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.