Study of the antioxidant capacity of Miscanthus sinensis lignins

Experimental investigations on PVA/chitosan and PVA/chitin films for active food packaging using Oxytenanthera abyssinica lignin nanoparticles and its UV-shielding, antimicrobial, and antiradical effects

This study investigated the effect of adding lignin nanoparticles (LNPs) derived from Oxytenanthera abyssinica via alkali-acid nanoprecipitation method to polyvinyl alcohol/chitosan (PVA/CI) and polyvinyl alcohol/chitin (PVA/CH) films for the active food packaging applications. Adding LNPs at concentrations of 1 % and 3 % improved the films' thermal stability and mechanical properties. The lowest water solubility and moisture content were observed in PVA/CI/LNPs films. LNPs exhibited effective 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, with the highest values observed in PVA/CH/LNPS and PVA/CI/LNPS films with values of 87.47 and 88.74 % respectively. The addition of LNPs also improved the UV-blocking abilities of the films. PVA/CH/LNP3 and PVA/CI/LNP3 have the smallest percentage transmission values of 3.34 % and 0.86 % in the UV range. The overall migration of dietary stimulants was lower in PVA/CI/LNPS and PVA/CH/LNPS films compared to PVA film. Antibacterial tests demonstrated the inhibitory capacity of the synthesized biofilms against both gram-positive and negative bacterial species, with the highest inhibitory value of 26 mm. The study suggests that PVA/CH/LNPS and PVA/CI/LNPS films have potential applications as active food packaging materials and can be explored in other potential applications such as drug delivery, tissue engineering, wound healing, and slow-release urea fertilizer development.

Conversion of archeological iron rust employing coconut husk lignin

Rust powder collected from an archeological iron was evaluated by complementary analyses such as FTIR, XRD, XRF, and SEM/EDX. The analyses revealed that lepidocrocite (L) was the major component in the archeological iron. Coconut husk (CH) can be classified as a type of lignocellulosic biomass of renewable resources that are widely available, especially in coastal areas. In this research, the isolated lignin extracted from CH is being studied as a potential alternative for environmentally friendly applications. The isolated lignin from soda and organosolv pulping went through several analyses such as FTIR, NMR (13C and 2D-HSQC), and TGA analyses. The analyses showed that lignin isolated via soda pulping has superior antioxidant capabilities due to its greater phenolic-OH content compared to lignin isolated from organosolv pulping. The effects of lignin concentrations, pH, and reaction time were utilized in rust conversion studies of an archeological iron. 5 wt% of soda lignin (SL) was revealed as the ideal condition in this rust conversion study with a value of 84.21 %. The treated rust powder with 5 wt% of SL was then further gone through several complementary analyses, which revealed that the treated rust had nearly transformed into an amorphous state.

Statistical evaluation of DPPH, ABTS, FRAP, and Folin-Ciocalteu assays to assess the antioxidant capacity of lignins

This research studies in detail four different assays, namely DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric ion reducing antioxidant potential) and FC (Folin-Ciocalteu), to determine the antioxidant capacity of standard substances as well as 50 organosolv lignins, and two kraft lignins. The coefficient of variation was determined for each method and was lowest for ABTS and highest for DPPH. The best correlation was found for FRAP and FC, which both rely on a single electron transfer mechanism. A good correlation between ABTS, FRAP and FC, respectively, could be observed, even though ABTS relies on a more complex reaction mechanism. The DPPH assay merely correlates with the others, implying that it reflects different antioxidative attributes due to a different reaction mechanism. Lignins obtained from paulownia and silphium have been investigated for the first time regarding their antioxidant capacity. Paulownia lignin is in the same range as beech wood lignin, while silphium lignin resembles wheat straw lignin. Miscanthus lignin is an exception from the grass lignins and possesses a significantly higher antioxidant capacity. All lignins possess a good antioxidant capacity and thus are promising candidates for various applications, e. g. as additives in food packaging or for biomedical purposes.

Nanogreen is the new future: the conversion of lignin and lignocellulosic wastes into nanomaterials

The lignocellulose biorefinery industry has assumed an important role within the current scenario. Lignin is an abundant and available biopolymer and one of the compounds present in the lignocellulosic waste. Therefore, processing lignin into new materials and nanomaterials, such as nanolignin, has attracted the attention of the scientific community. Lignin nanoparticles are materials that have excellent properties, such as biodegradability and non-toxicity, and have great potential as chelating agents, antimicrobials agents, UV protectors, nanofillers, adsorbents, catalysts, supercapacitors, emulsion stabilizers, delivered systems, drugs, and gene carriers. This review article covers the emergent scenario of nanolignin and the main aspects of scientific interest, such as the conversion and functionalization of lignin, the valorization of lignocellulose waste, and nanoparticle synthesis. A techno-economic evaluation of the biorefinery model of the nanolignin synthesis is presented based on the simulation of the process on the experimental and commercial databases available and reported by some authors. Finally, the techno-economic assessment is complemented by the life cycle assessment of various nanolignin synthesis pathways reported to evaluate the environmental implications and support this emergent technology development.

Preparation of alkali lignin extracted from ligno-cellulosic populus tremula fibers: Application to copper oxide nanoparticles synthesis, characterization, and methylene blue biosorption study

The green synthesis of nanoparticles using biogenic approaches constitutes a challenge for effective applications. The massive aliphatic hydroxyl groups of lignin exhibited excellent reduction properties allowing the production of metallic nanoparticles. In this work, alkali lignin was extracted from virgin populus tremula and used for the preparation of copper oxide nanoparticles. The analysis of the prepared nanoparticles was assessed using Fourier Transform Infra-red (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), and Transmission Electron Microscopy (TEM). FT-IR results displayed that different phytochemicals constituents of lignin extract were responsible for the production of CuO nanoparticles. XRD information demonstrated monoclinic CuO nanoparticles with a mean size of 12.4 nm. SEM images showed that some nanoparticles were quite separated from each other and some of them were agglomerated due to the oxidation of metal nanoparticles. TEM photos indicated that the overlap of the nanoparticles resulted in rectangular patterns due to the presence of lignin on the surface of CuO nanoparticles. Finally, the prepared CuO nanoparticles were applied for the removal of methylene blue from water. The results showed that the maximum adsorption capacity reached 85 mg/g at the following conditions: T = 20 °C, pH = 6, and time = 60 min.

Inspired by Skeletal Muscles: Study of the Physical and Electrochemical Properties of Derived Lignocellulose-Based Carbon Fibers

Skeletal muscles exhibit excellent properties due to their well-developed microstructures. Taking inspiration from nature that thick filaments and thin filaments are linked by "cross-bridges", leading to good stability and ion transport performance of muscles. In this work, extracted poplar lignin and microcrystalline cellulose (MCC) were connected by biomimetic covalent bonds, akin to biological muscle tissue, in which isophorone diisocyanate was used as the chemical crosslinking agent. Then, poplar lignin-MCC was mixed with polyacrylonitrile to serve as the precursor for electrospinning. The results show that due to the effective covalent-bond connection, the precursor fibers possess excellent morphology, smooth surface, good thermal stability, and high flexibility and toughness (average elongation-at-break is 51.84%). Therefore, after thermal stabilization and carbonization, derived lignocellulose-based carbon fibers (CFs) with a reduced cost, complete fiber morphology with a uniform diameter (0.48 ± 0.22 μm), and high graphitization degree were obtained. Finally, the electrodes fabrication and electrochemical testing were carried out. The results of electrochemical impedance spectroscopy (EIS) indicate that the Rs and Rct values of CFs supercapacitors are 1.18 Ω and 0.14 Ω, respectively. Results of cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) suggest that these CFs demonstrate great application potential in electrochemical materials.

Structural properties and antioxidation activities of lignins isolated from sequential two-step formosolv fractionation

In order to investigate the solubility behavior of lignin in formic acid (FA) solution Phragmites australis biomass was subjected to a sequential two-step formosolv fractionation using 88% FA followed by 70% FA to obtain four specific lignin fractions, designated as IFL-88%, IFSL-70%, IFIL-70% and IFL-EtAc. The structures of the four isolated lignin fractions were successfully characterized by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (2D-HSQC NMR), thermogravimetric analysis (TGA), and gas chromatography-mass spectroscopy (GC/MS). Furthermore, the total phenolic content of the four isolated lignin samples was assessed by Folin-Ciocalteu analysis. The data from structural properties revealed that depolymerization of the isolated lignin fractions occurred via β-O-4 cleavage, accompanied by competitive condensation reaction. Interestingly, 70% aqueous FA could separate specific lignin fractions with different antioxidant capacities of ABTS˙+ and DPPH radical scavenging activity. Due to the high total phenolic hydroxyl content (25%) and low molecular weight (Mw = 2760 Da) and polydispersity index (PDI = 1.5), IFL-EtAc lignin showed excellent antioxidant activity at the same concentration of 2.0 mg mL-1 in comparison with three other isolated lignin fractions, and it was even equal to that of commercial antioxidant butylated hydroxytoluene (BHT). These findings are helpful to separate specific lignins with higher value as potential antioxidants by sequential two-step formosolv fractionation in lignin chemistry.

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.

Ethanol organosolv lignin from different agricultural residues: Toward basic structural units and antioxidant activity

The growing interest in the substitution of synthetic food antioxidants by natural ones has fostered research on vegetable sources and the screening of raw materials for identifying new antioxidants. Special attention is focused on their extraction from inexpensive or residual sources from agricultural industries. Herein, the antioxidant activities of lignin obtained from 4 residual sources were investigated. The obtained lignin samples were characterized by different analytical techniques evaluating their chemical structure, phenolic content, thermal behavior and molecular weight. The antioxidant activity of the analyzed lignins was evaluated by the DPPH assay, the radical ABTS assay, and trivalent iron reduction method. It was found t that lignin antioxidants could scavenge free radicals and reduce oxidants. The high correlation between antioxidant capacity and its total phenol content indicated that phenolic hydroxyl groups were the main contributors to these lignins' antioxidant activity.

Solid acid facilitated deep eutectic solvents extraction of high-purity and antioxidative lignin production from poplar wood

Pure deep eutectic solvents (DESs) system of choline chloride (ChCl)/Lactic acid (Lac) were demonstrated to be an effective strategy for extraction of lignin. In this study, two kinds of different promising solid acid (SA) with DESs were designed to promote the pretreatment of lignocellulose. The SA of phosphotungstic acid (H₃O₄₀PW₁₂) and iron bromide (FeBr₃) were introduced into DESs to extract poplar wood lignin and evaluate the antioxidant activity. It was found that 82.2% and 80.9% of lignin were obtained from poplar wood under H₃O₄₀PW₁₂-ChCl/Lac acid and FeBr₃-choline ChCl/Lac system with 4 h and 8 h, respectively. The lignin fractions with a high purity (>89%), low molecular weight (Mw 1800-2000 g/mol). Besides, the antioxidant activities of lignin fractions were better than butyl hydroxyanisole (BHA). Therefore, DES lignin has prominent antioxidant activity and could developed a potential natural cosmetics and food packaging.

Characterization of lignin extracted from Acanthopanax senticosus residue using different methods on UV-resistant behavior

Acanthopanax senticosus has been used to extract active products. However, abundant Acanthopanax senticosus residues (ASR), which contain plenty of lignin are discarded after extraction. An appropriate extraction method should be chosen to obtain the lignin with such desirable properties. Thus, this study investigated the effect of alkali, milled wood, deep eutectic solvent and ethanol methods on the lignin. Lignin obtained from different extraction methods were characterized, yields, chemical structure, thermal behavior, molecular weight and phenolic content were evaluated. The results show that the process of lignin acquisition has a great influence on the properties of lignin. Moreover, the multifarious functional groups exist in lignin macromolecules, such as phenolic, ether groups and other chromophores, conferred good UV resistance to lignin. Among them, the lignin from alkali method has the most phenolic-OH groups and smallest molecular weight result in a good UV-resistant, the SPF value achieves 2.39 at 1% AL content, the alkali method was the best way to make sunscreen blended with cream take various factors into consideration. This study used lignin as a bioactive ingredient to provide UV-resistant property to sunscreen formulations. Furthermore, lignin extracted from Acanthopanax senticosus residue provides a new application for the treatment of herb residue waste.

Investigation on Green Synthesis, Biocompatibility, and Antibacterial Activity of Silver Nanoparticles Prepared Using Cistus incanus

This paper describes the plant-mediated preparation of silver nanoparticles with aqueous extract and infusion of Cistus incanus leaves. To evaluate aqueous extract and infusion antioxidant capacity and total phenolic content the DPPH and Folin-Ciocalteau methods were utilized. The antioxidant capacity and total phenolic content of extract and infusion were equal to 85.97 ± 6.54 mg gallic acid equivalents per gram of dry weight.; 10.76 ± 0.59 mg/mL and 12.65 ± 1.04 mg gallic acid equivalents per gram of dry weight.; 3.10 ± 0.14 mg/mL, respectively. The formed nanoparticles displayed the characteristic absorption band in the 380-450 nm wavelength range. The average size of particles was in the 68.8-71.2 nm range. Morphology and phase composition analysis revealed the formation of spherical nanoparticles with a face-centred cubic structure. Immune compatibility tests of nanoparticles and plant extracts showed no activation of the THP1-XBlue™ monocyte. Cytotoxicity tests performed with L929 mice fibroblasts showed that nanoparticles should be utilized at a concentration of 16 ppm. The minimum inhibitory concentrations determined with the microdilution method for nanoparticles prepared with plant infusion for S. aureus and S. epidermidis were 2 ppm and 16 ppm, respectively.

Effect of organosolv extraction on the structure and antioxidant activity of eucalyptus kraft lignin

In this study, three lignin fractions F1, F2, and F3 were obtained from eucalyptus kraft lignin (EKL) by solvent extraction with ethyl acetate, acetone, and acetone/water. The antioxidant activity of these lignin fractions were measured and evaluated by using the DPPH radical scavenging activity, ABTS radical cation scavenging activity and ferric reducing antioxidant power analysis. These lignin fractions were also characterized by applying Gel permeation chromatography, Fourier transform infrared, ³¹P NMR and 2D HSQC NMR techniques. The three different lignin fractions had rather different average molecular sizes, as well as different phenolic and methoxy functional contents. The ethyl acetate fraction (F1) with the lowest average molecular weight (2342 g/mol) and the highest phenolic hydroxyl content (4.2457 mmol/g) and methoxy groups (6.2714 mmol/g) showed high homogeneity and the highest antioxidant activity. Its DPPH scavenging activity, ABTS⁺ scavenging activity, and ferric reducing the antioxidant power were 68.67%, 75.57%, and 91.89 μmol/g, respectively. Moreover, the antioxidant activity of F1 and F2 was found to be higher than that of butylated hydroxytoluene. Therefore, solvent extraction was shown to be an effective way to separate lignin fractions with high homogeneity, high antioxidant activity, which could lead to application of lignin with higher value.

Chemical, Thermal and Antioxidant Properties of Lignins Solubilized during Soda/AQ Pulping of Orange and Olive Tree Pruning Residues

Some agroforestry residues such as orange and olive tree pruning have been extensively evaluated for their valorization due to its high carbohydrates content. However, lignin-enriched residues generated during carbohydrates valorization are normally incinerated to produce energy. In order to find alternative high added-value applications for these lignins, a depth characterization of them is required. In this study, lignins isolated from the black liquors produced during soda/anthraquinone (soda/AQ) pulping of orange and olive tree pruning residues were analyzed by analytical standard methods and Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (solid state 13C NMR and 2D NMR) and size exclusion chromatography (SEC). Thermal analysis (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC)) and antioxidant capacity (Trolox equivalent antioxidant capacity) were also evaluated. Both lignins showed a high OH phenolic content as consequence of a wide breakdown of β-aryl ether linkages. This extensive degradation yielded lignins with low molecular weights and polydispersity values. Moreover, both lignins exhibited an enrichment of syringyl units together with different native as well as soda/AQ lignin derived units. Based on these chemical properties, orange and olive lignins showed relatively high thermal stability and good antioxidant activities. These results make them potential additives to enhance the thermo-oxidation stability of synthetic polymers.

Lignin nanoparticles enter the scene: A promising versatile green tool for multiple applications

Strategies to take advantage of residual lignin from industrial processes are well regarded in the field of green chemistry and biotechnology. Quite recently, researchers transformed lignin into nanomaterials, such as nanoparticles, nanofibers, nanofilms, nanocapsules and nanotubes, attracting increasing attention from the scientific community. Lignin nanoparticles are seen as green way to use high-value renewable resources for application in different fields because recent studies have shown they are non-toxic in reasonable concentrations (both in vitro and in vivo assays), inexpensive (a waste generated in the biorefinery, for example, from the bioethanol platform) and potentially biodegradable (by fungi and bacteria in nature). Promising studies have tested lignin nanoparticles for antioxidants, UV-protectants, heavy metal absorption, antimicrobials, drugs carriers, gene delivery systems, encapsulation of molecules, biocatalysts, supercapacitors, tissue engineering, hybrid nanocomposites, wound dressing, and others. These nanoparticles can be produced from distinct lignin types and by different chemical/physical/biological methods, which will result in varied characteristics for their morphology, shape, size, yield and stability. Therefore, taking into account that the theme "lignin nanoparticles" is a trending topic, this present review is emerging and has the discuss the current status, covering from concepts, the formation mechanism, synthesis methods and applications, to the future perspectives and challenges linked to lignin-based nanomaterials, aiming at the viability and commercialization of this biotechnological product.

Antioxidant, antibacterial and antitumoural activities of kraft lignin from hardwood fractionated by acid precipitation

Kraft lignin, so far useful for energy generation, has been gathering considerable attention as an alternative material to replace fossil-based resources mainly due to its high phenolic content. However, the wide molecular weight distribution and chemical composition heterogeneity led to the development of fractionation methods. Herein, to narrow such characteristics we used eucalypt kraft lignin fractionated at pH's 9, 7, 5 and 3 by sequential acid precipitation. These lignin fractions were first characterised by simultaneous pyrolysis and trimethylsilylation (SPyT) with N-Methyl-N-(trimethylsilyl) trifluoroacetamide with posterior tests of antioxidant, antibacterial, and antitumour activities. We observed higher ratio of syringyl/guaiacyl groups and increase in antioxidant activity in those fractions with lower molecular weight (precipitated at lower pH's). Fractions precipitated at pH's 9 and 7 have shown an outstanding antibacterial activity against five bacteria. Moreover, fractions 7 and 5 presented at cytotoxicity tests higher ability to inhibit the growth of U87MG and T98G glioma cells, while only a slight inhibition of adult human fibroblasts (non-tumour cells) was detected.

Effect of sequential acid-alkaline treatment on physical and chemical characteristics of lignin and cellulose from pine (Pinus spp.) residual sawdust

Timber industry generates large amounts of residues such as sawdust. Softwoods have a significant economic value for timber production and the Pinus genus is widely utilized. Thus, the aim of this work was to study the hemicellulose extraction and lignin recovery from pine (Pinus spp.) residual sawdust (PRS) by sequential acid-alkaline treatment, generating a cellulose-rich solid fraction. The hemicellulose removed was 87.11% (wt·wt^-1) after dilute acid treatment at 130 °C, 4.5% (wt·wt^-1) of H₂SO₄ for 20 min at 120 rpm. Three temperatures were evaluated for recovering the lignin and the highest yield, 93.97% (wt·wt^-1), was achieved at 170 °C, 10% (wt·wt^-1) of NaOH for 90 min at 120 rpm. Lignin was characterized by Fourier-transform infrared spectroscopy, nuclear magnetic resonance and thermogravimetry. The resulting cellulose-rich fraction exhibited polymorphic transformation. The results demonstrated that PRS is a promising lignocellulosic residue whose lignin and carbohydrates can be readily obtained.

Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment

Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4' linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.

Preparation, Thermal, and Mechanical Characterization of UV-Cured Polymer Biocomposites with Lignin

The preparation and the thermal and mechanical characteristics of lignin-containing polymer biocomposites were studied. Bisphenol A glycerolate (1 glycerol/phenol) diacrylate (BPA.GDA) was used as the main monomer, and butyl acrylate (BA), 2-ethylhexyl acrylate (EHA) or styrene (St) was used as the reactive diluent. Unmodified lignin (L) or lignin modified with methacryloyl chloride (L-M) was applied as an ecofriendly component. The influences of the lignin, its modification, and of the type of reactive diluent on the properties of the composites were investigated. In the biocomposites with unmodified lignin, the lignin mainly acted as a filler, and it seemed that interactions occurred between the hydroxyl groups of the lignin and the carbonyl groups of the acrylates. When methacrylated lignin was applied, it seemed to take part in the creation of a polymer network. When styrene was added as a reactive diluent, the biocomposites had a more homogeneous structure, and their thermal resistance was higher than those with acrylate monomers. The use of lignin and its methacrylic derivative as a component in polymer composites promotes sustainability in the plastics industry and can have a positive influence on environmental problems related to waste generation.

From Black Liquor to Green Energy Resource: Positive Electrode Materials for Li-O2 Battery with High Capacity and Long Cycle Life

Black liquor has caused a tremendous degree of pollution and waste. Exploring the utilization of lignin, which is the major component of black liquor, has become a key factor in dealing with the problem. In this study, lignin derived from black liquor was used as a raw material to prepare carbon materials through different activation methods including KOH, H₃PO₄, and steam activation. The structure and properties of obtained samples were characterized as well as electrochemical performance when applied on a lithium-oxygen battery. Results of N₂ adsorption/desorption showed that all obtained samples possessed high surface area of over 1000 m²/g. XRD, Raman, and XPS also indicated that obtained samples possessed a large defect area and many functional groups. Electrochemical measurements illustrated that all obtained samples exhibited a high discharge capacity over 2.8 mAh/cm² at 0.02 mA/cm², while LKAC exhibited the highest discharge capacity of 7.2 mAh/cm². Cycling tests of all obtained samples indicated a long cycle life of at least 300 cycles. LSAC maintained a 100% retention rate of capacity and stable terminal voltage even after 800th cycle, and its cycling performance was investigated further by XRD and EIS. This study demonstrated excellent performance for lignin-based carbon materials, and provided alternative materials for positive electrode of lithium-oxygen battery.

Transparent Cellulose/Technical Lignin Composite Films for Advanced Packaging

Although recent work has shown natural lignin products are promising to fabricate various polymer based functional composites, high-value applications were challenged by their structural complexity and inhomogeneity. This work specially assessed the potential of four technical lignins for cellulose based functional films production. These four technical lignins were obtained by emerging pretreatment systems, i.e., lactic acid-betaine deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone (Soda/AQ) and the sodium salicylate hydrotrope, and their phenolic substructures were comparatively identified by prevalent ³¹P NMR technique. The influence of lignin chemical structure on the antioxidant potential and UV-shielding performance of the prepared cellulose/technical lignin composite films were assessed. Results showed severe organosolv and soda/AQ pretreatment produced technical lignins with higher total phenolic hydroxyl groups (3.37 and 3.23 mmol g-1 respectively), which also exhibited higher antioxidant activities. The composite films could effectively block the ultraviolet lights especially for UVB region (ultraviolet B, 280–315 nm) at only 5 wt.% lignin content. The contribution of lignin phenolic substructures to both antioxidant activity and UV-shielding property from high to low was syringyl > guaiacyl > p-hydroxyphenyl phenolic hydroxyl groups. This work provided some useful information that could facilitate upstream lignin extraction or downstream value-added applications.

Effect of Bay Leaves Essential Oil Concentration on the Properties of Biodegradable Carboxymethyl Cellulose-Based Edible Films

Films containing bay leaves essential oils (BEOs) were prepared and evaluated for edible packaging applications. The BEOs were extracted by the Soxhlet method, using ethanol or methanol as organic solvent. Then, films were prepared by “solvent casting” technique using carboxymethyl cellulose (CMC), with different concentrations for the as-obtained BEOs (from 1% to 30% wt.). The resulting films were characterized to evaluate their physical (thickness, moisture content, water solubility and water vapor permeability), optical (transparency and UV-light barrier), mechanical (tensile strength and elongation at break), antioxidant and antimicrobiological properties Attractive films were obtained for food active packaging applications, as they presented a high antioxidant activity (up to 99%) and total phenolic content, and good barrier properties against water vapor (50% improved of CMC) in the case of CMC-film containing 15% wt. ethanolic extract. Related to optical properties, UV-light barrier effect was increased (almost 100% of protection) avoiding typical lipids oxidation in food systems. High water solubility (93%) was also found, ensuring also their biodegradability. Moreover, it was demonstrated that developed films inhibit microorganisms’ growth (Escherichia coli and Candida glabrata), this avoiding an early food oxidation.

Lignin - An underutilized, renewable and valuable material for food industry

Lignin is the second most abundant biorenewable polymers only next to cellulose and is ubiquitous in various plant foods. In food industry, lignin often presented as a major component of by-products from plant foods. In the last decade, the food and nutritional interests of lignin attracted more and more attentions and great progresses have been accomplished. In the present review, the structure, physicochemical properties, dietary occurrence and preparation methods of lignin from food resources were summarized. Then, the versatile activities of food lignin were introduced under the subtitles of antioxidant, antimicrobial, antiviral, antidiabetic and other activities. Finally, the potential applications of food lignin were proposed as a food bioactive ingredient, an improver of food package films and a novel material in fabricating drug delivery vehicles and contaminant passivators. Hopefully, this review could bring new insights in exploiting lignin from nutrition- and food-directed views.

Two-stage alkali-oxygen pretreatment capable of improving biomass saccharification for bioethanol production and enabling lignin valorization via adsorbents for heavy metal ions under the biorefinery concept

Converting lignin into value-added products in current lignocellulosic biorefineries has been challenging, which in turn restricts the commercialization of many lignocellulosic biorefineries. In this work, a two-stage alkali-oxygen assisted liquid hot water pretreatment (AlkOx) was proposed as the first step of biorefinery. This alkali-oxygen pretreatment facilitated biomass fractionation by solubilizing majority of lignin in water-soluble fraction, while remaining most of cellulose and hemicellulose in water-insoluble fraction. As a result, biomass saccharification was significantly improved by selective removal and oxidative modification of lignin through alkali-oxygen pretreatment. Moreover, lignin residues from both pretreatment hydrolysate and enzymatic hydrolysate were shown to be favorable adsorbents for Pb(II) ions, with adsorption capacity of 263.16 and 90.91 mg/g, respectively. Results demonstrated that this integrated process could not only improve biomass saccharification but also enable lignin valorization, which encouraged the holistic utilization of lignin residues as part of an integrated biorefinery.

Multistage treatment of almonds waste biomass: Characterization and assessment of the potential applications of raw material and products

Almond shells are waste biomass generated in agro-industrial activities, which represent a resource that can be further valorized upon treatment. The purpose of this work was to assess new value-added products obtained through a novel multi-stage delignification process of almond shells. A comprehensive chemical characterization of the raw materials and products involved in each stage of the process was carried out. Moreover, an extensive mass balance was developed, providing a full understanding of the extraction process. The pulps produced did not display a significant cellulose loss and hence they could be exploited as cellulose-rich materials. On the other hand, the obtained lignins presented high purity values (≈90%) and a high reactivity, and their structures became more condensed and homogeneous after each extraction cycle. These features would allow their utilization as feedstock of renewable materials such bio-sourced phenolic resins.

Acetic acid lignins from Chinese quince fruit (Chaenomeles sinensis): effect of pretreatment on their structural features and antioxidant activities

In this study, three pretreatment processes were evaluated for their effects on the structural features and antioxidant activities of lignins extracted by the acetosolv process from the fruit of Chinese quince. The three pretreatments included dephenolization, sugar removal, and multiple processes (a combination of both dephenolization and sugar removal). The results showed that after sugar removal pretreatment, the carbohydrate content, the molecular weight and S/G value of the lignin fractions decreased. However, after dephenolization pretreatment, the carbohydrate content and the molecular weight of the lignin fractions increased. After sugar removal and dephenolization, there were increases in the temperatures corresponding to the maximal rate of decomposition (DTG_max) in all lignin fractions. The radical scavenging index of lignin after sugar removal pretreatment was higher compared to other pretreatments and no treatment. The results of these tests showed that sugar removal, as a pretreatment, enhanced lignin extraction, yielding pure and highly functional lignins. Additionally, dephenolization or multiple process were beneficial to the acquisition of macromolecular lignins. All the results provided references for the biorefinery of biomass rich in polyphenol and sugar compounds.

Three pretreatments, including sugar removal, dephenolization and multiple processes, are applied on the lignin extraction from Chinese quince fruits.

Attenuated Total Reflection Mid-Infrared (ATR-MIR) Spectroscopy and Chemometrics for the Identification and Classification of Commercial Tannins

Attenuated total reflection Fourier transform infrared (FT-IR) spectroscopy was used to characterize 40 commercial tannins, including condensed and hydrolyzable chemical classes, provided as powder extracts from suppliers. Spectral data were processed to detect typical molecular vibrations of tannins bearing different chemical groups and of varying botanical origin (univariate qualitative analysis). The mid-infrared region between 4000 and 520 cm(-1) was analyzed, with a particular emphasis on the vibrational modes in the fingerprint region (1800-520 cm(-1)), which provide detailed information about skeletal structures and specific substituents. The region 1800-1500 cm(-1) contained signals due to hydrolyzable structures, while bands due to condensed tannins appeared at 1300-900 cm(-1) and exhibited specific hydroxylation patterns useful to elucidate the structure of the flavonoid monomeric units. The spectra were investigated further using principal component analysis for discriminative purposes, to enhance the ability of infrared spectroscopy in the classification and quality control of commercial dried extracts and to enhance their industrial exploitation.

Hydrogen peroxide sensing and cytotoxicity activity of Acacia lignin stabilized silver nanoparticles

The study is aimed at detection of hydrogen peroxide (H2O2) using Acacia lignin mediated silver nanoparticles (AGNPs). The synthesis of AGNPs was achieved at conditions optimized as, 3 ml of 0.02% lignin and 1mM silver nitrate incubated for 30 min at 80°C and pH 9. Initial screening of AGNPs was performed by measuring the surface plasmon resonance peak at 410-430 nm using UV-vis spectrophotometer. Transmission electron microscopy, atomic force microscopy, X-ray diffraction and particle size analysis confirmed the spherical shaped face centered cubic structure and 10-50 nm size of AGNPs. The infrared spectroscopy study further revealed that the active functional groups present in lignin were responsible for the reduction of silver ions (Ag(+)) to metallic silver (Ag(0)). Lignin stabilized silver nanoparticles showed good sensitivity and a linear response over wide concentrations of H2O2 (10(-1) to 10(-6)M). Further, the in vitrocytotoxicity activity of the lignin mediated AGNPs (5-500 μg/ml) demonstrated toxicity effects in MCF-7 and A375 cell lines. Thus, lignin stabilized silver nanoparticles based optical sensor for H2O2 could be potentially applied in the determination of reactive oxygen species and toxic chemicals which further expands the importance of lignin stabilized silver nanoparticles.

Antimicrobial and antioxidant surface modification of cellulose fibers using layer-by-layer deposition of chitosan and lignosulfonates

To confer cellulose fibers antimicrobial and antioxidant activities, chitosan (CS)/lignosulfonates (LS) multilayers were constructed on fibers surfaces through layer-by-layer deposition technique. The formation of CS/LS multilayers on cellulose fibers surfaces was verified by X-ray photoelectron spectroscopy (XPS) and zeta potential measurement. The surface morphologies of CS/LS multilayers on fibers surfaces were observed by atomic force microscopy (AFM). The results showed that characteristic element (i.e. N and S element) content increased with increasing bilayers number, the surface LS content increased linearly as a function of bilayers. Zeta potential of modified fibers was inversed after deposition of each layer. AFM phase images indicated that the cellulose microfibrils on fibers surfaces were gradually covered by granular LS aggregate. The antimicrobial testing results demonstrated that CS/LS multilayers modified fibers with CS in the outermost layer exhibited higher antimicrobial activity against Escherichia coli. The antioxidant testing results showed that antioxidant activity of CS/LS multilayers modified fibers was better than that of original fibers under the same oxidation conditions.

Fractionation of hemp hurds by organosolv pretreatment and its effect on production of lignin and sugars

Fractionation of hemp hurds into its three main components, cellulose, hemicellulose, and lignin, was carried out using organosolv pretreatment. The effect of processing parameters, such as temperature, catalyst concentration, reaction time, and methanol (MeOH) concentration, on the dissolution and recovery of hemicellulose and lignin was determined. More than 75% of total hemicellulose and 75% of total lignin was removed in a single step with low amounts of degradation products under the following conditions: 165 °C, 3% H2 SO4 , 20 min reaction time, and 45% MeOH. Enzymatic hydrolysis of the residual pretreated biomass yielded up to 60% of cellulose-to-glucose conversion. The maximum recovery of the main components was obtained at a combined severity factor value of around one. Characterization of pretreated biomass and isolated lignin was carried out with FTIR and 2D (13) C-(1) H correlation HSQC NMR spectroscopy, the latter technique providing detailed structural information about the obtained methanol organosolv lignin (MOSL). Results suggested that xylopyranoside is the major carbohydrate associated with hemp lignin. The chemical properties of MOSL samples in terms of their phenolic group content and antioxidant capacity were also investigated. The results showed that MOSL samples have a high phenolic group content and antioxidant capacity relative to Klason lignin.

Can Lignin Wastes Originating From Cellulosic Ethanol Biorefineries Act as Radical Scavenging Agents?

Lignin is a co-product from the biorefinery and paper industries. Its non-energetic valorisation remains a field of extensive research and development. In this perspective, this study was undertaken to evaluate the radical scavenging ability of selected herbaceous lignins. These lignins, extracted from either Miscanthus (Miscanthus × giganteus) or switchgrass (Panicum virgatum L.), were selected as benchmarks for this study based on their chemical structure and average molecular weight. These technical lignins, which are side-products in the bioethanol production process, displayed a moderate antioxidant activity as evaluated by the 1,1-diphenyl-2-picrylhydrazil free radical scavenging test system. A correlation between the radical scavenging properties and the molecular features is proposed and discussed. Infrared spectroscopy was employed as a straightforward qualitative prediction tool for assessing the radical scavenging capacity.

Genoprotective effects of lignin isolated from oil palm black liquor waste

Black liquor waste (BLW), a major by-product of palm oil extraction process contains lignin as one of the constituents. Lignin isolated from BLW was evaluated for antioxidant and genoprotective properties and was compared with the commercial lignin for overall efficacy. Antioxidant compounds (phenolics and tannins) and antioxidant activities (phosphomolybdenum assay, ABTS(+) and FRAP assays) of lignin isolated from BLW were compared with commercial lignin. Bone marrow micronucleus (MN) test was employed for evaluating the dose-yield protective effect against cyclophosphamide (CP, 50mg/kg b.w.) induced genotoxicity in mouse. Results revealed isolated lignin to exhibit rich antioxidant activities. A decrease in MN frequency and recovery of P/N ratio (P: polychromatic erythrocytes, N: normochromatic erhythocytes) indicated protective effects of lignin against cyclophosphamide induced genotoxicity and cytotoxicity. The efficacy of BLW-derived lignin as an antioxidant and genoprotective agent was comparable to commercial lignin. Results on lignin isolated from BLW are envisaged to find potential applications in food and/or pharmaceutical industries.