Enhanced sugar production from pretreated barley straw by additive xylanase and surfactants in enzymatic hydrolysis for acetone–butanol–ethanol fermentation

•Effects of additive xylanase and surfactants on hydrolysis of barley straw were studied.•High sugar yields were obtained by combined application of xylanase and PEG 4000.•Surfactants contributed to the synergistic cooperation of xylanase with cellulase.•The hydrolysate of barley straw was efficiently utilized in biobutanol production.•The enhanced sugar production increased the ABE production yield.

This study aims to improve enzymatic sugar production from dilute sulfuric acid-pretreated barley straw for acetone–butanol–ethanol (ABE) fermentation. The effects of additive xylanase and surfactants (polyethylene glycol [PEG] and Tween) in an enzymatic reaction system on straw hydrolysis yields were investigated. By combined application of 2 g/100 g dry-matter (DM) xylanase and PEG 4000, the glucose yield was increased from 53.2% to 86.9% and the xylose yield was increased from 36.2% to 70.2%, which were considerably higher than results obtained with xylanase or surfactant alone. The ABE fermentation of enzymatic hydrolysate produced 10.8 g/L ABE, in which 7.9 g/L was butanol. The enhanced sugar production increased the ABE yield from 93.8 to 135.0 g/kg pretreated straw. The combined application of xylanase and surfactants has a large potential to improve sugar production from barley straw pretreated with a mild acid and that the hydrolysate showed good fermentability in ABE production.