In order to obtain separate streams, to be further used for different product lines, such as biofuels and different added-value products, corn and rice residues must be fractionated using environmental friendly processes such as autohydrolysis. This process enables the selective hydrolysis of hemicelluloses, and a high recovery of soluble xylo-oligosaccharides (XOS), with potential applications in the pharmaceutical, food, feed and chemical industries.
In this work, corn residues (leaves and stalks) and rice straw were subjected to non-isothermal autohydrolysis under different operational conditions, in order to assess the effects of reaction severity in products formation. The composition of both liquid and solid phases was evaluated and interpreted using the severity factor (Log Ro). The operational conditions for the maximal recovery of XOS were established at Log Ro=3.75 for corn residues and Log Ro=3.10 for rice straw.
The XOS containing liquors were purified using size-exclusion chromatography and the oligosaccharides mixtures separated into several fractions according to their apparent molecular mass. This process also enabled the removal of monosaccharides, acetic acid, furan derivatives and phenolic compounds. The XOS obtained were analyzed by HPLC using different techniques to characterize their degree of polymerization and chemical composition.
The purified XOS present a wide range of potential industrial applications.