Starch enzyme-catalyzed

Oligo- and higher saccharides are produced extensively by acid-and/or enzyme-catalyzed hydrolysis of starch, generally in the form of symps of mixtures (12). These products are classified by thek dextrose equivalency (DE), which is an indication of thek molecular size and is a measure of thek reducing power with the DE value of anhydrous D-glucose defined as 100. 

The glycosidic bond to an anomeric carbon can be either a or (3. Maltose, the disaccharide obtained by enzyme-catalyzed hydrolysis of starch, consists of two cv-D-glucopyranose units joined by a 1->4-o-glycoside bond. Cellobiose, the disaccharide obtained by partial hydrolysis of cellulose, consists of two /3-o-glucopyranose units joined by a 1—>4-/3-glycoside bond. 

Chakraborty, S., Sahoo, B., Teraka, I., Miller, L. M., Gross, R. A. (2005). Enzyme-Catalyzed regioselective modification of starch nanoparticles. Macromoleculess 38,61-68. 

Gums are tasteless, odorless, colorless, and nontoxic. None, except the starches and starch derivatives, are broken down by human digestive enzymes. All are subject to microbiological attack. All can be depolymerized by acid- and enzyme-catalyzed hydrolysis of the glycosidic (acetal) linkages joining the monomeric (saccharide) units. 

Starch molecules are digested in the stomach by enzymes called a-glycosidases, which break down the polysaccharide chain and release individual glucose molecules. As is usually the case with enzyme-catalyzed reactions, a-glycosidases are... 

III. Enzyme-catalyzed Reactions of Starch Synthesis in Plants and Algae... 

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... 

A large volume of tapioca starch is also used to make sweeteners and related products. This application primarily involves enzyme-catalyzed hydrolysis. Similar... 

In a maltodextrin process using enzyme-catalyzed conversion, the starch slurry (30% to 40% dry solids) is first pasted at a temperature of 80-90°C, and is then treated with a heat-stable bacterial alpha-amylase for liquefication. When stabilized with calcium ions, alpha-amylases from B. licheniformis or B. stearothermophilus can withstand temperatures of 90-105°C for at least 30 minutes,10 allowing sufficient process time to split the 1,4 bonds and form maltose and limit dextrins (see Chapter 7). 

Answer After an ear of corn has been removed from the plant, the enzyme-catalyzed conversion of sugar to starch continues. Inactivation of these enzymes slows down the conversion to an imperceptible rate. One of the simplest techniques for inactivating enzymes is heat denatura-tion. Freezing the corn lowers any remaining enzyme activity to an insignificant level. 

The commercial importance of amylolytic enzymes is rapidly increasing. These enzymes catalyze the hydrolytic reactions of amylose (unbranched starch) and amylopectin (branched starch). Amylases, according to their difference in modes of action, can be divided into ... 

Starch conversion refers to the process of converting starch into other products. It involves gelatinization, liquefaction, and saccharification. Liquefaction refers to the acid-or enzyme-catalyzed conversion of starch into maltodextrin. Starch, usually from wet milling of com, is pumped in a slurry to the conversion plant, where it undergoes one or more hydrolytic processes to yield mixtures of various carbohydrates in the form of syrups. The kind and amount of the various carbohydrates obtained depend upon the type of hydrolysis system used (acid, acid-enzyme, or enzyme-enzyme), the extent to which the hydrolytic reaction is allowed to proceed, and the type of enzyme(s) used. The fact that most starches consist of two different kinds of polymers... 

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