Reconstitution of cellulose and lignin after [C2mim][OAc] pretreatment and its relation to enzymatic hydrolysis.

Although the effects of cellulose crystallinity and lignin content as two major structural features on enzymatic hydrolysis have been extensively studied, debates regarding their effects still exist. In this study, reconstitution of cellulose and lignin after 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) pretreatment was proposed as a new method to study their effects on enzymatic digestibility. Different mechanisms of lignin content for reduction of cellulose hydrolysis were found between the proposed method and the traditional method (mixing of cellulose and lignin). The results indicated that a slight change of the crystallinity of the reconstituted materials may play a minor role in the change of enzyme efficiency. In addition, the present study suggested that the lignin content does not significantly affect the digestibility of cellulose, whereas the conversion of cellulose fibers from the cellulose I to the cellulose II crystal phase plays an important role when an ionic liquid pretreatment of biomass was conducted.