A series of room temperature ionic liquids (ILs), in which cholinium acts as the cation and amino acids as the anions, were prepared via a simple and green chemical route, and characterized. Most of the ILs dissolved lignin efficiently and selectively (with solubilities of 140-220 mg of lignin per g of IL). The solubility of xylan in these ILs (which ranged from <1 to 85 mg g -1 ) depended on the nature of the anion, while cellulose was scarcely soluble (<5 mg g -1 ). In addition, enzymatic hydrolysis of microcrystalline cellulose and rice straw was enhanced significantly after pretreatment using the IL [Ch][Gly].
Room temperature ionic liquids (RTILs) have been attracting increasing attention as electrolyte materials, catalysts and solvents for synthesis, catalysis and extraction etc., due to their excellent properties such as low vapor pressure, nonflammability, high thermal and chemical stability, and outstanding ability to dissolve a wide range of compounds. 1-3 Among a large number of ILs that have been synthesized and characterized, traditional ILs that consist of imidazolium or pyridinium cations and halide-containing anions have been demonstrated to be highly toxic and poorly biodegradable. 4 In addition, the feedstocks used to produce these ILs are of nonrenewable petroleum origin. Therefore in recent years, production of non-toxic and environmentally benign ILs from renewable materials has been proposed. 5,6 Choline, an essential nutrient, is known to be non-toxic and biodegradable. 7 Recently, a group of choliniumbased ILs have been synthesized and characterized. 8-11 These ILs showed excellent biodegradability 6 and low toxicity to filamentous fungi 6 and the freshwater crustacean Daphnia magna. 12 Amino acids, as one of the most abundant sources and chiral pools in nature, are excellent feedstocks for the synthesis of ILs, especially the ILs used in catalysis and synthesis, owing to their