Cellulose pretreatment with l-methyl-3-methylimidazolium dimethylphosphate for enzymatic hydrolysis

Abstract

This work has been focused on a cellulose pretreatment process using l-methyl-3-methylimidazolium dimethylphosphate ([DMIM]DMP) for subsequent hydrolysis over cellulase. Different operational variables (the amount of [DMIM]DMP, the pretreatment temperature, the pretreatment period) affecting the pretreatment were investigated. Additionally, the crystallinity index (CI) was characterized by FT-IR spectroscopy. The CI values including CI(IR), CI(IR-CI) and CI(IR-CII) were calculated. When correlated with these values, the concentrations of total reducing sugar (TRS) released after the pretreatment of microcrystalline cellulose (MC) were found to show a distinct relationship with the [CI(MC-CI) - CI(IR-CI)] values, and the result was verified by X-ray diffraction (XRD). Consequently, the optimum pretreatment conditions of crystalline transformation (from cellulose I to cellulose II) characterized by XRD are different from those of hydrolysis. This result suggests that other factors, in addition to cellulose crystallinity, affect the yields of glucose and total reducing sugar obtained by hydrolysis.