VALORIZATION OF WHEAT STRAW HEMICELLULOSE TO OBTAIN HIGH VALUE ADDED COMPOUNDS

摘要

Lignocellulose materials (LM) such as wheat straw can be used to obtain value added compounds such as xylooligosaccharides (XOS). XOS are produced from xylan, main component of hemicellulose. LM is formed by cellulose, hemicellulose and lignin. This structure must be altered in a pretreatment process in order to reduce the crystallinity of cellulose and facilitate the hydrolysis process. Steam explosion is a highly effective pretreatment process for wheat straw. During the pretreatment the hemicellulose is solubilized and recovered in the liquid fraction (LF). Xylooligosaccharides with degree of polymerization (DP) ranging from 2 to 6, are considered potential nondigestible sugars (NDOs), are known to have health benefits as prebiotics. The main goal of this work is the production of XOS with low DP from the liquid fraction. Enzymes β-glucanase and endoxylanase (Novozyme) and accessory enzyme α-L-arabinofuranosidase (Megazyme) were used. Endo-β-1,4-xylanases cleaves the glycosidic linkage in the xylan backbone releasing oligosaccharides. The assays were performed with enzymes individually and supplemented with α-L-arabinofuranosidase. A previous fractionation (SEC) of the LF was performed following the enzymatic hydrolysis in the same conditions that in previous tests. The results suggest that the process is effective in production of XOS. 83% and 79% of the available XOS were obtained during enzymatic hydrolysis with endoxylanase and β-glucanase respectively. A small increase of XOS was generated when arabinofuranosidase was added to the heavy oligomers fraction.