Revolutionizing lignocellulosic biomass: A review of harnessing the power of ionic liquids for sustainable utilization and extraction

Ionic liquids in C-H activation: synthesis and functionalization of heterocycles and carbocycles

This review illustrates various roles played by ionic liquids in organic transformations, such as solvents, additives, promoters, electrolytes and catalysts for the synthesis and functionalization of heterocycles and carbocycles through C-H activation reactions. Ionic liquids offer several advantages such as high stability, intrinsic conductivity, non-volatility, and recyclability, making them appealing alternatives to traditional organic solvents in sustainable organic synthesis. Their unique properties enhance reaction performance, as seen with recyclable [EMIM]BF4 in quinazolinone synthesis and [TMG][CF3COO] in amide production, direct diarylation of 6,7-benzindoles, regioselective reactions with aryl iodides, catalytic cyclopropanation with tetrabutylammonium acetate (TBAA), and propargylamine synthesis via A3 coupling reactions. The use of functionalized ionic liquids like [Bmim]PF6 with phosphine-ligated Pd(II) enhances product isolation, facilitates reactions under mild conditions, and promotes reusability, contributing to environmentally friendly pathways. Thus, this review highlights various ionic liquids used in different reactions, emphasizing their benefits in improving yields, solubility, and product separation in catalytic processes.

Low dosage ionic liquid-driven mild and selective lignocellulosic deconstruction of corn stover using biphasic co-solvent systems

Ionic liquids (ILs) are highly effective in lignocellulose pretreatment due to their excellent solvation properties. However, the single-phase nature of conventional IL pretreatment not only causes component mixing, complicating separation and utilization, but also limits large-scale application due to the high cost. To address these challenges, this study developed a biphasic pretreatment system combining the protic IL [BHEM]mesy with aqueous pentanol, aiming to efficiently fractionate corn stover under mild conditions. The effects of varying conditions on corn stover composition were systematically investigated. The optimal pretreatment conditions (10 % IL, 60 % pentanol, 140 °C, 60 min) resulted in 91.6 % cellulose content in solid residue with 89.3 % hemicellulose and 82.9 % lignin removal. Enzymatic hydrolysis of pretreated residues was significantly better than residues pretreated with IL or pentanol alone. In the biphasic system, 70.8 % of the available xylose dissolved into the aqueous phase, while the organic phase facilitated the recovery of 82.9 % lignin with high phenolic hydroxyl. Quantum chemical calculations revealed that the IL-pentanol co-solvent system reduces IL consumption while exhibiting higher reactivity than either component alone. This study demonstrates a cost-effective and efficient approach for lignocellulose pretreatment, offering significant potential for high-value utilization of its components.

A two-step strategy promotes the dissolution of corn stover-based lignocellulosic biomass in DBU/CO2/DMSO solvent system

The dissolution and homogeneous processing of lignocellulosic biomass presents a significant challenge for advanced biorefineries. In this work, we firstly investigated the dissolution behavior of corn stover-based lignocellulose in 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU)/CO2/DMSO solvent system. The dissolution proportion reached 74.3 % via a two-step procedure, which involved pretreating of corn stover in DBU/DMSO solvent at 140 °C for 4 h, followed by dissolution at 50 °C for 6 h under 5 MPa CO2. Furthermore, the solubility of the corn stover can be improved by ball-milling treatment. Rheological behavior revealed that the solution viscosity and the intermolecular interactions decreased following ball-milling treatment. Subsequently, a small amount of wood pulp cellulose was incorporated to produce mechanically robust, fully UV-shielding, and all-biomass composite films. The tensile strength of the composite film containing 50 wt% wood pulp cellulose reached 47 MPa. This study provides significant insights into the development of green dissolution systems for lignocellulose and the development of lignocellulose-based advanced materials.

Utilization of structure-specific lignin extracted from coconut fiber via deep eutectic solvents to enhance the functional properties of PVA nanocomposite films

This study utilized deep eutectic solvents (DES) based on choline chloride/lactic acid (ChCl/LA) to deconstruct coconut fibers. The effects of DES with different temperatures and molar ratios on the yield of lignin, recovery rate of residues, structural changes in lignin and solid residues, and saccharification efficiency were investigated. The results showed that acidic DES treatment effectively deconstructed the coconut fibers, resulting in a high lignin yield of 68.51 % while enhancing the enzymatic saccharification of cellulose, reaching a glucose yield of 85.88 %. The structural characterization of lignin revealed that acidic DES primarily cleaved β-O-4 bonds, yielding coconut fiber lignin with lower molecular weight and higher phenolic hydroxyl groups. Uniform and smooth coconut fiber lignin nanoparticles (CFLNPs) with excellent antioxidant activity were finally obtained by antisolvent method. Furthermore, PVA/CFLNPs nanocomposite films were prepared based on acidic DES CFLNPs. The results of the structural and functional analysis showed that CFLNPs significantly improved the thermal stability, mechanical properties, hydrophobicity, antioxidant and antibacterial activity of the nanocomposite films. In general, this work achieved efficient deconstruction of coconut fibers, providing insights for biorefining in the future, and more importantly, the potential to use the CFLNPs as a choice for active food packaging.

Harnessing deep eutectic solvent for enhanced inulinase production from agricultural via submerged fermentation with Aspergillus niger

This study aimed to enhance inulinase production from agricultural biomass pretreated with deep eutectic solvents (DES) using Aspergillus niger A42 (ATCC 204447). Barley husk (BH), wheat bran (WB), and oat husk (OH) were selected as substrates and were pretreated using different molar ratios of choline chloride: glycerol (ChCl: Gly) and choline chloride: acetic acid (ChCl: AA). DES pretreatment was followed by dilute sulfuric acid hydrolysis. The fermentable sugar content (FSC), sugar profiles, and inhibitory components in the hydrolysates were analyzed. DES pretreatment improved the FSC in all substrates, with wheat bran showing the highest FSC of 72.54 g/mL. Considering the fermentable sugar contents, ChCl: Gly (1:2) was selected as the most suitable DES. The analysis of biomass composition after pretreatment indicated a reduction in extractives and lignin, along with an increase in cellulose content. Subsequently, inulinase fermentation using Aspergillus niger A42 has demonstrated that DES-pretreated wheat bran was the most effective substrate, yielding 416.05 U/mL inulinase activity (Iase) and 486.22 U/mL invertase-type (Sase) activity. The enzyme solution was partially purified via Spin-X UF membranes (50 kDa cut-off), resulting in Iase activity of 769.93 U/mL and Sase activity of 566.69 U/mL. The purification coefficients were 1.88 and 0.92 for inulinase and invertase-type activity, respectively. In conclusion, DES pretreatment was successfully applied to produce inulinase enzyme from BH, WB, and OH. Among the materials studied, WB emerged as the most suitable biomass for producing inulinase from Aspergillus niger A42.

Influence of Artocarpus hirsutus (AH) cellulose micro fiber, bamboo fiber in thermoplastic biocomposites

In this experiment Artocarpus hirsutus (AH) fiber was utilized as the filler material for bamboo fiber (NF)/polyethylene (PE) biocomposites. This was a waste to wealth approach by utilising biomaterial and also can reduce the use of PE plastics. The crystallinity index (Crl) of 45.1%, 56.4%, 67% was observed in AH, alkali treated (NaOH) and cellulose AH fiber respectively. The combination with 20 wt% NF/3 wt% cellulose AH filler observed better tensile and flexural strength. Agglomeration at 4, 5 wt% affects the flexural properties by lesser interfacial adhesion with filler/matrix phase, having properties reducing up to 20.3 MPa. Comparing to cellulose AH filler, both alkali treated and untreated AH filler combinations possess lesser flexural strength. The addition of natural fibers increases the tensile and flexural modulus property with better properties at 30 wt% NF/5 wt% cellulose AH filler combination. The Impact strength doesn't observe high influence with filler incorporation. This AH fiber hasn't been explored in detail for mechanical and hydrophilic properties with incorporation with PE matrix. This fabricated composite is suited for bioengineering applications.

Xylooligosaccharides: A comprehensive review of production, purification, characterization, and quantification

Xylooligosaccharides (XOS), short-chain polymers with prebiotic properties, have gained significant commercial attention over the past few decades due to their potential as nutraceutical components. Derived from lignocellulosic biomass (LCB), XOS serve as health promoting compounds with applications across multiple sectors, including food pharmaceutical and cosmetic. This comprehensive review provides an overview of XOS production, purification, characterization, and quantification, highlighting their derivation from various sources such as agricultural waste, agro-economical forest residues, and nutrient-dense energy crops. The production of XOS involves enzymatic hydrolysis, acid hydrolysis, and steam explosion, each offering distinct advantages and limitations in terms of cost-effectiveness and scalability for industrial applications. Methods for purification including chromatographic techniques, membrane filtration, capillary electrophoresis (CE) and enzyme-linked immunosorbent assay (ELISA) are evaluated based on their efficiency and feasibility. Characterization techniques such as nuclear magnetic resonance (NMR) spectroscopy, high-performance liquid chromatography (HPLC), and mass spectrometry (MS) provide detailed insight into XOS structure and composition. Conclusively, XOS are promising biological macromolecules with significant industrial and scientific interest due to their diverse applications and potential for cos-effective large-scale production.

Advanced functional materials based on nanocellulose/Mxene: A review

The escalating need for a sustainable future has driven the advancement of renewable functional materials. Nanocellulose, derived from the abundant natural biopolymer cellulose, demonstrates noteworthy characteristics, including high surface area, crystallinity, mechanical strength, and modifiable chemistry. When combined with two-dimensional (2D) graphitic materials, nanocellulose can generate sophisticated hybrid materials with diverse applications as building blocks, carriers, scaffolds, and reinforcing constituents. This review highlights the progress of research on advanced functional materials based on the integration of nanocellulose, a versatile biopolymer with tailorable properties, and MXenes, a new class of 2D transition metal carbides/nitrides known for their excellent conductivity, mechanical strength, and large surface area. By addressing the challenges and envisioning future prospects, this review underscores the burgeoning opportunities inherent in MXene/nanocellulose composites, heralding a sustainable frontier in the field of materials science.

Enhancing detoxification of inhibitors in lignocellulosic pretreatment wastewater by bacterial Action: A pathway to improved biomass utilization

The process of preprocessing techniques such as acid and alkali pretreatment in lignocellulosic industry generates substantial solid residues and lignocellulosic pretreatment wastewater (LPW) containing glucose, xylose and toxic byproducts. In this study, furfural and vanillin were selected as model toxic byproducts. Kurthia huakuii as potential strain could tolerate to high concentrations of inhibitors. The results indicated that vanillin exhibited a higher inhibitory effect on K. huakuii (3.95 % inhibition rate at 1 g/L than furfural (0.45 %). However, 0.5 g/L vanillin promoted the bacterial growth (-2.35 % inhibition rate). Interestingly, the combination of furfural and vanillin exhibited antagonistic effects on bacterial growth (Q<0.85). Furfural and vanillin could be bio-transformed into less toxic molecules (furfuryl alcohol, furoic acid, vanillyl alcohol, and vanillic acid) by K. huakuii, and inhibitor degradation rate could be promoted by expression of antioxidant enzymes. This study provides important insights into how bacteria detoxify inhibitors in LPW, potentially enhancing resource utilization.

Innovative ionic liquid pretreatment followed by wet disk milling treatment provides enhanced properties of sugar palm nano-fibrillated cellulose

In order to accommodate the increased demand for innovative materials, intensive research has focused on natural resources. In pursuit of advanced substances that exhibit functionality, sustainability, recyclability, and cost-effectiveness, the present work attempted an alternative study on cellulose nanofibers derived from sugar palm fiber. Leveraging an innovative approach involving ionic liquid (IL) pre-treatment, bleaching, and wet disc mill technique, nano-fibrillated cellulose (NFC) was successfully obtained from the sugar palm fiber source. Remarkably, 96.89% of nanofibers were extracted from the sugar palm fiber, demonstrating the process's efficacy and scalability. Further investigation revealed that the sugar palm nano-fibrillated cellulose (SPNFC) exhibited a surface area of 3.46 m2/g, indicating a significant interface for enhanced functionality. Additionally, the analysis unveiled an average pore size of 4.47 nm, affirming its suitability for various applications that necessitate precise filtration. Moreover, the surface charge densities of SPNFC were found to be -32.1 mV, offering opportunities for surface modification and enhanced interactions with various materials. The SPNFC exhibit remarkable thermal stability, enduring temperatures of up to 360.5 °C. Additionally, the isolation process is evident in a significant rise in the crystallinity index, escalating from 50.97% in raw fibers to 61.62% in SPNFC. These findings shed light on the vast potential and distinct features of SPNFC, opening the path for its application in a wide array of industries, including but not limited to advanced materials, biomedicine, and environmental engineering.