Combined use of completely bio-derived cholinium ionic liquids and ultrasound irradiation for the pretreatment of lignocellulosic material to enhance enzymatic saccharification

Completely bio-derived cholinium ionic liquids (ILs) such as choline acetate (ChOAc) are reported to be less expensive, more biocompatible, and more biodegradable and bio-renewable in comparison with the imidazolium ILs that are conventionally used for the pretreatment of lignocellulosic biomass. We demonstrated here, for the first time, that the cholinium-IL-assisted pretreatment of lignocellulosic biomass is enhanced by ultrasound irradiation in comparison with conventional heating. The cellulose saccharification ratio of bamboo powder was approximately 55% when pretreated thermally in ChOAc at 110 °C for 60 min. Conversely, after ultrasonic pretreatment in the same IL at 25 °C for 60 min, 92% of cellulose was hydrolyzed to glucose. Moreover, X-ray diffractometry and Fourier-transform infrared spectrometry analyses revealed that the cellulose crystallinity of pretreated bamboo powder was lower in case of ultrasonic pretreatment in ChOAc than in case of thermal pretreatment in the same IL.

• Totally bio-derived cholinium ionic liquid (IL) was used to pretreat lignocellulose.
• We suggested pretreatment method using the cholinium IL and ultrasound.
• This was more efficient than the existing method using the cholinium IL and heating.