Ionic liquids as a tool for lignocellulosic biomass fractionation

Abstract

Lignocellulosic biomass composes a diversity of feedstock raw materials representing an abundant and renewable carbon source. In majority lignocellulose is constituted by carbohydrate macromolecules, namely cellulose and hemicellulose, and by lignin, a polyphenilpropanoid macromolecule. Between these biomacromolecules, there are several covalent and non-covalent interactions defining an intricate, complex and rigid structure of lignocellulose. The deconstruction of the lignocellulosic biomass makes these fractions susceptible for easier transformation to large number of commodities including energy, chemicals and material within the concept of biorefinery. Generally, the biomass pre-treatment depends on the final goal in the biomass processing. The recalcitrance of lignocellulose materials is the main limitation of its processing once the inherent costs are excessively high for the conventional pre-treatments. Furthermore, none of the currently known processes is highly selective and efficient for the satisfactory and versatile use, thus, new methodologies are still studied broadly. The ionic liquid technology on biomass processing is relatively recent and first studies were focused on the lignocellulosic biomass dissolution in different ionic liquids (ILs). The dissolution in IL drives to the structural changes in the regenerated biomass by reduction of cellulose crystallinity and lignin content contrasting to the original biomass. These findings provided ILs as tools to perform biomass pre-treatment and the advantageous use of their specific properties over the conventional pre-treatment processes. This review shows the critical outlook on the study of biomass dissolution and changes occurred in the biomass during this process as well as on the influence of several crucial parameters that govern the dissolution and further pre-treatment process. The review of currently known methods of biomass fractionation in IL and aqueous-IL mixtures is also discussed here and perspectives regarding these topics are given as well.

Ionic liquid-tolerant microorganisms and microbial communities for lignocellulose conversion to bioproducts

“…In all these treatments, the substantial degradation of lignin is accompanied by considerable reduction in fermentable sugar content of the feedstock, resulting in a loss of 20-35% of the mass of lignocellulose (Galbe and Zacchi 2007;Lee et al 2009). In contrast, recent reports give ample evidence that pretreating biomass with ionic liquids can disrupt the interactions between plant cell wall polymers, resulting in significant improvements in enzymatic hydrolysis kinetics while preventing the loss of fermentable sugars and facilitating the fractionation of biomass (Cheng et al 2011;da Costa Lopes et al 2013;Li et al 2010;Li et al 2009;Mora-Pale et al 2011;Singh et al 2009;Zakrzewska et al 2010;Zavrel et al 2009). …”

“…A reduction in crystallinity was observed after IL pretreatment of switchgrass, maple wood, yellow pine, and hardwood red oak (Lee et al 2009;Li et al 2010;Sun et al 2009). Moreover, in IL pretreated biomass samples, cellulose can be easily recovered with the addition of anti-solvents, such as water, methanol, ethanol, and acetone, and the enzymatic hydrolysis of the recovered cellulose is much greater than that of untreated cellulose (da Costa Lopes et al 2013;Dadi et al 2006;Lee et al 2009;Li et al 2009;Singh et al 2009;Sun et al 2009;Zhao et al 2009a). …”

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

“…297 An example is lignocellulosic biomass processing with ILs that allows for the efficient fractionation into main components, such cellulose, hemicellulose, lignin and phenolic compounds. [298][299][300][301][302][303][304] Besides the ability of ILs to dissolve and pre-treat, the solvent power and high selectivity of ILs also allows for the extraction of specific targeted biomolecules from biomass, as demonstrated in literature. 305 In fact, the heterogeneity of food waste generally leads to the disadvantage of adopting multi-step fractionation strategies to obtain target compounds.…”

Extraction of Wheat Straw with Aqueous Tetra-n-Butylphosphonium Hydroxide

“…The properties that can be affected are e.g., 'hydrophobicity', as well as charged and polar interactions (Huddleston et al 2001). These properties can also translate into efficient biopolymer dissolution (da Costa Lopes et al 2013a). By noting the acidity of the cation, the cellulose dissolution capabilities of acid-base conjugate ILs can be predicted.…”