Hemicelluloses: from wood to the fermenter

Abstract

The valorisation of hemicelluloses, as a subproduct of the pulping process, can be achieved with extraction of wood chips by primary hydrolysis (auto or acid catalysed) before cooking, where part of them are dissolved. However, the extracts of the hardwood used in this work (Eucalyptus globulus) could contain oligomers, mainly xylose based, that must be further hydrolysed to become a raw material for fermentation to produce e.g. bioethanol. The primary extract from an acid hydrolysis can be directly metabolised by microorganisms being a secondary hydrolysis worthless. On the other hand, twice the monosaccharides concentration was obtained when a secondary hydrolysis was performed, over the extracts obtained from the primary auto-hydrolysis. The best conditions for that reaction include 3 h of hydrolysis, with 4 %(w/w) of H2SO4 and the highest concentration of solids (i.e. avoiding the dilution of primary extracts), which led to a secondary hydrolysis yield as high as 84 %.