Evolution of miscanthus and switchgrass composition with the harvest period, with different crop husbandry conditions and with focus on the hemicelluloses monosaccharidic composition

-Miscanthus and switchgrass are promising perennial lignocellulosic crops in the field of bioenergy and biorefinery owing to their high fiber content, high biomass yield, high dry matter content and low input needs for their growth. The optimal valorization of their cellulosic and hemicellulosic components in lignocellulose-based biorefineries requires a good knowledge of their available biomass contents, and of their molecular composition. The main chemical components (cellulose, hemicelluloses, lignin, total soluble sugars, starch, proteins and mineral compounds) and more specifically the monosaccharidic composition of cellulose and hemicelluloses (cellulosic glucan, xylan, arabinan, mannan, galactan and hemicellulosic glucan) were analyzed in two perennial lignocellulosic crops: miscanthus giganteus (Miscanthus x giganteus J.M.Greef & Deuter ex Hodk. & Renvoize ; cultivar: Bical) and switchgrass (Panicum virgatum L. ; cultivar: Cave-in-rock). Both crops were fertilized with 0, 80 or 160 kgN ha-1 and harvested in October or March. Cellulose and hemicelluloses contents range respectively from 32.0 to 47.6 and from 24.0 to 34.3 g (100gDM)-1 while lignin, total soluble sugars, proteins and mineral compounds contents range from 6.1 to 12.8, 0 to 2.2, 0.6-5.6 and 0.8 to 6.2 g (100gDM)-1, respectively The main hemicellulosic components and their corresponding range expressed in g (100gDM)-1 were by order of decreasing importance : xylan (18.0 to 27.8), arabinan (1.90 to 3.88), hemicellulosic glucan (0.93 to 2.74), galactan (0.26 to 1.50) and mannan (0 to 0.92). Plant species and harvest period has the most significant influence on main chemical components and structural polysaccharide composition, while the influence of nitrogen fertilization is only rarely significant except on the protein conten