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Wood-plastic material from a novel reactive processing method (co-refining by steam-explosion) was investigated by 13C solid state nuclear magnetic resonance (NMR) and dynamic mechanical analysis (DMA). NMR spectra indicated chemistry of the material changed as a result from co-steam-explosion. It was also observed from NMR analysis that the crystallinity of the cellulose increased in the presence of iPP during steam-explosion co-processing. By using variable contact time cross pulse experiments, the relaxation parameters (TCH and T1ρ) for the constitutive components were evaluated to reveal the level of interactions. T1ρ values for steam-exploded wood had values similar to those published in literature, which are independent relaxation values for lignin and cellulose. However, for co-steam-exploded wood and iPP, the independent value of lignin relative to the amorphous cellulose was absent. It is proposed that lignin adopts an alternate arrangement during co-steam-explosion processing. This arrangement is transient because the independent relaxation of lignin is recovered after the application of heat during compression molding. DMA demonstrated a mechanical reinforcing effect of the steam-exploded wood without influencing the glass transition of polypropylene for the compression molded co-steam-exploded sample. The paper concludes by describing a hypothetical scheme for a meta-stable interaction of wood bio-polymers and iPP. [ABSTRACT FROM AUTHOR]

Renewable feedstocks are sought for clean technology applications, including energy storage applications. In this study, LignoForce™ lignin, a biobased aromatic polymer commercially isolated from wood, was fractioned into two parts using acetone, and the resulting lignin fractions had distinct thermo-rheological behavior. These two fractionated lignins were combined in various ratios and transformed into nanofibers by electrospinning. Subsequently, electrospun fiber materials were disrupted by agitating the mats in water, and the materials were transformed into ultralight 3D aerogels through lyophilization and post-process controlled heating. Using only this combination of two fractions, the morphology of lignin nanofibers was tailored by heat treatment, resulting in lignin aerogels with high flexibility and significant shape recovery properties. Various microscale structures of lignin fibers impacted the resulting physical properties of the elastic aerogel materials, such as resilience, compressive strength, and electrical conductivity for the corresponding carbonized samples. By exploiting lignin's sensitivity to heat and tailoring the thermal properties of the lignin through fractionation, the work provided an interesting path to form robust lignin-derived functional materials without any toxic chemical additives and significant ability to serve as free-standing electrodes with specific capacitance values better than some graphene-based supercapacitors., (© 2024 Wiley‐VCH GmbH.)

There has been a resurgence of studies on xylan particles describing various properties and exploring new applications. The aim of this study was to analyze xylan hydrate crystals in the wet state and after air-drying using state-of-art imaging techniques in order to assess the impact of water on both crystallinity and particle morphology. Xylan from esparto grass (Stipa tenacissima) was crystallized and formed convex platelets, termed 'nanotiles'. Fully hydrated xylan crystals were examined in a layer of vitreous ice by cryogenic electron microscopy. Selected area electron diffraction of the xylan hydrate crystals revealed an oriented crystalline core, unlike the dried crystals that showed no orientation. The surface topographies and thickness of wet and air-dried xylan nanotiles were observed using atomic force microscopy imaging in both liquid and in air. X-ray diffraction was used to assess the crystallinity of xylan nanotiles after drying to varying levels. Air-dried crystals gave diffraction maxima corresponding to xylan hydrate, while wet crystals gave diffraction maxima corresponding to xylan dihydrate. This study offers new insight into xylan hydrate particles, focusing on the role of water on their crystallinity, ultrastructure, and orientation of the crystalline layers., Competing Interests: Declaration of competing interest AJ acknowledges financial support from a Doctoral Canada Graduate Scholarship (CGS-D) from the Natural Sciences and Engineering Research Council of Canada (NSERC). SR acknowledges financial support from the Advanced Renewable Materials Innovation Fund, the Edwina and Paul Heller Memorial Fund, the Canada Research Chairs Program, Tier 2, in Advanced Renewable Materials #950-232330 and the NSERC / Discovery Grants Program – Individual Sponsor Reference Number: RGPIN-2020-05465. YO acknowledges Agence Nationale de la Recherche (ANR grant number: ANR-21-CE29-0016-1) and Glyco@Alps (ANR-15-IDEX-02) for the financial support and the NanoBio-ICMG platform (FR 2607) for granting access to the electron microscopy facility., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Valorization of underutilized biobased feedstocks like hetero-polysaccharides is critical for the development of the biorefinery concept. Towards this goal, highly uniform xylan micro/nanoparticles with a particle size ranging from 400 nm to 2.5 μm in diameter were synthesized by a facile self-assembly method in aqueous solutions. Initial concentration of the insoluble xylan suspension was utilized to control the particle size. The method utilized supersaturated aqueous suspensions formed at standard autoclaving conditions without any other chemical treatments to create the resulting particles as solutions cooled to room temperature. Processing parameters of the xylan micro/nanoparticles were systematically studied and correlated with both the morphology and size of xylan particles. By adjusting the crowding of the supersaturated solutions, highly uniform dispersions of xylan particles were synthesized of defined size. The xylan micro/nanoparticles prepared by self-assembly have a quasi-hexagonal shape, like a tile, and depending upon solution concentrations xylan nanoparticles with a thickness of <100 nm were achieved at high concentrations. Based on the usefulness of polysaccharide nanoparticles, like cellulose nanocrystals, these particles have potential for unique structures for hydrogels, aerogels, drug delivery, and photonic materials. This study highlights the formation of a diffraction grating film for visible light with these size-controlled particles., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Scott Renneckar reports financial support was provided by Canada Research Chairs. Huaiyu Zhang reports financial support was provided by China Scholarship Council. Scott Renneckar reports financial support was provided by Natural Sciences and Engineering Research Council of Canada. Scott Renneckar reports financial support was provided by Edwina and Paul Heller Memorial Fund., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Reactive amine compounds are critical for a vast array of useful chemicals in society, yet a limited number of them are derived from renewable resources. This study developed an efficient route to obtain aminated building blocks from phenolic resources derived from nature, such as lignin and tannic acid, for enhancing their utility in applications such as epoxy resins, nylons, polyurethanes, and other polymeric materials. The reaction utilized a carbon storage compound, 2-oxazolidinone as a solvent and as a reagent circumventing the need of hazardous chemistry of conventional amination routes such as those involving formaldehyde. Both free acids and hindered phenolics were readily converted into aminoethyl derivatives resulting in aromatics with primary amine functionality. The aminated compounds, with the potential for enhanced reactivity, can pave the way toward more advanced renewable building blocks., (© 2023 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Enzyme-mediated hydrolysis of cellulose always starts with an initial rapid phase, which gradually slows down, sometimes resulting in incomplete cellulose hydrolysis even after prolonged incubation. Although mechanisms such as end-product inhibition are known to play a role, the predominant mechanism appears to be reduced cellulose accessibility to the enzymes. When using Simon's stain to quantify accessibility, the accessibility of mechanically disintegrated and phosphoric acid-swollen cellulose substrates decreased as hydrolysis proceeded. In contrast, the poor initial accessibility of Avicel remained low throughout hydrolysis. However, washing the residual cellulose increased cellulose accessibility, likely due to the removal of tightly bound but non-productive enzymes which blocked access to more active enzymes in solution. Atomic force microscopy (AFM) analysis of the initial and residual cellulose collected when the hydrolysis plateaued, showed an increase in the roughness of the cellulose surface, possibly resulting in the tighter binding of less active cellulases., 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 Elsevier Ltd. All rights reserved.)

Introducing vinyl groups onto the backbone of technical lignin provides an opportunity to create highly reactive renewable polymers suitable for radical polymerization. In this work, the chemical modification of softwood kraft lignin was pursued with etherification, followed by direct esterification with acrylic acid (AA). In the first step, phenolic hydroxyl and carboxylic acid groups were derivatized into aliphatic hydroxyl groups using ethylene carbonate and an alkaline catalyst. The lignin was subsequently fractionated using a downward precipitation method to recover lignin of defined molar mass and solubility. After recovery, the resulting material was then esterified with AA, resulting in lignin with vinyl functional groups. The first step resulted in approximately 90% of phenolic hydroxyl groups being converted into aliphatic hydroxyls, while the downward fractionation resulted in three samples of lignin with defined molar masses. For the esterification reaction, the weight ratio of reagents, reaction temperature, and reaction time were evaluated as factors that would influence the modification efficacy. 13 C NMR spectroscopy analysis of lignin samples before and after esterification showed that the optimized reaction conditions could reach approximately 40% substitution of aliphatic hydroxyl groups. Both steps only used lignin and the modifying reagent (no solvent), with the possibility of recovery and reuse of the reagent by dilution and distillation. An additional second esterification step of the resulting lignin sample with acetic acid or propionic acid converted 90% of remaining hydroxyl groups into short-chain carbon aliphatic esters, making a hydrophobic material suitable for further copolymerization with synthetic hydrophobic monomers.

The pre-adsorption of non-catalytic/blocking proteins onto the lignin component of pretreated biomass has been shown to significantly increase the effectiveness of subsequent enzyme-mediated hydrolysis of the cellulose by limiting non-productive enzyme adsorption. Layer-by-layer adsorption of non-catalytic proteins and enzymes onto lignin was monitored using Quartz Crystal Micro balancing combined with Dissipation monitoring (QCM-D) and conventional protein adsorption. These methods were used to assess the interaction between soft/hardwood lignins, cellulases and the three non-catalytic proteins BSA, lysozyme and ovalbumin. The QCM-D analysis showed higher adsorption rates for all of the non-catalytic proteins onto the lignin films as compared to cellulases. This suggested that the "blocking" proteins would preferentially adsorb to the lignin rather than the enzymes. Pre-incubation of the lignin films with blocking proteins resulted in reduced adsorption of cellulases onto the lignin, significantly enhancing cellulose hydrolysis., 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 © 2022 Elsevier Ltd. All rights reserved.)

Bacterial catabolic pathways have considerable potential as industrial biocatalysts for the valorization of lignin, a major component of plant-derived biomass. Here, we describe a pathway responsible for the catabolism of acetovanillone, a major component of several industrial lignin streams. Rhodococcus rhodochrous GD02 was previously isolated for growth on acetovanillone. A high-quality genome sequence of GD02 was generated. Transcriptomic analyses revealed a cluster of eight genes up-regulated during growth on acetovanillone and 4-hydroxyacetophenone, as well as a two-gene cluster up-regulated during growth on acetophenone. Bioinformatic analyses predicted that the hydroxyphenylethanone (Hpe) pathway proceeds via phosphorylation and carboxylation, before β-elimination yields vanillate from acetovanillone or 4-hydroxybenzoate from 4-hydroxyacetophenone. Consistent with this prediction, the kinase, HpeHI, phosphorylated acetovanillone and 4-hydroxyacetophenone. Furthermore, HpeCBA, a biotin-dependent enzyme, catalyzed the ATP-dependent carboxylation of 4-phospho-acetovanillone but not acetovanillone. The carboxylase's specificity for 4-phospho-acetophenone ( k cat / K s M = 34 ± 2 mM -1 s -1 ) was approximately an order of magnitude higher than for 4-phospho-acetovanillone. HpeD catalyzed the efficient dephosphorylation of the carboxylated products. GD02 grew on a preparation of pine lignin produced by oxidative catalytic fractionation, depleting all of the acetovanillone, vanillin, and vanillate. Genomic and metagenomic searches indicated that the Hpe pathway occurs in a relatively small number of bacteria. This study facilitates the design of bacterial strains for biocatalytic applications by identifying a pathway for the degradation of acetovanillone.

Characterizing microorganisms and enzymes involved in lignin biodegradation in thermal ecosystems can identify thermostable biocatalysts. We integrated stable isotope probing (SIP), genome-resolved metagenomics, and enzyme characterization to investigate the degradation of high-molecular weight, 13 C-ring-labeled synthetic lignin by microbial communities from moderately thermophilic hot spring sediment (52 °C) and a woody "hog fuel" pile (53 and 62 °C zones). 13 C-Lignin degradation was monitored using IR-GCMS of 13 CO 2 , and isotopic enrichment of DNA was measured with UHLPC-MS/MS. Assembly of 42 metagenomic libraries (72 Gb) yielded 344 contig bins, from which 125 draft genomes were produced. Fourteen genomes were significantly enriched with 13 C from lignin, including genomes of Actinomycetes (Thermoleophilaceae, Solirubrobacteraceae, Rubrobacter sp.), Firmicutes (Kyrpidia sp., Alicyclobacillus sp.) and Gammaproteobacteria (Steroidobacteraceae). We employed multiple approaches to screen genomes for genes encoding putative ligninases and pathways for aromatic compound degradation. Our analysis identified several novel laccase-like multi-copper oxidase (LMCO) genes in 13 C-enriched genomes. One of these LMCOs was heterologously expressed and shown to oxidize lignin model compounds and minimally transformed lignin. This study elucidated bacterial lignin depolymerization and mineralization in thermal ecosystems, establishing new possibilities for the efficient valorization of lignin at elevated temperature., (© 2022. The Author(s).)

The limited utilization of reliable tools and standards for determination of the softwood kraft lignin molar mass and the corresponding molecular conformation hampers elucidation of the structure-property relationships of lignin. At issue, conventional size exclusion chromatography (SEC) is unable to robustly measure the molar mass because of a lack of calibration standards with a similar structure to lignin. In the present work, the determination of the absolute molar mass of acetylated technical lignin was revisited utilizing SEC combined with multi-angle light scattering with a band pass filter to suppress the fluorescence. Fractionated lignin isolated using sequential techniques of solvent and membrane methods was used to enhance the clarity of light-scattering profiles by narrowing the molar mass distribution of lignin fractions. Further information on the molecular conformation of derivatized samples was studied utilizing a differential viscometer, and chemical structures were identified by NMR spectroscopy analysis. Through the help of fractionation, intrinsic viscosity values were determined for the different fractions as a function of molecular weight cut-off membranes. The derivatized acetone-soluble lignin was found to possess a lower molecular weight and an extremely compact structure relative to the derivatized acetone-insoluble fraction based on a significantly lower "α" value in the Mark-Houwink-Sakurada plot (0.15 acetone-soluble vs 0.33 acetone-insoluble). The differences in geometry were supported by the linkage analysis from NMR showing the acetone-soluble part containing fewer native linkages. In both of these examples, kraft lignin behaved like a solid sphere, limiting the ability to provide entanglements between molecular chains. From this standpoint, macroscopic properties of lignin are justified with this knowledge of a dense and extremely compact structure.

The valorization of lignin, a major component of plant-derived biomass, is essential to sustainable biorefining. We identified the major monoaromatic compounds present in black liquor, a lignin-rich stream generated in the kraft pulping process, and investigated their bacterial transformation. Among tested solvents, acetone extracted the greatest amount of monoaromatic compounds from softwood black liquor, with guaiacol, vanillin, and acetovanillone, in an approximately 4:3:2 ratio, constituting ~90% of the total extracted monoaromatic content. 4-Ethanol guaiacol, vanillate, and 4-propanol guaiacol were also present. Bacterial strains that grew on minimal media supplemented with the BL extracts at 1mM total aromatic compounds included Pseudomonas putida KT2442, Sphingobium sp. SYK-6, and Rhodococcus rhodochrous EP4. By contrast, the extracts inhibited the growth of Rhodococcus jostii RHA1 and Rhodococcus opacus PD630, strains extensively studied for lignin valorization. Of the strains that grew on the extracts, only R. rhodochrous GD01 and GD02, isolated for their ability to grow on acetovanillone, depleted the major extracted monoaromatics. Genomic analyses revealed that EP4, GD01, and GD02 share an average nucleotide identity (ANI) of 98% and that GD01 and GD02 harbor a predicted three-component carboxylase not present in EP4. A representative carboxylase gene was upregulated ~100-fold during growth of GD02 on a mixture of the BL monoaromatics, consistent with the involvement of the enzyme in acetovanillone catabolism. More generally, quantitative RT-PCR indicated that GD02 catabolizes the BL compounds in a convergent manner via the β-ketoadipate pathway. Overall, these studies help define the catabolic capabilities of potential biocatalytic strains, describe new isolates able to catabolize the major monoaromatic components of BL, including acetovanillone, and facilitate the design of biocatalysts to valorize under-utilized components of industrial lignin streams., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Navas, Dexter, Liu, Levy-Booth, Cho, Jang, Mansfield, Renneckar, Mohn and Eltis.)

Plants inherently display a rich diversity in cell wall chemistry, as they synthesize an array of polysaccharides along with lignin, a polyphenolic that can vary dramatically in subunit composition and interunit linkage complexity. These same cell wall chemical constituents play essential roles in our society, having been isolated by a variety of evolving industrial processes and employed in the production of an array of commodity products to which humans are reliant. However, these polymers are inherently synthesized and intricately packaged into complex structures that facilitate plant survival and adaptation to local biogeoclimatic regions and stresses, not for ease of deconstruction and commercial product development. Herein, we describe evolving techniques and strategies for altering the metabolic pathways related to plant cell wall biosynthesis, and highlight the resulting impact on chemistry, architecture, and polymer interactions. Furthermore, this review illustrates how these unique targeted cell wall modifications could significantly extend the number, diversity, and value of products generated in existing and emerging biorefineries. These modifications can further target the ability for processing of engineered wood into advanced high performance materials. In doing so, we attempt to illuminate the complex connection on how polymer chemistry and structure can be tailored to advance renewable material applications, using all the chemical constituents of plant-derived biopolymers, including pectins, hemicelluloses, cellulose, and lignins., (© 2021. The Author(s).)

Thermal swamps are unique ecosystems where geothermally warmed waters mix with decomposing woody biomass, hosting novel biogeochemical-cycling and lignin-degrading microbial consortia. Assembly of shotgun metagenome libraries resolved 351 distinct genomes from hot-spring (30-45 °C) and mesophilic (17 °C) sediments. Annotation of 39 refined draft genomes revealed metabolism consistent with oligotrophy, including pathways for degradation of aromatic compounds, such as syringate, vanillate, p-hydroxybenzoate, and phenol. Thermotolerant Burkholderiales, including Rubrivivax ssp., were implicated in diverse biogeochemical and aromatic transformations, highlighting their broad metabolic capacity. Lignin catabolism was further investigated using metatranscriptomics of sediment incubated with milled or Kraft lignin at 45 °C. Aromatic compounds were depleted from lignin-amended sediment over 148 h. The metatranscriptomic data revealed upregulation of des/lig genes predicted to specify the catabolism of syringate, vanillate, and phenolic oligomers in the sphingomonads Altererythrobacter ssp. and Novosphingobium ssp., as well as in the Burkholderiales genus, Rubrivivax. This study demonstrates how temperature structures biogeochemical cycling populations in a unique ecosystem, and combines community-level metagenomics with targeted metatranscriptomics to identify pathways with potential for bio-refinement of lignin-derived aromatic compounds. In addition, the diverse aromatic catabolic pathways of Altererythrobacter ssp. may serve as a source of thermotolerant enzymes for lignin valorization.

Hydrogen evolution from biomass photoreforming has been widely recognized as a promising strategy for relieving the pressure from energy crisis and environmental pollution, as it could generate sustainable H 2 and value-added bioproducts simultaneously. Combining p-type semiconductors with n-type semiconductors to form n-p heterojunction is an effective strategy to improve the photocatalytic quantum efficiency by enhancing the separation of photogenerated electrons and holes, which could greatly facilitate the realization of such biomass photorefinery concept. However, the incompact contact between the n-type and p-type semiconductors often induces the aggregation of photogenerated electrons and holes. In this work, we design and synthesize an ultrafine n-p heterojunction TiO 2 -NiO core-shell structure to overcome the incompact contact in the n-p interface. When the n-p heterojunction photocatalysts are evaluated for photocatalytic water splitting and biomass lignin photoreforming respectively, the as-fabricated TiO 2 -NiO nanocomposite with 3.25% NiO demonstrates the highest hydrogen generation of 23.5 mmol h -1 g -1 from water splitting and H 2 (0.45 mmol h -1 g -1 ) and CH 4 (0.03 mmol h -1 g -1 ) cogeneration with reasonable amount of fatty acids (palmitic acid and stearic acid) production from lignin photoreforming. The excellent photocatalytic activity is ascribed to the synergistic effects of high crystallinity of TiO 2 ultrafine nanoparticles, core-shell structure and n-p heterojunction with NiO nanoclusters. This present work demonstrates a simple and efficient method to fabricate ultrafine n-p heterojunction core-shell structure for noble-metal free catalyst for both water splitting and biomass photoreforming., 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 © 2020 Elsevier Inc. All rights reserved.)

Lignin is known to limit the enzyme-mediated hydrolysis of biomass by both restricting substrate swelling and binding to the enzymes. Pretreated mechanical pulp (MP) made from Aspen wood chips was incubated with either 16% sodium sulfite or 32% sodium percarbonate to incorporate similar amounts of sulfonic and carboxylic acid groups onto the lignin (60 mmol/kg substrate) present in the pulp without resulting in significant delignification. When Simon's stain was used to assess potential enzyme accessibility to the cellulose, it was apparent that both post-treatments enhanced accessibility and cellulose hydrolysis. To further elucidate how acid group addition might influence potential enzyme binding to lignin, Protease Treated Lignin (PTL) was isolated from the original and modified mechanical pulps and added to a cellulose rich, delignified Kraft pulp. As anticipated, the PTLs from both the oxidized and sulfonated substrates proved less inhibitory and adsorbed less enzymes than did the PTL derived from the original pulp. Subsequent analyses indicated that both the sulfonated and oxidized lignin samples contained less phenolic hydroxyl groups, resulting in enhanced hydrophilicity and a more negative charge which decreased the non-productive binding of the cellulase enzymes to the lignin., (Copyright © 2020 Wu, Chandra, Takada, Liu, Renneckar, Kim, Kim and Saddler.)

In this work, a lab-designed apparatus was developed to collect and record the CO 2 amount during the hydroxyethyl modification of lignin. We presented the CO 2 volume amount and the production rate under different reaction conditions (80 - 120 °C and 2 - 6 hrs). Nuclear magnetic resonance spectroscopy was performed to analyze the chemical structure of the hydroxyethyl lignin corresponding with different amounts of CO 2 that evolved during the reaction. The aliphatic hydroxyl, aromatic hydroxyl, and carboxylic acid groups were analyzed and tabulated. The acetylated hydroxyethyl lignin samples were characterized by 13 C NMR to obtain the aliphatic hydroxyl (primary and secondary), phenol (ortho substituted and ortho-free), hydroxyethyl, methoxy, and aromatic hydrogen groups semi-quantitatively. Fourier-transform infrared (FTIR) spectroscopy was adopted to analyze the surface functional groups including alkyl aryl ether bond, carboxylic acid groups, and aromatic hydroxyl groups. Gel permeation chromatography combined with a multi-angle light scattering detector and differential refractive index detector were used to obtain the molar mass of lignin before and after the modification., Competing Interests: The authors declare that they have no known competing financial interests influenced the work reported in this article., (© 2020 The Authors.)

To assess the impact of alkalinity on sulfonation and the enzyme-mediated hydrolysis of softwood cellulose, Lodgepole pine chips were impregnated with 8% sodium sulfite and increasing loadings of sodium carbonate before thermomechanical pulping. It was apparent that alkali addition enhanced lignin sulfonation with an additional 4% loading of sodium carbonate proving optimal. TEM indicated that sulfonation predominantly occurred within the secondary-cell-wall lignin, increasing cellulose accessibility to the cellulase enzymes. Although increasing alkalinity did not significantly enhance lignin sulfonation, likely due to the lower acetyl content of the softwood chips, it increases mannan solubilization. Despite their smaller particle size, softwood pellets were more poorly sulfonated, probably due to their higher lignin content and lower amount of acid groups. This more condensed lignin structure was confirmed by 2D-NMR and GPC analyses which indicated that the EMAL derived from softwood pellets contained less native β-O-4 linkages and had a higher molecular weight., 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 © 2020 Elsevier Ltd. All rights reserved.)

Natural materials are highly anisotropic, maximizing performance of the polymeric structures while conserving mass and enhancing function. In synthetic materials, nanoscale fibers produced by electrospinning often contain molecular alignment of polymers along the fiber axis achieving some similarity to natural fibers. In this study, isolated softwood kraft lignin (SKL) was electrospun into aligned fibers utilizing a special collector. The molecular organization of lignin within the aligned nanofibers was investigated by polarized light optical microscopy. Furthermore, the functional groups that had preferred alignment along the fiber axis were identified with polarized Fourier transform infrared (FTIR) spectroscopy based on dichroism measurements. In addition, nanocrystalline cellulose (NCC) was added to the lignin solutions in order to create composite nanofibers. Both the orientation of NCC within the nanoscale fibers and the impact this component had on the degree of orientation of SKL within the aligned nanofibers were revealed by utilizing polarized FTIR. Finally, solvent cast lignin films were analyzed for their anisotropic polarizability, demonstrating birefringence with and without nanocrystalline cellulose. The work provided unique insight into both preferred orientation (fibers) and assembly (films) for technical lignin due to processing.

Functionalized cellulose nanocrystals (CNC) have unique properties that make them attractive in various applications such as drug delivery, hydrogels, and emulsions. However, the predominant chemical methods currently used to functionalize cellulose nanocrystals have a large environmental footprint. Although greener methods are desirable, the relatively inert nature of cellulose crystals presents a major challenge to their potential modification in aqueous media. In the work reported here, carbohydrate binding modules (CBMs) were used to introduce new functionality to cellulose surfaces. CBM2a, which has a strong affinity for crystalline cellulose, was functionalized with an alkyne at the terminal amine position. The alkyne group, which was introduced onto the cellulose surface with CBM2a, underwent a Click reaction with polyethylene glycol (PEG) to modify CNC surfaces. This provided a strong, non-covalent modification of cellulose surfaces that was carried out in a one-pot reaction in aqueous media. The CBM-PEG modification of cellulose surfaces increased CNC redispersion after drying and improved suspension stability based on steric interactions. It was apparent that hybrid polysaccharide-protein, self-assembled nanoparticles could be effectively produced, with potential for nanomedicine, immunoassay, and drug delivery applications.

An aqueous biopolymer dispersion coating system was synthesized utilizing softwood kraft lignin and a long chain organic acid. The chemical treatment of lignin was a two-step procedure, which first consisted of hydroxyethylation of the phenolic groups on lignin utilizing ethylene carbonate and an alkaline catalyst. This first step resulted in the lignin containing more than 80% aliphatic hydroxyl functionality ( 1 H NMR). Following this step, oleic acid was reacted with hydoxyethyl lignin in order to form ester derivatives. With nearly a total reduction in absorbance in the hydroxyl stretching region, FT-IR analysis showed the majority of the hydroxyl groups was esterified forming an ethyl oleate derivative. Semi-quantitative 13 C NMR analysis of the lignin revealed 88% substitution of the lignin hydroxyl groups. This derivative was soluble in organic solvent such as toluene and tetrahydrofuran. Solutions of lignin derivatives were slowly precipitated through dialysis, resulting in a stable dispersion of lignin microparticles in distilled water. The 1-2 μm average diameter size of the precipitated particles was found with dynamic light scattering of the suspensions. Spray and spin coating were used to apply the lignin derivative dispersion to different surfaces. For both coating methods, the lignin-based particles enhanced the hydrophobicity of all the substrates tested, resulting in increased water contact angles for glass, kraft pulp sheets and solid wood. Benign reagents involved in the coating synthesis utilized natural compounds that are known to repel water in nature. Combined with the avoidance of volatile organic solvents during application, this process provided a low environmental footprint solution for synthesis of hydrophobic coatings.

Lignin is a renewable biopolymer considered as a potential precursor for low-cost carbon materials. Thermal oxidative stabilization (TOS) is an important processing step to maintain fiber geometry during carbonization, yet the impact of  TOS on the properties of lignin-based carbon materials has not been clearly identified in the literature. Yield, change in fiber diameter/distribution, elemental composition, and mechanical properties were explored for both stabilized and carbonized lignin fibers. Vibrational spectroscopy and solid-state 13 C nuclear magnetic resonance spectroscopy were used to analyze the changes in lignin molecular structure after exposure to various heating conditions during the TOS steps. Further, studies were focused on the effects of TOS conditions on the resulting carbon structure of fiber mats through Raman spectroscopy measurements and electrical conductivity analysis. Although TOS conditions influenced the properties of the oxidized lignin fiber mats, properties of the carbonized samples were invariant to the TOS procedures used in this study over most of the conditions. As a result, there was flexibility for the parameters (time and temperature) in the TOS process when conditioning softwood lignin materials for carbon fibers., Competing Interests: The authors declare no competing financial interest.

This study reports coupling methods of chitosan (CTS) and TEMPO-oxidized nanofibrilliated cellulose (TONCs). Coupling chitosan, a cationic polysaccharide, to anionic TONCs is preformed through physical crosslinking via ionic bond formation at room temperature and carefully controlled pH and mass ratio. After heating, the carboxyl group of TONCs and the ammonium group of chitosan react into an amide covalent bond linkage CONH. Fourier Transform infrared spectroscopy, 13 C solid-state nuclear magnetic resonance, are used to confirm the bonds. Films of the modified TONC are produced by casting and exchanging method and atomic force microscopy and thermogravimetric analysis was used to study the film properties. Further, the tensile strength of the CTS-TONCs films is improved for the covalent bond produced indicating a straight forward method to augment the properties of these all-polysaccharide films., (Copyright © 2018. Published by Elsevier Ltd.)

Although bacterial cellulose (BC) is a fascinating, highly pure cellulose material for various downstream applications, production has been challenged by its low productivity. This work reported a facile route to significantly enhance BC yield without compromising its structural advantages via adding mesoporous halloysite nanotubes (HNTs) in the culture medium at static cultivations. The BC productivity of Gluconacetobacter xylinus was increased from 2.2 to 5.9 g L -1 after 15 days of cultivation when 2 wt% of HNTs was added into the standard fructose medium. It appeared that the dual functionality of cell immobilization and oxygen release of the HNTs were responsible for enhancing the BC productivity. Moreover, the HNTs-resulted BC pellicle exhibited negligible content of HNTs contamination (∼2 wt%), higher degree of crystallinity (87.7%) and porosity (assessed by water holding capacity, 12.7 g g -1 ), and showed promising applications especially in the bio-adsorption field., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A new family of materials comprised of cellulose, cellulose nanomaterials (CNMs), having properties and functionalities distinct from molecular cellulose and wood pulp, is being developed for applications that were once thought impossible for cellulosic materials. Commercialization, paralleled by research in this field, is fueled by the unique combination of characteristics, such as high on-axis stiffness, sustainability, scalability, and mechanical reinforcement of a wide variety of materials, leading to their utility across a broad spectrum of high-performance material applications. However, with this exponential growth in interest/activity, the development of measurement protocols necessary for consistent, reliable and accurate materials characterization has been outpaced. These protocols, developed in the broader research community, are critical for the advancement in understanding, process optimization, and utilization of CNMs in materials development. This review establishes detailed best practices, methods and techniques for characterizing CNM particle morphology, surface chemistry, surface charge, purity, crystallinity, rheological properties, mechanical properties, and toxicity for two distinct forms of CNMs: cellulose nanocrystals and cellulose nanofibrils.

Physiochemical methods have generally been used to "open-up" biomass substrates/pulps and have been the main method used to fibrillate cellulose. However, recent work has shown that canonical cellulase enzymes such as endoglucanases, in combination with "amorphogenesis inducing" proteins such as lytic polysaccharide monooxygenases (LPMO), swollenin and hemicellulases, are able to increase cellulose accessibility. In the work reported here different combinations of endoglucanase, LPMO and xylanase were applied to Kraft pulps to assess their potential to induce fibrillation at low enzyme loading over a short time period. Although gross fiber properties (fiber length, width and morphology) were relatively unchanged, over a short period of time, the intrinsic physicochemical characteristics of the pulp fibers (e.g. cellulose accessibility/DP/crystallinity/charge) were positively enhanced by the synergistic cooperation of the enzymes. LPMO addition resulted in the oxidative cleavage of the pulps, increasing the negative charge (~100 mmol kg -1 ) on the cellulose fibers. This improved cellulose nanofibrilliation while stabilizing the nanofibril suspension (zeta potential ζ = ~60 mV), without sacrificing nanocellulose thermostability. The combination of endoglucanase, LPMO and xylanases was shown to facilitate nanofibrillation, potentially reducing the need for mechanical refining while resulting in a pulp with a more uniform nanofibril composition.

Nanocellulose is growing in popularity due to its versatile properties and applications. However, there is a void of knowledge regarding the environmental fate of nanocellulose and the response of environmental microbial communities that are historically adapted to non-nano cellulose forms. Given its distinction in terms of size and chemical and physical properties, nanocellulose could potentially resist biodegradation and/or pose a xenobiotic influence on microbial communities during wastewater treatment or in receiving environments. In this study, biodegradation of H 2 SO 4 hydrolyzed nanocrystalline cellulose (HNC) was compared with that of microcrystalline cellulose using two distinct anaerobic cellulose-degrading microbial consortia initially sourced from anaerobic digester (AD) and wetland (W) inocula. Equivalent cellulose masses were dosed and monitored with time by measurement of liberated glucose. HNC biodegraded at slightly faster rate than microcrystalline cellulose (1st order decay constants: 0.62 ± 0.08 wk -1 for HNC versus 0.39 ± 0.05 wk -1 for microcrystalline cellulose for the AD consortium; 0.69 ± 0.04 wk -1 for HNCversus 0.58 ± 0.05 wk -1 for microcrystalline cellulose for the W consortium). 16S rRNA (total bacteria) and cel48 (glycoside hydrolase gene family 48, indicative of cellulose-degrading potential) genes were observed to be more enriched in the HNC condition for both consortia. According to Illumina amplicon sequencing of 16S rRNA genes, the composition of the consortia underwent distinct shifts in concert with HNC versus microcrystalline cellulose degradation. This study demonstrates that the biodegradation of cellulose is not inhibited in the nano-size range, particularly in the crystalline form, though the microbes and pathways involved likely differ., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Glycerol thermal processing (GTP) of hardwood biomass at temperatures between 200 and 240°C facilitated stepwise biopolymer fractionation, while limiting significant degradation of the major hemicellulose, glucuronoxylan, into water-extractable oligosaccharides. After GTP pretreatment and sequential water and organic solvent extraction, up to 80% of the initial xylan remained in the pretreated biomass. The majority of the xylan from GTP pretreated and water/solvent extracted biomass was removed using a mild alkali extraction and the composition was compared to xylan directly isolated from untreated hardwood. The precipitated xylan from the neutralized alkaline filtrate was isolated as a water insoluble xylan portion (WIX). The residual xylan dissolved in the neutralized filtrate was precipitated in cold methanol and recovered as the water soluble xylan portion (WSX). Results showed that xylan in WIX was in a polymeric form with a number average degree of polymerization (DP) over 100, whereas the WSX had a much lower average DP of 27 (ca) and contained more substitution. As the processing severity increased during GTP pretreatment, the proportion of WIX increased and the purity of the xylan within the WIX sample reached 84% based on compositional analysis. FT-IR analysis of WIX revealed that xylan isolated after GTP contained peaks related to a reduced carbonyl signal compared to the control. Furthermore, crude WSX contained less xylan with more lignin contamination at severe GTP conditions. The recovery of the xylan in two portions facilitated a preferential purification strategy resulting in WIX with an extremely narrow polydispersity index between 1.1 and 1.25, dependent upon the GTP severity. This study provided insight into fractionating higher molecular weight xylan that may serve value-added applications such as healthcare materials and advanced packaging., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Biomass was heated (200-240°C) in the presence of glycerol, for 4-12 min, under shear to disrupt the native cell wall architecture. The impact of this method, named glycerol thermal processing (GTP), on saccharification efficiency of the hardwood Liquidambar styraciflua, and a control cellulose sample was studied as a function of treatment severity. Furthermore, the enzymatic conversion of samples with varying compositions was studied after extraction of the structural polymers. Interestingly, the sweet gum processed materials crystallinity index increased by 10% of the initial value. The experiments revealed that the residual lignin was not a barrier to limiting the digestibility of cellulose after pretreatment yielding up to 70% glucose based on the starting wood material. Further xylan removal greatly improved the cellulose hydrolysis rate, converting nearly 70% of the cellulose into glucose within 24h, and reaching 78% of ultimate glucan digestibility after 72 h., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Nanocellulose is of research interest due to its extraordinary optical, thermal, and mechanical properties. The incorporation of guest nanoparticles into nanocellulose substrates enables production of novel nanocomposites with a broad range of applications. In this study, gold nanoparticle/bacterial cellulose (AuNP/BC) nanocomposites were prepared and evaluated for their applicability as surface-enhanced Raman scattering (SERS) substrates. The nanocomposites were prepared by citrate mediated in situ reduction of Au(3+) in the presence of a BC hydrogel at 303 K. Both the size and morphology of the AuNPs were functions of the HAuCl4 and citrate concentrations. At high HAuCl4 concentrations, Au nanoplates form within the nanocomposites and are responsible for high SERS enhancements. At lower HAuCl4 concentrations, uniform nanospheres form and the SERS enhancement is dependent on the nanosphere size. The time-resolved increase in the SERS signal was probed as a function of drying time with SERS 'hot-spots' primarily forming in the final minutes of nanocomposite drying. The application of the AuNP/BC nanocomposites for detection of the SERS active dyes MGITC and R6G as well as the environmental contaminant atrazine is illustrated as is its use under low and high pH conditions. The results indicate the broad applicability of this nanocomposite for analyte detection.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

This study focused on the assembly characteristics of debranched xylan onto cellulose surfaces. A rye arabinoxylan polymer with an initial arabinose/xylose ratio of 0.53 was debranched with an oxalic acid treatment as a function of time. The resulting samples contained reduced arabinose/xylose ratios significantly affecting the molecular architecture and solution behavior of the biopolymer. With this treatment, an almost linear xylan with arabinose DS of only 0.04 was obtained. The removal of arabinose units resulted in the self-assembly of the debranched polymer in water into stable nanoparticle aggregates with a size around 300 nm with a gradual increase in crystallinity of the isolated xylan. Using quartz crystal microbalance with dissipation monitoring, the adsorption of xylan onto model cellulose surfaces was quantified. Compared to the nonmodified xylan, the adsorption of debranched xylan increased from 0.6 to 5.5 mg m(-2). Additionally, adsorption kinetics suggest that the nanoparticles rapidly adsorbed to the cellulose surfaces compared to the arabinoxylan. In summary, a control of the molecular structure of xylan influences its ability to form a new class of polysaccharide nanoparticles in aqueous suspensions and its interaction with nanocellulose surfaces.

Background: The in-depth understanding of the enzymatic hydrolysis of cellulose with heterogeneous morphology (that is, crystalline versus amorphous) may help develop better cellulase cocktail mixtures and biomass pretreatment, wherein cost-effective release of soluble sugars from solid cellulosic materials remains the largest obstacle to the economic viability of second generation biorefineries., Results: In addition to the previously developed non-hydrolytic fusion protein, GC3, containing a green fluorescent protein (GFP) and a family 3 carbohydrate-binding module (CBM3) that can bind both surfaces of amorphous and crystalline celluloses, we developed a new protein probe, CC17, which contained a mono-cherry fluorescent protein (CFP) and a family 17 carbohydrate-binding module (CBM17) that can bind only amorphous cellulose surfaces. Via these two probes, the surface accessibilities of amorphous and crystalline celluloses were determined quantitatively. Our results for the enzymatic hydrolysis of microcrystalline cellulose (Avicel) suggested that: 1) easily accessible amorphous cellulose on the surface of Avicel is preferentially hydrolyzed at the very early period of hydrolysis (that is, several minutes with a cellulose conversion of 2.8%); 2) further hydrolysis of Avicel is a typical layer-by-layer mechanism, that is, amorphous and crystalline cellulose regions were hydrolyzed simultaneously; and 3) most amorphous cellulose within the interior of the Avicel particles cannot be accessed by cellulase., Conclusions: The crystallinity index (CrI), reflecting a mass-average (three-dimensional) cellulose characteristic, did not represent the key substrate surface (two-dimensional) characteristic related to enzymatic hydrolysis.

Introducing porosity in electrospun scaffolds is critical to improve cell penetration and nutrient diffusion for tissue engineering. Nanofibrous cellulose scaffolds were prepared by electrospinning cellulose acetate (CA) followed by saponification to regenerate cellulose. Using a computer-assisted design approach, scaffolds underwent laser ablation resulting in pores with diameters between 50 and 300 μm without damaging or modifying the surrounding scaffold area. A new mineralization method was employed in conjunction with microablation using commercial phosphate buffered saline (PBS) to soak carboxymethylcellulose surface-modified electrospun scaffolds. The resulting crystals within the scaffold on the interior of the pore had a calcium to phosphate ratio of 1.56, similar to hydroxyapatite. It was observed that porosity of the cellulose scaffolds enhanced osteoblast cell attachment at the edge of the pores, while mineralization enhanced overall cell density., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Alkali metal counter-cations alter the electron density of phenolates in solution by electrostatic interactions. This change in electron density affects their reactivity toward formaldehyde, hydroxymethylphenols, and isocyanates during polymerization. The electronic perturbation of phenolic model compounds in the presence of alkali metal hydroxides was investigated with (13)C and (1)H nuclear magnetic resonance in polar solvents relative to non-ionic controls, altering the chemical shifts of the model compounds, thus indicating changes in electron density using the chemical shift as a proxy. These shifts were attributed to Coulombic electrostatic interactions of the counter-cation with the phenolate anion that correlated to hydrated ionic radius and solvent dielectric constants. The predicted relative reaction rates for formaldehyde addition based on electron density ranking from (13)C nuclear magnetic resonance of the phenolic models was compared with the literature values. Predictions for condensation reactions of 2- and 4-hydroxymethylphenol from chemical shifts were consistent with published results. The results permit predictions for the reaction of phenolic compounds for the formation of thermosetting polymeric materials., (Copyright © 2012 John Wiley & Sons, Ltd.)

Unusual fractions of cellulose microfibrils from woody material with dimensions of hundreds of nanometers in length and single digit angstrom thickness were obtained by intensive sonication of TEMPO-oxidized cellulose fibers. These cellulose microfibril fragments, composed of many mono- and bilayer molecular sheets, were analyzed with scattering and spectroscopy techniques to understand the structural changes at the supramolecular level. XRD data indicated that sonication breaks the cellulose microfibrils along its (200) planes, yet some form of the Iβ crystalline structure is still retained with reduced crystallinity. The Raman and FTIR analysis indicated structural changes to the cellulose microfibrils do not occur until after sonication; furthermore, AFM observation indicates that the structural changes began to occur within 5 min of sonication. An altered supramolecular structure is evident after sonication: major features from cellulose I are preserved, although certain spectral features similar to mercerized and ball milled cellulose appeared in its FTIR and Raman spectra. These spectral differences are traced to changes in the methine environment, hydroxymethyl conformations, and skeletal vibrations. By integrating the present findings and previous research, a cellulose molecular sheet delamination scheme is proposed to describe this microfibril fragmentation along its (200) plane.

Novel cellulose based-scaffolds were studied for their ability to nucleate bioactive calcium phosphate crystals for future bone healing applications. Cellulose-based scaffolds were produced by electrospinning cellulose acetate (CA) dissolved in a mixture of acetone/dimethylacetamide (DMAc). The resulting nonwoven CA mats containing fibrils with diameters in the range of 200 nm to 1.5 μm were saponified by NaOH/ethanol for varying times to produce regenerated cellulose scaffolds. Biomimetic crystal growth nucleated from the fiber surface was studied as a function of surface chemistry. Regenerated cellulose scaffolds of varying treatments were soaked in simulated body fluid (SBF) solution. Scaffolds that were treated with CaCl(2), a mixture of carboxymethyl cellulose (CMC) and CaCl(2), and NaOH and CaCl(2), were analyzed using X-ray photoelectron spectroscopy, X-ray powder diffraction, and scanning electron microscopy to understand the growth of bioactive calcium phosphate (Ca-P) crystals as a function of surface treatment. The crystal structure of the nucleated Ca-P crystals had a diffraction pattern similar to that of hydroxyapatite, the mineralized component of bone. The study shows that the scaffold surface chemistry can be manipulated, providing numerous routes to engineer cellulosic substrates for the requirements of scaffolding.

The assembly of dissolved technical lignins in aqueous and organic medium has been studied at the solid-liquid interface. Adsorption of alkali lignin onto gold coated crystals treated with a cationic polymer was determined using a quartz crystal microbalance with dissipation monitoring. Complete coverage of the cationic surface with alkali lignin occurred at low solution concentration, revealing a high affinity coefficient under both alkali and neutral conditions. With additional adsorption studies from organosolv lignin in organic solvent and spectroscopic analysis of mixtures of cationic polymer and alkali lignin, a noncovalent interaction between lignin's aromatic rings and the cation of the quaternary ammonium group was shown to exist. The work underscores how polyphenolic biopolymers can strongly interact with cations through noncovalent interactions to control molecular architecture.

Surface chemistry of wood is based on the exposed surface that is the combination of the intact and cut cellular wall material. It is inherently complex and changes with processing history. Modification of wood surfaces through noncovalent attachment of amine containing water soluble polyelectrolytes provides a path to create functional surfaces in a controlled manner. Adsorption of polyethylenimine (PEI) and polydiallydimethylammonium chloride (PDDA) to wood was quantified as a function of solution conditions (pH and ionic strength). Polycation adsorption was maximized under basic pH without the addition of electrolyte. Added salt either had marginal influence or decreased adsorption of polycation, indicating interactions are strongly influenced by Coulombic forces. PEI adsorption could be modeled by both a Langmuir and Freundlich equations, although the wood surface is known to be heterogeneous. After adsorption of polycations, layer-by-layer assembled films were created on the wood surface. Layered films masked ultrastructural features of the cell wall, while leaving the microscale features of wood (cut lumen walls and openings) evident. These findings revealed for the first time that nanoscale films on wood can be deposited without changing the microscopic and macroscopic texture. Functionalized wood surfaces created by nanoscale films may have a future role in adhesives systems for wood composites, wood protection, and creating new functional features on wood.

A biomimetic approach was taken for studying the adsorption of a model copolymer (pullulan abietate, DS 0.027), representing the lignin-carbohydrate complex, to a model surface for cellulose fibers (Langmuir-Blodgett thin films of regenerated cellulose). Adsorption results were assayed using surface plasmon resonance spectroscopy (SPR) and atomic force microscopy (AFM). Rapid, spontaneous, and desorption-resistant surface modification resulted. This effort is viewed as a critical first step towards the permanent surface modification of cellulose fibers with a layer of molecules amenable to either enzymatic crosslinking for improved wood composites or thermoplastic consolidation.