Utilization of guaiacol-based deep eutectic solvent for achieving a sustainable biorefinery

Development of Eco-Friendly Date Palm Biomass-Based Hydrogels for Enhanced Water Retention in Soil

The growth of plants highly depends on the soil's water availability and properties. Hydrogels (HGs) have been used for decades to enhance soil water retention, whereas developing eco-friendly and sustainable HGs for agricultural applications is still necessary to ensure water and food security. In this study, renewable and cost-effective HGs were prepared from all-lignocellulose fibers of date palm biomass after carboxymethylation followed by citric acid (CA) crosslinking. HGs showed high equilibrium swelling capacity (EWC%), even in salty media, whereas purified HGs showed about 700-400 EWC% in deionized water. Further, HGs' effect on germination was studied on Chico III tomato, mint, Basilico red, and chia seeds. The results revealed that HGs enhanced the soil properties, with taller and healthier plants observed in HG-amended soil. FTIR, thermal analysis, and microscope imaging were utilized to evaluate HGs' and raw materials' characteristics. The findings in this study support the idea that all-lignocellulose could be used for HG production without separation.

Lignin-derived deep eutectic solvent for biomass fractionation based on α,γ-diol lignin stabilization strategy

Overcoming the biomass recalcitrance is crucial for thermal converting raw biomass into high-value chemicals. Consequently, the growing emphasis on sustainable and efficient pretreatment methods has become a key goal of research in the biorefinery field. This study proposes a novel lignin-derived deep eutectic solvent (LDES) pretreatment method to promote biomass pyrolysis based on α,γ-diol lignin stabilization strategy. It effectively deconstructed the complex biomass structure while significantly inhibiting lignin recondensation and undesirable deposition. This process achieved exceptional delignification (97.05 %) and hemicellulose removal (83.09 %), while maintaining 84.12 % of the cellulose, thus facilitating a high levoglucosan yield of 38.93 wt% in subsequent pyrolysis. Additionally, the isolated lignin had a low molecular weight (1873 g/mol) and well-preserved β-O-4 linkages (28.37/100Ar), rendering it ideal for the preparation of platform chemicals and lignin-based materials. This study highlights the potential of tunable and functional LDES as a promising pretreatment solvent, facilitating efficient fractionation and valorization of biomass, and achieving the concept of "closed-loop" biorefinery.

Exploration of biomass fractionation and lignin removal for enhancing enzymatic digestion of wheat-stalk through deep eutectic solvent Cetyl trimethyl ammonium chloride:Lactic acid treatment

The cationic surfactant-based deep eutectic solvents (DESs) have attracted extensive attention due to their effectual destruction of the natural anti-degradation barrier structure in lignocellulose. In this research, functional DES Cetyl trimethyl ammonium chloride:Lactic acid (CTAC:LA molar ratio 1:0.5 to 1:6) was fabricated for pretreating wheat-stalk. The relationships of accessibility, lignin removal, xylan separation, and enzymolysis efficiency were explored. The highest delignification (88.3 %) and xylan removal (89.0 %) were obtained through the treatment with CTAC:LA (1:4, mol/mol, 160 °C, 60 min), acquiring 86.8 % of enzymolysis efficiency. The structure of CTAC:LA-treated wheat-stalk was changed to porous state, while the accessibility and crystallinity were substantially improved to 668.2 mg/g and 57.6 %, respectively. The lignin surface area declined from 672.7 to 335.4 m2/g. Furthermore, the structure of lignin disrupted by CTAC:LA was analyzed by 2D-HSQC NMR, implying that CTAC:LA could cleave the CO covalent bond and CC bond and degrade the S- and H-units in wheat-stalk lignin through interaction. The potential pretreatment mechanism was proposed through comprehensive exploration at the molecular level and macro level, and this built pretreatment process held great promise for valorizing biomass into highly valuable chemicals.

Valorization of rapeseed straw through the enhancement of cellulose accessibility, lignin removal and xylan elimination using an n-alkyltrimethylammonium bromide-based deep eutectic solvent

n-Alkyltrimethylammonium bromide (CnTAB)-based deep eutectic solvent (DESs) has potential in the efficient delignification and utilization of carbohydrates in biomass. In this research, DESs containing Brønsted acid and Lewis acid were prepared with CnTAB (alkyl-chain length 12-18), organic acids and metal chlorides, and the optimal treatment conditions were acquired by pretreatment optimization. Through the pretreatment with TTAB/LCA/Fe3+ (1:4:0.0111, mol:mol:mol) (162.5 °C, 61.7 min), lignin (89.2 %) and xylan (77.9 %) were effectively eliminated, and the hydrophobicity of rapeseed straw substantially declined from 4.62 to 2.09 m2/g, acquiring the highest enzymatic saccharification efficiency of 92.5 %. The relationship of DES properties and enzymatic saccharification efficiency was explored. Additionally, hemicellulose in rapeseed straws could be efficiently transformed into furfural (3.75 g/L) and xylo-oligosaccharides (3.64 g/L). To clarify the structural and property changes brought by pretreatment, rapeseed straws were testified by FT-IR, SEM and CLSM and deeply discussed. The interaction between lignocellulose and TTAB/LCA/Fe3+ was elucidated by molecular dynamics simulations and quantum chemical calculations, explaining the effectual treatment performance and hemicellulose upgrading at the molecular level. Eventually, a potential pretreatment mechanism of TTAB/LCA/Fe3+ was proposed. This established TTAB/LCA/Fe3+ treatment holds great promise for valorization of biomass into biofuels and biobased chemicals.

Potassium Hydroxide-Mediated Pretreatment of Sugarcane Bagasse: High-Efficiency Enzymatic Hydrolysis and Excellent Sugar Recovery

Sugarcane bagasse, an important by-product of the sugar industry, is the fibrous residue remaining from sugarcane stalks following the extraction of sugarcane juice. In this study, the efficacy of potassium hydroxide (KOH) pretreatment on sugarcane bagasse under mild conditions is examined, and its effectiveness was assessed through enzymatic saccharification at various solid loadings. After pretreatment with a KOH dosage of 15 wt.%, a solid-liquid ratio of 1:10, and reaction time at 90 °C for 2 h, enzymatic saccharification experiments were performed to observe the change rule for the sugar recovery yield. The results showed that the glucose concentration achieved 47.6 ± 1.1 g/L under optimal conditions. With a specified solid loading of 5% and an enzyme dosage of 20 FPU cellulase/g-substrate, the total sugar yield reached as high as 81.6 ± 1.1%. Additionally, the entire fermentable sugar production process was clean and sustainable, which is crucial for converting lignocelluloses to advanced bioenergy or chemicals.

Novel ternary deep eutectic solvent fractionation for effective utilization of willow

A novel ternary deep eutectic solvent (TDES), consisting of zinc chloride, ethylene glycol and alpha hydroxy carboxylic acids (i.e., glycolic acid, citric acid and malic acid), was first proposed to effectively fractionate and convert willow (Salix matsudana cv. Zhuliu) into fermentable sugar. In particular, the zinc chloride/ethylene glycol/malic acid (ZnCl2/EG/MA) TDES system showed remarkable fractionation performance with 91.66 % xylan and 90.12 % lignin removals at 130 °C for 1.5 h, resulting in 96.01 % glucose yield in the subsequent enzymatic hydrolysis stage. Moreover, the regenerated lignin showed regular nanoparticle morphology and good antioxidant properties. Even after four recycling, the TDES showed 70.16 % of delignification and 83.70 % glucose yield with the TDES pretreated willow. Overall, this study demonstrated an effective solvent fractionation approach to maximize the utilization of total lignocellulose under mild conditions.

Efficient extraction of lignin from moso bamboo by microwave-assisted ternary deep eutectic solvent pretreatment for enhanced enzymatic hydrolysis

Applications of deep eutectic solvent (DES) systems to separate lignocellulosic components are of interest to develop environmentally friendly processes and achieve efficient utilization of biomass. To enhance the performance of a binary neutral DES (glycerol:guanidine hydrochloride), various Lewis acids (e.g., AlCl3·6H2O, FeCl3·6H2O, etc.) were introduced to synthesize a series of ternary DES systems; these were coupled with microwave heating and applied to moso bamboo. Among the ternary DES systems evaluated, the FeCl3-based DES effectively removed lignin (81.17%) and xylan (85.42%), significantly improving enzymatic digestibility of the residual glucan and xylan (90.15% and 99.51%, respectively). Furthermore, 50.74% of the lignin, with high purity and a well-preserved structure, was recovered. A recyclability experiment showed that the pretreatment performance of the FeCl3-based DES was still basically maintained after five cycles. Overall, the microwave-assisted ternary DES pretreatment approach proposed in this study appears to be a promising option for sustainable biorefinery operations.

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.

Applications of biomass-derived solvents in biomass pretreatment - Strategies, challenges, and prospects

Biomass pretreatment is considered a key step in the 2nd generation biofuel production from lignocellulosic biomass. Research on conventional biomass pretreatment solvents has mainly been focused on carbohydrate conversion efficiency, while their hazardousness and/or carbon intensity were not comprehensively considered. Recent sustainability issues request further consideration for eco-friendly and sustainable alternatives like biomass-derived solvents. Carbohydrate and lignin-derived solvents have been proposed and investigated as green alternatives in many biomass processes. In this review, the applications of different types of biomass pretreatment solvents, including organic, ionic liquid, and deep eutectic solvents, are thoroughly discussed. The role of water as a co-solvent in these pretreatment processes is also reviewed. Finally, current research challenges and prospects of utilizing biomass-derived pretreatment solvents for pretreatment are discussed. Given bioethanol's market potential and increasing public awareness about environmental concerns, it will be a priority adopting sustainable and green biomass pretreatment solvents in biorefinery.