Natural arginine-based deep eutectic solvents for rapid microwave-assisted pretreatment on crystalline bamboo cellulose with boosting enzymatic conversion performance

A designed ZrOCl2/ethylene glycol deep eutectic solvent for efficient lignocellulose valorization

Deep eutectic solvents (DESs) hold great potential in biorefining because they can efficiently deconstruct the recalcitrant structure of lignocellulose. In particular, inorganic salts with Lewis acids have been proven to be effective at cleaving lignin-carbohydrate complexes. Herein, a Zr-based DES system composed of metal chloride hydrate (ZrOCl2·8H2O) and ethylene glycol (EG) was designed and used for poplar powder pretreatment. Zr4+-based salts provide sufficient acidity for lignocellulose depolymerization. The acidity of the DES was analysed by the Kamlet-Taft solvatochromic parameter, and the results demonstrated that the acidity can be regulated by the DES composition. Under the optimum conditions (ZrOCl2·8H2O:EG molar ratio of 1:2), the DES pretreatment removes nearly 100 % hemicellulose and 94.7 % lignin. The recovered lignin exhibited a low polydispersity of 1.7. The cellulose residues deliver an efficiency of 94.4 % upon enzymatic digestion. Moreover, the DES can be easily recovered with high yield and purity, and the recycled DES still maintains high delignification and enzymatic hydrolysis efficiencies. The proposed DES pretreatment technology is promising for biomass valorization.

One-pot extraction of nanocellulose from raw durian husk fiber using carboxylic acid-based deep eutectic solvent with in situ ultrasound assistance

Nanocellulose (CNF) has emerged as a promising alternative to synthetic petroleum-based polymers, but the conventional preparation process involves multiple tedious steps, heavily dependent on chemical input, and proves cost-inefficient. This study presented an, in situ ultrasound-assisted extraction using deep eutectic solvent (DES) based on choline chloride and oxalic acid for more facile production of CNF from raw durian husk fibers. FESEM analysis confirmed the successful extraction of web-like nanofibril structure with width size ranging from 18 to 26 nm. Chemical composition analysis and FTIR revealed the selective removal of lignin and hemicellulose from the raw fiber. As compared to post-ultrasound treatment, in situ ultrasound-assisted extraction consistently outperforms, yielding a higher CNF yield with finer fiber width and significantly reduced lignin content. Integrating this eco-friendly in situ ultrasonication-assisted one-pot extraction method with a 7.5 min interval yielded the highest CNF yield of 58.22 % with minimal lignin content. The superior delignification ability achieved through the proposed in situ ultrasound-assisted protocol surpasses the individual efficacy of DES and ultrasonication processes, neither of which yielded CNF in our experimental setup. This single-step fabrication process significantly reduces chemical usage and streamlines the production steps yielding web-structured CNF that is ideal for sustainable application in membrane and separator.

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.

Towards valorization of rice straw into bioethanol and lignin: Emphasizing critical role of deep eutectic solvent components in biorefining process

Deep eutectic solvents (DESs) offer a potential opportunity in biomass utilization industries. This work emphasized the impact of hydrogen bond donors (HBD) and acceptors (HBA) on deconstruction and valorization of rice straw. Acidity, alkyl chain length, hydrogen bonding ability and functional groups of HBD and HBA appeared to be important factors affecting the fractionated pulps and lignins, which further influenced ethanol fermentation. Among the candidate DESs, lactic acid/guanidine hydrochloride (LGH) was proved to be the most suitable one due to the excellent delignification and xylan removal. For the downstream fermentation process, 0.47 g g-1 of bioethanol with 0.55 g/L h-1 of productivity can be obtained from the LGH pulp's hydrolysate. Mass balance showed 302.8 g bioethanol and 119.0 g technical lignin can be co-generated from 1 kg dried rice straw. This "green" valorization strategy offers a promising scheme in biorefinery of lignocelluloses.

Microwave-assisted DES fabrication of lignin-containing cellulose nanofibrils and its derived composite conductive hydrogel

Deep eutectic solvents (DES) have been regarded as green solvents in the biorefinery of lignocellulosic biomass, but long duration time has severely limited efficiency. The microwave-assisted DES pretreatment along with enzymatic hydrolysis and high-pressure homogenization process was proposed to produce lignin-containing cellulose nanofibrils (LCNF) from corncob. Benefiting from microwave-assisted DES pretreatment, the duration time was greatly shortened; meanwhile the effects of different kinds of DES on the resultant LCNF were investigated. The results showed that, the microwave-assisted DES fabricated LCNF (M-LCNF) was successfully obtained, exhibiting good nano size, thermal stability, colloidal stability, and fluorescence. M-LCNF was further introduced into phytic acid (PA) enhanced poly(acrylamide-co-acrylic acid) (P(AM-co-AA)) network and constructed composite conductive hydrogels (PLP). The obtained hydrogels exhibited good mechanical strength, UV blocking ability, fluorescence, and conductivity. A simple battery assembled with the resultant PLP as electrolyte had an out voltage of 2.41 V. The composite conductive hydrogel showed good sensing performance towards different stimuli (e.g., stretching and compression) and human motions in real time. It is expected that this research would provide an alternative way for green fabrication of LCNF and potential application of LCNF in flexible sensors.

Preparation of nanocellulose and its applications in wound dressing: A review

Nanocellulose, as a nanoscale polymer material, has garnered significant attention worldwide due to its numerous advantages including excellent biocompatibility, thermal stability, non-toxicity, large specific surface area, and good hydrophilicity. Various methods can be employed for the preparation of nanocellulose. Traditional approaches such as mechanical, chemical, and biological methods possess their own distinct characteristics and limitations. However, with the growing deterioration of our living environment, several green and environmentally friendly preparation techniques have emerged. These novel approaches adopt eco-friendly technologies or employ green reagents to achieve environmental sustainability. Simultaneously, there is a current research focus on optimizing traditional nanocellulose preparation methods while addressing their inherent drawbacks. The combination of mechanical and chemical methods compensates for the limitations associated with using either method alone. Nanocellulose is widely used in wound dressings owing to its exceptional properties, which can accelerate the wound healing process and reduce patient discomfort. In this paper, the principle, advantages and disadvantages of each preparation method of nanocellulose and the research findings in recent years are introduced Moreover, this review provides an overview of the utilization of nanocellulose in wound dressing applications. Finally, the prospective trends in its development alongside corresponding preparation techniques are discussed.

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.