Ionic Liquid and Sulfuric Acid-Based Pretreatment of Bamboo: Biomass Delignification and Enzymatic Hydrolysis for the Production of Reducing Sugars

The present work investigates the efficiency of two pretreatment pathways of biomass, namely ionic liquid (IL) and dilute sulfuric acid (H2SO4) hydrolysis. Both processes are compared in terms of their composition and enzymatic saccharification efficacy. For the IL process, bamboo was dissolved in 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) at different temperatures (90, 110, 130, and 150 degrees C) for 3 h. These pretreated bamboo samples were then characterized by thermogravimetric analysis and X-ray diffraction to evaluate the biomass crystallinity and thermal decomposition temperature. The crystallinity index, thermal decomposition temperature, hemicellulose, and lignin content of bamboo were found to decrease after [Emim] [OAc] pretreatment. Further, the IL pretreated biomass significantly enhanced the enzymatic saccharification of cellulose component of bamboo. The enzymatic hydrolysis rate for IL pretreated biomass was 4.7 times higher than that of the acid pretreated biomass. This was primarily attributed to the difference in the crystallinity and delignification in the IL process. To improve the enzymatic hydrolysis efficiency of bamboo, a combined pretreatment (dilute acid + ionic liquid) process was also employed and compared with IL pretreated cellulose and bamboo samples. The consequences of this investigation revealed that IL pretreatment may offer novel favorable circumstances compared to a dilute acid pretreatment process for bamboo which can deliver high sugar yields with IL pretreatment.