Starch, degrading enzyme

Of particular importance for modifications of starch are the enzyme degradation products such as glucose symps, cyclodextrins, maltodextrins, and high fmctose com symps (HFCS). Production of such hydrolysis products requites use of selected starch-degrading enzymes such as a-amylase,... 

Table 4. Starch-Degrading Enzymes of Industrial Importance...

Enzymes to degrade crosslinked hydroxypropylated starch derivative and xanthan gum polymer systems are available [158,1246]. Specific enzymes are efficient in reducing the near wellbore damage induced by the starch polymer to eventually return permeabilities to the range of 80% to 98% without the use of acid systems. 

Table IV shows the biochemical features of thomostable a-glucosidase purified 140-fold from C. thermohydrosulfuricum (Saha and Zeikus, unpublished work). The enzyme has a 162,000 molecular weight and displayed an optimum temperature for activity of 75°C. Notably, the protein preparation hydrolyzed both a-1,6 and a-1,4 linkages. This enzyme appears to play an important role in starch degradation by C. thermohydrosulfuricum because it can hydrolyze the degradation intermediates formed by the organism s unique amylopullulanase.

B. Swensson Starch-degrading enzymes—structure/function insights and improvements by protein engineering... 

As noted in Section 4.3 (see also Chapter 3), a sul mutation in maize that causes a deficiency of isoamylase, an enzyme normally considered to be mainly involved in starch degradation in plants and in C. reinhadtii, results in accumulation of a water-soluble polysaccharide, phytoglycogen, instead of starch.45 19,291 In C. reinhardtii, the mutation results in complete loss of starch, but in higher plants, the lower amount of amylopectin seen in the mutant plant may be related to the severity of the enzyme deficiency.292,293... 

A third starch solution was prepared as above, and, while hot, an enzyme was added (1.5% of the starch weight) and mixed thoroughly. The mixture was allowed to cool to ambient temperature, and the starch degradation was completed within 4 hours. 

Figure 4-19 Schematic Representation of the Action of Starch-Degrading Enzymes. (A) Amylose and amylopectin, (B) action of a-amylase on amylose and amylopectin, (C) action of a debranching enzyme on amylose and amylopectin, (D) action of amyloglucosidase and debranching enzyme on amylose and amylopectin. Source Reprinted from H.S. Olsen, Enzymic Production of Glucose Syrups, in Handbook of Starch Hydrolysis Products and Their Derivatives, M.W. Kearsley and S.Z. Dziedzic, eds., p. 36, 1995, Aspen Publishers, Inc.

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