BACKGROUND: Lignocellulosic biomass offers many potential advantages in comparison with the traditionally used sugars or starchy biomass since it is very widely available and does not compete with food and feed production. The abundance and high carbohydrates content of barley straw make it a good candidate for bioethanol production in Europe. Since biomass must be pretreated before enzymatic hydrolysis to improve the digestibility of both the cellulose and the hemicellulose biomass, the use of ionic liquids (IL) has been proposed as an environment-friendly pretreatment of biomass. RESULTS: Different pretreatment conditions were investigated to determine the effects of the experimental conditions (temperature and time) on the enzymatic digestibility of pretreated material. The pretreatment of barley straw with 1-ethyl-3-methyl imidazolium acetate treatment resulted in up to a 9-fold increase in the cellulose conversion and a 13-fold increase in the xylan conversion when compared with the untreated barley straw. CONCLUSION: Ionic liquid pretreatment of barley straw at 110 degrees C for 30 min, followed by enzymatic hydrolysis, leads to a sugar yield of 53.5 g per 100 g raw material. It is then ready available for conversion into ethanol and is equivalent to more than 86% from potential sugars. The increase in saccharification was possible due to rupture of the ligninhemicellulose linkages by treatment with 1-ethyl-3-methyl imidazolium acetate. (c) 2012 Society of Chemical Industry