Use of Buckwheat Straw to Produce Ethyl Alcohol Using Ionic Liquids

Common buckwheat (Fagopyrum esculentum Moench) is an annual spring-emerging crop that is classified among dicotyledons, yet due to the manner of its cultivation, use, and chemical composition of seeds. The use of buckwheat straw for energy purposes, for example, for the production of second generation bioethanol might enable its wider application and increase the cost-effectiveness of tillage. In this study, we examined the usability of buckwheat straw for the production of bioethanol. We pretreated the raw material with using ionic liquids and subsequently performed enzymatic hydrolysis and alcoholic fermentation. The obtained chemometric data was analyzed using the Partial Least Squares (PLS) regression model. PLS regression in combination with the spectral analysis within near-infrared (NIR) spectrum allowed for the rapid determination of amount of cellulose in the raw material and also provided information on the changes taking place in its structure. According to our results, we obtained good results for the combination of 1-ethyl-3-methylimidazolium acetate as the ionic liquid and Cellic CTec2 and the enzymatic preparation for the pretreatment of buckwheat straw. The highest concentration of glucose following 72 hours of enzymatic hydrolysis was found to be around 5.5 g/dm3. The highest concentration of ethanol (3.31 g/dm3) was obtained with the combination of 1-butyl-3-methylimidazolium acetate for the pretreatment and the cellulase from Trichoderma reesei for enzymatic hydrolysis. In summary, the efficiency of the fermentation process is strictly associated with the pool of available fermenting sugars, and it depends on the type of ionic liquid used during the pretreatment and on the enzymatic preparation. It is possible to obtain bioethanol from buckwheat straw using ionic liquid for the pretreatment of the raw material prior to the enzymatic hydrolysis and alcoholic fermentation of the material.