Understanding the relationship between the structural properties of lignin and their biological activities

Development of Ultraviolet-Shielding Bamboo/Silk Fibroin Hybrid Films with Good Mechanical Properties: A Proof Study on Human Keratinocyte Cells

In this study, we report the preparation and characterization of water-stable films with UV-shielding and good mechanical properties, exploiting the synergistic effect of regenerated silk fibroin and bamboo-derived cellulose. Silk fibroin (SF)/bamboo (B) hybrid films are achieved by solubilizing both silk and bamboo fibers in formic acid with added CaCl2. Infrared spectroscopy indicates that SF, when combined with bamboo, undergoes a conformational transition, providing evidence of an increase in SF crystallinity. Exploiting the intrinsic absorption of SF in the ultraviolet region, UV-Vis spectroscopy was used to assess the glass transition temperature (Tg) of SF/B films, showing a decrease in Tg by increasing the SF content. The addition of 10 wt% SF to the B matrix improved the elastic modulus by about 10% while conserving the strain at break with respect to the neat B films, increasing the UV shielding properties, while water absorption suggested the material's hydrophilic and swelling capacity even after one month. The hybrid films showed, under solar irradiation, a photoprotective behavior on keratinocyte human cells by increasing cellular viability. These findings may find potential applications in functional fabrics.

Green Extraction of Reed Lignin: The Effect of the Deep Eutectic Solvent Composition on the UV-Shielding and Antioxidant Properties of Lignin

Lignin, the second most abundant natural polymer, is a by-product of the biorefinery and pulp and paper industries. This study was undertaken to evaluate the properties and estimate the prospects of using lignin as a by-product of the pretreatment of common reed straw (Phragmites australis) with deep eutectic solvents (DESs) of various compositions: choline chloride/oxalic acid (ChCl/OA), choline chloride/lactic acid (ChCl/LA), and choline chloride/monoethanol amine (ChCl/EA). The lignin samples, hereinafter referred to as Lig-OA, Lig-LA, and Lig-EA, were obtained as by-products after optimizing the conditions of reed straw pretreatment with DESs in order to improve the efficiency of subsequent enzymatic hydrolysis. The lignin was studied using gel penetration chromatography, UV-vis, ATR-FTIR, and 1H and 13C NMR spectroscopy; its antioxidant activity was assessed, and the UV-shielding properties of lignin/polyvinyl alcohol composite films were estimated. The DES composition had a significant impact on the structure and properties of the extracted lignin. The lignin's ability to scavenge ABTS+• and DPPH• radicals, as well as the efficiency of UV radiation shielding, decreased as follows: Lig-OA > Lig-LA > Lig-EA. The PVA/Lig-OA and PVA/Lig-LA films with a lignin content of 4% of the weight of PVA block UV radiation in the UVA range by 96% and 87%, respectively, and completely block UV radiation in the UVB range.

Modifying lignin: A promising strategy for plant disease control

Lignin is a complex polymer found in the cell walls of plants, providing structural support and protection against pathogens. By modifying lignin composition and structure, scientists aim to optimize plant defense responses and increase resistance to pathogens. This can be achieved through various genetic engineering techniques which involve manipulating the genes responsible for lignin synthesis. By either up regulating or down regulating specific genes, researchers can alter the lignin content, composition, or distribution in plant tissues. Reducing lignin content in specific tissues like leaves can improve the effectiveness of defense mechanisms by allowing for better penetration of antimicrobial compounds. Overall, Lignin modification through techniques has shown promising results in enhancing various plants resistance against pathogens. Furthermore, lignin modification can have additional benefits beyond pathogen resistance. It can improve biomass processing for biofuel production by reducing lignin recalcitrance, making the extraction of sugars from cellulose more efficient. The complexity of lignin biosynthesis and its interactions with other plant components make it a challenging target for modification. Additionally, the potential environmental impact and regulatory considerations associated with genetically modified organisms (GMOs) require careful evaluation. Ongoing research aims to further optimize this approach and develop sustainable solutions for crop protection.

Hydroxyapatite-lignin hybrid systems as improved poly(vinyl chloride) fillers: From preparation to application

In this study, new, functional hydroxyapatite-lignin hybrid systems were designed and characterized. The efficacy of the mechanical method utilized to obtain these systems was confirmed by Fourier transform infrared spectroscopy. The hybrid materials were also noted for their good electrokinetic stability and thermal stability. The introduction of 2.5 to 10 wt% hydroxyapatite-lignin systems into an unplasticized PVC blend using a two-step kneading and pressing method resulted in composites with relatively homogeneous distribution, as confirmed by SEM observations. The processing properties of the filler-containing blends were investigated using plastographometric analysis and MFR tests. The introduction of a lignin-predominant hybrid system into the PVC matrix results in a significant improvement of thermal stability, softening temperature, and tensile strength, while maintaining sufficient impact strength for numerous applications. Hybrid materials containing higher amounts of added lignin are promising materials with bacteriostatic properties. This can be utilized to stabilize and prevent the deposition of microorganisms, as well as the formation of biofilms, on material surfaces, thereby limiting the spread of pathogens. New eco-composites based on PVC and a hybrid filler containing lignin show promise in producing components with surfaces resistant to bacterial colonization. Hence, these materials could be used in medical and hospital equipment.

Analysis of ginseng rusty root symptoms transcriptome and its pathogenesis directed by reactive oxygen species theory

Ginseng rusty root symptoms (GRS) is a primary disease of ginseng, which seriously decreases the yield and quality of ginseng and causes enormous losses to ginseng production. GRS prevention and control is still challenging due to its unclear etiology. In this study, the phloem tissue of healthy Panax ginseng (AG), the nonred tissue of the phloem epidermis around the lesion (BG), and the red lesion site tissue of GRS (CG) were extracted for mRNA transcriptomic analysis; 35,958 differentially expressed genes (DEGs) were identified and were associated with multiple stress resistance pathways, reactive oxygen species (ROS), and iron ion binding. Further study showed that the contents of O2 •-, H2O2, and malondialdehyde (MDA) were significantly increased in BG and CG tissues. Under anaerobic conditions caused by excessive soil moisture, the overproduction of ROS destroys cell membranes, simultaneously converting Fe2+ to Fe3+ and depositing it in the cell wall, which results in GRS, as evidenced by the success of the GRS induction test.

Lignin derivatives-based hydrogels for biomedical applications

Recently, numerous studies have been conducted on renewable polymers derived from different natural sources, exploring their suitability for diverse biomedical applications. Lignin as one of the main components of lignocellulosic has garnered significant attention as a promising alternative to petroleum-based polymers. This interest is primarily due to its cost-effectiveness, biocompatibility, eco-friendly nature, as well as its antioxidant and antimicrobial properties. These characteristics could be more beneficial when incorporating lignin into the formulation of value-added products. Although lignin has a chemical structure that is suitable for various applications, these characteristics require modifications to guarantee that the resultant materials display the desired biological, chemical, and physical properties when applied in the creation of biodegradable hydrogels, particularly for biomedical purposes. This study delineates the recent modification approaches that have been employed in the creation of lignin-based hydrogels. These strategies encompass both chemical and physical interactions with other polymers. Additionally, this review encompasses an examination of the current applications of lignin hydrogels, spanning their use as scaffolds for tissue engineering, carriers for pharmaceuticals, materials for wound dressings and biosensors, and elements in flexible and wearable electronics. Finally, we delve into the challenges and constraints associated with these materials, discuss the necessary steps required to attain the appropriate properties for the development of innovative lignin-based hydrogels, and derive conclusions based on the presented findings.

A facile strategy to fabricate lignocellulose-based slow-release fertilizers via a high-performance treatment of rice straw using deep eutectic solvents

Lignin-based slow-release fertilizers (SRFs) have attracted widespread attention due to their ability to enhance nutrient utilization efficiency and reduce environmental pollution in agricultural production. However, the extraction and separation processes of lignin from biomass sources are intricate, involving substantial quantities of non-reusable toxic reagents. Here, a sustainable and eco-friendly approach using deep eutectic solvents (DES) was employed to treat rice straw, effectively dissolving the lignin present. Subsequently, the in-situ lignin regeneration was facilitated through the addition of a zinc chloride solution. The regenerated lignin was tightly wrapped around and connected to cellulose micro/nanofibers, forming a homogeneous slurry. A simple coating technique was employed to uniformly coat urea particles with the lignocellulosic slurry, yielding lignocellulose-based SRFs. Results revealed that the nutrient release of the lignocellulose-based coated fertilizers in water exceeded 56 days. A pot trial demonstrated that the application of lignocellulose-based SRFs significantly promoted the growth of rice and improved grain yield (by 10.7 %) and nitrogen use efficiency (by 34.4 %) compared to the urea treatment in rice production. Furthermore, the DES demonstrated consistently high efficiency in biomass processing even after four cycles of reuse. This green strategy offers a novel approach for the preparation of SRFs coating materials, promoting agricultural sustainability.

Unfolding of Lignin Structure Using Size-Exclusion Fractionation

The heterogeneous and recalcitrant structure of lignin hinders its practical application. Here, we describe how new approaches to lignin characterization can reveal structural details that could ultimately lead to its more efficient utilization. A suite of methods, which enabled mass balance closure, the evaluation of structural features, and an accurate molecular weight (MW) determination, were employed and revealed unexpected structural features of the five alkali lignin fractions obtained with preparative size-exclusion chromatography (SEC). A thermal carbon analysis (TCA) provided quantitative temperature profiles based on sequential carbon evolution, including the final oxidation of char. The TCA results, supported with thermal desorption/pyrolysis gas chromatography-mass spectrometry (TD-Py-GC-MS) and 31P NMR spectroscopy, revealed the unfolding of the lignin structure as a result of the SEC fractionation, due to the disruption of the interactions between the high- and low-MW components. The "unraveled" lignin revealed poorly accessible hydroxyl groups and showed an altered thermal behavior. The fractionated lignin produced significantly less char upon pyrolysis, 2 vs. 47%. It also featured a higher occurrence of low-MW thermal evolution products, particularly guaiacol carbonyls, and more than double the number of OH groups accessible for phosphitylation. These observations indicate pronounced alterations in the lignin intermolecular association following size-exclusion fractionation, which may be used for more efficient lignin processing in biorefineries.

Bioactive and Hemocompatible PLA/Lignin Bio-Composites: Assessment of In Vitro Antioxidant Activity for Biomedical Applications

In this study, acetylated soda lignin (ASL) and non-acetylated soda lignin (SL) were extruded with PLA in different concentrations to fabricate antioxidant polylactic acid (PLA)/lignin composites for potential biomedical applications. After lignin acetylation, good compatibility was observed between PLA and lignin in scanning electron microscopy images. All the PLA/ASL composites displayed higher mechanical properties than PLA/SL composites. PLA/ASL5 displayed the highest mechanical characteristics with elongation at break of 10% and tensile strength of 57 MPa, while PLA/SL15 and PLA/SL20 demonstrated superior UV-blocking potential with UV transmittance less than 10%. Addition of ASL in PLA lead to an increase in the hydrophobic character, with all the PLA/ASL displaying a higher water contact angle. The antioxidant test using 2,2-diphenyl-1-picrylhydrazyl assay showed that PLA/SL composites rendered superior radical scavenging activity (RSA), with PLA/SL20 composites displaying an RSA of 80%. Furthermore, in vitro antioxidant activity and cytocompatibility were analyzed using human colon cancer cells (HCT-15) and gastric epithelial cells (NCC-24). In vitro antioxidant activity, evaluated by H2O2 exposure was confirmed by a live/dead assay. PLA/SL composites protected both types of cells from oxidative stress. In addition, all PLA/SL and PLA/ASL composites promoted cell proliferation compared to PLA. PLA/SL5 and PLA/SL10 displayed the highest cell proliferation of all composites. Lastly, all PLA/SL and PLA/ASL composites had a hemoglobin release less than 2%. The antioxidant properties, cytocompatibility, and hemocompatibility of lignin/PLA demonstrated in our study indicate that these lignin/PLA composites possess the desirable attributes for potential biomedical applications.

Sustainable Biomass Lignin-Based Hydrogels: A Review on Properties, Formulation, and Biomedical Applications

Different techniques have been developed to overcome the recalcitrant nature of lignocellulosic biomass and extract lignin biopolymer. Lignin has gained considerable interest owing to its attractive properties. These properties may be more beneficial when including lignin in the preparation of highly desired value-added products, including hydrogels. Lignin biopolymer, as one of the three major components of lignocellulosic biomaterials, has attracted significant interest in the biomedical field due to its biocompatibility, biodegradability, and antioxidant and antimicrobial activities. Its valorization by developing new hydrogels has increased in recent years. Furthermore, lignin-based hydrogels have shown great potential for various biomedical applications, and their copolymerization with other polymers and biopolymers further expands their possibilities. In this regard, lignin-based hydrogels can be synthesized by a variety of methods, including but not limited to interpenetrating polymer networks and polymerization, crosslinking copolymerization, crosslinking grafted lignin and monomers, atom transfer radical polymerization, and reversible addition-fragmentation transfer polymerization. As an example, the crosslinking mechanism of lignin-chitosan-poly(vinyl alcohol) (PVA) hydrogel involves active groups of lignin such as hydroxyl, carboxyl, and sulfonic groups that can form hydrogen bonds (with groups in the chemical structures of chitosan and/or PVA) and ionic bonds (with groups in the chemical structures of chitosan and/or PVA). The aim of this review paper is to provide a comprehensive overview of lignin-based hydrogels and their applications, focusing on the preparation and properties of lignin-based hydrogels and the biomedical applications of these hydrogels. In addition, we explore their potential in wound healing, drug delivery systems, and 3D bioprinting, showcasing the unique properties of lignin-based hydrogels that enable their successful utilization in these areas. Finally, we discuss future trends in the field and draw conclusions based on the findings presented.

Extraction and Characterization of Acidolysis Lignin from Turkey Oak (Quercus cerris L.) and Eucalypt (Eucalyptus camaldulensis Dehnh.) Wood from Population Stands in Italy

Acidolysis lignins from the species Quercus cerris L. and Eucalyptus camaldulensis Dehnh. were isolated and characterized using high pressure size exclusion chromatography (HP-SEC), Fourier-transform (FTIR) infrared spectroscopy, analytical pyrolysis-gas chromatography-mass spectrometry (Py-GCMS), and two-dimensional heteronuclear single quantum coherence (2D HSQC) NMR spectroscopy. The acidolysis lignins from the two different species varied in chemical composition and structural characteristics, with Q. cerris L. lignin having a higher S/G ratio and higher molar mass averages with a bimodal molar mass distribution. The different analytical techniques FTIR spectroscopy, Py-GCMS, and 2D NMR spectroscopy provided consistent results regarding the S/G ratio of the lignins from the two wood species. Based on the determined high S/G ratio of both oak and eucalypt lignin, the two wood sources could be promoted as substrates for efficient lignin isolation in modern forest biorefineries in order to develop innovative lignin-based value-added biorefinery products.

In vitro evaluation of alkaline lignins as antiparasitic agents and their use as an excipient in the release of benznidazole

The Amazon rainforest is considered the largest tropical timber reserve in the world. The management of native forests in the Amazon is one of the most sensitive geopolitical issues today, given its national and international dimension. In this work, we obtained and characterized physicochemical lignins extracted from branches and leaves of Protium puncticulatum and Scleronema micranthum. In addition, we evaluated in vitro its potential as an antioxidant, cytotoxic agent against animal cells and antiparasitic against promastigotes of Leishmania amazonensis, trypomastigotes of T. cruzi and against Plasmodium falciparum parasites sensitive and resistant to chloroquine. The results showed that the lignins obtained are of the GSH type and have higher levels of guaiacyl units. However, they show structural differences as shown by spectroscopic analysis and radar charts. As for biological activities, they showed antioxidant potential and low cytotoxicity against animal cells. Antileishmanial/trypanocidal assays have shown that lignins can inhibit the growth of promastigotes and trypomastigotes in vitro. The lignins in this study showed low anti-Plasmodium falciparum activity against susceptible strains of Plasmodium falciparum and were able to inhibit the growth of the chloroquine-resistant strain. And were not able to inhibit the growth of Schistosoma mansoni parasites. Finally, lignins proved to be promising excipients in the release of benznidazole. These findings show the potential of these lignins not yet studied to promote different biological activities.

Lignin-derived polyphenols with enhanced antioxidant activities by chemical demethylation and their structure-activity relationship

Lignin valorization to biobased polyphenols antioxidants is increasingly attractive in the modern industry due to their inherent phenolic structures. Herein, lignin-derived polyphenols with enhanced antioxidant activities were prepared from the most available technical lignin including organosolv lignin (OL), alkali lignin (AL), and enzyme lignin (EL) by iodocyclohexane (ICH) chemical demethylation. The structural evolution of lignin indicated that the C_Ar-OCH₃ group and the C_Ar-O-C_alkyl side-chain could be effectively transformed into the C_Ar-OH group, resulting in a significant increase of the phenolic-OH content and a slight decrease of the molecular weight. The 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·) scavenging activity was in the order of ICHOL-24 > ICHAL-24 > ICHEL-24 ≈ FA > BHT, and the IC₅₀ value of ICHOL-24 was 0.56 times lower than that of BHT. The structure-activity relationship demonstrated the activities were quasi-linearly related to phenolic-OH contents and could be affected by molecular weights. The H/G/S proportions of lignin could be an indicator for accurate screening of efficient lignin-derived polyphenols antioxidants (LPA). It was preliminarily estimated to have economic feasibility for producing LPA from technical lignin by demethylation compared with synthetic or natural antioxidants. This work will help to develop efficient biobased antioxidants for lignin valorization.

Comparative transcriptome and metabolome analyses of cherry leaves spot disease caused by Alternaria alternata

Alternaria alternata is a necrotrophic fungal pathogen with a broad host range that causes widespread and devastating disease in sweet cherry (Prunus avium). We selected a resistant cultivar (RC) and a susceptible cultivar (SC) of cherry and used a combined physiological, transcriptomic, and metabolomic approach to investigate the molecular mechanisms underlying the plant's resistance to A. alternata, of which little is known. We found that A. alternata infection stimulated the outbreak of reactive oxygen species (ROS) in cherry. The responses of the antioxidant enzymes and chitinase to disease were observed earlier in the RC than in the SC. Moreover, cell wall defense ability was stronger in the RC. Differential genes and metabolites involved in defense responses and secondary metabolism were primarily enriched in the biosynthesis of phenylpropanoids, tropane, piperidine and pyridine alkaloids, flavonoids, amino acids, and α-linolenic acid. Reprogramming the phenylpropanoid pathway and the α-linolenic acid metabolic pathway led to lignin accumulation and early induction of jasmonic acid signaling, respectively, in the RC, which consequently enhanced antifungal and ROS scavenging activity. The RC contained a high level of coumarin, and in vitro tests showed that coumarin significantly inhibited A. alternata growth and development and had antifungal effect on cherry leaves. In addition, differentially expressed genes encoding transcription factors from the MYB, NAC, WRKY, ERF, and bHLH families were highly expressed, they could be the key responsive factor in the response of cherry to infection by A. alternata. Overall, this study provides molecular clues and a multifaceted understanding of the specific response of cherry to A. alternata.

High value valorization of lignin as environmental benign antimicrobial

Lignin is a natural aromatic polymer of p-hydroxyphenylpropanoids with various biological activities. Noticeably, plants have made use of lignin as biocides to defend themselves from pathogen microbial invasions. Thus, the use of isolated lignin as environmentally benign antimicrobial is believed to be a promising high value approach for lignin valorization. On the other hand, as green and sustainable product of plant photosynthesis, lignin should be beneficial to reduce the carbon footprint of antimicrobial industry. There have been many reports that make use of lignin to prepare antimicrobials for different applications. However, lignin is highly heterogeneous polymers different in their monomers, linkages, molecular weight, and functional groups. The structure and property relationship, and the mechanism of action of lignin as antimicrobial remains ambiguous. To show light on these issues, we reviewed the publications on lignin chemistry, antimicrobial activity of lignin models and isolated lignin and associated mechanism of actions, approaches in synthesis of lignin with improved antimicrobial activity, and the applications of lignin as antimicrobial in different fields. Hopefully, this review will help and inspire researchers in the preparation of lignin antimicrobial for their applications.

Efficient Azo Dye Biodecolorization System Using Lignin-Co-Cultured White-Rot Fungus

The extensive use of azo dyes by the global textile industry induces significant environmental and human health hazards, which makes efficient remediation crucial but also challenging. Improving dye removal efficiency will benefit the development of bioremediation techniques for textile effluents. In this study, an efficient system for azo dye (Direct Red 5B, DR5B) biodecolorization is reported, which uses the white-rot fungus Ganoderma lucidum EN2 and alkali lignin. This study suggests that the decolorization of DR5B could be effectively enhanced (from 40.34% to 95.16%) within 48 h in the presence of alkali lignin. The dye adsorption test further confirmed that the alkali-lignin-enhanced decolorization of DR5B was essentially due to biodegradation rather than physical adsorption, evaluating the role of alkali lignin in the dye biodegradation system. Moreover, the gas chromatography/mass spectrometry analysis and DR5B decolorization experiments also indicated that alkali lignin carried an excellent potential for promoting dye decolorization and displayed a significant role in improving the activity of lignin-modifying enzymes. This was mainly because of the laccase-mediator system, which was established by the induced laccase activity and lignin-derived small aromatic compounds.

Determination of the Structures of Lignin Subunits and Nanoparticles in Solution by Small-Angle Neutron Scattering: Towards Improving Lignin Valorization

Lignin nanoparticles (LNPs) are usually produced from lignin solution through supersaturation. The structure of the lignin in solution is still poorly understood due to structural variability of isolated lignins. Here, lignins were extracted from different plants to establish a general pattern of their structure in several lignin solvents. Lignin molecules (lignin subunits) and larger aggregates were observed in dimethyl sulfoxide (DMSO), ethylene glycol (EG) and 0.1 N NaOD solutions by small-angle neutron scattering (SANS). It was proposed that the aggregates were composed of lignin subunits with a higher molecular weight and a higher ratio of the aliphatic to phenolic hydroxyl groups. The size, shape, and compactness are important factors that affect the uses of the LNPs, which were obtained from the SANS data for the first time. A discrepancy in the radius between SANS and DLS was discovered, pointing to a large hydration shell around the LNPs in aqueous solutions. The cytotoxicity of the corncob lignin, kraft lignin, and their LNPs were measured and compared.

Surface chemistry and bioactivity of colloidal particles from industrial kraft lignins

The morphology control of lignin through particle size reduction to nanoscale seems to be a suitable conversion technology to overcome the intrinsic limitations of its native form to develop a wide range of biomaterials with high performance. Colloidal lignin particles (CLPs) in the range of 150-200 nm were synthesised from hardwood and softwood kraft lignins by the solvent shifting method. The initial molecular features of kraft lignins were evaluated in terms of purity, molecular weight distribution, and chemical functionalities. The impact of the lignin source and structure on the morphology, size distribution, and surface chemistry of CLPs was evaluated by particle size analyser, SEM, TEM and ¹H NMR. The results evidenced the influence of the botanical origin on the morphology and surface chemistry of particles. Furthermore, the antioxidant properties and cytotoxicity of lignins and corresponding CLPs, towards lung fibroblast cells were compared. CLPs from hardwood kraft lignins exhibited higher antioxidant power against DPPH free radical and a higher cytotoxic effect (IC₃₀ = 67-70 μg/mL) against lung fibroblast when compared to CLPs from softwood kraft lignin (IC₃₀ = ~91 μg/mL). However, the cytotoxicity of these biomaterials was dose-dependent, suggesting their potential application as active ingredients in cosmetic and pharmaceutic products at low concentrations.

Alkyl polyglycosides enhanced the dark fermentation of excess sludge and plant waste to produce hydrogen: performance and mechanism

Alkyl polyglycosides (APG), a biodegradable biosurfactant, have been widely used in environmental pollution control. However, the application of APG to enhance anaerobic dark fermentation of excess sludge (ES) and plant waste (PW) to improve hydrogen production has not been reported so far. In order to fill this gap, the effect of APG on hydrogen production from ES and PW was studied in mesophilic (30 °C) environment. The results showed that APG increased the yield of hydrogen, and the recommended dose was 0.15 g/g (calculated as volatile suspended solids), accompanied by 18.7 mL/g. The contribution of APG self-degradation to hydrogen can be ignored. Mechanism investigation revealed that APG promoted the dissolution, hydrolysis, and acidification of complex organic matter, and when the content of APG was 0.15 g/g, the concentration of dissolved chemical oxygen demand (COD) was as high as 3151 mg/L; however, the dissolved concentration of COD in the blank group was only 1548 mg/L. In addition, APG improved the output of volatile fatty acids (VFA). APG promoted the proportion of acetate and butyrate in VFA, which was conducive to hydrogen production. As for the process of methanogenesis, APG reduced the consumption of hydrogen and accumulates hydrogen. This work provides an alternative strategy for the recycling of organic waste and the enhanced generation of hydrogen.

Lignin-carbohydrate complexes suppress SCA3 neurodegeneration via upregulating proteasomal activities

Lignin-carbohydrate complexes (LCCs) represent a group of macromolecules with diverse biological functions such as antioxidative properties. Polyglutamine (polyQ) diseases such as spinocerebellar ataxia type 3 (SCA3) comprise a set of neurodegenerative disorders characterized by the formation of polyQ protein aggregates in patient neurons. LCCs have been reported to prevent such protein aggregation. In this study, we identified a potential mechanism underlying the above anti-protein aggregation activity. We isolated and characterized multiple LCC fractions from bamboo and poplar and found that lignin-rich LCCs (BM-LCC-AcOH and PR-LCC-AcOH) effectively eliminated both monomeric and aggregated mutant ataxin-3 (ATXN3polyQ) proteins in neuronal cells and a Drosophila melanogaster SCA3 disease model. In addition, treatment with BM-LCC-AcOH or PR-LCC-AcOH rescued photoreceptor degeneration in vivo. At the mechanistic level, we demonstrated that BM-LCC-AcOH and PR-LCC-AcOH upregulated proteasomal activity. When proteasomal function was impaired, the ability of the LCCs to suppress ATXN3polyQ aggregation was abolished. Thus, we identified a previously undescribed proteasome-inducing function of LCCs and showed that such activity is indispensable for the beneficial effects of LCCs on SCA3 neurotoxicity.

Sustainable lignin and lignin-derived compounds as potential therapeutic agents for degenerative orthopaedic diseases: A systemic review

Lignin, the most abundant natural and sustainable phenolic compound in biomass, has exhibited medicinal values due to its biological activities decided by physicochemical properties. Recently, the lignin and its derivatives (such as lignosulfonates and lignosulfonate) have been proven efficient in regulating cellular process and the extracellular microenvironment, which has been regarded as the key factor in disease progression. In orthopaedic diseases, especially the degenerative diseases represented by osteoarthritis and osteoporosis, excessive activated inflammation has been proven as a key stage in the pathological process. Due to the excellent biocompatibility, antibacterial and antioxidative activities of lignin and its derivatives, they have been applied to stimulate cells and restore the uncoupling bone remodeling in the degenerative orthopaedic diseases. However, there is a lack of a systemic review to state the current research actuality of lignin and lignin-derived compounds in treating degenerative orthopaedic diseases. Herein, we summarized the current application of lignin and lignin-derived compounds in orthopaedic diseases and proposed their possible therapeutic mechanism in treating degenerative orthopaedic diseases. It is hoped this work could guide the future preparation of lignin/lignin-derived drugs and implants as available therapeutic strategies for clinically degenerative orthopaedic diseases.

Unveiling the Biocompatible Properties of Date Palm Tree (Phoenix dactylifera L.) Biomass-Derived Lignin Nanoparticles

Searching for sustainable, ecofriendly, and renewable precursors for nanostructured material synthesis is a fascinating area pertaining to feasibility in various applications. Especially, lignin-based material preparation is essential for unraveling the usage of lignin by valorization. Hence, we have synthesized lignin nanoparticles (LNPs) using date palm tree (Phoenix dactylifera L.) biomass as a precursor in this investigation. The LNP's morphological and thermal features were assessed. Moreover, we have evaluated the LNP's cytocompatibility properties by adopting in vitro approach. The P. dactylifera L. (PD) biomass-derived LNP's morphological features show a spherical shape with a 10-100 nm diameter. The LNPs have a decreased cell viability of ∼8% at a high concentration exposure to human mesenchymal stem cells (hMSCs) for 48 h. However, the LNPs do not cause any cellular and nuclear morphology changes in hMSCs. The mitochondrial membrane potential assessment results confirm healthy mitochondria with high mitochondrial membrane potential in LNP-treated cells. The intracellular reactive oxygen species (ROS) generation assay results revealed that LNPs do not trigger ROS generation in hMSCs. We examined the upregulation of GSTM3 and GSR genes and the downregulation of SOD1 genes in LNP-treated hMSCs, but no significant changes were observed. Our study concluded that PD biomass-derived LNPs have a good cytocompatibility and an antioxidant property. Thus, they can be applicable for various biological, cosmetic, and environmental applications.

Ultrastructural elucidation of lignin macromolecule from different growth stages of Chinese pine

Understanding of the morphological changes at different growth stages and lignin accumulation pattern for pine biomass plays the key role in facilitating the further development of value-added utilization and downstream conversion processes. This work systematically revealed the morphological change and lignin accumulation pattern in Chinese pine branches cell walls via confocal Raman microscopy (CRM) technology. Meanwhile, the structural characteristics of isolated lignin samples from different growth stages were synthetically characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) techniques. The results indicated that the content of pith in adult pine new branch was bigger than juvenile trees. With the increase of physiological age, the branches in adult pine could accumulate more lignin both in overall content and the concentration of cell corner middle layer. Moreover, the significantly increases of molecular weights and the β-O-4, β-β linkages content revealed that the lignin macromolecule of pine would polymerize faster in the adult stage (14, 35 years). The panorama generated from the structural and chemical features of pine native lignin not only benefited to understand the biosynthetic pathways and lignin macromolecules structural variation in plant cell walls from different growth stages but also contributed to the valorization and deconstruction of biomass.

Understanding the mechanism of polybrominated diphenyl ethers reducing the anaerobic co-digestion efficiency of excess sludge and kitchen waste

Polybrominated diphenyl ethers (PBDEs) widely existing in the environment can pose a serious threat to the ecological safety. However, the influence of PBDEs on methane production by excess sludge (ES) and kitchen waste (KW) anaerobic co-digestion and its mechanism is not clear. To fill this gap, in this work, the co-digestion characteristics of ES and KW exposed to different levels of PBDEs at medium temperature were investigated in sequencing batch reactor, and the related mechanisms were also revealed. The results showed that PBDEs reduced methane production and the proportion of methane in the biogas. Methane yield decreased from 215.3 mL/g· volatile suspended solids (VSS) to 161.5 mL/(g·VSS), accompanied by the increase of PBDE content from 0 to 8.0 mg/Kg. Volatile fatty acid (VFA) yield was also inhibited by PBDEs; especially when PBDEs were 8.0 mg/Kg, VFA production was only 215.6 mg/g VSS, accounting for 75.7% of that in the control. Mechanism investigation revealed PBDEs significantly inhibited the processes of hydrolysis, acidogenesis, acetogenesis, and methanogenesis. Further study showed that PBDEs could inhibit the degradation and bioavailability of ES and KW, but it had a greater inhibition on the utilization of KW. Enzyme activity investigation revealed that all the key enzyme activities related to methane production were suppressed by PBDEs.

Deciphering the linkage type and structural characteristics of the p-hydroxyphenyl unit in Pinus massoniana Lamb compressed wood lignin

To reveal the existence of p-hydroxyphenyl (H) units in compressed wood lignin, four different milled wood lignins were extracted using Pinus massoniana Lamb compressed wood, Pinus massoniana Lamb normal wood, and sugarcane bagasse as raw materials. Then, three dehydrogenation polymers (DHPs) were synthesized using coniferyl/p-coumaryl alcohol as raw materials to reveal the interunit linkages of H units. The lignin and DHP samples were systematically characterized by ¹H, ¹³C, 2D HSQC, and ³¹P NMR techniques. Compared with the opposite wood milled wood lignin (OW-MWL) and the normal wood milled wood lignin (NW-MWL), the compressed wood milled wood lignin (CW-MWL) contained a large amount of H units, and the H/G ratio and the p-hydroxyphenyl OH group contents were 0.15 and 1.09 mmol/g, respectively. Through the characterization of CW-MWL and DHPs, it was revealed that p-hydroxyphenyl units mainly coupled with other units by β-O-4, β-β, and β-5 linkages. Compared to the sugarcane bagasse milled wood lignin, it was clearly demonstrated that the H unit rather than p-coumarate ester occurred in CW-MWL. This study comprehensively explored the structural characteristics and linkages of H units in compress wood lignin, and provided useful information for revealing the participation of H units in the construction of lignin macromolecules.

Effect of Two-Step Formosolv Fractionation on the Structural Properties and Antioxidant Activity of Lignin

The formosolv fractionation process has been demonstrated to be an effective approach toward lignin recovery as an antioxidant from lignocellulosic biomass. In this study, four lignin fractions, FL-88%, FSL-70%, FIL-70% and FL-EtAc, were isolated from Phragmites australis biomass through two-step formosolv fractionation (88% formic acid delignification followed by 70% aqueous formic acid fractionation). To better understand the structural properties of the lignin obtained from this fractionation process, four isolated lignins were successfully characterized by gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, thermogravimetric analysis (TGA) and gas chromatograph-mass spectroscopy (GC/MS). It was found that lignin depolymerization via β-O-4 cleavage occurred via a formylation, elimination and hydrolysis mechanism, accompanied by a competitive condensation reaction. Noteworthily, two-step formosolv fractionation can produce specific lignin fractions with different ABTS and DPPH radical scavenging activities. The FL-EtAc fraction with low molecular weight (M_w = 2748 Da) and good homogeneity (PDI = 1.5) showed excellent antioxidant activity, compared with the other three isolated lignin fractions, even equal to that of commercial antioxidant BHT at the same concentration of 2.0 mg·mL⁻¹. These findings are of great help for specific lignin from biomass as a natural antioxidant in the future.

A structure-activity understanding of the interaction between lignin and various cellulase domains

To elucidate the structure-activity relationship between lignin and various cellulase domains, four lignin fractions with specific structures and molecular weight were prepared from bamboo kraft lignin (BKL) and used to investigate the adsorption mechanism between different cellulase domains by fluorescence spectroscopy and SDS-PAGE. Endo-cellulase 6B exhibited a higher affinity to BKL fractions than the carbohydrate-binding module (CBM4A) of cellulase, which is positively correlated to molecular weight. The thermodynamic mechanism showed that the adsorption between BKL fractions and endo-cellulase 6B was dominated by van der Waals and electrostatic forces, while hydrophobic force is the driver for BKL fractions to adsorb CBM4A. Structure-activity relationship between lignin fractions and cellulase domain revealed that thermodynamics and interaction forces were more easily affected by the structure of BKL, including S/G ratio, molecular weight and hydrophobicity. The aforementioned results demonstrated that lignin's structure plays a critical role in its adsorption with various cellulase domains.

A Biomimetic Platelet-Rich Plasma-Based Interpenetrating Network Printable Hydrogel for Bone Regeneration

Repair of bone defects caused by trauma or diseases is the primary focus of prosthodontics. Hydrogels are among the most promising candidates for bone tissue regeneration due to their unique features such as excellent biocompatibility, similarities to biological tissues, and plasticity. Herein, we developed a type of novel biomimetic interpenetrating polymeric network (IPN) hydrogel by combining methacrylated alginate and 4-arm poly (ethylene glycol)-acrylate (4A-PEGAcr) through photo-crosslinking. Platelet-rich plasma (PRP), a patient-specific source of autologous growth factors, was incorporated into the hydrogel, and thereafter the hydrogels were biological mineralized by simulated body fluid (SBF). Physical properties of hydrogels were comprehensively characterized. In vitro studies demonstrated that the incorporation of PRP and biomineralization promoted the biocompatibility of hydrogel. Strikingly, the osteogenic bioactivities, including ALP activity, mineralized nodule formation, and expression of osteogenic markers were found substantially enhanced by this biomineralized PRP-hydrogel. Finally, a rabbit model of bone defect was employed to assess in vivo bone regeneration, micro-CT analysis showed that the biomineralized PRP-hydrogels could significantly accelerate bone generation. We believed that this novel biomineralized PRP-incorporated IPN hydrogel could be promising scaffolds for bone tissue regeneration.

Recent advances in biological activities of lignin and emerging biomedical applications: A short review

As an abundant biopolymer, lignin gains interest owing to its renewable nature and polyphenolic structure. It possesses many biological activities such as antioxidant activity, antimicrobial activity, and biocompatibility. Studies are being carried out to relate the biological activities to the polyphenolic structures. These traits present lignin as a natural compound being used in biomedical field. Lignin nanoparticles (LNPs) are being investigated for safe use in drug and gene delivery, and lignin-based hydrogels are being explored as wound dressing materials, in tissue engineering and 3D printing. In addition, lignin and its derivatives have shown the potential to treat diabetic disease. This review summarizes latest research results on the biological activities of lignin and highlights potential applications exampled by selective studies. It helps to transform lignin from a waste material into valuable materials and products.

Green solvents-based molecular weight controllable fractionation process for industrial alkali lignin at room temperature

The molecular weight is one of the most important factors influencing the utilization of industrial lignin obtained from chemical pulping process. In this paper, a facile operative green solvent system was successfully developed for molecular weight-controllable fractionation of industrial alkali lignin (IAL) at room temperature. The results showed that through adjusting the ratio of water, ethanol and γ-Valerolactone (GVL), the industrial lignin was fractionated into six levels with molecular weight stepwise controllable from low to high. The fractionation is a physical process according to FTIR and 2D-HSQC NMR analysis, and the chemical structure of lignin has not changed. Additionally, the polydispersity of fractionated lignin with higher molecular weight tends to be narrower. The content of hydroxyl and carboxyl group is higher for the fractionated lignin with lower molecular weight, which would be beneficial for the chemical reactivity in the down-stream application.

Synthesis and Antibacterial Properties of Oligomeric Dehydrogenation Polymer from Lignin Precursors

The lignin precursors of coniferin and syringin were synthesised, and guaiacyl-type and guaiacyl-syringyl-type oligomeric lignin dehydrogenation polymers (DHP and DHP-GS) were prepared with the bulk method. The carbon-13 nuclear magnetic resonance spectroscopy showed that both DHP-G and DHP-GS contained β-O-4, β-5, β-β, β-1, and 5-5 substructures. Extraction with petroleum ether, ether, ethanol, and acetone resulted in four fractions for each of DHP-G (C11-C14) and DHP-GS (C21-C24). The antibacterial experiments showed that the fractions with lower molecular weight had relatively strong antibacterial activity. The ether-soluble fractions (C12 of DHP-G and C22 of DHP-GS) had strong antibacterial activities against E. coli and S. aureus. The C12 and C22 fractions were further separated by preparative chromatography, and 10 bioactive compounds (G1-G5 and GS1-GS5) were obtained. The overall antibacterial activities of these 10 compounds was stronger against E. coli than S. aureus. Compounds G1, G2, G3, and GS1, which had the most significant antibacterial activities, contained β-5 substructures. Of these, G1 had the best antibacterial activity. Its inhibition zone diameter was 19.81 ± 0.82 mm, and the minimum inhibition concentration was 56.3 ± 6.20 μg/mL. Atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) showed that the antibacterial activity of G1 was attributable to a phenylcoumarin dimer, while the introduction of syringyl units reduced antibacterial activity.

Salix spp. Bark Hot Water Extracts Show Antiviral, Antibacterial, and Antioxidant Activities-The Bioactive Properties of 16 Clones

Earlier studies have shown that the bark of Salix L. species (Salicaceae family) is rich in extractives, such as diverse bioactive phenolic compounds. However, we lack knowledge on the bioactive properties of the bark of willow species and clones adapted to the harsh climate conditions of the cool temperate zone. Therefore, the present study aimed to obtain information on the functional profiles of northern willow clones for the use of value-added bioactive solutions. Of the 16 willow clones studied here, 12 were examples of widely distributed native Finnish willow species, including dark-leaved willow (S. myrsinifolia Salisb.) and tea-leaved willow (S. phylicifolia L.) (3 + 4 clones, respectively) and their natural and artificial hybrids (3 + 2 clones, respectively). The four remaining clones were commercial willow varieties from the Swedish willow breeding program. Hot water extraction of bark under mild conditions was carried out. Bioactivity assays were used to screen antiviral, antibacterial, antifungal, yeasticidal, and antioxidant activities, as well as the total phenolic content of the extracts. Additionally, we introduce a fast and less labor-intensive steam-debarking method for Salix spp. feedstocks. Clonal variation was observed in the antioxidant properties of the bark extracts of the 16 Salix spp. clones. High antiviral activity against a non-enveloped enterovirus, coxsackievirus A9, was found, with no marked differences in efficacy between the native clones. All the clones also showed antibacterial activity against Staphylococcus aureus and Escherichia coli, whereas no antifungal (Aspergillus brasiliensis) or yeasticidal (Candida albicans) efficacy was detected. When grouping the clone extract results into Salix myrsinifolia, Salix phylicifolia, native hybrid, artificial hybrid, and commercial clones, there was a significant difference in the activities between S. phylicifolia clone extracts and commercial clone extracts in the favor of S. phylicifolia in the antibacterial and antioxidant tests. In some antioxidant tests, S. phylicifolia clone extracts were also significantly more active than artificial clone extracts. Additionally, S. myrsinifolia clone extracts showed significantly higher activities in some antioxidant tests than commercial clone extracts and artificial clone extracts. Nevertheless, the bark extracts of native Finnish willow clones showed high bioactivity. The obtained knowledge paves the way towards developing high value-added biochemicals and other functional solutions based on willow biorefinery approaches.

The Effect of Ball Milling Time on the Isolation of Lignin in the Cell Wall of Different Biomass

Ball milling technology is the classical technology to isolate representative lignin in the cell wall of biomass for further investigation. In this work, different ball milling times were carried out on hardwood (poplar sawdust), softwood (larch sawdust), and gramineous material (bamboo residues) to understand the optimum condition to isolate the representative milled wood lignin (MWL) in these different biomass species. Results showed that prolonging ball milling time from 3 to 7 h obviously increased the isolation yields of MWL in bamboo residues (from 39.2% to 53.9%) and poplar sawdust (from 15.5% to 35.6%), while only a slight increase was found for the MWL yield of larch sawdust (from 23.4% to 25.8%). Importantly, the lignin substructure of ß-O-4 in the MWL samples from different biomasses can be a little degraded with the increasing ball milling time, resulting in the prepared MWL with lower molecular weight and higher content of hydroxyl groups. Based on the isolation yield and structure features, milling time with 3 and 7 h were sufficient to isolate the representative lignin (with yield over 30%) in the cell wall of bamboo residues and poplar sawdust, respectively, while more than 7 h should be carried out to isolate the representative lignin in larch sawdust.

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.