Amylose depolymerization

Star-branched butyl rubber, 4 437-438 copolymers, 4 445-446 Starch(es), 4 703-704, 20 452-453 as blood substitute, 4 111-112 cationic, 18 114-115 in cereal grains, 26 271-274 in cocoa shell from roasted beans, 6 357t compression effects in centrifuges, 5 513 depolymerization, 4 712 in ethanol fermentation, 10 534—535 etherified, 20 563 as a flocculant, 11 627 high-amylose, 26 288 Mark-Houwink parameters for, 20 558t modified and unmodified, 12 52-53 in paper manufacture, 18 122-123 performance criteria in cosmetic use, 7 860t... 

In the field of polymer science, the most extensively used transferase is phosphorylase (systematic name (1 4)-a-D-glucan phosphate a-D-glucosyltransferase EC 2.4.1.1). Although this enzyme is responsible for the depolymerization of linear a-( 1 4) glycosidic chains in vivo it can also be used to synthesize linear a-( 1 4) glycosidic chains (amylose) in vitro. 

Specifically, D-glucose < maltose < maltotriose < amylose < starch < amylo-pectin < cellulose (Greenwood, 1967). Trends indicated are that thermochemical stability increases with the DP, branching, and 1,4-fi bonding. Chemical bonds other than 1,4-a and 1,4-(3 introduce heat and acid instability. Either of these two bonds is less easily depolymerized when the sixth pyranose carbon is oxidized to the carboxyl group rather than esterified for this reason, low-methoxyl pectin is more stable than high-methoxyl pectin. 

Pringsheim held the view that the Schardinger dextrins arose through the bacterial depolymerization of starch to the fundamental units the amylose fraction being broken down to the alpha series of dextrins or poly-... 

The reactions of amylose, cellulose, inulin, starch, and xylans, and their constituent monosaccharides have been rather well studied. These polysaccharides dissolve in hydrogen fluoride at temperatures above — 20°, and undergo depolymerization to give the corresponding glycosyl fluorides fur-... 

The effects of y-radiation on the depolymerization and selected physical properties of amylose in the solid state and in solution have been investigated under conditions of graft copolymerization. Irradiation furnished an alkali-sensitive material (G-value for scission 2.8), most likely owing to the presence of a j8-alkoxycarbonyl structure. The G-value (1.3) obtained on irradiation of solid amylose at 0 °C under nitrogen is lower than values previously reported for amylose and other polysaccharides. A solution of amylose in water was protected against y-radiation by the addition of DMSO (G-value of 2.3 vs. 30). A solvent system of DMSO-acetic acid-water degraded y-irradiated amylose less than did aqueous DMSO. 

The most important natural binder still in use today is starch, though it is now frequently used in combination with synthetic binders. Com starch is more common in the USA, whereas potato starch is more prevalent in Europe. Native starch containing two fractions of amylose (linear chain) and amylopectin (branched chain) is not suitable for coating paper and board because the amylose fraction tends to undergo retrogradation and the viscosity of coating colors made with native starch is too high [5]. For these reasons, only treated (i.e., depolymerized) or chemically modified starches are used. Most paper mills carry out their own starch preparations in-house. 

Wang, Y., Hollingsworth, R. I. Kasper, D. I. (1998). Ozonolysis for selectively depolymerizing polysaccharides containing p d-aldosidic linkages. PNAS, 95,6584-6589. Warrand, J. Janssen, H-G. (2007). Controlled production of oligosaccharides from amylose by acid-hydrolysis under microwave treatment Comparison with conventional heating. 

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