Fig. 1. Schematic representation of plant cell wall polysaccharides. Cellulose and P-1,3/1,4- glucan are composed of glucose residues (red). P-1,4-xyloglucan is a glucose-based polymer substituted by xylose residues (green) themselves possibly linked to galactose (blue) and fucose (black). P-1,4-arabinoxylan is a xylose backbone linked with arabinose (orange), and/or with glucuronic acid acid (white). Xylose could be substituted by acetyl groups (blue circle). P-1,4-mannan is a mannose polymer (dark red) linked to some galactose residues and sometimes acetylated. a-1,4-polygalacturonan is formed of linear chains of galacturonic acid (pale yellow) linked by rhamnose (pink). Galacturonic residues could be either methylated (red circle) or linked to xylose residues. Rhamnogalacturonan is highly ramified and is also called "hairy region" for this reason. The basic backbone is a rhamnose-galacturonic acid motif. Side chain of arabinose, galactose, mixed or not, linear or not, forms a very complex and variable structure. Adapted from Dalboge (1997).

Table 1. Lignin, glucose and xylose contents of hop, destarched wheat bran, corn cops and birch. Results are expressed as % of dry matter (unpublished results from the laboratory). Klason lignin was quantified as the acid-soluble residue after sulfuric acid hydrolysis (Remond et al. 2010) and sugar contents were estimated by enzymatic methods as described in Phalip et al. (2009).