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.