72% conversion in a one-pot reaction... 

Starch (amylose and amylopectin) hydrolysis along with ester-fication, etherification or oxidation have been previously discussed as available methods for producing starch derivatives with improved water dispersibilities and reduced retrogradation potential (, ). Since oxidative and hydrolytic reactions are simple, easily controlled chemical modifications, starch-derived polymers made by hydrolysis alone or oxidative and hydrolytic processes were developed and tested. 

We thus elucidated that three of the four cellulase components are endo- or random-type and the other is exo-type. However, it is difficult to distinguish between the components of least or lowest random-type and those of exo-type. It is rather easy to identify an endo-type cellulase component. In contrast, it is very difficult to determine a cellulase to be exo-type because if the enzyme has a glycosyl-transferring activity the hydrolysis product is not a single sort, which is one of the necessary conditions to be an exo-type. Based on our experiments, measurement of the time course of CMC using a sample of medium substitution degree seems to be the best method of diagnosis to determine a cellulase component to be endo- or exo-type. With some enzymes, direction of mutarotation of reaction products is useful to resolve this problem, as is illustrated by the classic example of the starch hydrolysis by a- and /3-amylases. If this is true for our cellulases, the mutarotation of reaction products would be a... 

Starch can be broken down in two ways, both of which take place in the presence of water. Hence the reactions are known as hydrolysis reactions. Hydrolysis of starch is the key reaction that enables us to use this energy source. If starch is boiled for about one hour with dilute hydrochloric acid, it is broken down into its monomers, glucose molecules. 

If starch is mixed with saliva and left to stand for a few minutes, it will break down to maltose, a disaccharide (that is two joined monosaccharides). The enzyme present in the saliva, called amylase, catalyses this hydrolysis reaction. 

The porous internal structures of A-type starch granules agree with known features for example, A-type starches exhibit faster chemical penetration and derivatization reactions,325 have weak points, are more susceptible to enzyme-catalyzed hydrolysis,38... 

Various refinements of starch content analysis have been reported. The methods are based on starch hydrolysis, followed by polarimetry,305 high-pressure liquid chromatography306 or reaction with glucose oxidase/peroxidase.307,308 An iodine reaction can be used to determine the botanical origin of starch.309 The molecular weight distribution is determined by size-exclusion chromatography.310,311... 

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