Co-fermentation of hemicellulose and starch from barley straw and grain for efficient pentoses utilization in acetone–butanol–ethanol production

•Two co-fermentations of hemicellulose and starch-based biomass were studied.•Lower concentration of H2SO4 resulted in good ABE fermentability in process I.•Process II facilitated pentoses utilization during the fermentation.•Process II could relieve the effect of inhibitors on fermentation.•Process II is attractive for ABE production from hemicellulosic biomass.

This study aims to efficiently use hemicellulose-based biomass for ABE (acetone–butanol–ethanol) production by co-fermentation with starch-based biomass. Two processes were investigated: (I) co-fermentation of sugars derived from hemicellulose and starch in a mixture of barley straw and grain that was pretreated with dilute acid; (II) co-fermentation of straw hemicellulosic hydrolysate and gelatinized grain slurry in which the straw was pretreated with dilute acid. The two processes produced 11.3 and 13.5 g/L ABE that contains 7.4 and 7.8 g/L butanol, respectively. In process I, pretreatment with 1.0% H2SO4 resulted in better ABE fermentability than with 1.5% H2SO4, but only 19% of pentoses were consumed. In process II, 95% of pentoses were utilized even in the hemicellulosic hydrolysate pretreated with more severe condition (1.5% H2SO4). The results suggest that process II is more favorable for hemicellulosic biomass utilization, and it is also attractive for sustainable biofuel production due to great biomass availability.