Deep Eutectic Solvent Aqueous Solutions as Efficient Media for the Solubilization of Hardwood Xylans

Abstract

This work contributes to the development of integrated lignocellulosic-based biorefineries by the pioneering exploitation of hardwood xylans by solubilization and extraction in deep eutectic solvents (DES). DES formed by choline chloride and urea or acetic acid were initially evaluated as solvents for commercial xylan as a model compound. The effects of temperature, molar ratio, and concentration of the DES aqueous solutions were evaluated and optimized by using a response surface methodology. The results obtained demonstrated the potential of these solvents, with 328.23 g L of xylan solubilization using 66.7 wt % DES in water at 80 °C. Furthermore, xylans could be recovered by precipitation from the DES aqueous media in yields above 90 %. The detailed characterization of the xylans recovered after solubilization in aqueous DES demonstrated that 4-O-methyl groups were eliminated from the 4-O-methylglucuronic acids moieties and uronic acids (15 %) were cleaved from the xylan backbone during this process. The similar M values of both pristine and recovered xylans confirmed the success of the reported procedure. DES recovery in four additional extraction cycles was also demonstrated. Finally, the successful extraction of xylans from Eucalyptus globulus wood by using aqueous solutions of DES was demonstrated.

Fast and Efficient Method to Evaluate the Potential of Eutectic Solvents to Dissolve Lignocellulosic Components

“…Somehow, ChCl:UREA allowed better dispersion of xylose crystals than other ESs surpassing the solute-solute interactions at high xylose mass fractions. The high performance of ChCl:UREA for xylose dissolution in this study is in agreement with the results reported by Morais et al [38] reporting the highest xylan solubility in this ES.…”

“…Although several studies have reported success using ESs in the fractionation of several biomass matrices, such as corn residues [27], corn straw [28], rice straw [29], woodchip [30], corn cob [31], and algae [32], there is still limited knowledge about their ability to dissolve each macromolecular component. There are some studies that focused on evaluating the dissolution ability of ESs for individual biomass components [24,29,[33][34][35][36] and understanding the key factors governing the dissolution process [33,[37][38][39]. For instance, Morais et al [38] demonstrated that xylans can be solubilized in aqueous solutions of ESs.…”

“…There are some studies that focused on evaluating the dissolution ability of ESs for individual biomass components [24,29,[33][34][35][36] and understanding the key factors governing the dissolution process [33,[37][38][39]. For instance, Morais et al [38] demonstrated that xylans can be solubilized in aqueous solutions of ESs. As proof of concept, further extraction of hemicelluloses from wood (Eucalyptus globulus) with a higher yield than that obtained with aqueous or alkaline solutions was accomplished successfully.…”

α‐Chitin dissolution, N‐deacetylation and valorization in deep eutectic solvents

“…This technique can be effectively used for the determination of the particle size and their dissolution rate kinetics, hence being studied in this work. Chitin dissolution in two alkaline DESs has already been shown by others, yet it is possible to prepare eutectic mixtures with different characteristics, for instance, pH . In this sense, herein four distinct DESs were selected to further extend this study as different hydrogen bonds can be established between chitin and these solvents.…”

“…These dissolution results showed that it is possible to dissolve chitin in DESs with different pH and not only in alkaline ones . Therefore, an acidic ([Ch]Cl:LA), a neutral (Bet:G) and an alkaline ([Ch]Cl:U) DESs were selected to perform the homogenous N‐deacetylation of chitin using a final 30 wt% concentration of NaOH.…”