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Abstract The robustness of a high-redox potential laccase has been enhanced by swapping its second cupredoxin domain with that from another fungal laccase, which introduced a pool of neutral mutations in the protein sequence without affecting enzyme functionality. The new laccase showed outstanding stability to temperature, pH (2–9) and to organic solvents, while maintaining the ability to oxidize high-redox potential substrates. By engineering the signal peptide, enzyme secretion levels in Saccharomyces cerevisiae were increased, which allowed to purify the engineered enzyme for further characterization. The purified domain-swap laccase presented higher activity in the presence of ethanol or methanol, superior half-lives at 50–70 °C, improved stability at acidic pH, and similar catalytic efficiency for DMP albeit a lower one for ABTS (due to a shift in optimum pH). A new N-glycosylation site and a putative new surface salt-bridge were evaluated as possible determinants for the improved stability by site-directed mutagenesis. Although neither seemed to be strictly responsible for the improved thermostability, the new salt bridge was found to notably contribute to the high stability of the swapped enzyme in a broad pH range. Finally, the application potential of the new laccase was demonstrated with the enzymatic treatment of kraft lignin, an industrially relevant lignin stream, at high temperature, neutral pH and short incubation times.

The SiO2/Al2O3 mole ratio, pore size, and acid sites are the key parameters of zeolite's activity in lignin pyrolysis. In this study, the comparison of individual Y and M zeolites, the combined 'Y + M' sample after regeneration, and their effect on lignin pyrolysis were studied in five cycles (regeneration and reuse). The results were explained using Brunauer, of heavy oil for the combined 'Y + M' sample indicated the enhanced cleavage of lignin structures in pyrolysis. These results support the higher catalytic activity of regenerated zeolites for the combined 'Y + M' sample compared with individual Y and M zeolites due to the improved MSA and TAS. Emmet, and Teller (BET), micropore surface area (MSA), and total acid sites (TAS) analyses. In comparison with the individual Y or M zeolite sample, the consistent higher catalytic activities of the combined 'Y + M' sample in repeated cycles were observed. Pyrolysis heavy oils were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The NMR analyses revealed that with increased zeolite regeneration cycles, p-hydroxy phenyl and methoxyl groups increased. Decreases in guaiacyl phenolic hydroxyl were less for the combined 'Y + M' sample than the individual Y and M zeolites. Lower weight average (Mw). [ABSTRACT FROM AUTHOR]

The organic phase obtained from the slow pyrolysis of lignin contains several highly functional chemical families. These make lignin‐based oil, which is suitable for producing several end products. The composition and quality of the liquid phase are crucial for identifying the downstream processes. They are affected by several factors, including the feedstock precipitation process, pyrolysis conditions, and the presence of an in situ or ex situ catalytic agent. In this regard, this work aims to predict the yield of the slow pyrolysis products from kraft lignin and the composition of the liquid phase under different conditions. A kinetic model based on a lumped approach is employed. A temperature range from ambient to 1100 K and a heating rate from 2 to 200 °C min−1 are applied. The results predicted from the study are compared under selected conditions against lab‐scale experimental data, which show the strong capabilities of the model employed. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Lignin is a natural, renewable resource with potential to be used in biomaterials. Due to its complex structure, its efficient dissolution is still challenging, which hinders its applicability at large scale. This challenge become harder considering the current need of sustainable and environmentally friendly solvents. To the best of our knowledge, this work reports for the first time the dissolution of kraft lignin in levulinic acid, a "green" solvent, and compares its efficiency with common carboxylic acids and sulfuric acid. It has been found that levulinic acid has a high capacity to dissolve kraft lignin at room temperature (40 wt% solubility), and it efficiency is not compromised when diluting the acid with water (up to 40 wt% water content). The Kamlet-Taft π⁎ parameter of the different acidic solvents was estimated and found to correlate well with their solubility performance. Lignins previously dissolved in levulinic and formic acids were selected to be regenerated and minor differences were found in thermal stability and morphological structure, when compared to native kraft lignin. However, an increase in the content of the carbonyl groups in the regenerated lignin material was observed. [ABSTRACT FROM AUTHOR]

The heterogeneity and complexity of lignin necessitate a deep understanding to select the most appropriate lignin valorization and convert it into value-added products. The objective of this research is to investigate the features of organosolv and Kraft lignins, in order to understand the effects of the sources and the isolation treatment, through the comparison of physicochemical and thermal properties. Various techniques have been employed such us Fourier transform infrared spectroscopy (FTIR), carbon solid state nuclear magnetic resonance 13CNMR, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. It was found that lignin produced from the hardwood using the Kraft process provided the greatest yield compared to other combinations. Softwood pretreatments achieve almost higher sugar yield than hardwood treatments. The infrared spectroscopy analysis confirms the existence of different monolignols. Organosolv lignins showed a predominance of guaiacyl and syringyl units. To provide additional information, the principle components analysis, as a powerful chemometric method, has also been applied to evaluate the FTIR data. NMR spectroscopy of lignins demonstrated the presence of essential functional chemical groups. It is also revealed that the nature of the treatment and the source of lignin samples affect the thermal properties. Overall, lignin isolated from Aleppo pine using Kraft process presented better thermal stability than that of organosolv lignin. [ABSTRACT FROM AUTHOR]

Understanding the factors that govern the graft polymer structure is of central importance to the development of technologies for converting polymers into carbon materials. In this work, poly (acrylonitrile-g-lignin) was synthesized by one-pot semi-batch solution polymerization of acrylonitrile (AN) with different amounts of Kraft lignin (KL), aiming the carbon materials producing. The synthesis process parameters to obtain poly (acrylonitrile-g-lignin) hybrid polymers from different KL contents were optimized. The purpose of this work was to substitute part of the AN by KL, with the KL amount varying from 0 to 35 wt.% in the copolymer and to investigate the consequent effects on the grafting percent, viscosity, overall monomer conversion, molar masses, thermal properties and carbon yield. The results obtained show the success in preparation of the grafted polymers with KL and that this insertion improved the thermal stability of the polymers and the carbon yield. The molar masses of poly (AN-g-KL) showed direct relationship with the amount of KL used and the grafting percentage. The results showed that the grafting percentage and viscosity of solutions decreases as the concentration of KL increased. The molar mass results and thermal properties showed a direct relationship to the KL concentration in the synthesized copolymer. Among the proportions of AN/KL studied, the copolymer 75/25 (P-25KL) presented the most promising results for application as carbon material precursor. [ABSTRACT FROM AUTHOR]

In this work, Kraft lignin (KL), glyoxalated KL and its blends with polyacrylonitrile (PAN/KL) were electrospun by solution electrospinning in order to investigate the morphology of the mats to be used in carbon material applications. The process parameters to obtain PAN/KL nanofibers with higher amount of KL and without defects were optimized. Three types of KL were used in this work: non-purified (KL), purified (KLp) and glyoxalated (KLg). The effects of the glyoxalation reaction time and the ratio of glyoxal-to-KL were, also, investigated in order to improve the molar mass of the KL. The results show that the molar mass of each glyoxalated KL increases compared to that of the standard KL. The molar mass remained unchanged with increasing the reaction time and ratio of glyoxal-to-KL. All obtained nanofiber mats were characterized by scanning electron microscopy (SEM) and their morphology showed to be dependent on the ratio of the PAN/KL used. Increasing the KL content decreases the diameter of the nanofibers. The maximum KL content in the PAN/KL blend, required to produce nanofibers without defects and with small fiber diameter, was 50 wt.%, making this material promising for a carbon material precursor. For the case of KLg, nanomats with beads were obtained with 70 and 80 wt.% KLg in the blend. Thermal properties of the nanomats showed a direct relationship to the content of KL used and its molar mass. In addition, these results point to a new approach for the application of KL and PAN/KL nanofibers. [ABSTRACT FROM AUTHOR]

In this work, silanized and aminated lignin (SAL) was synthesized in one step and its adsorption of Congo red and Cu(II) ions in aqueous solution was explored. Lignin was subjected to amine-silanization with (3-aminopropyl) triethoxysilane (APTES). Structural characterization substantiated successful amine-silanzation of lignin and formation of multi-layer APTES intermolecular crosslinked structure. The prepared SAL (nitrogen content = 6.1%) exhibited enhanced molecular weight, thermal stability, and water- and organic solvent-resistance properties. Additionally, the present of the porous structure of particle surface and an increase in the specific surface area and zeta potential promoted the accessibility of contaminants to the effective adsorption sites of SAL. Adsorption experiments showed that both Congo red and Cu(II) ion could be completely removed at original pH value, and their adsorption involved electrostatic attraction and complexation, respectively. The adsorption isotherms and kinetics were well described by the Langmuir and pseudo-second-order equations, respectively. The results showed that SAL is a promising adsorbent for the treatment of effluents. Unlabelled Image • A one-step approach for silanization and amination of lignin (SAL) was developed. • Both Congo red and Cu(II) ions could been completely removed at initial pH value. • SAL is a promising adsorbent for the treatment of effluents. [ABSTRACT FROM AUTHOR]

Lignin is the second most abundant polymer after cellulose in lignocellulosic biomass. Its aromatic composition and recalcitrant nature make its valorization a major challenge for obtaining low molecular weight aromatics compounds with high value‐added from the enzymatic depolymerization of industrial lignins. The oxidation reaction of lignin polymer using laccases alone remains inefficient. Therefore, researches are focused on the use of a laccase‐mediator system (LMS) to facilitate enzymatic depolymerization. Until today, the LMS system was studied using water‐soluble lignin only (commercial lignins, modified lignins, or lignin model compounds). This work reports a study of three LMS systems to depolymerize the three major industrial lignins (organosolv lignin, Kraft lignin, and sodium lignosulfonate). We show that an enzymatic depolymerization of these lignins can be achieved by LMS using laccase from Trametes versicolor, 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt as mediator and a cosolvent (25% of 1,4‐dioxane) to enhance the solubilization of lignins. [ABSTRACT FROM AUTHOR]

Kraft lignin can be extracted from black liquor generated during wood digestion. At present, water soluble kraft lignin is prepared chemically. Here, a method for the preparation of a purified form of CO2‐precipitated softwood kraft lignin, which forms a stable aqueous solution at a pH value of 8.9 is described. The lignin samples are characterized by thermogravimetric analysis, IR spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The comparison of water‐washed lignin with reference samples of unwashed‐ and acid‐washed lignin shows that the water‐washed lignin has a higher molecular weight compared to the reference samples, while the content of hydroxyl and methoxyl groups is similar. Solubility studies show that drying of washed lignin has a significant effect on its dissolution in water. Charge titration and dynamic light scattering experiments show that water‐washed lignin forms a stable colloid in aqueous solution. [ABSTRACT FROM AUTHOR]

Size exclusion chromatography with multi-angle laser light-scattering detectors was applied for acetylated softwood and hardwood kraft lignins (Ac-SKL and Ac-HKL) and 8-O-4′ type of linear polymeric lignin model (Ac-M-8O4′) to compare their swelling behaviors. The plot of molar mass (MM) vs. retention time for Ac-M-8O4′ was similar to that of polystyrene, which revealed that Ac-M-8O4′ exhibited swelling behavior that was similar to that of polystyrene. However, the MM values of both Ac-KLs were larger than those of polystyrene standards at any retention time. This difference indicated that both Ac-KLs had a more compact structure than those of polystyrene and Ac-M-8O4′. One hypothesis is that the larger MM of both Ac-KLs stems from their branched structures. To verify this hypothesis, the frequency of 5-5′ interunit linkage in lignin samples was determined by 1H NMR after nitrobenzene oxidation. A linear relationship between MM and 5-5′ abundance was observed in the high MM region. [ABSTRACT FROM AUTHOR]

The solvolysis of technical lignins was evaluated using water/ethanol solvent mixture with the aim of producing monomeric aromatic compounds in a continuous flow bench reactor. Four lignins issued from various biomasses (softwood, wheat straw) and extracted using different pulping processes (kraft, soda, organosolv) were engaged in the study. Before being converted, these lignins (two kraft, a soda, and an organosolv) were characterized by a multitechnique approach coupling compositional analysis, NMR, IR, GC, and SEC. Data thus obtained allowed us to point out the main differences in terms of structure and chemical composition. Based on its high solubility in water and water/ethanol mixture, alkaline lignin (i.e., from the kraft process) was used to optimize the reaction parameters. Thus, we found out that working at 225 °C under 8 MPa nitrogen using a 1-wt% basic solution of lignin allowed to operate the reactor without difficulties (no foam formation, no char) when a 1/1 water/ethanol mixture was used. Under these conditions, alkaline lignin was converted up to 76%. Other lignins were then evaluated leading to conversions between 46 and 74%. The reaction mixture obtained was fractioned to PM (precipitated matter), OP (organic products), and AP (aqueous phase soluble products) to allow careful analyses of the products. Analytical data obtained showed particularly that the number of β-O-4 linkages in the remaining solid material (PM) decreases significantly (up to − 95%) that correlated with the formation of monomeric organic compounds in OP, however in low amount due to over reactions leading to compounds evolving in the aqueous phase. Generally, whatever the lignin, guaiacol is the main aromatic compound observed under all reaction conditions evaluated. [ABSTRACT FROM AUTHOR]

In an attempt to diversify lignin applications, in this study, electrospun mats composed of ultrathin carbon fibers from Eucalyptus globulus Lignin (EKL) and sugarcane bagasse Kraft lignin (BKL) capable of detecting certain human body motions were fabricated and their chemical structures fully investigated accordingly. Results suggested that the main chemical structure of EKL was slightly linear with sinapyl alcohol and coniferyl alcohol as the basic units and pinoresinol, arylglycerol- β -aryl ether, phenylcoumaran, with diphenylethane as the main linkages. The slightly linear EKL and cross-linked BKL tended to form amorphous carbon and graphite crystallites under the same heat treatment process respectively, thereby resulting in a large difference in the resistance of fabricated sensors. The amplitude of signals due to changes in the relative resistance (△R/R 0) for EKL ultrathin carbon fiber (CF)-based sensor was approximately 9 × 104 during the finger bending process, while large (△R/R 0 ~380) and small (△R/R 0 < 10) relative resistance variations due to BKL-CF-based sensors were detected during the arm bending and finger pressing motions respectively. [ABSTRACT FROM AUTHOR]

• A biomass-based macromonomer (KL-TPEG) was prepared. • The retention of the aliphatic C=C bond and the grafting ratio was determined. • KL-TPEG had favorable dispersion stability on the cement particles. • The dispersion ability of KL-TPEG was enhanced with the grafting ratio of TPEG. In order to develop a biomass-based superplasticizer, kraft lignin (KL) was grafted with isopentenol polyoxyethylene ether (TPEG) to prepare a novel macromonomer (KL-TPEG). It was shown that the retention ratio of the aliphatic C C bond increased from 81.07% to 90.20% with the increase of m(TPEG)/m(KL). When the grafting ratio was increased, the average number of TPEG grafted on one KL molecule was approximately 1.4, 3.1, 4.6, 6.2 and 7.6. The star-like structure was also confirmed by FT-IR, 1H NMR and GPC. KL-TPEG had favorable surface activity and dispersion stability on the cement particles. It was illustrated that the shear stress and shear viscosity of the cement slurries with KL-TPEG were significantly less than that of blank slurry. The dispersion-retention ability of KL-TPEG on the slurry was also gradually enhanced with the increase of the grafting ratio of TPEG. It was seldom reported on the biomass-based TPEG. Through modified with KL, the rheology behavior and the dispersion-retention ability of TPEG was greatly improved, and the cost of TPEG was also reduced, thus this study not only promoted the development of biomass-based macromonomer, but also helped for the high value utilization of lignin. [ABSTRACT FROM AUTHOR]

Kraft lignin valorization is the cornerstone for the establishment of biorefineries based on residual fractions from the pulping processes. From the precipitation process to depolymerization, various strategies have emerged, all focused on obtaining high yields or higher purity monomers. The strategy used in this study was to modify the structure of the precipitated Kraft lignin with different oxidative enzymatic treatments, with the purpose of facilitating subsequent catalytic depolymerization. The treatments were performed with different concentrations of lacasse and mediator, and then lignin structure and chemical composition were analyzed to find the optimal treatment for depolymerization. Chemometric methods based on infrared signals were used as fast tools to reduce the complexity of the chemical information generated from lignin characterization, and were therefore used to distinguish the most appropriate chemoenzymatic treatment. The results of the chemical catalysis showed higher conversion yields of the Kraft lignin after the enzymatic process than after using only chemical catalysis. The primary compounds obtained were catechol and its derivatives, thus validating its selection by means of infrared spectroscopy and chemometrics. In conclusion, it was possible to choose a straightforward chemoenzymatic process that improves the conversion of the Kraft lignin to aromatic compounds with the help of non‐destructive, low‐cost, and fast tools. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Lignins are among the most abundant renewable resources on the planet. However, their application is limited by the lack of efficient dissolution and extraction methodologies. In this work, a systematic and quantitative analysis of the dissolution efficiency of different alkaline-based aqueous systems (i.e. lithium hydroxide, LiOH; sodium hydroxide, NaOH; potassium hydroxide, KOH; cuprammonium hydroxide, CuAOH; tetrapropylammonium hydroxide, TPAOH and tetrabutylammonium hydroxide, TBAOH) is reported, for the first time, for kraft lignin. Phase maps were determined for all systems and lignin solubility was found to decrease in the following order: LiOH > NaOH > KOH > CuAOH > TPAOH > TBAOH, thus suggesting that the size of the cation plays an important role on its solubility. The π ∗ parameter has an opposite trend to the solubility, supporting the idea that cations of smaller size favor lignin solubility. Dissolution was observed to increase exponentially above pH 9–10 being the LiOH system the most efficient. The soluble and insoluble fractions of lignin in 0.1 M NaOH were collected and analyzed by several techniques. Overall, data suggests a greater amount of simple aromatic compounds, preferentially containing sulfur, in the soluble fraction while the insoluble fraction is very similar to the native kraft lignin. • Several alkaline-based solvents were used to dissolve kraft lignin. • The size of the cation was found to play an important role on lignin solubility. • Low polarizability of the solvent favors the lignin solubility. • The soluble lignin fraction has a greater amount of simple aromatic compounds. • The soluble lignin fraction has a higher sulfur content than the insoluble fraction. [ABSTRACT FROM AUTHOR]

Lignin based materials and chemicals with outstanding sustainability have drawn increasingly attentions. However, the dark color of lignin limits the utilization in color-depended fields. In this work, the factors that influence the color of lignin were investigated and mechanisms were illustrated by GPC, NBO, 2D HSQC, XPS, SEM, and visible light spectrum. It is found that the condensed structures were mainly separated at higher pH due to its high molecular weight and low solubility. The condensation contributes to the conjugation and unsaturation, which resulted in the dark-color of the lignin precipitated at high pH value. The oxidation is not crucial for the color darkening of lignin in drying, it is the micro aggregation that dominantly determined the color degree. The concentration of chromophore was decreased owing to the decrease of bulk density (caused by the alleviation of aggregation), which endowed lignin with the bright seeing macroscopically. Notably, the selection of light-colored lignin needs to be individually considered regarding different use, since the dominating factors that influence the color at solid or solution are totally different. In summary, this work offers guidance for acquiring light-colored lignin and helps people select the light-colored lignin properly regarding utilizations. Essential knowledge and mechanism were illustrated to reveal the true reason that results in the color distinction of lignin. Unlabelled Image [ABSTRACT FROM AUTHOR]

Unmodified kraft lignin was used to create a starch-based adhesive via the Stein Hall process. Lignin up to 35 wt% was used in several formulations. Lignin was incorporated in both the carrier and slurry portions of the formulations and the effect on adhesive strength and water resistance was studied. The addition of lignin resulted in a significant increase in adhesive strength when the lignin was added solely to the slurry portion. When lignin was added solely to the carrier portion, the adhesive strength decreased. Other formulations, where lignin was present in both the carrier and slurry portions, showed moderate increases in adhesive strength. Finally, the addition of lignin increased the water-resistance of the adhesive bond in the paperboard. [ABSTRACT FROM AUTHOR]

Kraft lignin (KL) and castor oil (CO) were used as polyols in the synthesis of bio-based polyurethanes (PUs) in the absence of both solvents and catalysts at room temperature with simultaneous film formation. KL was purified (PKL), and both KL and PKL were fully characterized. CO was mixed with different percentages of PKL (0%, 10%, 30%, and 50%), as well as with polymeric methyl phenyl diisocyanate. After degassing, the reaction mixture was stirred; when the medium viscosity was suitable for spreading, it was poured onto a glass plate, and the thickness was adjusted using an extender. The storage modulus (E′, 25 °C) and tensile strength of the lignopolyurethane films (LignoPU COPKL) were higher than those of the control film (PU CO). LignoPU COPKL30 and LignoPU COPKL50 did not break under the conditions that the other films broke under. It was noted phase segregation (rigid and flexible domains) for LignoPU COPKL30 and LignoPU COPKL50 , and the glass transition temperature (T g) of the flexible domains (96.2 °C and 52.3 °C, respectively) was higher than that of PU CO (8.4 °C). The formed films were also characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, contact angles, and swelling tests. To our knowledge, the approach of this study is unprecedented. • Kraft lignin purified (LKP) and castor oil (CO): used as polyols • LKP characterization: Klason lignin 89.0%, sugars 4.9%, Mw 2331 g/mol, Mw/Mn 2.0 • Diversified ratio CO/LKP used to synthesize lignopolyurethanes → film formation • 70%CO/30%LKP and 50%CO/50%LKP led to phase segregation (rigid and flexible domains) • Storage modulus and tensile strength increased with the percentage of LKP. [ABSTRACT FROM AUTHOR]

Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, 31P NMR, 13C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T 50% values, suggesting a better stability towards degradation. • Kraft and organosolv lignin were modified by different chemical reactions. • Carboxymethylation, sulfomethylation, and methylation reactions were effective on reacting with the lignin hydroxyl groups. • Higher thermal stability and water dispersion were obtained by the incorporation of the functional groups into lignin. [ABSTRACT FROM AUTHOR]

Bioadhesives are promising alternatives to formaldehyde-based adhesives, owing to their excellent low formaldehyde emissions and sustainable raw materials. Among these, lignin-isolate soy protein bioadhesives (LISP), produced from soy protein and lignin, exhibiting significant potential applications across various wood products. This study addresses previously unidentified environmental impacts and economic feasibility of large-scale LISP bioadhesive production. This study evaluates the techno-economics and cradle-to-gate life cycle environmental impacts of a novel LISP bioadhesive production from isolated soy protein and kraft lignin, including the depolymerization of kraft lignin on a commercial scale by optimizing experimental results. Technoeconomic analysis shows that the estimated production cost of LISP bioadhesive produced at 30 MT/batch plant was $1.32/kg and the minimum selling price was $1.40/kg. Life cycle assessment shows that the global warming impact of LISP bioadhesive production of was 2.20 kg CO 2 eq/kg. The utilization of steam was the primary contributor to these emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

• Catalytic pyrolysis of kraft lignin to produce monocyclic aromatic hydrocarbon products was systematically explored. • Oxygen functionalities and polycyclic aromatic hydrocarbons were significantly suppressed over Cu/HZSM-5. • Cu/HZSM-5 catalyst yielded 70.59 mg/g mononuclear aromatic hydrocarbons with 70.23% selectivity. • Metal loading and carrier gas flow rate for catalytic pyrolysis were optimized. • Regeneration of the catalyst can maintain the activity after 5 repeated experiments. Lignin catalytic pyrolysis presents a promising and sustainable approach to producing aromatic molecules. Herein, we investigated the effect of modified zeolite with copper (Cu/HZSM-5) catalyst on efficiently pyrolyzed kraft lignin into aromatic hydrocarbons (AHs) production, especially mononuclear aromatic hydrocarbons (MAHs). Time-of-flight mass spectrometry (TOF-MS) was employed to compare the volatile product profiles of lignin during catalytic pyrolysis. The highest yield of MAHs reached 70.59 mg/g based on dry lignin at 550 °C, accounting for 70.23% among lignin pyrolysis products, compared to the pristine HZSM-5 zeolite catalytic system with MAHs yield of only 54.31 mg/g and of 40.34% in products. At 550 °C and 60 s residence time, the 5% Cu/HZSM-5 catalyst demonstrated the best performance compared to all other catalysts in terms of selectively producing MAHs. The results are ascribed to the enhancement of decarboxylation and aromatization processes by the doping of copper. This work demonstrates a cost-effective pathway that potentially converts kraft lignin into aromatic hydrocarbon production at a phenomenally high selectivity, providing a concept for industrial application toward biomass utilization and high value-added production. [ABSTRACT FROM AUTHOR]

[Display omitted] • T. xylanilyticus grows on lignin-rich substrates as kraft lignin and steam exploded wheat straw. • Oxidoreductases and hemicellulases are expressed differently depending on the substrate. • Oxidoreductases are likely involved in detoxification process in cultures with lignins. • Despite few lignin structural modifications phenolic compounds are released in the culture media. Major challenge in biorefineries is the use of all lignocellulosic components, particularly lignins. In this study, Thermobacillus xylanilyliticus grew on kraft lignin, steam-exploded and native wheat straws produced different sets of phenoloxidases and xylanases, according to the substrate. After growth, limited lignin structural modifications, mainly accompanied by a decrease in phenolic acids was observed by Nuclear Magnetic Resonance spectroscopy. The depletion of p -coumaric acid, vanillin and p -hydroxybenzaldehyde combined to vanillin production in the culture media indicated that the bacterium can transform some phenolic compounds. Proteomic approaches allowed the identification of 29 to 33 different hemicellulases according to the substrates. Twenty oxidoreductases were differentially expressed between kraft lignin and steam-exploded wheat straw. These oxidoreductases may be involved in lignin and aromatic compound utilization and detoxification. This study highlights the potential value of Thermobacillus xylanilyticus and its enzymes in the simultaneous valorization of hemicellulose and phenolic compounds from lignocelluloses. [ABSTRACT FROM AUTHOR]

[Display omitted] • Proposed a technology for lignin depolymerization under hydrogen-free condition. • L-acid site and the hydrogenation site enhanced the depolymerization efficiency. • The monomer yield reached 38.09 wt%, which has rarely been reported. • It solved the challenge of traditional hydrogenation technology of lignin. Efficient depolymerization of lignin to produce valuable liquid fuels and phenolic compounds is essential to improve the effective utilization and contribution towards energy sustainability. However, challenges arise due to its complex three-dimensional structure, the inclination of intermediates to condense, and the excessive dependence of depolymerization reaction on high-pressure hydrogen. Herein, a novel Ni- and Zn- modified Y-zeolite (Ni 1 Zn 1 /HY a) was prepared to attain effective lignin conversion under conditions devoid of exogenous hydrogen, by utilizing formic acid as an in situ hydrogen donor. Ni 1 Zn 1 /HY a selectively activated and decomposed formic acid, continuously releasing H 2 for lignin depolymerization. It stabilized active intermediates and inhibited condensation through synergistic interactions between Lewis acid (L-acid) and hydrogenation active sites, resulting in a depolymerization rate that effectively competes with the condensation rate. Following a 24 h reaction at 290 °C, the yields of liquid products and petroleum ether soluble (PES) reached 91.70 % and 67.74 %, respectively, without any coke production. Further, the higher heating value increased from 25.41 MJ kg−1 to 32.47 MJ kg−1. [ABSTRACT FROM AUTHOR]

In this study, a lignin-based hydrogel for wastewater treatment was prepared by incorporating kraft lignin (KL) into a poly (vinyl alcohol) (PVA) matrix. The underwater structural stability of the KL-PVA hydrogel was guaranteed through physicochemical crosslinking, involving freeze–thaw process and chemical crosslinking reaction. The KL-PVA hydrogel displayed superior compressive characteristics compared to the original PVA hydrogel. This improvement was attributed to the chemical crosslinking and the reinforcing effect of the incorporated KL microparticles. The incorporation of anionic KL microparticles into the PVA three-dimensional network structure enhanced the cationic methylene blue (MB) and crystal violet (CV) adsorption efficiency of the prepared KL-PVA hydrogel. The MB adsorption results were well explained by pseudo-2nd order kinetics model and Langmuir isotherm model. Electrostatic forces, hydrogen bonding and π-π stacking interactions were the main adsorption mechanisms between cationic dyes and KL surfaces, indicating the potential of KL-PVA hydrogel as an effective adsorption material. Moreover, regulating the molecular weight of PVA not only prevented lignin leakage from the KL-PVA hydrogel but also elevated the KL content within the hydrogel, consequently improving its dye removal performance. For KL-PVA hydrogel with high molecular weight PVA, the MB and CV adsorption capacities were 193.8 mg/g and 190.0 mg/g, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Complex lignin substrates are critical for functional screening of industrial enzymes. • ABTS is a poor predictor of multicopper-oxidase activity on industrial lignins. • Twelve lignin-active multicopper-oxidases from diverse fungi were identified. • Multicopper-oxidase activity on lignin did not correlate with taxonomic origin. Laccase-like multicopper oxidases are recognized for their potential to alter the reactivity of lignins for application in value-added products. Typically, model compounds are employed to discover such enzymes; however, they do not represent the complexity of industrial lignin substrates. In this work, a screening pipeline was developed to test enzymes simultaneously on model compounds and industrial lignins. A total of 12 lignin-active fungal multicopper oxidases were discovered, including 9 enzymes active under alkaline conditions (pH 11.0). Principal component analysis revealed the poor ability of model compounds to predict enzyme performance on industrial lignins. Additionally, sequence similarity analyses grouped these enzymes with Auxiliary Activity-1 sub-families with few previously characterized members, underscoring their taxonomic novelty. Correlation between the lignin-activity of these enzymes and their taxonomic origin, however, was not observed. These are critical insights to bridge the gap between enzyme discovery and application for industrial lignin valorization. [ABSTRACT FROM AUTHOR]

Chemical characterization of kraft lignin (KL) from mixed hardwoods (Acacia spp. from Vietnam and mixed hardwoods (mainly Quercus spp.) from Korea) was conducted for its future applications. To compare the structural changes that occurred in KL, two milled wood lignins (MWLs) were prepared from the same hardwood samples used in the production of KL. Elemental analysis showed that the MWL from acacia (MWL-aca) and mixed hardwood (MWL-mhw) had almost similar carbon content, methoxyl content, and C9 formula. KL had high carbon content but low oxygen and methoxyl contents compared to MWLs. The C9 formula of KL was determined to be C9H7.29O2.26N0.07S0.12(OCH3)1.24. The Mw of KL and MWLs was about 3000 Da and 12,000–13,000 Da, respectively. The structural features of KL and MWLs were investigated by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectrometry (1H, 13C NMR). The analyses indicated that KL underwent severe structural modifications, such as γ-carbon cleavage, demethylation, and polycondensation reactions during kraft pulping, which resulted in increased aromatic content and decreased aliphatic content. The main linkages in lignin, β-O-4 moieties, were hardly detected in the analysis as these linkages were extensively cleaved by nucleophilic attack of SH- and OH- during pulping.

Degradation of lignin constitutes a key step in processing biomass to become useful monomers but it remains challenging. Compared to fungi, bacteria are much less characterized with respect to their lignin metabolism, although it is reported that many soil bacteria, especially actinomycetes, attack and solubilize lignin. In this work, we screened 43 filamentous actinomycetes by assaying their activity on chemically different substrates including a soluble and semi-degraded lignin derivative (known as alkali lignin or Kraft lignin), and we discovered a novel and valuable peroxidase activity produced by the recently classified actinomycete Nonomuraea gerenzanensis. Compared to known fungal manganese and versatile peroxidases, the stability of N. gerenzanensis peroxidase activity at alkaline pHs and its thermostability are significantly higher. From a kinetic point of view, N. gerenzanensis peroxidase activity shows a Km for H2O2 similar to that of Phanerochaete chrysosporium and Bjerkandera enzymes and a lower affinity for Mn2+, whereas it differs from the six Pleurotus ostreatus manganese peroxidase isoenzymes described in the literature. Additionally, N. gerenzanensis peroxidase shows a remarkable dye-decolorizing activity that expands its substrate range and paves the way for an industrial use of this enzyme. These results confirm that by exploring new bacterial diversity, we may be able to discover and exploit alternative biological tools putatively involved in lignin modification and degradation.

The feasibility of incorporating purified kraft lignin, at different concentrations ranging from 5 to 29%, into fiberboards made from corn residues was studied. The lignin was obtained from black liquor, which is a residue of the paper industry. Corn stalk raw material and its thermomechanically produced fiber were characterized in terms of their chemical composition. The physical and mechanical properties of the resulting fiberboards were evaluated. The fiberboards produced following a wet process had good mechanical and water resistance properties that satisfied the requirements of the relevant standards. In addition, a Life Cycle Thinking (LCT) approach suggested that lignin-based fiberboards are environmentally preferable than those based on thermosetting resins.

Various chemical compounds emerged including kraft lignin (KL) during the processes of papermaking. These chemical compounds in effluent of the paper industry have hazardous environmental impacts. KL is liable for causing pollution of aquatic and water bodies; hence, it must be minimized in order to maintain a healthy and sustainable environment. In the present study, KL degradation was performed with ligninolytic bacterium Serratia liquefaciens and we confirmed biotransformation of KL to various less polluted or harmless compounds. KL being degraded as 1000 mg/L–1 concentration with incubating 30°C for 72, 168, and 240 h, shaking at 120 rpm under laboratory conditions. We found 65% maximum degradation of KL and 62% decolorization by the treatment with S. liquefaciens for 240 h (10 days). After being the treatment of KL, clear changes were observed in its morphology (using scanning electron microscopy and stereo microscopy), hydrodynamic size (using dynamic light scattering), and the functional groups [using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR–FTIR)]. Biotransformation of KL monitored by Gas Chromatography–Mass Spectrometry (GC–MS) revealed formation of various metabolites. In addition to degradation of KL, detoxification (involving biotransformation into various metabolites) was assessed using cytotoxicity assays 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide [MTT and calcein-acetoxymethyl (AM) assays] using a human kidney cell line (NRK-52E), which indicated improved cell survival rates (74% for the bacteria-treated KL solution treated for 240 h) compared to the control (27%). Thus, the present study suggests that bacteria S. liquefaciens might be useful in reducing the pollution of KL by transforming it into various metabolites along with cytotoxicity reduction for environmental protection.

The reaction of esterification of plasticized Kraft lignin (KL) with succinic and maleic anhydrides using reactive extrusion (REX) was studied in detail. DMSO, glycol and glycerol were found to be efficient plasticizers for lignin. The chemical structure of these new lignin esters was determined using Solid-state 13C CP-MAS NMR and FT-IR analysis. 31P NMR analysis of phosphitylated lignins showed that the aliphatic OH groups of lignin had superior reactivity under the reactive extrusion reaction conditions. The formation of monoesters was confirmed by HSQC NMR spectroscopy. Molecular weight changes after extrusion process were studied using GPC/SEC chromatography. Thermal properties of these polymers were assessed by TGA analysis. The results were compared to lignin esters modified in classical batch conditions. These results show that REX can be used as a new fast, solvent free, and continuous process for lignin valorization.

Using isocyanate-functionalized Kraft lignin as a reactive macromonomer for the preparation of polyurethane foams by a prepolymer technique is a well-known strategy to incorporate the biomacromolecule into a higher value polymer material. However, as of today the mechanical properties of the resulting materials are still insufficient for a number of possible applications. One reason for this limitation is that the reaction pathway and the morphological arrangement of such foams is of uttermost complexity and depends on a large number of influencing material-intrinsic factors. One important parameter is the reactivity of the functionalized lignin, which has a great impact on the interphase reaction kinetics and thus, on the geometry and mechanical properties of the resulting polyurethane foams. The reactivity is implied, amongst others, by the electron affinity of the isocyanate moiety. Herein, we investigate the reactivity of Kraft lignin modified with different commercially used isocyanates in the reaction with conventional polyols. Therefore, differently reactive prepolymers were synthesized, characterized and polyurethane foams were prepared thereof by using these compounds and the foam formation kinetics, morphological as well as mechanical properties were investigated. Finally, the results were supported by quantum mechanical calculations of the electron affinities of representative model compounds for the lignin-based prepolymers. This work gives rise to a better understanding of the effect of the reactivity and isocyanate structure linked to Kraft lignin on the polyurethane formation and enables rational choice of the isocyanate for pre-functionalization of lignin to prepare materials with better mechanical performance.

The demand for high-performance bio-based materials towards achieving more sustainable manufacturing and circular economy models is growing significantly. Kraft lignin (KL) is an abundant and highly functional aromatic/phenolic biopolymer, being the main side product of the pulp and paper industry, as well as of the more recent 2nd generation biorefineries. In this study, KL was incorporated into a glassy epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) and an amine curing agent (Jeffamine D-230), being utilized as partial replacement of the curing agent and the DGEBA prepolymer or as a reactive additive. A D-230 replacement by pristine (unmodified) KL of up to 14 wt.% was achieved while KL-epoxy composites with up to 30 wt.% KL exhibited similar thermo-mechanical properties and substantially enhanced antioxidant properties compared to the neat epoxy polymer. Additionally, the effect of the KL particle size was investigated. Ball-milled kraft lignin (BMKL, 10 μm) and nano-lignin (NLH, 220 nm) were, respectively, obtained after ball milling and ultrasonication and were studied as additives in the same epoxy system. Significantly improved dispersion and thermo-mechanical properties were obtained, mainly with nano-lignin, which exhibited fully transparent lignin-epoxy composites with higher tensile strength, storage modulus and glass transition temperature, even at 30 wt.% loadings. Lastly, KL lignin was glycidylized (GKL) and utilized as a bio-based epoxy prepolymer, achieving up to 38 wt.% replacement of fossil-based DGEBA. The GKL composites exhibited improved thermo-mechanical properties and transparency. All lignins were extensively characterized using NMR, TGA, GPC, and DLS techniques to correlate and justify the epoxy polymer characterization results.

The main objective of this study was to discover new packaging materials that could integrate one of the most expected properties, such as UV protection, with a self-cleaning ability defined as photocatalytic performance. Accordingly, new hybrid additives were used to transform LDPE films into materials with complex performance properties. In this study, titanium dioxide-lignin (TL) hybrid systems with a weight ratio of inorganic to organic precursors of 5-1, 1-1, and 1-5 were prepared using a mechanical method. The obtained materials and pristine components were characterized using measurement techniques and research methods, such as Fourier-transform infrared spectroscopy (FTIR), thermal stability analysis (TGA/DTG), measurement of the electrokinetic potential as a function of pH, scanning electron microscopy (SEM), and particle size distribution measurement. It was found that hydrogen bonds were formed between the organic and inorganic components, based on which the obtained systems were classified as class I hybrid materials. In the next step, inorganic-organic hybrid systems and pristine components were used as fillers for a low-density polyethylene (LDPE) composite, 5 and 10% by weight, in order to determine their impact on parameters such as tensile elongation at break. Polymer composites containing titanium dioxide in their matrix were then subjected to a test of photocatalytic properties, based on which it was found that all materials with TiO 2 in their structure exhibit photocatalytic properties, whereby the best results were obtained for samples containing the TiO 2 -lignin hybrid system (1-1). The mechanical tests showed that the thin sheet films had a strong anisotropy due to chill-roll extrusion, ranging from 1.98 to 3.32. UV-Vis spectroscopy revealed four times higher light absorption for composites in which lignin was present than for pure LDPE, in the 250-450 nm range. On the other hand, the temperature at 5% and 30% weight loss revealed by TGA testing increased the highest performance for LDPE/TiO 2 materials (by 20.4 °C and 8.7 °C, respectively).

Current production of functional coatings majorly relies on petrochemical formulations. While they have provided substantial benefits, their fabrication processes as well as their disposal created widespread ecological catastrophes. Thus, there is a pressing demand and calls for a radical transformation to develop sustainable solutions by using renewable building blocks. Herein, we report on a novel coating formulation by combining largely undervalued kraft lignin from the forest industry, with genetically engineered and recombinantly produced spider silk-inspired protein through the industrial biotechnology platform. Unmodified kraft lignin was used as the main bulk component in the coating given its abundance and low cost. The nanometer-thin spider silk-inspired protein (SSIP) was used as a primary layer exhibiting dual functionalities: (i) modulating the mechanical properties of inherently brittle kraft lignin, (ii) substantially increasing the interfacial binding of kraft lignin to the underlying rigid silica substrate with the mismatched physicochemical properties. Our findings demonstrate how synergistic interplay components could result in scalable and durable functional coatings which could potentially be used in various medical and industrial applications in the future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)