Deep Eutectic Solvent Applications in Lignocellulosic Biomass Valorization

Deep eutectic solvents (DESs) have emerged as versatile, green reaction media for the effective fractionation of lignocellulosic biomass into its principal components—cellulose, hemicellulose and lignin. Formed from mixtures of hydrogen‐bond acceptors (typically choline chloride) and hydrogen‐bond donors (such as organic acids, polyols or diols), DESs display tailored polarity and hydrogen‐bonding capabilities that facilitate selective delignification and depolymerisation under mild conditions. By stabilising reactive lignin intermediates, DESs preserve β-O-4 linkages and minimise condensation, yielding high-quality lignin streams amenable to downstream valorisation into aromatic monomers or novel polymeric materials. Concurrently, the residual cellulose fraction exhibits enhanced enzymatic digestibility, enabling efficient conversion into fermentable sugars. Recent studies have demonstrated that DES systems can be finely tuned—for instance by incorporating diols to provide protective functions, or by adjusting pKa and polarity parameters—to achieve rapid, energy-efficient biomass deconstruction with low environmental impact. Scalability and solvent recyclability remain key considerations, and ongoing work is exploring the integration of DES pretreatment with emerging intensification technologies, such as microwave irradiation, to further reduce residence times and life-cycle impacts. The global significance of this approach lies in its potential to underpin sustainable biorefineries that co-produce renewable fuels, chemicals and materials from abundant lignocellulosic feedstocks.

Research from Nature Portfolio

Recent studies have described the design of ternary DES systems comprising choline chloride, oxalic acid and a diol such as ethylene glycol. By providing a stabilising medium for reactive lignin fragments, these solvents enable efficient fractionation of hardwood and agricultural residues while maintaining high β-O-4 content in the isolated lignin. The protected lignin stream can be selectively depolymerised to monophenolic compounds, and the cellulose-rich fraction delivers near-quantitative glucose yields upon enzymatic hydrolysis. Crucially, the DES can be recovered with minimal loss of efficacy and reused over multiple cycles.

Earlier foundational work demonstrated that a low-melting mixture of boric acid and choline chloride effectively divides wood biomass into non-condensed lignin, carbohydrate-rich residues and valuable hemicellulose derivatives. This solvent system yielded high-purity lignin suitable for selective conversion, and allowed the direct transformation of hemicelluloses into furan platform chemicals, illustrating the modular potential of DES-based fractionation routes.

Deep Eutectic Solvent Applications in Lignocellulosic Biomass Valorization publication trend

The graph below shows the total number of articles in deep eutectic solvent applications in lignocellulosic biomass valorization across all publications each year (not limited to Nature Index journals).

Technical terms

Deep eutectic solvent (DES): A mixture of two or more components that forms a eutectic with a melting point lower than those of the individual constituents, characterised by strong hydrogen-bond interactions.

Lignocellulosic biomass: Plant matter composed of cellulose, hemicellulose and lignin, representing a renewable feedstock for biofuel and bioproduct synthesis.

Delignification: The process of selectively removing lignin from lignocellulose to expose cellulose and hemicellulose for further conversion.

β-O-4 linkage: The dominant ether bond between aromatic units in native lignin, critical for determining lignin’s reactivity and depolymerisation pathways.

Fractionation: The separation of lignocellulosic biomass into its constituent polymers using physical or chemical means.

References

1. Enhancing lignocellulosic biorefinery sustainability: mechanisms and optimization of microwave-responsive deep eutectic solvents for rapid delignification. Biofuel Research Journal (2025).
2. Renewable deep eutectic solvents pretreatment improved the efficiency of anaerobic digestion by lignin extraction from willow. Energy Conversion and Management (2023).
3. Tunable and functional deep eutectic solvents for lignocellulose valorization. Nature Communications (2021).
4. Deep Eutectic Solvents for the Valorisation of Lignocellulosic Biomasses towards Fine Chemicals. Biomass (2021).
5. Using a low melting solvent mixture to extract value from wood biomass. Scientific Reports (2016).
6. The Effect of Acidic Ternary Deep Eutectic Solvent Treatment on Native Lignin. ACS Sustainable Chemistry & Engineering (2022).