Progress on ionic liquid pre-treatment for lignocellulosic biomass valorization into biofuels and bio-products

Energy security and environmental features are nowadays two major issues that have boosted the exploitation of an eco-friendly and renewable alternative to petrochemical resources. Lignocellulosic biomass (LCB) is an abundant and sustainable feedstock of great interest for the production of valuable chemicals and biofuels. It consists of three major components: cellulose, hemicellulose, and lignin. However, access to these biopolymers is impeded by the recalcitrance and the complex structure of the plant cell walls. Thus, a pre-treatment step is necessary to disorganize and/or fractionate the lignocellulosic matrix. The use of Ionic Liquids (ILs) in the LCB pre-treatment has gained considerable attention in recent years. ILs are emergent solvents with high thermal and chemical stability, low vapor pressure and tuneable properties, which allow an energy-efficient LCB pre-treatment in eco-friendlier conditions than conventional ones. However, the large-scale uptake of IL to pilot and industrial level is still hindered by their production cost and the need to understand more deeply the mechanism of their interaction with LCB, hydrolytic enzymes and microbial cells. This chapter outlines the potential application and the confronted challenges of IL use in LCB pre-treatment, their mechanism of interaction and dissolution of LCB and their biocompatibility.