DES: their effect on lignin and recycling performance

Deep eutectic solvents for the extraction of polyphenols from food plants

Deep Eutectic Solvents (DESs) offer a promising, sustainable alternative for extracting polyphenols from food plants, known for their health benefits. Traditional extraction methods are often costly and involve toxic solvents. This review discusses the basic concepts, preparation techniques, and factors influencing the effective and safe use of DESs in polyphenol extraction. DESs' adaptability allows integration with other green extraction technologies, such as microwave- and ultrasound-assisted extractions, enhancing their efficiency. This adaptability demonstrates the potential of DESs in the sustainable extraction of bioactive compounds. Current research indicates that DESs could play a significant role in the sustainable procurement of these compounds, marking an important advancement in food science research and development. The review underscores DESs as a realistic, eco-friendly alternative in the realm of natural extraction technologies, offering a significant contribution to sustainable practices in food science.

Synergistic microwave and acidic deep eutectic solvent-based pretreatment of Theobroma cacao pod husk biomass for xylooligosaccharides production

The bioconversion of lignocellulosic biomass into novel bioproducts is crucial for sustainable biorefineries, providing an integrated solution for circular economy objectives. The current study investigated a novel microwave-assisted acidic deep eutectic solvent (DES) pretreatment of waste cocoa pod husk (CPH) biomass to extract xylooligosaccharides (XOS). The sequential DES (choline chloride/citric acid, molar ratio 1:1) and microwave (450W) pretreatment of CPH biomass was effective in 67.3% xylan removal with a 52% XOS yield from total xylan. Among different XOS of varying degrees of polymerization, a higher xylobiose content corresponding to 69.3% of the total XOS (68.22 mg/g CPH) from liquid fraction was observed. Enzymatic hydrolysis of residual xylan from pretreated CPH biomass with low commercial xylanase (10 IU/g) concentration yielded 24.2% XOS. The MW-ChCl/citric acid synergistic pretreatment approach holds great promise for developing a cost-effective and environmentally friendly method contributing to the sustainable production of XOS from agricultural waste streams.

Preparation of spherical porous carbon from lignin-derived phenolic resin and its application in supercapacitor electrodes

Lignin is the most abundant aromatic biomass resource in nature and is the main by-product of paper industry and biorefinery industry, which has the characteristics of abundant source, renewable and low cost. Deep eutectic solvents (DES) are a nascent environmentally friendly solvent option that is gaining traction. DES composed of p-toluenesulfonic acid and choline chloride is used for batch treatment of alkaline lignin, and the bio-oil obtained is ternary polymerized with formaldehyde and phenol to obtain lignin phenolic resin. The porous carbon material is produced through a two-step carbonization process, utilizing phenolic resin derived from lignin as the primary source of carbon. The morphology and composition of the carbon were analyzed by SEM, TEM, XRD, TGA, XPS and Raman spectroscopy, the specific surface area and pore size distribution were analyzed by BET. The results showed that the specific surface area of the lignin-based phenolic resin was significantly higher than that of the pure phenolic resin carbon, and the porous carbon material that was acquired demonstrated a specific surface area of as much as 1026 m2/g. In the three-electrode system, the specific capacitance of DLPFC can reach 245.8 F/g (0.25 A/g), with a very small decrease in the value of specific capacitance at 10,000 cycles, with a retention of 97.62% (10 A/g). The porous carbon demonstrated a specific capacitance of 112.4 F/g at a current density of 0.5 A/g, and the capacitance retention rate could still reach 98.8% after 5000 charge/discharge cycles, with high cycling stability (in the two-electrode system). The prepared symmetrical supercapacitors exhibited high energy density and power density of 3.9 Wh/kg and 125.0 W/kg. The results suggest a new idea of high value-added application of lignin phenolic resin for high-performance supercapacitor electrodes.

Recent advances in biorefineries based on lignin extraction using deep eutectic solvents: A review

Considering the urgent need for alternative biorefinery schemes based on sustainable development, this review aims to summarize the state-of-the-art in the use of deep eutectic solvent pretreatment to fractionate lignocellulose, with a focus on lignin recovery. For that, the key parameters influencing the process are discussed, as well as various strategies to enhance this pretreatment efficiency are explored. Moreover, this review describes the challenges and opportunities associated with the valorization of extraction-derived streams and highlights recent advancements in solvent recovery techniques. Furthermore, the utilization of computational models for process design and optimization is introduced, as the initial attempts at the economic and environmental assessment of this lignocellulosic bioprocess based on deep eutectic solvents. Overall, this review offers a comprehensive perspective on the recent advances in this emerging field and serves as a foundation for further research on the potential integration of deep eutectic pretreatment in sustainable multi-product biorefinery schemes.

Switchable Deep Eutectic Solvents for Lignin Dissolution and Regeneration

Deep eutectic solvents (DESs) are promising for lignin dissolution and extraction. However, they usually possess high polarity and are difficult to recycle. To overcome this drawback, a variety of switchable ionic liquids (SILs) composed of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and alcohols was synthesized and screened. According to the thermodynamic modeling suggestions, the selected DBU-HexOH SIL was coupled with hydrogen-bond donors to form switchable-DES (SDES) systems with moderated viscosity, conductivity, and pH while maintaining switchability. The SDESs produced a well-improved lignin and lignin model compound solubility compared with those of SILs; charging CO2 into SDES (SDESCO2) caused a further increase in solubility. The solubility (25 °C) of syringic acid, ferulic acid, and milled wood lignin in SDESCO2 reached 230.57, 452.17, and 279.12 mg/g, respectively. Such SDES-dissolved lignin can be regenerated using acetone as an anti-solvent. The SDES-regenerated lignin exhibited a well-preserved structure with no noticeable chemical modifications. Furthermore, the SDESCO2 lignin possessed a higher molecular weight (Mw = 10,340 g/mol; Mn = 7672 g/mol), improved uniformity (polydispersity index = 1.35), and a higher guaiacyl lignin unit content compared with the original milled wood lignin. The SDES system proposed in the present work could benefit the fractionation of lignin compounds and facilitate downstream industrial processes.

Recent advances in pharmaceutical and biotechnological applications of lignin-based materials

Lignin, a versatile and abundant biomass-derived polymer, possesses a wide array of properties that makes it a promising material for biotechnological applications. Lignin holds immense potential in the biotechnology and pharmaceutical field due to its biocompatibility, high carbon content, low toxicity, ability to be converted into composites, thermal stability, antioxidant, UV-protectant, and antibiotic activity. Notably, lignin is an environmental friendly alternative to synthetic plastic and fossil-based materials because of its inherent biodegradability, safety, and sustainability potential. The most important findings related to the use of lignin and lignin-based materials are reported in this review, providing an overview of the methods and techniques used for their manufacturing and modification. Additionally, it emphasizes on recent research and the current state of applications of lignin-based materials in the biomedical and pharmaceutical fields and also highlights the challenges and opportunities that need to be overcome to fully realize the potential of lignin biopolymer. An in-depth discussion of recent developments in lignin-based material applications, including drug delivery, tissue engineering, wound dressing, pharmaceutical excipients, biosensors, medical devices, and several other biotechnological applications, is provided in this review article.