Potency of Deep Euteutic Solvent as an Alternative Solvent on Pretreatment Process of Lignocellulosic Biomass: Review

During the last decade Deep Euteutic Solvent (DES) is an alternative solvent and has proven to be effective in removing lignin and hemicellulose bonds, as well as reducing the crystallinity of cellulose in the pretreatment process of lignocellulosic biomass delignification. Until now, it has been reported that DES is a solvent that is widely used in various studies. DES is a solvent consisting of two or three ionic compositions which can be associated through hydrogen bonds, to form a euteutic mixture with a melting point lower than each individual component. In literature and research, these solvents are often referred to as environmentally friendly solvents. It is known that DES has physicochemical properties similar with ionic liquids but is more environmentally friendly and cheaper. Over the years, a number of studies have reported that the pre-treatment of lignocellulosic biomass delignification is carried out chemically and physically, such as the use of dilute acids, alkalis, and steam explosions. It was reported that this method is a process that uses a lot of energy, because it requires high temperature and pressure to remove lignin. However, the proposed method is currently based on the use of DES solvents which require less energy from chemical and physical processes. DES dissolves lignin and increases the availability of cellulose at low temperatures and pressures during the pre-treatment process. In this review it aims to explain the recent progress made regarding the contribution of DES and its potential on lignocellulosic biomass pre-treatment process. It also discussed the advantages of DES solvents that are environmentally friendly, cheap, non-toxic and low energy use.