The promotional effect of water-soluble extractives on the enzymatic cellulose hydrolysis of pretreated wheat straw

Enzymatic cellulose hydrolysis of pretreated wheat straw pulp to glucose is enhanced when the hydrolysis is performed in the presence of an aqueous extract of the wheat straw. A relative digestibility increase of about 10% has been observed for organosolv, alkaline and dilute acid pretreated wheat straw pulp (enzyme dose 2.5 FPU/g pulp). At lower enzyme doses, the extract effect increases leading to an enzyme dose reduction of 40% to obtain a glucose yield of 75% within 48 h using organosolv wheat straw pulp. Possibly, cellulase deactivation by irreversible binding to pulp lignin is reduced by competition with proteins in the extract. However, since the extract effect has also been demonstrated for lignin-lean substrates, other effects like improved accessibility of the pulp cellulose (amorphogenesis) cannot be excluded. Overall, this contribution demonstrates the positive effect of biomass extractives on enzymatic cellulose digestibility, thereby reducing costs for 2G biofuels and bio-based chemicals.