Structural Characterization of Lignin and Lignin-Carbohydrate Complex (LCC) from Ginkgo Shells (Ginkgo biloba L.) by Comprehensive NMR Spectroscopy

Formation and Chemical Structure of Carbon-13 Tracer Lignin-Carbohydrate Complexes (LCCs) During Kraft Pulping

In this study, a modified synthetic method for labeling a lignin dimer (guaiacylglycerol-β-guaiacyl ether-[α-13C]) was developed. The chemical structure of the target compound was analyzed using 1H-NMR, 13C-NMR, and other analytical techniques. Then, the 13C-labeled phenolic lignin model compound was subjected to kraft pulping in the presence of xylose. Finally, the resulting reaction products were fractionated using acid precipitation and ethyl acetate extraction, and each fraction was analyzed by carbon-13 nuclear magnetic resonance (13C-NMR) and two-dimensional heteronuclear multiple quantum coherence (HMQC) spectroscopy. This aimed to investigate the occurrence of lignin-carbohydrate complexes (LCCs) during the conventional kraft pulping process. Employing ethanol as the reaction medium facilitated the bromination of 4-acetylguaiacol-[α-13C], resulting in a homogeneous reaction and significantly improving the yield of the brominated product to over 90%. Additionally, kraft pulping of the phenolic lignin model compound in the presence of xylose led to the occurrence of minor quantities of benzyl ether-type lignin-carbohydrate complex (LCC) structures, which were predominantly detected in the ethyl acetate extractive.

Switchable Solvent for Separation and Extraction of Lignin from Lignocellulose Biomass: An Investigation of Chemical Structure and Molecular Weight

Lignin, the most abundant natural aromatic polymer, holds considerable promise for applications in various industries. The primary obstacle to the valorization of lignin into useful materials is its low molecular weight and diminished chemical reactivity, attributable to its intricate structure. This study aimed to treat lignocellulosic biomass using a switchable solvent (DBU-HexOH/H2O) derived from the non-nucleophilic superbase 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU), which efficiently separates and extracts lignin from poplar wood. Additionally, it sought to characterize fundamental properties of the extracted switchable solvent lignin (SSL) and propose a mechanism for its separation. In comparison to milled wood lignin, SSL exhibits a greater molecular weight, superior homogeneity, and enhanced stability. The SSL sample was analyzed using spectroscopies including infrared spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The findings indicated that the structure of SSL was preserved, with the switchable solvent primarily cleaving the C-C and α-O-4 bonds, resulting in a low hydroxyl content, an elevated H/C ratio, and a reduced O/C ratio. The SSL was successfully prepared to lignin nanoparticles (LNPs) with size range of 531-955 nm. This paper presents a technique for processing lignocellulosic biomass using a switchable solvent, highlighting advancements in lignin's structure and enhancing its use in the chemical sector.

Silver-Catalyzed Aqueous Electrochemical Valorization of Soda Lignin into Aliphatics and Phenolics

Transitioning from crude oil to renewable sources of carbon-based chemicals is critical for advancing sustainable development. Lignin, a wood-derived biomacromolecule, holds great potential as a renewable feedstock, but efficient depolymerization and dearomatization methods are required to fully unlock its potential. In this investigation, we present a silver-catalyzed aqueous electrocatalytic method for the selective depolymerization and partial dearomatization of soda lignin under mild, ambient conditions. Utilizing a water/sodium carbonate solvent system and a silver electrode to mediate the electrochemical reduction, we achieved significant lignin depolymerization over reaction times ranging from 5 to 20 h. Analysis by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) revealed sodium levulinate, sodium acetate, and sodium formate as the main aliphatic products, alongside various aromatic species in the depolymerized lignin products (DL). This selective conversion of lignin into both valuable aromatic compounds and reactive aliphatic intermediates offers promising opportunities for further synthesis of a wide range of organic chemicals, contributing to the development of a more sustainable and circular economy.

Comprehensive insights of pretreatment strategies on the structures and bioactivities variation of lignin-carbohydrate complexes

Introduction: Due to its unique structural features and bioactivities, the lignin-carbohydrate complex (LCC) displays great potential in vast industrial applications. However, the elucidation of how various pretreatment methods affect the structure and bioactivities remains unaddressed. Method: The three pretreatment methods were systematically studied on the variations of structures and bioactivities, and the Gramineae plant, i.e., wheat straw, was adopted in this study. The structures and bioactivities variation caused by different pretreatments were studied in detail. Result and Discussion: The results showed that compared to physical or chemical pretreatments, biological pretreatment was the most effective approach in improving the bioactivities of LCC. The LCC from biological pretreatment (enzymatic hydrolysis, ELCC4) had more functional groups while the lower weight-average molecular weight (Mw) and polydispersity index (PDI) were well-endowed. The highest antioxidant abilities against ABTS and DPPH of ELCC4 were high up to 95% and 84%, respectively. Furthermore, ELCC4 also showed the best ultraviolet (UV)-blocking rate of 96%, which was increased by 6% and 2% compared to LCC8 (physical pretreatment) and LLCC4 (chemical pretreatment). This work prospectively boosts the understanding of pretreatment strategies on the structures and bioactivities variation of LCC and facilitates its utilization as sustainable and biologically active materials in various fields.

Enhancing Liquefaction Efficiency: Exploring the Impact of Pre-Hydrolysis on Hazelnut Shell (Corylus avellana L.)

Hazelnut shells (HS), scientifically known as Corylus avellana L. shells, are waste produced by companies that process nuts. The main objective of this study was to find an efficient way to maximize the chemical potential of HS by solubilizing the hemicelluloses, which could then be used to recover sugars and, at the same time, increase the lignin content of this material to produce adhesives or high-strength foams. In order to optimize the pre-hydrolysis process, two different temperatures (160 and 170 °C) and times varying from 15 to 180 min were tested. All the remaining solid materials were then liquefied using polyalcohols with acid catalysis. The chemical composition of hazelnut shells was determined before and after the pre-hydrolysis. All of the process was monitored using Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR) by determining the spectra of solids and liquids after the pre-hydrolysis and liquefaction steps. The highest solubilization of hazelnut shells was found for 170 °C and 180 min, resulting in a 25.8% solubilization. Chemical analysis after the hydrolysis process showed a gradual increase in the solubilization of hemicelluloses as both the temperature and time of the reactor were increased. Simultaneously, the percentages of α-cellulose and lignin in the material also increased with rises in temperature and duration. FTIR-ATR allowed for the detection of significant spectral changes in the hazelnut shells from their initial state to the solid residue and further into the liquefied phase. This confirmed that pre-hydrolysis was effective in enhancing the chemical composition of the material, making it more suitable for the production of adhesives, polyurethane foams, or in the production of bioplastics and composite materials, combined with other biopolymers or synthetic polymers to enhance the mechanical properties and biodegradability of the resulting materials.

Extraction of super high-yield lignin-carbohydrate complexes from rice straw without compromising cellulose hydrolysis

Lignin-carbohydrate complexes (LCC) that exhibit both structural advantages of lignin and carbohydrates are promising amphiphilic biopolymers, but the extraction is challenged by its liable chemical bond cleavage between lignin and carbohydrates. This work proposed a facile chemical route to integrating the production of water-insoluble (WIS LCC) and water-soluble LCC (WS LCC) into the emerging deep eutectic solvent (DES) biorefinery at mild conditions. The tailored mechanochemical fractionation process of ball milling assisted aqueous alkaline DES could extract 24.2 % LCC in total, with the co-production of a highly hydrolysable cellulose fraction (98.7 % glucose conversion). The resulting LCC exhibited considerably high contents of β-O-4, phenyl glycoside, and ferulic acid linkage bonds. When 100 g starting straw was subjected to this technique route, 9.1 g WIS LCC, 15.1 g WS LCC and 45.5 g glucose were cascaded produced. It was proposed that the selective disruption of hydrogen bonding entangled network and the quasi-state dissolution of the whole biomass allowed the subsequent cascade fractionation of WIS LCC, WS LCC and highly hydrolysable cellulose through solution property adjustment. This work showed a promising approach for LCC production with high yield without compromising cellulose conversion potential, which has been challenging in the current lignocellulose biorefinery.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Effects of the Structure and Molecular Weight of Alkali-Oxygen Lignin Isolated from Rice Straw on the Growth of Maize Seedlings

The abundant and low-cost features of lignin in combination with its natural activities make it a fascinating biopolymer for valorization, especially, in agriculture as an active plant growth regulator. However, the structure-activity relationship of lignin in regulating plant growth and metabolism remains unclear. In this work, rice-straw-based low-molecular-weight (LWM, 1860 Da) and high-molecular-weight (HMW, 6840 Da) alkali-oxygen lignins are structurally and comparatively investigated to understand their effects on the growth and metabolism of maize seedlings. The results indicate that LMW lignin at 150 mg·L^-1 displays early growth stimulation in maize. Under the optimal concentration of LMW lignin (25 mg·L^-1), the growth of maize shoot is ∼83% higher than that of the control one. Furthermore, LMW lignin also has a positive effect on the upregulation of photosynthetic pigment, carbohydrate, and protein synthesis. In contrast, HMW lignin shows an overall inhibitory effect on the above-mentioned biochemical parameters. Based on the structural characterization, LMW lignin contains a higher syringyl/guaiacyl ratio (0.78) and carboxyl content (1.64 mmol·g^-1) than HMW lignin (0.43 and 1.27 mmol·g^-1, respectively), which demonstrates that methoxyl and carboxyl content of lignin may play a decisive role in seedling growth.

Biogas and Biomethane Production and Usage: Technology Development, Advantages and Challenges in Europe

In line with the low-carbon strategy, the EU is expected to be climate-neutral by 2050, which would require a significant increase in renewable energy production. Produced biogas is directly used to produce electricity and heat, or it can be upgraded to reach the “renewable natural gas”, i.e., biomethane. This paper reviews the applied production technology and current state of biogas and biomethane production in Europe. Germany, UK, Italy and France are the leaders in biogas production in Europe. Biogas from AD processes is most represented in total biogas production (84%). Germany is deserving for the majority (52%) of AD biogas in the EU, while landfill gas production is well represented in the UK (43%). Biogas from sewage sludge is poorly presented by less than 5% in total biogas quantities produced in the EU. Biomethane facilities will reach a production of 32 TWh in 2020 in Europe. There are currently 18 countries producing biomethane (Germany and France with highest share). Most of the European plants use agricultural substrate (28%), while the second position refers to energy crop feedstock (25%). Sewage sludge facilities participate with 14% in the EU, mostly applied in Sweden. Membrane separation is the most used upgrading technology, applied at around 35% of biomethane plants. High energy prices today, and even higher in the future, give space for the wider acceptance of biomethane use.

Thermal fluctuation and conformational effects on NMR parameters in β-O-4 lignin dimers from QM/MM and machine-learning approaches

Advanced solid-state and liquid-state nuclear magnetic resonance (NMR) approaches have enabled high throughput information about functional groups and types of bonding in a variety of lignin fragments from degradation processes and laboratory synthesis. The use of quantum chemical (QM) methods may provide detailed insight into the relationships between NMR parameters and specific lignin conformations and their dynamics, whereas a rapid prediction of NMR properties could be achieved by combining QM with machine-learning (ML) approaches. In this study, we present the effect of conformations of β-O-4 linked lignin guaiacyl dimers on ¹³C and ¹H chemical shifts while considering the thermal fluctuations of the guaiacyl dimers in water, ethanol and acetonitrile, as well as their binary 75 wt% aqueous solutions. Molecular dynamics and QM/MM simulations were used to describe the dynamics of guaiacyl dimers. The isotropic shielding of the majority of the carbon nuclei was found to be less sensitive toward a specific conformation than that of the hydrogen nuclei. The largest ¹H downfield shifts of 4-6 ppm were established in the hydroxy groups and the rings in the presence of organic solvent components. The Gradient Boosting Regressor model has been trained on 60% of the chemical environments in the dynamics trajectories with the NMR isotropic shielding (σ_iso), computed with density-functional theory, for lignin atoms. The high efficiency of this machine-learning model in predicting the remaining 40% σ_iso(¹³C) and σ_iso(¹H) values was established.

Physical and Chemical Properties of Acacia mangium Lignin Isolated from Pulp Mill Byproduct for Potential Application in Wood Composites

The efficient isolation process and understanding of lignin properties are essential to determine key features and insights for more effective lignin valorization as a renewable feedstock for the production of bio-based chemicals including wood adhesives. This study successfully used dilute acid precipitation to recover lignin from black liquor (BL) through a single-step and ethanol-fractionated-step, with a lignin recovery of ~35% and ~16%, respectively. The physical characteristics of lignin, i.e., its morphological structure, were evaluated by scanning electron microscopy (SEM). The chemical properties of the isolated lignin were characterized using comprehensive analytical techniques such as chemical composition, solubility test, morphological structure, Fourier-transform infrared spectroscopy (FTIR), 1H and 13C Nuclear Magnetic Resonance (NMR), elucidation structure by pyrolysis-gas chromatography-mass spectroscopy (Py-GCMS), and gel permeation chromatography (GPC). The fingerprint analysis by FTIR detected the unique peaks corresponding to lignin, such as C=C and C-O in aromatic rings, but no significant differences in the fingerprint result between both lignin. The 1H and 13C NMR showed unique signals related to functional groups in lignin molecules such as methoxy, aromatic protons, aldehyde, and carboxylic acid. The lower insoluble acid content of lignin derived from fractionated-step (69.94%) than single-step (77.45%) correlated to lignin yield, total phenolic content, solubility, thermal stability, and molecular distribution. It contradicted the syringyl/guaiacyl (S/G) units' ratio where ethanol fractionation slightly increased syringyl unit content, increasing the S/G ratio. Hence, the fractionation step affected more rupture and pores on the lignin morphological surface than the ethanol-fractionated step. The interrelationships between these chemical and physicochemical as well as different isolation methods were investigated. The results obtained could enhance the wider industrial application of lignin in manufacturing wood-based composites with improved properties and lower environmental impact.

Green Fabrication Approaches of Lignin Nanoparticles from Different Technical Lignins: A Comparison Study

The production of lignin nanoparticles (LNPs) has emerged as a way to overcome the highly variable and complex molecular structure of lignin. It can offer morphological control of the lignin polymer, allowing the formation of stable LNP dispersions in aqueous media, while increasing the potential of lignin for high-value applications. However, the polydispersity and morphology of LNPs varies depending on the lignin grade and preparation method, and a systematic comparison using different technical lignins is lacking. In this study, it was attempted to find a green fabrication method with a distinct solvent fractionation of lignin to prepare LNPs using three different technical lignins as starting polymers: BLN birch lignin (hardwood, BB), alkali Protobind 1000 (grass, PB), and kraft LignoBoost (softwood, LB). For that, three anti-solvent precipitation approaches to prepare LNPs were systematically compared: 70 % aqueous ethanol, acetone/water (3 : 1) and NaOH as the lignin solvent, and water/aqueous HCl as the anti-solvent. Among all these methods, the acetone/water (3 : 1) approach allowed production of homogeneous and monodisperse LNPs with a negative surface charge and also spherical and smooth surfaces. Overall, the results revealed that the acetone/water (3 : 1) method was the most effective approach tested to obtain homogenous, small, and spherical LNPs from the three technical lignins. These LNPs exhibited an improved stability at different ionic strengths and a wider pH range compared to the other preparation methods, which can greatly increase their application in many fields, such as pharmaceutical and food sciences.

Monitoring transformation of two tropical lignocellulosics and their lignins after residence in Benin soils

Thermally assisted Hydrolysis and Methylation (THM), and 2D-heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) spectroscopy were used to monitor the transformation of ramial chipped wood (RCW) from Gmelina arborea and Sarcocephalus latifolius, together with their organosolv lignins, following soil incubation in Benin (West Africa). Mesh litterbags containing RCW were buried in soils (10 cm depth) and were retrieved after 0, 6, 12 and 18 months of field incubation. Chemical analysis showed that total carbohydrate content decreased, while total lignin content increased as RCW decomposition progressed. Ash and mineral content of RCW increased significantly after 18 months of decomposition in soil. Significant N-enrichment of the RCW was determined following 18 months incubation in soils, reaching 2.6 and 1.9 times the initial N-content for G. arborea and S. latifolius. Results of THM showed that the S + G sum, corresponding to lignins, increased with RCW residence time in the soils, in contrast to the response of compounds derived from carbohydrates, the sum of which decreased. Remarkably, lignin interunit linkages, most notably β-O-4' aryl ethers, β-β' resinol, β-5' phenylcoumaran and p-PCA p-coumarate, survived after 18 months in the soil, despite their gradual decrease over the duration of the experiment.

Protective Effects of Lignin-Carbohydrate Complexes from Wheat Stalk against Bisphenol a Neurotoxicity in Zebrafish via Oxidative Stress

Lignin-carbohydrate complexes (LCCs) from different lignocellulosic biomass have shown biological qualities as antioxidant and immunostimulant. By contrast, the application of LCCs as protectant against neurotoxicity caused by different compounds is scarce. In this work, two kinds of LCCs with carbohydrate-rich and lignin-rich fractions were obtained from wheat stalk and used to protect against BPA-neurotoxicity in zebrafish. The results showed that BPA at a concentration of 500 µg/L results in neurotoxicity, including significant behavioral inhibition, and prevents the expression of central nervous system proteins in transgenic zebrafish models (Tg (HuC-GFP)). When the zebrafish was treated by LCCs, the reactive oxygen species of zebrafish decreased significantly with the change of antioxidant enzymes and lipid peroxidation, which was due to the LCCs' ability to suppress the mRNA expression level of key genes related to nerves. This is essential in view of the neurotoxicity of BPA through oxidative stress. In addition, BPA exposure had negative effects on the exercise behavior, the catalase (CAT) and superoxide dismutase (SOD) activity, and the larval development and gene expression of zebrafish larvae, and LCC preparations could recover these negative effects by reducing oxidative stress. In zebrafish treated with BPA, carbohydrate-rich LCCs showed stronger antioxidant activity than lignin-rich LCCs, showing their potential as a neuroprotective agents.

Solvothermal-Based Lignin Fractionation From Corn Stover: Process Optimization and Product Characteristics

Fractionation of lignocellulosic is a fundamental step in the production of value-added biobased products. This work proposes an initiative to efficiently extract lignin from the corn stover using a single-step solvothermal fractionation in the presence of an acid promoter (H2SO4). The organic solvent mixture used consists of ethyl acetate, ethanol, and water at a ratio of 30: 25:45 (v/v), respectively. H2SO4 was utilized as a promoter to improve the performance and selectivity of lignin removal from the solid phase and to increase the amount of recovered lignin in the organic phase. The optimal conditions for this extraction, based on response surface methodology (RSM), are a temperature of 180°C maintained for 49.1 min at an H2SO4 concentration of 0.08 M. The optimal conditions show an efficient reaction with 98.0% cellulose yield and 75.0% lignin removal corresponding to 72.9% lignin recovery. In addition, the extracted lignin fractions, chemical composition, and structural features were investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (2D-HSQC NMR). The results indicate that the recovered lignin primarily contains a β-O-4 linking motif based on 2D-HSQC spectra. In addition, new C-C inter-unit linkages (i.e., β-β, and β-5) are not formed in the recovered lignin during H2SO4-catalyzed solvothermal pretreatment. This work facilitates effective valorization of lignin into value-added chemicals and fuels.

Process development for tall oil lignin production

The aim of this work was to study the production and characterization of tall oil lignin (TOL) from tall oil soap (TOS) of the kraft pulping process following a new process (i.e., LignoTall). Also, the properties of the TOL and kraft lignin (KL) produced via LignoForce technology were compared. Although TOL and KL were generated from the same black liquor and softwood species, they had remarkably different characteristics, confirming the impact of the production methods on the physicochemical properties of the isolated lignin. TOL had higher molecular weight, O/C elemental ratio, sulfur content, and carboxylate-OH content but lower methoxy group content than did KL. The high sulfur group content (7.3%) of TOL can be very useful for the vulcanization process. Moreover, the high carboxylate-OH content of TOL (0.56 mmol/g) is desirable for its utilization in epoxy resin production.

Isolating High Antimicrobial Ability Lignin From Bamboo Kraft Lignin by Organosolv Fractionation

Lignin from different biomasses possess biological antioxidation and antimicrobial activities, which depend on the number of functional groups and the molecular weight of lignin. In this work, organosolv fractionation was carried out to prepare the lignin fraction with a suitable structure to tailor excellent biological activities. Gel permeation chromatography (GPC) analysis showed that decreased molecular weight lignin fractions were obtained by sequentially organosolv fractionation with anhydrous acetone, 50% acetone and 37.5% hexanes. Nuclear magnetic resonance (NMR) results indicated that the lignin fractions with lower molecular weight had fewer substructures and a higher phenolic hydroxyl content, which was positively correlated with their antioxidation ability. Both of the original lignin and fractionated lignins possessed the ability to inhibit the growth of Gram-negative bacteria (Escherichia coli and Salmonella) and Gram-positive bacteria (Streptococcus and Staphylococcus aureus) by destroying the cell wall of bacteria in vitro, in which the lignin fraction with the lowest molecular weight and highest phenolic hydroxyl content (L3) showed the best performance. Besides, the L3 lignin showed the ability to ameliorate Escherichia coli-induced diarrhea damages of mice to improve the formation of intestinal contents in vivo. These results imply that a lignin fraction with a tailored structure from bamboo lignin can be used as a novel antimicrobial agent in the biomedical field.

Accessing the position-specific 18O/16O ratios of lignin monomeric units from higher plants with highly selective hydrogenolysis followed by GC/Py/IRMS analysis

The ¹⁸O/¹⁶O of lignin at bulk, molecular and positional levels can be used to extract valuable information about climate, plant growth environment, plant physiology, and plant metabolism. Access to the individual oxygen isotope compositions (δ¹⁸O) in the lignin monomeric units is, however, challenging as depolymerization of lignin to release the monomeric units may cause isotope fractionation. We have developed a novel method to measure the δ¹⁸O of the three oxygens (O-3, O-4 and O-5) attached to the aromatic ring of the monomeric units (bearing no oxygen in their side chains) releasable by highly selective W₂C/AC (tungsten carbide supported by activated carbon)-catalyzed hydrogenolysis of lignin. O-4 is obtained by measuring the δ¹⁸O of H-type monomeric unit, while O-3 and O-5 can be calculated following isotope mass balance between H, G and S-type monomeric units measurable simultaneously with GC/Py/IRMS (gas chromatography-pyrolysis-isotope ratio mass spectrometry). The measurement precisions are better than 1.15 mUr and 4.15 mUr at molecular and positional levels, respectively. It was shown that there were a δ¹⁸O_H > δ¹⁸O_G > δ¹⁸O_S isotopic order in the herbaceous plant lignin and an (inclusive) opposite order in woody plant lignin. Such differences in isotopic order is likely to be caused by the fact that both L-tyrosine, which carries an ¹⁸O-enriched leaf water signal, and L-phenylalanine, which carries mainly a molecular O₂ isotopic signal, serve as the precursors for lignin biosynthesis in herbaceous plants while only the latter serves as precursor for lignin biosynthesis in woody plants. We have highlighted the potential application of such molecular and positional levels isotopic signals in plant physiological, metabolic, lignin biosynthetic and climate studies.

Prediction of methane production from co-digestion of lignocellulosic biomass with sludge based on the major compositions of lignocellulosic biomass

In the present study, the simplex lattice mixture design method was adopted to design the artificial biomass with different ratios of three major components (cellulose, hemicellulose, lignin). The methane yield from the co-digestion of the artificial/ natural biomass (corn stover, wheat stover, rice straw, and peanut stalk) samples with the mixed sludge at the mixture ratio of 1:1 based on total solid (TS) content was recorded for 50 days. The original mathematical prediction models for estimating the cumulative methane production, maximum methane production rate, and lag phase time were established based on the experimental results from the co-digestion of artificial biomass with sludge. To investigate the influence of the structural features of biomass and interactions among the components of biomass which contributing to the inhibition of methane production, the macroscopic factor (MF) was proposed. The mathematical models which revealed the relationship between MF and the methane production parameters were developed by the combination of the prediction results from the original mathematical prediction model and experimental results from the co-digestion of natural biomass with sludge. Modification of the original mathematical prediction models was carried out by considering MF. After modification, the relative error (RE) and root mean square error (RMSE) of the prediction model for cumulative methane production were declined from 19.00 to 30.18% and 42.38 mL/g VS_added to that of - 1.93~7.14% and 4.36 mL/g VS_added, respectively.

A review of NMR analysis in polysaccharide structure and conformation: Progress, challenge and perspective

Nuclear magnetic resonance (NMR) has been widely used as an analytical chemistry technique to investigate the molecular structure and conformation of polysaccharides. Combined with 1D spectra, chemical shifts and coupling constants in both homo- and heteronuclear 2D NMR spectra are able to infer the linkage and sequence of sugar residues. Besides, NMR has also been applied in conformation, quantitative analysis, cell wall in situ, degradation, polysaccharide mixture interaction analysis, as well as carbohydrates impurities profiling. This review summarizes the principle and development of NMR in polysaccharides analysis, and provides NMR spectra data collections of some common polysaccharides. It will help to promote the application of NMR in complex polysaccharides of biochemical interest, and provide valuable information on commercial polysaccharide products.

Lignin-derived (nano)materials for environmental pollution remediation: Current challenges and future perspectives

The supply of affordable drinking and sufficiently clean water for human consumption is one of the world's foremost environmental problems and a large number of scientific research works are addressing this issue Various hazardous/toxic environmental contaminants in water bodies, both inorganic and organic (specifically heavy metals and dyes), have become a serious global problem. Nowadays, extensive efforts have been made to search for novel, cost effective and practical biosorbents derived from biomass resources with special attention to value added, biomass-based renewable materials. Lignin and (nano)material adorned lignin derived entities can proficiently and cost effectively remove organic/inorganic contaminants from aqueous media. As low cost of preparation is crucial for their wide applications in water/wastewater treatment (particularly industrial water), future investigations must be devoted to refining and processing the economic viability of low cost, green lignin-derived (nano)materials. Production of functionalized lignin, lignin supported metal/metal oxide nanocomposites or hydrogels is one of the effective approaches in (nano)technology. This review outlines recent research progresses, trends/challenges and future prospects about lignin-derived (nano)materials and their sustainable applications in wastewater treatment/purification, specifically focusing on adsorption and/or catalytic reduction/(photo)degradation of a variety of pollutants.

Matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (negative ion mode) of French Oak lignin: A novel series of lignin and tricin derivatives attached to carbohydrate and shikimic acid moieties

RATIONALE

We report the top-down lignomic analysis of the virgin released lignin (VRL) small oligomers obtained from French Oak wood.

METHODS

We have used MALDI-TOF-MS in the negative ion mode for the analysis of the complex mixture of lignin oligomers extracted from French Oak wood. High-energy CID-TOF/TOF-MS/MS analyses were used to support the postulated precursor ion structures.

RESULTS

Twenty compounds were identified using MALDI-TOF-MS/MS of the VRL extracted from French Oak wood: seven tricin derivatives and/or flavonoids, three syringylglycerol derivatives, two syringol derivatives, two flavonolignin derivatives, and six miscellaneous compounds: luteoferol, lariciresinol isomer, 5-hydroxy guaiacyl derivative, syringyl -C₁₀ H₁₀ O₂ dimer, trihydroxy benzaldehyde derivative, and aryl tetralin lignan derivative. Most of the identified compounds were in the form of carbohydrate and/or shikimic acid complexes.

CONCLUSIONS

The analysis of this complex mixture led to the identification of a series of lignin dimers, novel lignin-carbohydrate complexes (LCC), and unique tricin derivatives linked to different types of carbohydrates and shikimic acid moieties. This finding supports the presence of lignin-carbohydrate complexes in the isolated VRL. These analyses also showed that French Oak lignin is abundant in syringol moieties present in the lignin syringyl units or tricin derivatives. Moreover, the identification of some lignin-carbohydrate and/or flavonoid-shikimic acid complexes could provide new insight into the relationship between the biosynthesis of lignin and tricin.

Isolation and Identification of a Novel Anti-protein Aggregation Activity of Lignin-Carbohydrate Complex From Chionanthus retusus Leaves

Lignin-carbohydrate complex (LCC) is the biological macromolecule that has been demonstrated to exert multiple biological functions, including antioxidant, anti-inflammation and anti-tumorigenesis, which support its broad application in the bioengineering field. However, it remains elusive the involvements of LCC in human neurological disorders, especially those with the overproduction of reactive oxygen species (ROS), such as spinocerebellar ataxias (SCAs). In this study, we found a previously undetermined anti-protein aggregation activity of LCC. Initially, two individual LCC preparations and carbohydrate-free lignin were isolated from the water-extracted waste residues of Chionanthus retusus (C. retusus) tender leaves. The chemical compositional analysis revealed that lignin (61.5%) is the predominant constituent in the lignin-rich LCC (LCC-L-CR), whereas the carbohydrate-rich LCC (LCC-C-CR) is mainly composed of carbohydrate (60.9%) with the xylan as the major constituent (42.1%). The NMR structural characterization showed that LCC-L-CR preparation is enriched in benzyl ether linkage, while phenyl glycoside is the predominant type of linkage in LCC-C-CR. Both LCC and lignin preparations showed antioxidant activities as exemplified by their abilities to scavenge free radicals in cultured mammalian cells and ROS in zebrafish. We further demonstrated a pronounced capability of LCC-L-CR in inhibiting the aggregation of expanded Ataxin-3, disease protein of SCA type 3, in human neuronal cells. Taken together, our study highlights the antioxidant and novel anti-protein aggregation activities of the C. retusus tender leaves-derived LCC.

Single and Mixed Feedstocks Biorefining: Comparison of Primary Metabolites Recovery and Lignin Recombination During an Alkaline Process

Cannabis sp. and Euphorbia sp. are potential candidates as indoor culture for the extraction of their high value-added metabolites for pharmaceutical applications. Both residual lignocellulosic materials recovered after extraction are studied in the present article as single or mixed feedstocks for a closed-loop bioprocesses cascade. An alkaline process (NaOH 3%, 30 min 160°C) is performed to separate the studied biomasses into their main components: lignin and cellulose. Results highlight the advantages of the multi-feedstocks approach over the single biomass in term of lignin yield and purity. Since the structural characteristics of lignin affect the potential applications, a particular attention is drawn on the comprehension of lignin structure alteration and the possible interaction between them during single or mixed feedstocks treatment. FTIR and 2D-NMR spectra revealed similar profiles in term of chemical functions and structure rather than novel chemical bonds formation inexistent in the original biomasses. In addition, thermal properties and molecular mass distribution are conserved whether hemp or euphorbia are single treated or in combination. A second treatment was applied to investigate the effect of prolonged treatment on extracted lignins and the possible interactions. Aggregation, resulting in higher molecular mass, is observed whatever the feedstocks combination. However, mixing biomass does not affect chemical structures of the end product. Therefore, our paper suggests the possibility of gathering lignocellulosic residues during alkali process for lignin extraction and valorization, allowing to forecast lignin structure and make assumptions regarding potential valorization pathway.

Dataset on structure-antioxidant activity relationship of active oxygen catalytic lignin and lignin-carbohydrate complex

The data presented in this article are related to the research article entitled “Structure-antioxidant activity relationship of active oxygen catalytic lignin and lignin-carbohydrate complex” (Jiang et al.). It supplements the article with thermostability of milled wood lignin (MWL) and alkali-oxygen lignin (AOL), main substructures of lignin in rice straw, main products and yield of nitrobenzene oxidation of lignin-carbohydrate complexes (LCCs), Fourier transform infrared spectroscopy of LCCs, radical (ABTS·) scavenging ability of lignins and signal assignment of lignins and LCCs in nuclear magnetic resonance spectra (¹H, ¹³C, 2D HSQC NMR). The dataset is made publicly available and can be useful for extending the structural and bioactive research and critical analyses of lignin and LCC.

Insight into Pretreatment Methods of Lignocellulosic Biomass to Increase Biogas Yield: Current State, Challenges, and Opportunities

Lignocellulosic biomass is recalcitrant due to its heterogeneous structure, which is one of the major limitations for its use as a feedstock for methane production. Although different pretreatment methods are being used, intermediaries formed are known to show adverse effect on microorganisms involved in methane formation. This review, apart from highlighting the efficiency and limitations of the different pretreatment methods from engineering, chemical, and biochemical point of views, will discuss the strategies to increase the carbon recovery in the form of methane by way of amending pretreatments to lower inhibitory effects on microbial groups and by optimizing process conditions.

Sulfonated Lignin-g-Styrene Polymer: Production and Characterization

Among sustainable alternatives for replacing fossil-based chemicals, lignin is widely available on earth, albeit the least utilized component of biomass. In this work, lignin was polymerized with styrene in aqueous emulsion systems. The reaction afforded a yield of 20 wt % under the conditions of 100 g/L lignin concentration, pH 2.5, 0.35 mol/L sodium dodecyl sulfate concentration, 5 mol/mol styrene/lignin ratio, 5 wt % initiator, 90 °C, and 2 h. The lignin-g-styrene product under the selected conditions had a grafting degree of 31 mol % of styrene, which was determined by quantitative proton nuclear magnetic resonance (NMR). The solvent addition to the reaction mixture and deoxygenation did not improve the yield of the polymerization reaction. The produced lignin-g-styrene polymer was then sulfonated using concentrated sulfuric acid. By introducing sulfonate group on the lignin-g-styrene polymers, the solubility and anionic charge density of 92 wt % (in a 10 g/L solution) and -2.4 meq/g, respectively, were obtained. Fourier-transform infrared (FTIR), static light scattering, two-dimensional COSY NMR, elemental analyses, and differential scanning calorimetry (DSC) were also employed to characterize the properties of the lignin-g-styrene and sulfonate lignin-g-styrene products. Overall, sulfonated lignin-g-styrene polymer with a high anionicity and water solubility was produced.