Novel renewable ionic liquids as highly effective solvents for pretreatment of rice straw biomass by selective removal of lignin

Abstract

Cholinium amino acids ionic liquids ([Ch][AA] ILs), a novel type of bio-ILs that can easily be prepared from renewable biomaterials, were investigated for pretreatment of rice straw by selective extraction of lignin from this abundant lignocellulosic biomass material. Of the eight ILs examined, most were demonstrated to be excellent pretreatment solvents. Upon pretreatment using these ILs, the initial saccharification rates of rice straw residues were substantially improved as well as the extent to which polysaccharides could be digested (>90% for cellulose and >60% for xylan). Enzymatic hydrolysis of pretreated rice straw by Trichoderma reesei cellulase/xylanase furnished glucose and xylose with the yields in excess of 80% and 30%, respectively. Detailed spectroscopic characterization showed that the enhancement of polysaccharides degestibility derived mainly from delignification rather than changes in cellulose crystallinity. The yields of fermentable reducing sugars were significantly improved after individual optimization of pretreatment temperature and duration. With [Ch][Lys] as the solvent, the sugar yields of 84.0% for glucose and 42.1% for xylose were achieved after pretreatment at 90°C for 5 h. The IL [Ch][Lys] showed excellent reusability across five successive batches in pretreatment of rice straw. These bio-ILs performed as well as or better than previously investigated non-renewable ILs, and thus present a new and environmentally friendly way to pretreat lignocellulose for production of fermentable sugars and total utilization of the biomass.

Chemical Pretreatment Methods for the Production of Cellulosic Ethanol: Technologies and Innovations

“…Carbohydrate losses are generally low and degradation products are significant only at severe conditions. Through the work of authors such as Cheng et al [193], Xie et al [172], Dadi et al [166], Hou et al [194], and others, it is known that significant sugar yields are achieved without the elimination of crystallinity.…”

critical review of ionic liquids for the pretreatment of lignocellulosic biomass

“…Cholinium ILs are a class of ILs that have low toxicity and are readily biodegradable. 48 Nockemann et al 49 demonstrated that the cholinium ILs, choline saccharinate and choline acesulfamate, can be prepared from easily available starting materials such as chicken feed additives (choline chloride) and artificial sweeteners (saccharinate and acesulfamate salts). In addition to biodegradability, the production of ILs from renewable materials is a very important consideration in a biorefinery and in this regard bio-based ILs have been prepared and tested for biomass pretreatment.…”

Catalytic Role of Ionic Liquids for Dissolution and Degradation of Biomacromolecules

“…Extended contact time facilitates extraction of lignin (Tan et al 2009;Hou et al 2012). A longer contact period enhances the diffusion of ILs into the pores of the biomass matrix, resulting in improved dissolution and extraction of lignin (Tan and Lee 2012).…”