Structure of Regenerated Celluloses Treated with Ionic Liquids and Comparison of their Enzymatic Digestibility by Purified Cellulase Components

摘要

In this study, regenerated celluloses were prepared from microcrystalline cellulose (MCC) by treatment with three ionic liquids (ILs) having 1-ethyl-3-methylimidazolium (Emim) as the cation, and the IL N-(2-methoxyethyl)-N,N-diethyl-N-methylammonium alanine ([N_(221ME)][Ala]), where the amino acid moiety is the anion. The crystal form of cellulose was transformed from cellulose I to cellulose II by dissolution with an IL and regeneration with anti-solvent. However, the crystallinity of the regenerated cellulose was different; the disordered chain region was increased in the order of [N_(221ME)] [Ala] < [Emim][OAc] < [Emim][DEP] < [Emim][Cl]. The monocomponent cellulase, especially endoglucanase, showed high hydrolyzing activity for regenerated cellulose compared with untreated cellulose. Furthermore, the degree of increase of hydrolyzing activity was almost coincident with the order of crystallinity. For the effective hydrolysis of cellulose treated with an IL, it is necessary to prepare the cellulase mixture containing an adequate ratio of each cellulase component according to crystal allomorph and the crystallinity of regenerated cellulose.