Native lignin

Relative to softwood lignins, native hardwood lignins provide thioacidolysis monomers in higher yield (between 2000 and 2800 pmoles per gram KL, Table 2.6). 

A technique based on ozonation, in contrast, provides information on the stmcture of the lignin side chain by degrading the aromatic rings (33). Thus the side chain of the dominant stmcture ia all native lignins, the arylglycerol—P-aryl ether moiety, can be obtained ia the form of erythronic and threonic acids. Ozonation proves to be an elegant method for determination of the stereospecificity ia lignin. 

The significance of phenoxy anions is well recognized in the isolation of kraft and other water-insoluble technical lignins by acid precipitation. The ioniza tion of phenoHc hydroxyl groups coupled with the reduction of molecular size renders native lignin soluble in the aqueous pulping solution, thus enabling its separation from the polysaccharide components of wood. 

Stevens, G. de, and F. F. Nord, Studies on native lignins and lignification. 

However, in 1939 this difficulty was obviated by Brauns extraction of about 3% lignin from spruce wood by means of the solvent, ethyl alcohol, at room temperature (9). He termed this preparation native lignin. It was found to be soluble in methanol, ethanol, dioxane, dilute sodium hydroxide and pyridine, and insoluble in water, ether, petroleum ether and benzene. Chemically it behaved the same as lignin as it exists in woody tissues. It also reduced Fehling s solution and gave a strong... 

Table 1. Chemical Composition of Spruce Native Lignin and Spruce Chemical Lignins.

Consequently, and in order to have a material which could be compared with spruce native lignin, sound samples of the softwood, white Scots pine, were infected with the brown rot"... 

As can be seen, the cellulolytic action of the fungus has indeed brought about a two-fold increase in the yield of extractable lignin. The native and enzymatically liberated lignins were then chemically compared and found to be identical in all respects examined (Table 4). 

Finally, in order to establish unequivocally the identity of the native and residual lignin of white Scots pine wood, the sound wood was first extracted with ethyl alcohol to remove the native lignin fraction. The extracted wood was then decayed by means of the brown rot fungi,... 

Porta vaillantii and Lenzites sepiaria, for a fifteen month period. At the end of this time the decayed samples yielded an alcohol extractable lignin in about 20% yield, which was once again found to be chemically identical with the native lignin. These results are recorded in Table 5-... 

Table 5- Comparison of the Native and Enzymatically Liberated Lignins from White Scots Pine with Spruce Native Lignin (99).

Spruce Native Lignins White Scots Pine Native White Scots Pine Liberated... 

Moreover, the identity of the native and enzymatically liberated lignins from this softwood is further corroborated by their ultraviolet and infrared absorption spectra (79), (99). (See page 88,92 and Fig. 1 and 5.)... 

These data amply confirm the original contention concerning the feasability of using cellulolytic enzyme systems for the isolation of additional amount of native lignin from various woody tissues. Moreover, this method can be applied not only to perennial plants, but also to annual plants. 

Table 8. Comparison of Bagasse Native Lignin with Bagasse Lignin (108) Liberated by Various Fungi.

Native Lignin Poria vaillantii Polyporus sulfureus Lentinus lepideus... 

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