Degradation, amylase resistance

Various theoretical models have been proposed to account for the distribution of products obtained on a-amylolysis. A comparison of experimental yields with those calculated for completely random hydrolysis shows that the action of higher-plant alpha-amylases cannot be explained in this way (see Table VII). The postulate that the enzymes degrade randomly to give small products (hexaose and shorter), which are resistant to further attack, does not predict yields in good agreement with experimental observation. If, however, certain bonds are assumed to be resistant to attack, whilst others are more susceptible, better agreement is obtained. For example, it has been proposed that cereal alpha-amylases do not readily attack the... 

Isoamylase is used primarily in the production of food ingredients from starch (e.g. glucose syrup, maltose and maltitol, trehalose, cyclodextrins and resistant starch). It is typically used in combination with other amylolytic enzymes, such as a-amylase, p-amylase and glucoamylase, which further degrade the linear dextrins that arise from the debranching activity of isoamylase. The recommended use levels range from 50 to 5000 lAU/g starch. 

D-Glucose and malto-oligosaccharides (DP 9) in starch hydrolysates have been separated by h.p.l.c. Oxidized (sodium hypochlorite) starch has been degraded by the joint actions of amyloglucosidase and a- and 3-amylases. An unidentified, modified trisaccharide, which resisted further enzymic degradation, was isolated. 

It is known that enzymes such as protease, hemicellulase, pecdnase, and amylase have very little effect on xanthan. This resistance to enzymatic attack is presumably due to the steric hindrance caused by the trisaccharide side chains and the sugar composition of the side chains. However, xanthan is completely biodegradable, and xanthanase has been reported (5). In addition, xanthan lyase is also known that cleaves the side-chain sugars and may have a role in xanthan degradation (6). The current knowledge of xanthan depolymerizadon is sdll incomplete, and xanthanase is not commercially available. 

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