Enzyme attack starch

After earlier workers had indicated the existence of several amylases in malt, conclusive evidence that the malt amylase is composed of at least two starch-splitting enzymes was furnished by Ohlsson. Both enzymes are capable of attacking starch and glycogen, but their action is very different. One enzyme, termed saccharogenic amylase by Ohls-... 

PROPERTIES OF SPECIAL INTEREST The a-glucopyranose linkage in starch is more susceptible to hydrolysis or enzyme attack than the / -glucopyranose linkage in cellulose, thus making starch more attractive for biodegradation applications than cellulose. 

Starch phosphorylase incorporates phosphate, rather than water, across the a-1,4 linkage between the penultimate and last glucose at the non-reducing end of the polysaccharide chain. One molecule of glucose-1-phosphate is released. This enzyme attacks amylose repetitively and amylopectin can be degraded to within two or three glucose residues of a a-1,6 branch linkage. 

Approximately 0.5% of most of the starches is still not hydrolyzed to glucose. This could be attributed to the densely branched portion of the starch which is not susceptible to enzyme attack due to steric hindrance. However, earlier studies showed that further increases in the amount of pullulanase resulted in an even lower conversion, suggesting enzyme inhibition which would be due to the molecular size of the pullulanase. Alternatively, the 0.5% unhydrolyzed portion could be products from the reverse reaction catalyzed by amyloglucosidase. 

FIGURE 6.3 Action of a-amylase family enzymes involved in degradation of starch. Arrows indicate points in the starch molecule where the enzyme attacks (Takata et al., 1992). 

Enzymes, ) derived from pancreatic extracts of slaughtered animals, were introduced already in 1913 into formulations of d. Only with the invention of proteolytic enzymes, derived from Bacillus subtilis or B. licheniformis, which are stable against alkali and higher temperatures, enzymes received a permanent position in d. Amylases are second in importance and attack starch-based soil. Lipases are used to remove remaining greasy soil. Cellulases are added in special d. to remove cotton fluffs and smoothen the surface of cotton fibers. 

While starches are commonly used, they are relatively poor viscosifiers. Acids and bacterial enzymes readily attack the acetal linkages resulting in facile depolymerization. Both formaldehyde and isothiazolones have been used as starch biocides (17). Development of improved high temperature water viscosifiers for drilling and other oil field applications is underway. For the... 

While the dough is being rested the amylase enzymes in the flour will attack the starch and soften the dough. 

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