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Xylan and xylan derivatives - biopolymers with valuable properties, 1. Naturally occurring xylans structures, isolation procedures and properties
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2000
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EngineeringGlycobiologyPolysaccharideXylan-type PolysaccharidesPhysical PropertiesXylan TypesPolymer ChemistryWood ComponentBiomass UtilizationNatural PolymerBiochemistryBiopolymersLigninValuable PropertiesBiomolecular EngineeringBiomanufacturingPolymer ScienceBiotechnologyHemicelluloseMedicineXylans StructuresXylan DerivativesPolymer Synthesis
Xylans constitute 25–35 % of woody plant biomass and up to 50 % of cereal grains, with major sources in agricultural and forest waste, yet their physicochemical and rheological properties remain largely unexplored. This review summarizes the availability of xylan‑type polysaccharides as a vast biopolymer resource for practical applications. The authors describe and compare extraction methods for isolating xylans from various plant sources and characterize their thermophysical and tensioactive properties. The review shows that xylan structural diversity depends on botanical source, that specific types such as glucuronoxylan, arabinoglucuronoxylan, and arabinoxylan can be obtained from particular plants with comparable properties, and that these xylans exhibit dietary fiber and immunological activities.
The availability of xylan-type polysaccharides, representing an immense resource of biopolymers for practical application, is summarized. Xylans constitute 25–35% of the dry biomass of woody tissues of dicots and lignified tissues of monocots and occur up to 50% in some tissues of cereal grains. The most potential sources of xylans include many agricultural crops such as straw, sorghum, sugar cane, corn stalks and cobs, hulls and husks from starch production, as well as forest and pulping waste products from hardwoods, in particular. The structural diversity and complexity of xylans is illustrated and shown to depend on the botanic source. Various extraction procedures suitable for the isolation of xylans from different plant sources are described and compared. It is suggested that certain structural types of xylans like glucuronoxylan, arabinoglucuronoxylan, and arabinoxylan can be prepared from certain plant sources with similar chemical and physical properties. In contrast to structural analyses, the physicochemical properties, including solubility, molecular weight and molecular weight distribution, and rheological properties have been studied only for few xylan types. From the functional properties, the thermophysical and tensioactive properties are described. Finally, the physiological activities of xylans, which represent important dietary fibers as well as the immunological activities of some xylan types, are presented.