Starch hydrolysis glucoamylase

The (3-amylases catalyze starch hydrolysis by a mechanism that gives inversion of configuration at the anomeric center. All known (3-amylases have an exo-mechanism and act on the non-reducing ends of starch polymer chains or starch polymer-derived chains. There are two general classes of (3-amylases, those that are classically known as (3-amylases and produce (3-maltose, and those that are known as glucoamylases and produce (3-D-glucose. 

F. Shiraishi, K. Kawakami, K. Kato, and K. Kusunoki, Hydrolysis of soluble starch by glucoamylase immobilized on ceramic monolith, Kagaku Kogaku Ronbunshu 9(i) 316 (1983). F. Shiraishi, K. Kawakami, T. Kojima, A. Yuasa, and K. Kusunoki, Maltose Production from soluble starch by 3 Amylase and debranching enzyme immobilized on ceramic monolith, Kagaku Kogaku Ronbunshu I4(3) 2SS (1988). 

Renneberg et al. (1984) described a microbial hybrid sensor for a-amylase assay. A membrane with coimmobilized B. subtilis cells and glucoamylase was attached to an O2 electrode. Starch and the a-amylase sample were added to the measuring cell. Low-molecular weight products of the a-amylase-catalyzed starch hydrolysis diffuse into the biocatalytic membrane where they are cleaved by glucoamylase to glucose, which is assimilated by the bacteria. The sensor responded linearly to a-amylase up to 1.5 U/ml. 

The formation of low-molecular weight products of the a-amylase-cat-alyzed starch hydrolysis can be assayed by using a glucoamylase-GOD electrode (Pfeiffer et al., 1980). The sensor is covered by a dialysis membrane with a cutoff of 15 kDa which prevents starch from reaching the enzymes. The cleavage products can easily diffuse into the bienzyme membrane where they are successively degraded to glucose by glu-coamylase. As only the (B-anomer is formed, the sensitivity of the method... 

Figure 3.98 Continuous hydrolysis of starch by glucoamylase in membrane reactor.

Reetz MT, Jaeger KE (1998) Overexpression, immobilization and biotechnological application of Pseudomonas lipases. Chem Phys Lipids 93 3-14 Reilly PJ (1979) Starch hydrolysis with soluble and immobilized glucoamylase. 

Another likely commercial starch is that from amaranth seed, an expanding crop for food use, particularly its flour. Amaranth starch granules (1—3 micrometers dia) have potential for numerous food appHcations, one of which is as a fat replacer because of their small size and especially after minor surface hydrolysis with a-amylase or glucoamylase to produce a fluffy surface (see Fat replacers). 

Roy, I. and Gupta, M.N., Hydrolysis of starch by a mixture of glucoamylase and pullulanase entrapped individually in calcium alginate beads, Enzyme Microbial Tech., 34 (2004) 26-32. 

Enzymes are also added to catalyze the hydrolysis or saccharification of starch. Malt produced by the germination of barley grain contains the enzymes that catalyze this hydrolysis. Sometimes called diastase, the enzymes are primarily a- and 6-amylase. Glucoamylase is a pure enzyme that can now be used. Both diastase and glucoamylase hydrolyze starch polysaccharide to the disaccharide, maltose. For fuel grade ethanol production, hydrolysis takes place at temperatures ranging from about 120°F to 140°F (50°C to 60°C) for about 1 hour. The final product of hydrolysis is called a wort. Solids can be filtered from the wort before continuing. 

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