Xylan hemicellulosic

There are many recent examples of xylanase induction in fungi grown on media containing xylan, hemicellulose-rich material and low molecular weight carbohydrates (42-66). It has generally been observed that higher... 

SB hulls are galactomannans, xylan hemicelluloses, uronic acids, and cellulose (Aspi-nall Whyte, 1964 Aspinall et ah, 1966 Aspinall et ah, 1967b, 1967d). 

Similar autoradiographic studies of developing xylem and phloem tissues have shown that the xylan hemicellulose component of the cell wall arises in the Golgi bodies. " ... 

D-Xylose Xylanes, hemicelluloses plant gums, glycosides... 

As shown in Table II, blends of native and modified xylan hemicellulose were prepared with a compositionally diverse group of biobased and potentially biodegradable polymers and resulting Tg values, determined by DSC, were compared to the individual polymers. If two blended polymers form a true thermodynamic solution, then a single Tg is observed for the resulting blend... 

Derivatives of hemicellulose components have properties similar to the ceUulosic equivalents but modified by the effects of thek lower molecular weight, more extensive branching, labile constituents, and more heterogeneous nature. Acetates, ethers, carboxymethylxylan (184), and xylan—poly(sodium acrylate) (185) have been prepared. 

Xylan-type polysaccharides are the main hemicellulose components of secondary cell walls constituting about 20-30% of the biomass of dicotyl plants (hardwoods and herbaceous plants). In some tissues of monocotyl plants (grasses and cereals) xylans occur up to 50% [6j. Xylans are thus available in huge and replenishable amoimts as by-products from forestry, the agriculture, wood, and pulp and paper industries. Nowadays, xylans of some seaweed represent a novel biopolymer resource [4j. The diversity and complexity of xylans suggest that many useful by-products can be potentially produced and, therefore, these polysaccharides are considered as possible biopolymer raw materials for various exploitations. As a renewable resource, xylans are... 

AGX are also the dominant hemicelluloses in the cell walls of hgnified supporting tissues of grasses and cereals. They were isolated from sisal, corncobs and the straw from various wheat species [4]. A more recent study on corncob xylans [30] showed the presence of a hnear, water-insoluble polymer... 

Potential resources of xylans are by-products produced in forestry and the pulp and paper industries (forest chips, wood meal and shavings), where GX and AGX comprise 25-35% of the biomass as well as annual crops (straw, stalks, husk, hulls, bran, etc.), which consist of 25-50% AX, AGX, GAX, and CHX [4]. New results were reported for xylans isolated from flax fiber [16,68], abaca fiber [69], wheat straw [70,71], sugar beet pulp [21,72], sugarcane bagasse [73], rice straw [74], wheat bran [35,75], and jute bast fiber [18]. Recently, about 39% hemicelluloses were extracted from vetiver grasses [76]. 

The rheological behavior of xylans has rarely been investigated [4,114,115]. The water-insoluble hemicellulose from the viscose process (containing > 85% xylan) was reported to form thixotropic aqueous dispersions of high... 

Glucomannans (GM) and galactoglucomannans (GGM), common constituents of plant cell walls, are the major hemicellulosic components of the secondary cell walls of softwoods, whereas in the secondary cell walls of hardwoods they occur in minor amounts. They are suggested to be present together with xylan and fucogalactoxyloglucan in the primary cell walls of higher plants [192]. These polysaccharides were extensively studied in the 1960s [6,193]. 

In a recent paper [213], various GM-rich hemicellulose fractions containing 26-64% mannose and 1.4-2.2% galactose were isolated from ramie (Boehmeria nivea), which is a perennial grass. This is unexpected, because hemicelluloses of grasses contain predominantly xylans [4]. 

During the past decade, MALDI-TOF MS has proven to be an effective tool for the analysis of oligo- and polymeric mannoglucans (for extensive reviews see [222,223]). SEC/MALDI mass spectrometry was employed in the analysis of hemicelluloses isolated by microwave heat-fractionation from spruce and aspen wood [94]. These methods allowed the separation and characterization of the oligo- and polysaccharide fractions derived from the xylan and mannan components of both woods [224]. 

For thousands of years, nature has provided humankind with a large variety of materials for the most diversified applications for its survival, such as food, energy, medicinal products, protection and defense tools, and others. The pharmaceutical industry has benefitted from such diversity of biomaterials and has exploited the use of natural products as sources of both drugs and excipients. One example of a promising biomaterial for pharmaceutical use is xylan, a hemicellulose largely found in nature, being considered the second most abundant polysaccharide after cellulose. 

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