Polysaccharides degradation process

The degradation process has a free radical mechanism. It is initiated by free radicals P that appear due to, for example, hydroperoxide decomposition induced thermally or by trace amounts of metal ions present in the polysaccharide. One cannot exclude even direct interaction of the polysaccharide with oxygen in its ground triplet state with biradical character. Hydroperoxidic and/or peracid moieties are easily formed by oxidation of semiacetal chain end groups. The sequence of reactions on carbon 6 of polysaccharide structural unit that ultimately may lead to chemiluminescence is shown in Scheme 11. 

Polysaccharide degrading enzymes have a long history of commercial application in food processing, horticulture, agriculture, and protein research. As with most other industrial enzymes, the economic use of polysaccharidases often depends on obtaining the maximum activity lifetime in the process environment and/or securing a recovery system that permits the sensible reuse of active enzymes from process streams. 

Chemical pulps are prepared by the digestion of wood chips with chemicals at high temperature (170-180°C) until much of the lignin has been removed. There is a concomitant loss of hemicelluloses, because of polysaccharide degradation due to chemical attack. Therefore yields are low, from 45-50%. Chemical pulping falls into two main classes, those based on pulping with sulphite liquors at various pH levels, and alkaline pulping of which the kraft process is by far the most important. 

Table III. Production of Polysaccharide Degrading Enzymes by Microbial Fermentation of Citrus Processing Wastes3...

Starch and cellulose can both be thermochemically degraded in alkaline solution to water-soluble compounds of relatively low molecular weight. (A parallel study examines more completely the nature of these compounds (15).) Both starch and cellulose degradation processes can be described by second-order kinetics, with the hydroxide ion concentration determined by the stoichiometry of polysaccharide conversion to organic acids. The thermochemical degradation activation energy in alkaline solution for both starch and cellulose is 39,500 calories/mole. 

Moreover, the HPAEC-PAD method is used for analyzing carbohydrates in wood, in pulp, and in the various process liquors [385]. One of the major goals in the pulping process is to minimize polysaccharide degradation. For this pur-... 

During lyophilization of hyaluronan solutions, polysaccharide degradation is initiated with phosphate ions [50]. For purification from proteins, proteolitic enzymes could also be used to reduce the viscosity of the biopolymer, particularly papain SH-groups that are reducing agents and accelerate the decomposition of hyaluronan [34], Trypsin, which contains Fe " ions, could also be used for the purification of hyaluronan and to initiate the depolymerization process. The use of 8-hydroxyquinoline prevents HA viscosity reduction [25]. In order to maintain the polymerization level of hyaluronan, the initial tissue must be thoroughly washed from blood, which contains ions of iron, copper and phosphate. 

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