Steam explosion process for the selective extraction of hemicelluloses polymers from spruce sawdust

The aim of this work was to study the effect of steam explosion conditions (severity factor, pH of pre-soaking medium) on the extraction of high molecular weight hemicelluloses from spruce sawdust. The highest yields were obtained at severity factor of 3.65 (47 and 44 mg/g or dry wood in neutral and basic mediums respectively). Treatment at high severity gave lower yield with lower molecular mass. A high extraction selectivity of high molecular weight hemicelluloses was observed as a function of the medium of the impregnation step: after a basic impregnation, similar to 90% of extracted hemicelluloses are arabinoglucuronoxylans (similar to 70 kDa) whereas after a water impregnation similar to 85% of galactoglucomannans (similar to 28 kDa) were recovered. FTIR, HSQC 2D and acetyl content analysis show that the GGM isolated are highly acetylated, with an acetylation rate very closed to the values reported for native AcGGM.