Polysaccharides lignin complexes

TFA has been used for about three years in our laboratory, and it has become our exclusive reagent for the total hydrolysis of polysaccharides. Moreover, dilute TFA is applied to partial hydrolysis of lignin-polysaccharide complexes (13). 

Ralph, J., and Helm, R. F., 1993, Lignin/hydroxycinnamic acid/ polysaccharide complexes synthetic models for regiochemical characterization, in Forage Cell Wall Structure and Digestibility, H. G. Jung, D. R. Buxton, R. D. Hatfield, and J. Ralph, eds., ASA, CSCA, SSSA, Madison, WI, pp. 201-246. 

Many studies have indicated that covalent linkages must exist between lignin and wood polysaccharides. Separation and analysis of lignin -carbohydrate complexes (LCC) have led to the conclusion that the hemicel-lulose components (xylan and galactoglucomannans in softwood) are bound to lignin mainly through arabinose, xylose, and galactose moieties as shown in Fig. 4-10. 

Lignins are complex, cell wall-bound, optically inactive phenolic heteropolymers covalently associated with both polysaccharides and proteins [102]. They are mainly localized in the impermeable water transport conduits of the xylem and other supporting tissues of all the vascular terrestrial plants, and result mainly from the oxidative... 

M Lawoko, G Henriksson, G Gellerstedt. New method for quantitative preparation of lignin-carbohydrate complex from unbleached softwood kraft pulp Lignin polysaccharide networks I. Holrforschung 57 69-74, 2003. 

There is numerous evidence that lignin and polysaccharides are covalently linked, forming manifestations of the so-called lignin-carbohydrate complex (LCC) [2,7,17-19]. In spite of there being relatively low amounts of these linkages in wood [20,21], they play a very important role, as almost all wood lignin is covalently linked to polysaccharides, mainly to hemicelluloses [22]. There are three types of LCC linkages benzyl ether, phenyl... 

The production of ethanol alone is not economically feasible without continued subsidies but a plant becomes profitable if it produces ethanol and furfural as co-products (10). The technology development in the Latvian State Institute of Wood Chemistry (LSIWC) provides an excellent possibility for producing both furfural and ethanol. As a result, the problem of the complete utilization of the deciduous wood polysaccharide complex yielding furfural and fermentable sugars to be used subsequently for the production of bioethanol and other microbial synthesis products has been solved. Residual lignin could be used as a calorific fuel. 

Arabinan. This highly soluble polymer is found in the extracts of many fmits and seeds, in the boiling water extracts of pine wood (127), in the extracts of marshmallow roots (A/t/jaea officina/is) (128), and aspen (63) and willow (Sa/ix a/ba F) (129) bark. Because arabinan can be isolated from mildly degraded pectin fractions, it is often difficult to determine whether it is a hemiceUulose or a labile fragment of a larger polysaccharide and/or lignin complex. Arabinans have a complex stmcture composed almost entirely of 5-linked a-L-arabinofuranosyl units with similar residues linked to them at C-2 and/or C-3 and is soluble in 70% aqueous methanol solution. 

Dietary fiber is a mixture of simple and complex polysaccharides and lignin. In intact plant tissue these components are organized into a complex matrix, which is not completely understood. The physical and chemical interactions that sustain this matrix affect its physicochemical properties and probably its physiological effects. Several of the polysaccharides classified as soluble fiber are soluble only after they have been extracted under fairly rigorous conditions. 

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