Direct bioethanol production from cellulose by the combination of cellulase-displaying yeast and ionic liquid pretreatment

The efficient production of biofuels from cellulosic biomass is a current imperative. The present study demonstrates direct bioethanol production from cellulose by cellulase-displaying yeast (arming yeast) using ionic liquid pretreatment. In this approach, all of the bioethanol production processes (pretreatment, saccharification, and fermentation) were conducted in a single vessel. In a preliminary test, the arming yeast showed resistance to cellulose-dissolving ionic liquids below a concentration of approximately 200 mM. Cellulose degradation and ethanol productivity by the arming yeast was dramatically enhanced by pretreatment with ionic liquids. The addition of free cellulases during fermentation significantly enhanced ethanol productivity in the arming yeast system, producing approximately 90% ethanol yield. Furthermore, in a preliminary examination, 82% of the ionic liquids in the culture medium could be recovered and recycled for the pretreatment of cellulose.