Improvement of Enzymatic Hydrolysis of Polysaccharides in Rice Straw by Cholinium Alkanoate Ionic Liquid Pretreatment

Pretreatment of lignocellulosic biomass is a key step in the production of biofuels by biorefinement. Recently, ionic liquid(IL) pretreatment of lignocellulosic biomass has attracted increasing interest. In this study, seven cholinium alkanoate([Ch][Alk]) ILs were synthesized via a neutralization reaction, and were used for the pretreatment of rice straw. At 25 ℃, the viscosities of these ILs ranged from 74 to 488 c P. After the pretreatment of rice straw by these ILs, the efficiency of the enzymatic hydrolysis of polysaccharides in rice straw was improved significantly. In addition, the pretreatment performance of ILs depended on the chain length of the anion. Among the tested ILs, cholinium butyrate([Ch][But]) proved to be the optimal solvent for the pretreatment of rice straw. Following the enzymatic hydrolysis of rice straw pretreated by [Ch][But] at 90 ℃ for 6 h, the yields of glucose and xylose reached 70.62% and 41.47%, respectively. This type of IL could selectively remove lignin and xylan from rice straw, while retaining the cellulose crystalline structure, which significantly improved the efficiency of the subsequent enzymatic hydrolysis.