Isolation Of Lignin Research Articles

Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics

Uncovering the structure of lignin from biorefinery has an important effect on lignin catalytic depolymerization and the production of bioenergy. In this study, two biorefinery lignins were isolated from tobacco stalks via alkaline and deep eutectic solvent (DES) catalyzed delignification processes, and the lignin heterogeneity structural characteristics were elucidated by gel permeation chromatography, 2D-HSQC, FT-IR, etc., to understand the relationship between the structure and the thermal characteristics of lignin. It was found that the lignins presented various structural characteristics and components, in which the predominant interunit linkages of black liquor lignin are β-O-4 and β-β linkages, and the β-O-4 linkages disappeared by DES treatment. DES lignins exhibited lower molecular weights and yields than black liquor lignin. Thermogravimetric analysis and fixed-bed pyrolysis were also performed to investigate the lignin thermal behavior. The results show that the DES approach can improve the bio-oil production from lignin and highlight the potential of DES lignin as a promising feedstock in the lignin pyrolysis process. This work provides a valuable example of the conversion of biorefinery lignin into pyrolysis products.

Characterization of sugar maple and red oak bark: Efficient lignin extraction via the Organosolv and acidic dioxane process

The barks of two wood species, sugar maple (SM) and red oak (RO), were investigated to characterize their chemical composition and isolate the lignins they contain, representing relatively underexplored and underutilized polymers. Characterizing these two barks involved assessing extractive components, Klason and acid-soluble lignin, ash content, and sugars. It was observed that RO bark had a higher concentration of extractive substances and a lower Klason lignin content compared to SM bark. The Klason lignin content in the barks of the SM and RO bark was measured at 35.0% and 26.4%, respectively, higher than values reported for corresponding to wood of the same species, 21.8% and 22.2%, respectively, for RO and SM. Lignin isolation from bark was achieved by utilizing Organosolv catalytic and acid dioxane processes. Notably, the Organosolv process yielded lignins of considerably higher purity. The structural analysis of the bark lignins was peformed by combination of spectroscopic methods: FTIR,13P NMR, and solid-state NMR. Compared to dioxane lignins, a higher concentration of OH bound to syringyl and guayacyl units were found in Organosolv lignins. In contrast, aliphatic OH units are more important in dioxane lignins than in Organosolv lignins. Furthermore, sugar analysis was conducted via HPLC, thermal analysis was conducted through DSC and TGA, and ash composition identification was done using ICP-OES. Notably, higher Mw and Mn values are determined by GPC for dioxane lignins than for Organosolv lignins.

Quantitative 13C-IS pyrolysis-GC-MS lignin analysis: Overcoming matrix effects in animal feed and faeces

Recently, a pyrolysis-GC-MS methodology for specific lignin quantification and structural characterisation was developed, relying on the use of uniformly 13C-labeled polymeric lignin isolate as internal standard (IS). The 13C-IS py-GC-MS method has been validated for grasses, woods, and applied in various showcases. To study the fate of lignin in animals, this method still requires careful validation in animal feeds and, especially complex faecal samples, hence the aim of this work. Hereto, faecal material was collected from pigs fed with wheat straw as lignin source and subjected to the py-GC-MS analytical platform for thorough examination of IS pyrolysis behaviour in terms of response and structural features. Next, 13C-ISpy-lignin contents and corrected Klason lignin contents were compared. Most importantly, we revealed that pyrolysis behaviour of 13C-IS lignin and 12C-sample lignin was differently affected in the faecal matrix, resulting in the ultimate underestimation of 13C-ISpy-lignin contents. In-depth examination and evaluation of matrix constituents showed that predominantly matrix ash was responsible for the effects observed. We further demonstrated that said matrix effects can be overcome by water extraction of the samples prior to analysis. Our validation and approach extend the use of the specific 13C-IS py-GC-MS methodology for accurate quantitative lignin analysis to biomass samples with complex matrices like pig faeces, and now call for application in future digestibility studies.

Streamlined fractionation for recovery of high-yield xylo-oligosaccharides, pure lignin and ethanol from poplar using short-chain organic acid/pentanol biphasic system

Biphasic pretreatment offers a sustainable method by integrating the fractionation of hemicellulose, lignin, and cellulose into a single process, thereby enhancing biomass resource utilization while reducing environmental impact. However, this process faces the challenge of diverse hemicellulose products with low added value. This study employed organic acid-catalyzed water/pentanol biphasic pretreatment to selectively convert hemicellulose into xylooligosaccharides (XOS), while simultaneously separating lignin and cellulose. Both the organic acids and pentanol used are biodegradable and compatible. The lactic acid (LA)/pentanol biphasic system was particularly effective for XOS production and lignin removal, attributed to the high acidity of LA and its relatively low partition coefficients in the water/pentanol system, crucial factors influencing hemicellulose and lignin separation efficiency. The XOS yields reached 46.9 %, while the lignin removal rate was 74.6 %. Additionally, LA/pentanol pretreatment significantly enhanced cellulose digestibility, demonstrated by an ethanol production of 54.1 g/L during simultaneous saccharification fermentation at 15 % solids loading. The recovered lignin from the organic phase retained the structural characteristics of native lignin. It also had a low molecular weight and abundant phenolic hydroxyl groups, indicating its suitability for further valorization. Pentanol maintained its performance after four cycles of reuse, demonstrating the stability and reusability of the solvent system. This study highlighted the potential of the LA/pentanol biphasic system for simultaneous hemicellulose conversion and lignin isolation, offering a simplified and sustainable one-step valorization route for biomass.

Isolation and Structural Characterization of Natural Deep Eutectic Solvent Lignin from Brewer's Spent Grains.

Brewer's spent grains (BSG) offer valuable opportunities for valorization beyond its conventional use as animal feed. Among its components, lignin-a natural polymer with inherent antioxidant properties-holds significant industrial potential. This work investigates the use of microwave-assisted extraction combined with acidic natural deep eutectic solvents (NaDESs) for efficient lignin recovery, evaluating three different NaDES formulations. The results indicate that choline chloride-lactic acid (ChCl-LA), a NaDES with superior thermal stability as confirmed via thermogravimetric analysis (TGA), is an ideal solvent for lignin extraction at 150 °C and 15 min, achieving a balance of high yield and quality. ChCl-LA also demonstrated good solubility and cell disruption capabilities, while microwaves significantly reduced processing time and severity. Under optimal conditions, i.e., 150 °C, 15 min, in the presence of ChCl-LA NaDES, the extracted lignin achieved a purity of up to 79% and demonstrated an IC50 (inhibitory concentration 50%) of approximately 0.022 mg/L, indicating a relatively strong antioxidant activity. Fourier transform infrared (FTIR) and 2D-HSQC NMR (heteronuclear single quantum coherence nuclear magnetic resonance) spectroscopy confirmed the successful isolation and preservation of its structural integrity. This study highlights the potential of BSG as a valuable lignocellulosic resource and underscores the effectiveness of acidic NaDESs combined with microwave extraction for lignin recovery.

The Influence of Washing of Rice Straw Lignin Isolation on Polyurethane Synthesis for Coating in Biomedical Application

This study examined the effectiveness of different washing methods in improving the quality and functionality of rice straw lignin for its application in the synthesis of polyurethane as a coating material for biomedical pulp. The findings demonstrated that lignin subjected to triple washing (LW3) displayed the highest level of purity, as evidenced by elevated values of ph-OH and total phenolic content. LW3 exhibited the lowest syringyl/guaiacyl ratio, however, it had the highest mean molecular weight. Moreover, the LW3 was employed as a precursor for the production of polyurethane. Kidney trays coated with polyurethane demonstrated prolonged resistance to hot and cold water for over 4 hours. This coating effectively adhered to the fibers of the tray and sealed the pores, resulting in enhanced water resistance. This study offers valuable insights into the advancement of sustainable biobased materials for the purpose of utilizing agricultural byproducts in the synthesis of polymers for various high-value applications.

Isolation of β-O-4-rich lignin from Birch in high yields enabled by continuous flow supercritical water treatment.

The continuous flow supercritical water (scH2O) treatment of Birch wood (T = 372-382 °C; t = 0.3-0.7 s; p = 260 bar) followed by alkali extraction of lignin allowed for the isolation of lignin and lignin carbohydrate complexes (LCCs) with a high number of β-O-4 moieties in the range 29-57/100 Ar (evaluated by quantitative 13C NMR analysis) in yields ranging between 13-19 wt% with respect to the initial wood. A "lightning rod effect" of carbohydrates has been claimed to explain the low degradation of β-O-4 bonds during the process. The structure of the isolated lignin was thoroughly elucidated via comprehensive NMR studies (HSQC, 13C and 31P). A low degree of condensation (DC) < 5% was found for all the lignin samples, which was only slightly dependent on the reaction severity. The number of aliphatic -OH, phenolic -OH, and -COOH groups was in the range 3.37-5.25, 1.41-2.31 and 0.39-0.73 mmol/g, respectively. The number of -COOH groups increased with increased severity, suggesting that oxidation can occur during the scH2O treatment. Furthermore, by simply varying the reaction severity, it was possible to tune important lignin properties, like the molar mass and the glass transition temperature (Tg).

Capability lignin from Acacia crassicarpa black liquor as an environmentally benign antibacterial agent to produce antibacterial and hydrophobic textiles

Recently, the growing health awareness of society on the utilization of fabrics has led to an increasing demand for natural-based antibacterial textiles. Lignin, a generous polyphenol compound in nature, is capable of preventing bacterial growth; in particular, it dwells bacteria closely together on human skin, such as Staphylococcus epidermidis, Bacillus subtilis, Propionibacterium acnes, and Staphylococcus aureus. However, the antibacterial properties of lignin are limited by factors such as the lignin concentration, source, and type of bacteria. This study aimed to evaluate the potency of lignin as an antibacterial agent for textiles. Moreover, the thermal properties and wettability of the textile after lignin coating were also investigated. This study showed that lignin isolation methods significantly contributed to the inhibition of bacterial growth in the clear zone diameter. In addition, the lignin structure, lignin concentration, and type of bacteria had notably different antibacterial effects. SEM images showed that lignin was successfully coated on the fiber, and the antibacterial textile was successfully fabricated with clear zones in the range of 0.1–0.5 cm against four different bacteria. Lignin did not significantly improve the thermal stability of the textile, as proven by the TGA results. After the HDTMS coating by dispersion method, the wettability of the lignin-textile improved to that of the hydrophobic material, with a contact angle greater than 119.05° with excellent antibacterial properties (clear zone of 0.1–0.43 cm).

Herbal Medicines Genkwadaphnin as Therapeutic Agent for Cancers and Other Human Disorders: A Review of Pharmacological Activities through Scientific Evidence

Backgrounds: Daphnane-type diterpenes are an important class of phytochemicals found to be present in the family Euphorbiaceae and Thymelaeaceae. It has anti-leukaemic, antihyperglycaemic, and anti-fertility activities in medicine. Daphne genkwa is indigenous to the Yangtze River and Yellow River of China. Daphne genkwa contains significant amounts of daphnane- type diterpenes. Phytochemical analysis of Daphne genkwa led to the isolation of flavonoids, lignins, coumarins, caffeotannic acids, and genkwadaphnin. Methods: Present review highlighted the biological potential of genkwadaphnin in medicine. All the scientific data of Daphne genkwa, and genkwadaphnin were collected from Google, Google Scholar, Science Direct, Scopus, and PubMed and analyzed in the present work to know the therapeutic potential of genkwadaphnin in medicine. Detailed pharmacological activities of genkwadaphnin were analyzed in the present work through scientific data analysis of various research works. Results: Genkwadaphnin is a daphnane diterpene ester molecule mainly isolated from the Daphne genkwa, Dendrostellera lessertii, Daphne odorata, Gnidia latifolia, and Gnidia glaucus. Genkwadaphnin has been reported to exert therapeutic potential against hepatocellular carcinoma, human colon cancer, squamous cell carcinoma, and leukemia. Further, it has a significant role in innate immunity, melanogenesis, skeletal diseases, inflammatory cytokines, and natural killer cell. However, pharmacokinetics and metabolomics aspects of genkwadaphnin were also discussed in the present work. Further, more scientific data on human clinical trials is needed to ensure the safety and efficacy of genkwadaphnin in medicine. Conclusion: In the present work, a successful review had been achieved by the above-mentioned scientific data, which signified the therapeutic potential of genkwadaphnin in medicine.

The Impact of Lignin Biopolymer Sources, Isolation, and Size Reduction from the Macro- to Nanoscale on the Performances of Next-Generation Sunscreen.

In recent years, concerns about the harmful effects of synthetic UV filters on the environment have highlighted the need for natural sun blockers. Lignin, the most abundant aromatic renewable biopolymer on Earth, is a promising candidate for next-generation sunscreen due to its inherent UV absorbance and its green, biodegradable, and biocompatible properties. Lignin's limitations, such as its dark color and poor dispersity, can be overcome by reducing particle size to the nanoscale, enhancing UV protection and formulation. In this study, 100-200 nm lignin nanoparticles (LNPs) were prepared from various biomass by-products (hardwood, softwood, and herbaceous material) using an eco-friendly anti-solvent precipitation method. Pure lignin macroparticles (LMPs) were extracted from beech, spruce, and wheat straw using an ethanol-organosolv treatment and compared with sulfur-rich kraft lignin (KL). Sunscreen lotions made from these LMPs and LNPs at various concentrations demonstrated novel UV-shielding properties based on biomass source and particle size. The results showed that transitioning from the macro- to nanoscale increased the sun protection factor (SPF) by at least 2.5 times, with the best results improving the SPF from 7.5 to 42 for wheat straw LMPs and LNPs at 5 wt%. This study underscores lignin's potential in developing high-quality green sunscreens, aligning with green chemistry principles.

Mechanochemical Tailoring of Lignin Structure: Influence of Different Particle Sizes in the Organosolv Process.

The autocatalyzed ethanolic organosolv process is gaining increasing attention for the sulfur-free isolation of lignin, which is subsequently used as a renewable substitute for various fossil-based applications. For the first time, the mechanochemical influence of seven different particle sizes of two different biomasses on the respective organosolv lignin structure is examined. Wine pruning (Pinot Noir) and wine pomace (Accent) are used for organosolv process with particle sizes ranging from 2.0-1.6mm to less than 0.25mm. As particle size decreases, the weight-average molecular weight increases, while the total phenol content decreases significantly. Additionally, the distribution of the lignin-typical monolignols and relevant substructures, as determined by two-dimensional heteronuclear nuclear magnetic resonance spectra single quantum coherence (HSQC), is observed. The degree of grinding of the biomass has a clear chemical-structural influence on the isolated HG and HGS organosolv lignins. Therefore, it is crucial to understand this influence to apply organosolv lignins in a targeted manner. In the future, particle size specifications in the context of the organosolv process should be expressed in terms of distribution densities rather than in terms of a smaller than specification.

Green preparations of nanolignin from acid-saccharification-treated sugarcane trash

Characterization of isolated lignin and utilization of nanotechnology to produce nanolignin as a functional material are paramount. Lignin was extracted from acid-saccharification sugarcane trash (SCT-ASac) to produce acid-saccharification lignin (ASac-lignin). Then, lignin was further processed to nanolignin by a self-assembly dialysis process using THF:ethanol (1:1) as the solvent. The chemical, physical, and thermal properties of the lignin were evaluated, and the nanolignin size was confirmed via morphological analysis and PSA. SCT-ASac treatment prior to lignin isolation affects the structure of SCT and enhances the accessibility of lignin. Furthermore, this pretreatment can reduce residual carbohydrates, increasing the purity value. ASac-lignin has a nonconjugated phenolic group structure with a high number of β-O-4 bonds, a syringyl content, aromatic groups with low thermal stability, and a molecular weight with good phenolic hydroxyl content and total phenolic compounds. The obtained nanolignin is a spherical and more uniform particle with sizes less than 100 nm. ASac-nanolignin has the potential to be an environmentally friendly material in derivative lignin synthesis.

Reactive Eutectic Media for Lignocellulosic Biomass Fractionation.

This study introduces an alternative approach towards lignocellulosic biomass fractionation. For this purpose, reactive eutectic media (REM) based on ammonium formate and different organic acids are investigated, possible products are identified, and the REM are employed for lignin extraction and terminal isolation of cellulose pulp from beech wood. The method promises a considerable process intensification by simultaneous separation of high purity cellulose pulp, lignin isolation as a cationically modified species, and production of value-added chemicals from reaction products of the REM. This study puts a further focus on the generated cellulose pulp and investigates it with respect to surface charge and fiber length.

Investigation of the alkaline hydrogen peroxide pretreatment: From cellulose saccharification to lignin isolation

Alkaline hydrogen peroxide (AHP) pretreatment, a green and effective technology for biomass fractionation, was studied to overcome the recalcitrance of bamboo for lignin isolation and facilitating enzymatic saccharification. In order to explore the impact of AHP pretreatment on the cellulose saccharification of bamboo, the glucan/xylan recovery, lignin removal, and structural properties of solid substrate were investigated in this research. AHP pretreatment at 90 ℃ for 60 min with 3.0 % H2O2 resulted in the maximum glucan/xylan hydrolysis yield reaching 90.62 % and 88.30 %, respectively. Specially, for the first time, the recovered lignin from the AHP liquid possesses up to 59.84/100Ar of β-O-4 linkages, abundant ferulic acid (FA), and p-coumarate (pCE) structures, as well as a homogeneous molecular structure with high purity (84.04%-96.20%) and preferable antioxidant activities (IC50: 0.015–0.018 mg/mL). These results provided theoretical support for the comprehensive valorization of lignocellulose, which is favorable for achieving viable biorefineries.

Isolation and characterisation of lignin using natural deep eutectic solvents pretreated kenaf fibre biomass

Extraction of lignin via green methods is a crucial step in promoting the bioconversion of lignocellulosic biomasses. In the present study, utilisation of natural deep eutectic solvent for the pretreatment of kenaf fibres biomass is performed. Furthermore, extracted lignin from natural deep eutectic solvent pretreated kenaf biomass was carried out and its comparative study with commercial lignin was studied. The extracted lignin was characterized and investigated through Infrared Fourier transform spectroscopy, X-ray Diffraction, thermogravimetric analysis, UV–Vis spectroscopy, and scanning electron microscopy. FTIR Spectra shows that all samples have almost same set of absorption bands with slight difference in frequencies. CHNS analysis of natural deep eutectic solvent pretreated kenaf fibre showed a slight increase in carbon % from 42.36 to 43.17% and an increase in nitrogen % from − 0.0939 to − 0.1377%. Morphological analysis of commercial lignin shows irregular/uneven surfaces whereas natural deep eutectic solvent extracted lignin shows smooth and wavy surface. EDX analysis indicated noticeable peaks for oxygen and carbon elements which are present in lignocellulosic biomass. Thermal properties showed that lignin is constant at higher temperatures due to more branching and production of extremely condensed aromatic structures. In UV–VIS spectroscopy, commercial lignin shows slightly broad peak between 300 and 400 nm due to presence of carbonyl bond whereas, natural deep eutectic solvent extracted lignin does not show up any peak in this range. XRD results showed that the crystallinity index percentage for kenaf and natural deep eutectic solvent treated kenaf was 70.33 and 69.5% respectively. Therefore, these innovative solvents will undoubtedly have significant impact on the development of clean, green, and sustainable products for biocatalysts, extraction, electrochemistry, adsorption applications.

Interaction among lignocellulosic biomass components in thermochemical processes

This research aims to evaluate the thermal behavior of main components of biomass (hemicellulose, cellulose and lignin) in order to identify their synergistic effect in thermochemical processes. These components were isolated from sugarcane bagasse and straw using different chemical treatments and their chemical and physical-chemical characterizations were performed. Results showed that chemical treatments were adequate for cellulose and lignin isolation, although it was verified that more adequate methodologies must be sought for hemicellulose isolation. The thermogravimetric analysis of each sample and their mixtures in inert (N2) and oxidant (synthetic air) atmospheres allowed investigating the synergism among the components. It was observed that the synergistic effect was more pronounced in DTG curves in an oxidizing atmosphere. There was a weak interaction effect between cellulose and hemicellulose, but hemicellulose allowed reducing cellulose decomposition rate. Moreover, the mixture between hemicellulose and lignin showed a synergistic effect on lignin, which promoted an increase in hemicellulose decomposition rate, while hemicellulose anticipated the main event of lignin decomposition in an oxidizing atmosphere. It was found that lignin had a positive effect on cellulose decomposition in an oxidizing atmosphere, thus inhibiting its decomposition, while cellulose promoted an increase in lignin decomposition rate in its final event. Ultimately, results for the synergistic effect allowed detecting other components besides isolated elements in the biomass structure in smaller amounts, which nevertheless affect the behavior of its thermal decomposition.

Bioethanol production from organosolv treated beech wood chips obtained at pilot scale

Second generation bioethanol represents an important biofuel, but innovations on biomass pre-treatment and fermentation are needed to improve efficiency and cost-effectiveness in its production. In this work, beech wood chips were treated using an acetone-based organosolv fractionation process at pilot scale, resulting in the isolation of lignin, a high-purity cellulosic pulp and a liquid stream containing hemicellulose sugars. The hemicellulose stream (C5 stream) contained xylose as major sugar and also contained fermentation inhibitors such as furanics, organic acids and phenolics. The cellulosic pulp was enzymatically hydrolysed producing a glucose-rich stream (C6 stream). These streams were used as fermentation substrates by the yeasts Saccharomyces cerevisiae and Spathaspora passalidarum, in separate cultures. Addition of ammonium phosphate or of yeast extract and peptone (YP) as nitrogen sources improved yeast growth. The C6 stream was readily fermentable. When at a sugar concentration of 192 g L−1 and supplemented with YP, the ethanol titre reached 91 g L−1, with a yield of 0.49 g ethanol per g consumed sugars. The C5 stream required detoxification to achieve fermentability. In detoxified C5 stream, S. passalidarum produced 0.46 g ethanol per gram consumed sugars. Fermentation of the resulting streams at 10-L scale confirmed the results obtained at laboratory scale. As alternative approach, sequential fermentation of the C5 stream by S. passalidarum followed by C6 stream addition and inoculation with S. cerevisiae resulted in almost complete sugar utilization and an ethanol yield of 0.41 g per gram consumed sugar albeit with a lower ethanol productivity.

Production of Sodium Lignosulfonate (SLS) Surfactant from Oil Palm Empty Fruit Bunches (OPEFB) Using Microwave

The aim of this study was to investigate the effect of using a microwave in synthesizing Sodium Lignosulfonate (SLS) surfactant made of Oil Palm Empty Fruit Bunches (OPEFB) which contains lignin as the content to be processed, especially in the sulfonation process. The observed variables are the NaHSO3 concentration ranging from 0.1 M to 0.7 M, reaction time ranging from 30 minutes to 90 minutes, and microwave power ranging from 300 W to 750 W. on the yield and comparing the results of SLS synthesized with microwave to those obtained through conventional heating methods in the sulfonation process. The process encompassed several steps, including drying, milling, delignification, lignin isolation, and sulfonation using microwaves. Afterward, the SLS results were subjected to analysis through FTIR and HLB testing. The findings revealed a positive correlation between NaHSO3 concentration, reaction time, microwave power, and the yield of SLS Product, with the optimal conditions being at the NaHSO3 concentration of 0.7 M, microwave power of 600 W, and reaction time of 75 minutes. Moreover, the microwave method demonstrated greater efficiency in increasing the SLS Product yield by up to 24% compared to the conventional method.

FACILE PRODUCTION OF 4-HYDROXYBENZOIC ACID FROM OIL PALM EMPTY FRUIT BUNCH CELL WALLS BY ALKALI DEGRADATION AT ROOM TEMPERATURE

Oil palm empty fruit bunches are biorefinery waste produced from the oil palm factory. Palm lignin is partially ended with p-hydroxybenzoylated structure, which is a promising resource to produce 4-hydroxybenzoic acid. Herein, 4-hydroxybenzoic acid is produced by the degradation of oil palm empty fruit bunch cell walls with sodium hydroxide solution at room temperature without lignin isolation. The 4-hydroxybenzoic acid was obtained as the only main monomeric product from the process. The yield of 4-hydroxybenzoic acid can reach 7.87&amp;#37; based on the amount of oil palm empty fruit lignin. The sodium hydroxide concentration is the most important factor that affects the 4-hydroxybenzoic acid production yield and selectivity. The possible 4-hydroxybenzoic acid production routes were proposed. And the production route is considered to be formed mainly by the cleavage of C-O bonds at the &amp;gamma;-hydroxyl position of the syringyl unit in oil palm empty fruit bunch lignin.

A systematic study on the processes of lignin extraction and nanodispersion to control properties and functionality

This article is analyzing differences in chemistry and structure of lignins isolated using various protocols and reveals influence of their properties on nanolignins prepared at different pH.