Selective removal of lignin with sodium chlorite to improve the quality and antioxidant activity of xylo-oligosaccharides from lignocellulosic biomass

Room-temperature phosphorescent transparent wood

Transparent wood with high transmittance and versatility has attracted great attention as an energy-saving building material. Many studies have focused on luminescent transparent wood, while the research on organic afterglow transparent wood is an interesting combination. Here, we use luminescent difluoroboron β-diketonate (BF2bdk) compounds, methyl methacrylate (MMA), delignified wood, and initiators to prepare room-temperature phosphorescent transparent wood by thermal initiation polymerization. The resultant PMMA has been found to interact with BF2bdk via dipole-dipole interactions and consequently enhance the intersystem crossing of BF2bdk excited states. The transparent wood matrix can provide a rigid environment for BF2bdk triplets and serve as oxygen barrier to suppress non-radiative decay and oxygen quenching. The prepared afterglow material has the characteristics of diverse composition, long afterglow emission lifetimes, and high photoluminescence quantum yield. This afterglow transparent wood also demonstrates potential application value in areas such as high mechanical strength, good hydrophobicity, and high cost-effectiveness.

Oxidative purification of microplastics in riverine suspended matter samples - Solving the challenge of plant debris removal for microplastic analysis

Riverine suspended matter (river-SPM) contains large amounts of natural particles consisting of cellulose and lignin, posing a challenge for microplastic (MPs) analysis. Additionally, organic matter composition under seasonal and discharge-related dynamics varies for each river. Therefore, this study attempted to identify a universally applicable clean-up procedure to remove matrix particles with high organic matter content, mainly plant debris, from the river-SPM samples. This study tested six digestion procedures adapted from existing (ligno)cellulosic digestion/oxidation methods with a river-SPM sample followed by density separation using sodium polytungstate. From these, NaOCl treatment (CL) showed the highest efficiency of organic matter removal, eliminating 96-100 % of the matrix weight. Exposure of tested MPs (in size range of 100-500 μm) in the CL protocol showed no adverse effect on polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene terephthalate (PET). Similarly, no detrimental matrix effects were found on 100 μm spherical PS standard particles spiked in the river-SPM. This procedure achieved high recovery rates of tested plastics (92-100 %). In terms of method applicability, the procedure was successfully applied to samples from different seasons containing various matrix concentrations and compositions. Although samples with high amounts of plant debris needed to undergo this procedure twice, only minor alteration of the particle surface and IR spectrum of PS presented and no adverse effect on PP. To further tackle the high and varied concentration of plant-derived matrix in river-SPM samples, a novel sequential oxidation protocol (2DOCL) combining cellulose dissolution, Fenton's oxidation, and NaOCl oxidation was developed, resulting in a more (time) effective and predictable process, demonstrating no severely destructive effect on tested plastics. The sequential digestion protocol can be optimized for certain matrices as applying all steps will not be necessary.

Xylooligosaccharide Production From Lignocellulosic Biomass and Their Health Benefits as Prebiotics

Lignocellulosic biomass (LCB) comprising of wheat bran, coconut husk, rice husk, cereals straw, and other hardwood and softwoods is a good source for the production of xylooligosaccharides (XOS) (prebiotic). XOS produced are nondigestible carbohydrates being stable under stomach pH and digestive enzymes so they can be easily delivered to the intestine in native form, thus stimulating the growth of probiotics. Here we review about the raw material, production, purification, and application of XOS with health benefits. Importance of XOS being valuable food ingredient is increasing as they perform a variety of functions, including reduction in cholesterol levels, gastrointestinal health maintenance, anticancer and antioxidant properties, and modulation of immune system. We also discuss the different characterization methods which are necessary to determine the degree of polymerization (DP) of XOS. Low DP (xylobiose and xylotriose) is usually preferred for the application of XOS in various sectors. This review emphasizes the growing significance of XOS as a prebiotic, serving as nourishment for probiotics.

Production and biological activity of β-1,3-xylo-oligosaccharides using xylanase from Caulerpa lentillifera

In this study, β-1,3-xylanase (Xyl3088) was designed and prepared by constructing the expression vector plasmid and expressing and purifying the fusion protein. β-1,3-xylo-oligosaccharides were obtained through the specific enzymatic degradation of β-1, 3-xylan from Caulerpa lentillifera. The enzymolysis conditions were established and optimized as follows: Tris-HCl solution 0.05 mol/L, temperature of 37 °C, enzyme amount of 250 μL, and enzymolysis time of 24 h. The oligosaccharides' compositions and structural characterization were identified by thin-layer chromatography (TLC), ion chromatography (IC) and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS). The IC50 values for scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis-3-ethyl-benzothiazoline-p-sulfonic acid (ABTS+), and superoxide anion radical (•O2-) were 13.108, 1.258, and 65.926 mg/mL for β-1,3-xylo-oligosaccharides, respectively, and 27.588, 373.048, and 269.12 mg/mL for β-1,4-xylo-oligosaccharides, respectively. Compared with β-1,4-xylo-oligosaccharides, β-1,3-xylo-oligosaccharides had substantial antioxidant activity and their antioxidant effects were concentration dependent. β-1,3-xylo-oligosaccharides also possessed a stronger anti-inflammatory effect on RAW 264.7 cells stimulated by lipopolysaccharide (LPS) than β-1,4-xylo-oligosaccharides. At a working concentration of 100 μg/mL, β-1,3-xylo-oligosaccharides inhibited the release of NO and affected the expression of IL-1β, TNF-α, and other proteins secreted by cells, effectively promoting the release of pro-inflammatory mediators by immune cells in response to external stimuli and achieving anti-inflammatory effects. Therefore, β-1,3-xylo-oligosaccharides are valuable products in food and pharmaceutical industries.

Hollow carbon fiber wrapped by regular rGO wave-like folds for efficient solar driven interfacial water steam generation

Efficient seawater desalination is an effective way to solve the shortages of fresh water and energy but with limitations of the low fresh water production rate and high cost. Here, a hollow carbon fiber (HCF) wrapped by regular reduced graphene oxide (rGO) wave-like folds (rGO@HCF) is prepared on account of the differences in thermal shrinkage performance between graphene oxide (GO) and willow catkins fiber. Under one sun irradiation (1 kW m-2), the dry and wet surface temperature of the resulting evaporator reached up to 119.1 °C and 61.7 °C, respectively, and the water steam production rate reached 3.42 kg m-2 h-1. Also, for the outdoor experiment, the rGO@HCF exhibits good evaporator performance which reach up 27.8 kg m-2 day-1. Additionally, rGO@HCF also shows good seawater desalination performance and excellent durability for longtime work. DSC results indicate that the evaporation enthalpy of bulk water and adsorbed water decreased from 2503.92 to 1020.54 J g-1. The excellent evaporating performance is mainly attributed to the regular wave-like microstructure surface of the HCF, which can enhance the light absorption, reduced the vaporization enthalpy of the adsorption water. The findings not only introduce a novel approach for agricultural utilization, but also establish a crucial theoretical foundation for the design of regular wave-like microstructures.

Unraveling interplay between lignocellulosic structures caused by chemical pretreatments in enhancing enzymatic hydrolysis

To investigate the interplay between substrate structure and enzymatic hydrolysis (EH) efficiency, poplar was pretreated with acidic sodium-chlorite (ASC), 3 % sodium-hydroxide (3-SH), and 3 % sulfuric acid (3-SA), resulting in different glucose yields of 94.10 %, 74.35 %, and 24.51 %, respectively, of pretreated residues. Residues were fractionated into cellulose, lignin and unhydrolyzed residue after EH (for lignin-carbohydrate complex (LCC) analysis) and analyzed using HPLC, FTIR, XPS, CP MAS 13C NMR and 2D-NMR (Lignin and LCC analysis). After delignification, holocellulose exhibited a dramatic increase in glucose yield (74.35 % to 90.82 % for 3-SH and 24.51 % to 80.0 % for 3-SA). Structural analysis of holocellulose suggested the synergistic interplay among cellulose allomorphs to limit glucose yield. Residual lignin analysis from un/pretreated residues indicated that higher β-β' contents and S/G ratios were favorable to the inhibitory effect but unfavourable to the holocellulose digestibility and followed the trend in the following order: 3-SA (L3) > 3-SH (L2) > native-lignin (L1). Analysis of enzymatically unhydrolyzed pretreated residues revealed the presence of benzyl ether (BE1,2) LCC and phenyl glycoside (PG) bond linking to xylose (X) and mannose (M), which yielded a xylan-lignin-glucomannan network. The stability, steric hindrance and hydrophobicity of this network may play a central role in defining poplar recalcitrance.

Microplastic and adhesive free, multifunctional, circular economy approach-based biomass-derived drinking straws

Generation of voluminous single-use plastic waste and byproducts from agricultural harvests such as rice straws (RSs) are major global challenges due to their disposal issues, contributing to greenhouse gas emissions, and affecting the ecological system with threats to human health. A scalable, low-cost, and eco-friendly strategy for fabricating cellulose-silica-based drinking straws, free from microplastics and adhesive, through strategic valorization of RS is reported. Functionalization by delignification-cum-crosslinking of RS leads to development of straws with high water stability (∼5 days), solvothermal stability (0°C-95°C), tensile strength (128 MPa), low migration values (<60 mg/kg), improved biodegradability (∼126 days) with reduced wettability and hydrophobicity. RS drinking straws show antibacterial, self-cleaning, self-healing, anti-fizzing, reusable, and generate significantly lower carbon footprint (<99.8% and <53.34% global warming potential than metal and polylactic acid straws). Repurposing of agro-wastes from farms to commercially viable drinking straws which biodegrades after its consumption achieves the goal of circular economy and sustainable development.

Research of saccharides and related biocomplexes: A review with recent techniques and applications

Saccharides and biocompounds as saccharide (sugar) complexes have various roles and biological functions in living organisms due to modifications via nucleophilic substitution, polymerization, and complex formation reactions. Mostly, mono-, di-, oligo-, and polysaccharides are stabilized to inactive glycosides, which are formed in metabolic pathways. Natural saccharides are important in food and environmental monitoring. Glycosides with various functionalities are significant in clinical and medical research. Saccharides are often studied with the chromatographic methods of hydrophilic interaction liquid chromatography and anion exchange chromatograpy, but also with capillary electrophoresis and mass spectrometry with their on-line coupling systems. Sample preparation is important in the identification of saccharide compounds. The cases discussed here focus on bioscience, clinical, and food applications.

Transparent and Efficient Wood-Based Triboelectric Nanogenerators for Energy Harvesting and Self-Powered Sensing

Wood possesses several advantageous qualities including innocuity, low cost, aesthetic appeal, and excellent biocompatibility, and its naturally abundant functional groups and diverse structural forms facilitate functionalization modification. As the most sustainable bio-based material, the combination of wood with triboelectric nanogenerators (TENGs) stands poised to significantly advance the cause of green sustainable production while mitigating the escalating challenges of energy consumption. However, the inherent weak polarizability of natural wood limits its development for TENGs. Herein, we present the pioneering development of a flexible transparent wood-based triboelectric nanogenerator (TW-TENG) combining excellent triboelectrical properties, optical properties, and wood aesthetics through sodium chlorite delignification and epoxy resin impregnation. Thanks to the strong electron-donating groups in the epoxy resin, the TW-TENG obtained an open-circuit voltage of up to ~127 V, marking a remarkable 530% enhancement compared to the original wood. Furthermore, durability and stability were substantiated through 10,000 working cycles. In addition, the introduction of epoxy resin and lignin removal endowed the TW-TENG with excellent optical characteristics, with optical transmittance of up to 88.8%, while preserving the unique texture and aesthetics of the wood completely. Finally, we show the application prospects of TW-TENGs in the fields of self-power supply, motion sensing, and smart home through the demonstration of a TW-TENG in the charging and discharging of capacitors and the output of electrical signals in different scenarios.

Process design for acidic and alcohol based deep eutectic solvent pretreatment and high pressure homogenization of palm bunches for nanocellulose production

This research aimed to study on nanocellulose production from palm bunch using process design and cost analysis. Choline chloride based deep eutectic solvent pretreatment was selected for high-purity cellulose separation at mild condition, followed by nano-fibrillation using mechanical treatment. Three types of choline chloride-based deep eutectic solvents employing different hydrogen-bond donors (HBDs) namely lactic acid, 1,3-butanediol and oxalic acid were studied. The optimal cellulose extraction condition was choline chloride/lactic acid (ChLa80C) pretreatment of palm empty bunch at 80 °C followed by bleaching yielding 94.96%w/w cellulose content in product. Size reduction using ultrasonication and high-pressure homogenization produced nanocellulose at 67.12%w/w based on cellulose in raw material. Different morphologies of nanocellulose were tunable in the forms of nanocrystals, nano-rods and nanofibers by using dissimilar deep eutectic solvents. This work offered a sustainable and environmentally friendly process as well as provided analysis of DES pretreatment and overview operating cost for nanocellulose production. Application of nanocellulose for the fabrication of highly functional and biodegradable material for nanomedicine, electronic, optical, and micromechanical devices is achievable in the near future.

Facile production of cellulose nanofibers from raw elephant grass by an aluminum chloride-enhanced acidic deep eutectic solvent

To develop a greener and more efficient method for producing cellulose nanofibers (CNFs) from raw plants, an AlCl3-enhanced ternary deep eutectic solvent, DES2 (consisting of choline chloride, citric acid, and AlCl3·6H2O in a molar ratio of 1:0.4:0.08), was synthesized. Raw elephant grass (EG) was pretreated with DES2, followed by sodium chlorite (NaClO2) bleaching and ultrasonic disruption to extract high-performance CNFs. The DES2 and NaClO2 treatments effectively removed hemicellulose and lignin, achieving removal rates of 99.23 % and 99.62 %, respectively, while maintaining a cellulose content of 78.3 %. DES2 demonstrated easy recyclability and maintained excellent biomass pretreatment performance even after multiple cycles. Following a brief 30-min intermittent ultrasound treatment, the resulting CNFs demonstrated superior crystallinity, increased carboxyl content, and a narrower width distribution compared to CNFs obtained from AlCl3-free DES1. Optimized conditions at 110 °C yielded CNFs with 85.3 % crystallinity, 0.64 mmol/g carboxyl content, 5.15 nm width distribution, and excellent dispersion in water for at least six months. Additionally, CNFs enhanced the tensile strength of chia seed mucilage (CM) composite films, showing a significant improvement to 26.6 MPa, representing a 231.3 % increase over the control film. This study offers a promising approach for efficiently producing CNFs from raw plants.

In Vitro and In Vivo Protective Effects of Agaro-Oligosaccharides against Hydrogen Peroxide-Stimulated Oxidative Stress

In our previous research, we investigated the anti-inflammatory activity of the agaro-oligosaccharides prepared from the agar of Gracilaria lemaneiformis (AO). In the present study, in order to further explore the bioactivities of AO, the antioxidant activity of AO was investigated in vitro in Vero cells and in vivo in zebrafish. AO scavenged alkyl, 1,1-diphenyl-2-picrylhydrazyl, and hydroxyl radicals at the IC50 value of 4.86 ± 0.13, 3.02 ± 0.44, and 1.33 ± 0.05 mg/mL, respectively. AO significantly suppressed hydrogen peroxide (H2O2)-stimulated oxidative damage by improving cell viability. This happened via suppressing apoptosis by scavenging intracellular reactive oxygen species (ROS). Furthermore, the in vivo results displayed that AO protected zebrafish against H2O2-stimulated oxidative damage by reducing the levels of intracellular ROS, cell death, and lipid peroxidation in a dose-dependent manner. These results indicate that AO effectively alleviated in vitro and in vivo oxidative damage stimulated by H2O2, and suggest the potential of AO in the cosmetic and functional food industries.

Xylopentose production from crop residue employing xylanase enzyme

To produce xylo-oligosaccharides (XOS) from the agriculture waste, which included, green coconut and vegetable cocktail. The two pretreatment - hydrogen peroxide-acetic acid (HP-AC) and sodium hypochlorite-sodium hydroxide (SH-SH) - were used for this study. The optimal conditions for the pretreatment were 80 °C, 4.0 % NaClO, and 2 h, followed by 0.08 % NaOH, 55 °C, and 1 h. Further enzymatic hydrolysis of green coconut (GC) and vegetable cocktail (VC) were performed and found in case of GC, the best outcomes were observed. Different types of XOS were obtained from the treated biomass whereas a single type of XOS xylo-pentose was obtained in high quantity (96.44 % and 93.09 % from CG and VC respectively) with the production of other XOS < 2 %. This study presents a reasonably secure and economical method for turning secondary crop residue into XOS and fermentable sugars.

Revealing the key role of structural cross-link between lignin and polysaccharides during fast pyrolysis of lignocellulose

Lignin-carbohydrate complex (LCC) is the native existing form of major components in lignocellulose. In this study, the structural cross-link between lignin and polysaccharides in lignocellulose was quantitatively estimated with carboxymethylation-separation (CM-Sep) method, and its influence on lignocellulose pyrolysis was systematically investigated. The cross-linked lignin was found to positively correlate with the production of small molecules and furan derivatives while negatively affecting the generation of anhydrous sugars. Content of small molecules was increased by 97% while that of anhydrous sugars was decreased by 47% in pyrolytic products with levoglucosan yield lowered by 54 wt% in the existence of cross-linked lignin. Furthermore, the impact of cross-linked lignin was revealed to be significantly distinguished from free lignin. Impeded glycosidic end formation and boosted glycosyl ring scission as well as lignin fragmentation were responsible for the distinction. Excellent correlations between structural cross-link and lignocellulose pyrolytome could facilitate product prediction and process design.

Microwave irradiation assisted intensive and quick delignification of lignocellulosic biomass, and confirmation by spectral, morphological and crystallinity characterization

The purpose of this work was to use a microwave-assisted technique to improve and accelerate lignin removal from rice straw biomass. Using a Box-Behnken experimental design, the effect of four critical process parameters, viz. microwave power (480-800 W), irradiation time (4-12 min), bleaching solution concentration (0.4-3.0 %), and bleaching time (1-5 h) on the delignification (%) was investigated, and the process was optimised using response surface methodology. The experimental data best fitted a quadratic model with an R² of 0.9964. The optimized value of process parameters (in aforementioned sequence) was found to be 671 W, 8.66 min, 2.67 %, and 1 h respectively, for the best delignification of 93.51 percent.The absence of lignin peaks (1516 and 1739 cm^-1) was corroborated by deconstructed morphological structure and higher crystallinity in the optimised delignified sample (53.7 %).

Selective Catalytic Transfer Hydrogenation of Lignin to Alkyl Guaiacols Over NiMo/Al-MCM-41

Efficient deoxygenation of lignin-derived bio-oils is central to their adoption as precursors to sustainable liquid fuels in place of current fossil resources. In-situ catalytic transfer hydrogenation (CTH), using isopropanol and formic acid as solvent and in-situ hydrogen sources, was demonstrated over metal-doped and promoted MCM-41 for the depolymerization of oxygen-rich (35.85 wt%) lignin from Chinese fir sawdust (termed O-lignin). A NiMo/Al-MCM-41 catalyst conferred an optimal lignin-derived oil yield of 61.6 wt% with a comparatively low molecular weight (M_w =542 g mol^-1 , M_n =290 g mol^-1 ) and H/C ratio of 1.39. High selectivity to alkyl guaiacols was attributed to efficient in-situ hydrogen transfer from isopropanol/formic acid donors, and a synergy between surface acid sites in the Al-doped MCM-41 support and reducible Ni/Mo species, which improved the chemical stability and quality of the resulting lignin-derived bio-oils.

Boosting levoglucosan and furfural production from corn stalks pyrolysis via electro-assisted seawater pretreatment

The seawater electrochemical pretreatment (ECP) was employed to upgrade the bio-oil of corn stalk in the paper. The seawater and its simulants were used as electrolytes without additional reagents. Moreover, the effect of seawater ECP under different conditions on the products distribution of pyrolysis bio-oil of pretreated corn stalks was investigated. The results showed that pretreatment effectively deconstructed the lignin and made cellulose exposed. Especially, under the optimum conditions (3.5 wt% NaCl, 15 V and 4 h), most of lignin was destroyed, and cellulose and hemicellulose were remained in residual solids. Furthermore, the levoglucosan and furfural were enriched in the pyrolysis bio-oil of corn stalk after seawater ECP, reaching 23.22 % and 14.14 %, respectively. Overall, this work presented a novel and green pretreatment process to optimize the components and structure of corn stalks as well as upgrade the bio-oil of corn stalk pyrolysis.