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In this paper, we describe an approach for producing both high quality and high quantity of lignin by studying structural change of lignin during treatment of poplar wood in γ-valerolactone (GVL) for a range of temperatures (80–120 °C) and reaction time at temperature (1–24 h).

To date, little is known about the evolution of fern genomes, with only two small genomes published from the heterosporous Salviniales. Here we assembled the genome of Alsophila spinulosa, known as the flying spider-monkey tree fern, onto 69 pseudochromosomes. The remarkable preservation of synteny, despite resulting from an ancient whole-genome duplication over 100 million years ago, is unprecedented in plants and probably speaks to the uniqueness of tree ferns. Our detailed investigations into stem anatomy and lignin biosynthesis shed new light on the evolution of stem formation in tree ferns. We identified a phenolic compound, alsophilin, that is abundant in xylem, and we provided the molecular basis for its biosynthesis. Finally, analysis of demographic history revealed two genetic bottlenecks, resulting in rapid demographic declines of A. spinulosa. The A. spinulosa genome fills a crucial gap in the plant genomic landscape and helps elucidate many unique aspects of tree fern biology.

Thioacidolysis is widely used for lignin structural characterization by cleaving β-aryl ethers to release syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) monomers followed by GC analysis. However, the traditional thioacidolysis method requires tedious extraction steps with chlorinated solvent underlying harmful to health, limiting its efficiency and application. Herein, an improved thioacidolysis method with high sensitivity for the quantitation of lignin-derived monomers was developed. The improved protocol used a quick, streamlined procedure to recover the monomeric products using ethyl acetate as extracting solvent and MS detector in multi-reaction monitoring mode to enhance its ability to detect extremely low concentration (0.1 ppb with signal-to-noise higher than 2) of monomeric products. Additionally, a fast GC program was established to speed up the GC quantitation. Several representative lignocellulose samples, including gymnosperm, angiosperm, and poaceae, were used to test this tailored method. The results demonstrated that the ratios of lignin monomer compositions determined by this method were consistent with that of traditional procedure despite the slightly higher monomer yields measured. More importantly, this method uses non-chlorinated solvent for microscale extraction and requires no evaporation step for workup, which is a green and efficient way for the quantification of lignin monomer compositions.

Hydroxycinnamoyl shikimates were reported in 2005 to be intermediates in monolignol biosynthesis. 3-Hydroxylation of p-coumarate, originally thought to occur via coumarate 3-hydroxylase (C3H) from p-coumaric acid or its CoA thioester, was revealed to be via the action of coumaroyl shikimate 3′-hydroxylase (C3′H) utilizing p-coumaroyl shikimate as the substrate, itself derived from p-coumaroyl-CoA via hydroxycinnamoyl-CoA: shikimate hydroxycinnamoyltransferase (HCT). The same HCT was conjectured to convert the product, caffeoyl shikimate, to caffeoyl-CoA to continue on the pathway starting with its 3-O-methylation. At least in some plants, however, a more recently discovered caffeoyl shikimate esterase (CSE) enzyme hydrolyzes caffeoyl shikimate to caffeic acid from which it must again produce its CoA thioester to continue on the monolignol biosynthetic pathway. HCT and CSE are therefore monolignol biosynthetic pathway enzymes that have provided new opportunities to misregulate lignification. To facilitate studies into the action and substrate specificity of C3H/C3′H, HCT, and CSE enzymes, as well as for metabolite authentication and for enzyme characterization, including kinetics, a source of authentic substrates and products was required. A synthetic scheme starting from commercially available shikimic acid and the four key hydroxycinnamic acids (p-coumaric, caffeic, ferulic, and sinapic acid) has been developed to provide this set of hydroxycinnamoyl shikimates for researchers.

Hemicelluloses account for 15–30 % of the lignocellulosic biomass and are considered as abundant renewable biopolymers. They are the major byproducts from pulping and other biorefinery industries, but are highly underutilized and usually burned as low value fuel. In this study, glucuronoxylan recovered from dissolving pulp mill were used to produce a high-quality bio-based emulsifier. Octylamine, dodecylamine and hexadecylamine were used to modify oxidized glucuronoxylan in order to improve the amphipathic properties of glucuronoxylan. Alkyl aminated glucuronoxylan emulsions showed smaller droplet size, higher emulsion activity and lower zeta potential compared to that of unmodified glucuronoxylan emulsions. With the increasing of alkyl contents, the emulsifying properties were improved. However, when the contents of alkyl groups increased beyond a certain value, the emulsifying properties were not changed significantly. Furthermore, the alkyl chain length also had a positive impact on emulsifying properties of alkylamine aminated glucuronoxylans. These results suggest that alkyl aminated glucuronoxylans have the potential to substitute for petroleum-based emulsifiers in many applications.

Although measuring lignin contents is a routine operation for biomass compositional analysis in process development aiming at efficient utilization of woody biomass, it is still a challenging task requiring many steps, hazardous reagents, heating, and a significant time. A facile spectroscopic method, our CASA (Cysteine–Assisted Sulfuric Acid) method, was developed to quantify the lignin content of lignocellulosic biomass, based on an extraordinary system in which biomass samples are fully dissolved in 72% H2SO4 containing cysteine at 24 °C in 60 min. Using synthetic lignins, the lignin absorptivities were determined to be 17.25 g−1 L cm−1 for softwood lignin and 11.23 g−1 L cm−1 for hardwood lignin and monocot lignin. Seven softwoods, six hardwoods, and six monocots were tested using the CASA method. A high coefficient of determination (R2 = 0.95) was found between the CASA results and the acid-insoluble lignin contents, and an even better R2 (0.98) was obtained when the CASA data were correlated with the total lignin contents.

Aimed at decreasing the environmental pollution caused by petroleum-derived packing materials, many efforts have been directed towards fabricating biodegradable substitutes, especially of cellulose-based film with functional properties. In this paper, a totally plant-derived antibacterial film was successfully prepared. Regenerated cellulose films were used as substrate and poacic acid, a decarboxylated product from 8–5-diferulic acid, as fungicides. The physical properties and thermal stability of the prepared plant-derived antibacterial films were characterized, and the antibacterial activity was also assessed as the function poacic acid contents. The morphology showed that the cellulose/poacic acid films exhibited a homogeneous and smooth surface and poacic acid was successfully incorporated into cellulose films as revealed by Fourier-transform infrared (FT-IR) spectroscopy and fluorescent microscopy. It was noted that both the tensile strength and thermal stability of the antibacterial films decreased due to the incorporation of the poacic acid. Remarkably, the prepared cellulose/poacic acid films exhibited superior antibacterial activity against Staphylococcus aureus. The notable properties of the cellulose/poacic acid films are promising for applications in food and medical packaging to enhance their safety.

Lignocellulosic biomass is mainly composed of polysaccharides and lignin. The complexity and diversity of the plant cell wall polymers makes it difficult to isolate the components in pure form for ...

Soda process is one of the most important pulping processes in paper industry producing large quantities of alkali lignins that can afford plenty of biofuels, aromatic chemicals and materials. However, the structural and size-related heterogeneities and complexities hinder the development in these directions. Herein, we report new insights into the structure of alkali lignin, through investigating the formation and transformation of enol ether and arylglycerol structures that are significant responsible for the structural transformation from native lignin to alkali lignin. Four-type enol ethers composed of G/S units in hardwood alkali lignin were identified by 2D HSQC NMR. A series of alkali lignins prepared by alkali treatment of eucalyptus cellulolytic enzyme lignin under various temperatures were analyzed by 2D HSQC NMR, 31P NMR and gel permeation chromatography (GPC). Upon these analyses and related model compound studies, it was found that the arylglycerols formed from native β-O-4 linkages tends to be oxidized with the further degradation of aryl ether bonds, and that the enol ether linkages are facile to be hydrolyzed or oxidized in the air. These insights improve the mechanistic understanding for the structural evolution and the diversity of alkali lignins and will aid the development of further lignin valorization strategies.

Lignin is a renewable and the most abundant aromatic source that can be used for extensive chemicals and materials. Although approximately 50 million tons of lignin are produced annually as a by-product of the pulp and paper industry, it is currently underutilized. It is important to know the structural features of technical lignin when considering its application. In this work, we have demonstrated the formation of low-molecular-weight constituents from hardwood (Eucalyptus) lignin, which produces much more low-molecular-weight constituents than softwood (spruce) lignin, after a chemical pulping process, and analyzed the micromolecular compositions in the alkali lignin after fractionation by dichloromethane (DCM) extraction. By applying analytical methods (gel-permeation chromatography, 2D NMR and GC-MS) with the aid of evidence from authenticated compounds, a great treasure trove of lignin-derived phenolic compounds from Eucalyptus alkali lignin were disclosed. Except for some common monomeric products, as many as 15 new lignin-derived monomers and dimers including syringaglycerol, diarylmethane, 1,2-diarylethanes, 1,2-diarylethenes, (arylvinyl ether)-linked arylglycerol dimers and isomeric syringaresinols were identified in the DCM-soluble fraction. Regarding the formation and evolution of the Cα-condensed β-aryl ether structure, a novel route that is potentially responsible for the high content of β-1 diarylethenes and diarylethanes in the lignin low-molecular-weight fraction, in addition to the β-1 (spirodienone) pathway, was proposed. This work not only provides novel insights into the chemical transformation of S–G lignin during the alkali pulping process, but also discovered lignin-derived phenolic monomers and dimers that can potentially be used as raw materials in the chemical or pharmaceutical industries.

Lignin condensation reactions are hard to avoid or control during separation, which is a deterrent to lignin isolation and post-conversation, especially for the full utilization of lignocelluloses. Selective protection of β-aryl ether linkages in the isolation process is crucial to lignin valorization. Herein, a two-step acid/alkali separation method assisted with l-cysteine for

The complexity of lignin structure impedes efficient cell wall digestibility. Native lignin is composed of a mixture of three dominant monomers, coupled together through a variety of linkages. Work over the past few decades has demonstrated that lignin composition can be altered through a variety of mutational and transgenic approaches such that the polymer is derived almost entirely from a single monomer. In this study, we investigated changes to lignin structure and digestibility in Arabidopsis thaliana in near-single-monolignol transgenics and mutants and determined whether novel monolignol conjugates, produced by a FERULOYL-CoA MONOLIGNOL TRANSFERASE (FMT) or a p-COUMAROYL-CoA MONOLIGNOL TRANSFERASE (PMT), could be integrated into these novel polymers to further improve saccharification efficiency. Monolignol conjugates, including a new conjugate of interest, p-coumaryl p-coumarate, were successfully integrated into high-H, high-G and high-S lignins in A. thaliana. Regardless of lignin composition, FMT- and PMT-expressing plants produced monolignol ferulates and monolignol p-coumarates, respectively, and incorporated them into their lignin. Through the production and incorporation of monolignol conjugates into near-single-monolignol lignins, we demonstrated that substrate availability, rather than monolignol transferase substrate preference, is the most important determining factor in the production of monolignol conjugates, and lignin composition helps dictate cell wall digestibility.

Stretchable and antifreezing conductive hydrogels, especially prepared from natural polymers, are beneficial for important and rapidly growing stretchable electronic devices. Unfortunately, the pot...

Both value-added utilization of low-rank renewable feedstocks to prepare catalytic materials and selective transformation of bioderived aldehydes are very attractive topics. Herein, lignosulfonate, a waste by-product from the paper industry, was simply assembled with ZrCl4 under non-toxic hydrothermal conditions for scalable preparation of Zr-containing polyphenolic biopolymer catalysts (Zr LS). Systematic characterizations indicated that the strong coordination between Zr4+ and phenolic hydroxyl groups in lignosulfonate led to the formation of strong Lewis acid-base couple sites (Zr4+−O2−) and porous inorganic-organic framework structure (mesopores centered at 6.1 nm), while the inherent sulfonic groups in lignosulphonate could serve as Bronsted acidic sites. The cooperative role of these versatile acid−base sites in Zr LS afforded excellent catalytic performance for Meerwein-Ponndorf-Verley (MPV) reaction of a broad range of bioderived platform chemicals under mild conditions (80 °C), especially of furfural (FF) to furfuryl alcohol (FA), in quantitative yields (96%) with high FA formation rate of 9600 μmol g−1 h−1 and TOF of 4.37 h−1. Kinetic studies revealed that the activation energy of the MPV reduction of FF was as low as 52.25 kJ/mol, accounting for the high reaction rate. Isotopic labelling experiments demonstrated direct hydrogen transfer from the α-C of 2-PrOH to the α-C of FF on acid-base sites was the rate-determining step. Moreover, Zr LS showed good recyclability for at least seven reaction cycles.

Technical lignins, mostly generated as byproducts from the pulping industry, are highly abundant aromatic sources. However, they are underutilized due to their complexity, as well as structural alt...

Glucuronoxylans, a low-value byproduct from pulping, biomass pretreatment and other biomass processing industries, have been considered to be potentially used as emulsifiers. However, the poor amphipathic property of glucuronoxylans limits their application as emulsifiers. To improve the amphipathic property of glucuronoxylans and develop high quality natural-based/green emulsifiers, glucuronoxylans were chemically modified by alkenyl succinic anhydrides to produce a novel emulsifer. The effects of degree of substitution (DS) and alkenyl chain length on the emulsifying properties of long-chain succinic anhydride modified glucuronoxylans were investigated. Dodecenyl succinic anhydride–glucuronoxylans (DDSA–glucuronoxylans) emulsions showed much smaller droplet size, lower zeta potential, higher emulsifying activity and better emulsion stability compared to that of glucuronoxylans emulsion. When DS increased from 0.014 to 0.09, the emulsifying properties of DDSA–glucuronoxylans were improved. However, when DS increased beyond 0.09, the emulsifying properties were not changed significantly. Furthermore, the alkenyl chain length also has a positive impact on emulsifying properties of long-chain succinic anhydride modified glucuronoxylans. These results suggested that long-chain succinic anhydride modified glucuronoxylans had a potential to be used as emulsifiers, while the DS and chain length should be kept at a proper value.

Exploring both high-performance catalytic materials from non-edible lignocellulosic biomass and selective hydrodeoxygenation of bioderived molecules will enable value-added utilization of renewable feedstocks to replace rapidly diminishing fossil resources. Herein, we developed a scale-up and sustainable method to fabricate gram-quantities of highly dispersed cobalt nanocatalysts sheathed in multilayered N-doped graphene (Co@NG) by using a biomacromolecule carboxymethyl cellulose (CMC) as a raw material. The ionic gelation of CMC, urea and Co2+ ions leads to uniform dispersion and chelation of different species, consequently resulting in the formation of highly distributed Co nanoparticles (NPs) (10.91 nm) with N-enriched graphene shells in the solid-state thermolysis process. The usage of urea as a non-corrosive activation agent can introduce a porous belt-like nanostructure and abundant doped nitrogen. Among all the prepared catalysts in this work, the optimized Co@NG-6 with the largest specific surface area (627 m2 g−1), the most and strongest basic sites, and the highest proportion of pyridinic-N (37.6%) and mesopores exhibited excellent catalytic activity (99% yield of 2-methoxy-p-cresol) for base-free transfer hydrodeoxygenation (THD) of vanillin using bioderived formic acid (FA) as a H source at 160 °C for 6 h. The poisoning tests and electron paramagnetic resonance (EPR) spectra verified that the strong interaction between N atoms and encapsulated Co NPs provided synergistic effects, which were essential for the outstanding catalytic performance of Co@NG-6. The deuterium kinetic isotope effect study clearly demonstrated that the formation of Co-H−via β-hydride elimination and protonation was the rate-determining step, and protic N–H+ and hydridic Co-H− were considered to be active intermediate species in the THD reaction. Furthermore, Co@NG-6 was highly stable for recycling owing to the graphene shells preventing Co NPs from corrosion and aggregation.

Pinoresinol is a high-value monolignol-derived lignan used in plant defense and with human health-supporting effects. The synthetic yield and isolation efficiency of racemic pinoresinol from coniferyl alcohol by conventional radical coupling methods is sub-optimal. In this work, a facile and efficient synthetic approach was developed to synthesize pinoresinol with much higher yield. By using 5-bromoconiferyl alcohol, which was synthesized in high yield from 5-bromovanillin, to make 5,5′-bromopinoresinol via a peroxidase-mediated radical coupling reaction takes advantage of the smaller variety of radical coupling products from the 5-substituted monolignol, producing simpler product mixtures from which 5,5′-bromopinoresinol may be readily crystalized with good yield (total yield of 44.1% by NMR; isolated crystalline yield of 24.6%). Hydro-debromination of the crystalline 5,5′-bromopinoresinol to pinoresinol was essentially quantitative. Gram quantities of pinoresinol were conveniently synthesized by using this approach. This simple alternative pathway to make pinoresinol will impact pinoresinol-related research including structural characterization and modification of lignins, as well as clinical applications of pinoresinol and its derivatives.

Canonical lignification occurs via the coupling of phenolic radicals, in which chain extension can occur only from phenolic ends of growing polymer chains. Radical coupling of catechyl monomers, including caffeyl and 5-hydroxyconiferyl alcohols, gives rise to benzodioxane units in the polymer. Anticipating that a catechol could oxidize to its o-benzoquinone analog under the dehydrogenative (oxidative) conditions of lignification, we examined the possibility that an o-benzoquinone, as the diene component, could also incorporate into lignin via another mechanism, the Diels–Alder cycloaddition reaction. The o-benzoquinone derived from methyl 5-hydroxyvanillate and 4-O-methylconiferyl alcohol served as models for the diene and dienophile, respectively, and produced Diels–Alder products in vitro. Two types of Diels–Alder products were found: (i) when the 1,2-diketone of the quinone acts as the diene in a hetero-Diels–Alder reaction, a benzodioxane structure was produced with a different regiochemistry than the benzodioxane isomer produced via radical coupling; (ii) when the quinone's diene participated in the Diels–Alder reaction, a distinctive oxatricyclo structure was produced. Both features may be used as markers for the occurrence of Diels–Alder reactions in lignification. Examination of natural lignins derived from catechyl monomers, however, did not reveal evidence for such products. The conclusion is that the only significant reactions in lignification are combinatorial radical coupling reactions of the single-electron-oxidized phenolics and that polymer chain extension therefore occurs only from the phenolic end-units even in the special case of plants that utilize catechyl monomers for lignification.

Lignocellulosic biomass is mainly composed of polysaccharides and lignin. The complexity and diversity of the plant cell wall polymers makes it difficult to isolate the components in pure form for characterization. Many current approaches to analyzing the structure of lignocellulose, which involve sequential extraction and characterization of the resulting fractions, are time-consuming and labor-intensive. The present study describes a new and facile system for rationally derivatizing and dissolving coarsely ground plant cell wall materials. Using ionic liquids (EmimAc) and dichloroacetyl chloride as a solvent/reagent produced mildly acetylated whole cell walls without significant degradation. The acetylated products were soluble in DMSO

Phenolation is a commonly used method to improve the reactivity of lignin for various applications. In this study, resinol lignin models (syringaresinol and pinoresinol) and eucalyptus alkali lignin were treated under acid-catalyzed phenolation conditions to investigate the products derived from resinol (β-β) structures of lignins. The phenolation products were characterized by means of GC-MS and NMR spectroscopy following separation using flash chromatography and thin-layer chromatography. A series of new naphthalene products were identified from phenolation of syringaresinol, and the corresponding guaiacyl analogs were also identified by GC-MS. The C1-Cα bond of these resinol compounds was cleaved to release syringol or guaiacol during phenolation. In addition, diphenylmethane products formed from phenol or phenol and syringol/guaiacol were found in the phenolation products. Comparatively, more naphthalene products were obtained by phenolation from syringaresinol than those obtained from pinoresinol. HSQC NMR characterization of the phenolated alkali lignin revealed that naphthalene structures formed in the phenolated lignin.

Arabinoxylan (AX) was extracted from sugarcane bagasse and modified through crosslinking with glutaraldehyde (GA). The effects of crosslinking degree on the rheological and coating properties of glutaraldehyde crosslinked arabinoxylan (GAX) were investigated. To better evaluate the degree of crosslinking, the crosslink index was used to represent the degree of crosslinking for the GAX in this study. The viscosity of the GAX solution increased when the degree of crosslinking increased, and the solution demonstrated non-Newtonian flow behavior. A high degree of crosslinking was detrimental to the film and coating properties of the GAX. At an optimum degree of crosslinking, the tensile strength of the GAX films increased by approximately 170% and 60% compared with that of the AX and GAX with the highest degree of crosslinking, respectively; the tensile strength of the GAX-coated paper increased by approximately 15% compared with that of the GAX with the highest degree of crosslinking. When calcium carbonate was mixed with the paper coating adhesives, the GAX showed comparable coating properties to that of polyvinyl alcohol, demonstrating its potential to substitute petroleum-based paper coating adhesives.

Bacterial cellulose (BC) with its ultrafine nano-reticular structure may provide great support and distribution to metal nanoparticles. In this study, polyethylenimine was introduced into dialdehyde BC to improve the binding stability between BC and palladium (Pd) nanoparticles. The Pd nanoparticle-embedded BC (Pd-BC) was further composited with plant fibers to fabricate a paper-like “dip-catalyst” through a paper handsheet making method. This catalyst has structural features including the fact that PEI-BC provides a great distribution and binding stability to Pd particles, while plant fibers as a supporting component may reduce the cost of fabrication, provide mechanical strength, and improve the contact between the reactants and Pd particles due to their porosity. The dip-catalyst or catalyst sheet was employed in the Suzuki–Miyaura reaction, providing a high reaction rate, a yield of nearly 100% and a high turnover frequency (TOF). It demonstrated an easy reusability and an extensive recycling capability with the same catalyst sheet being used 26 times and still having a yield of nearly 90%. This catalyst sheet produced from sustainable materials is expected to play an important role in organic synthesis.

We report a green fabrication of conductive paper based on in situ polymerization of polymerizable deep eutectic solvents (PDESs) through a screen printing process. By pre-designed circuit paths and careful integration, on-demand input/output 3D circuits can be achieved, showing its flexibility to origami electronics.

As a highly abundant natural and renewable aromatic polymer, lignin has been proven to be a good UV-absorber and natural broad-spectrum sun blocker. The structure-activity relationship of lignin under UV radiation remains unclear due to lignin’s complexity and heterogeneity. Here we report the structure influence of lignin on its anti-UV radiation properties of sun protection factor (SPF), UV absorbance, and antioxidant activity by using different lignin model compounds, including β–O–4, β–β, and β–5 dimers, etc., representing the structures of both native lignins and technical lignins. Meanwhile, UV protection properties of six lignin preparations, including cellulolytic enzyme lignin (CEL), organosolv lignin (OL), and kraft lignin (KL) of pinus kesiya and eucalyptus, were also evaluated for better comparison. SPF values of sunscreen preparations were increased but varied with the same addition of each single model compound into the pure cream or commercial sunscreen. In particular, the SPF value of the sunscreen has been greatly enhanced by the addition of a certain molar concentration of a single model compound (0.0558 mmol, around 2 wt%) into the low SPF commercial sunscreen, which was attributed to the synergistic effects of lignin models and inherent sunscreen agent. By comparing, lignin models containing β–O–4 linkage displayed the least desirable UV protection properties in this work, and side-chain difference, especially the existence of conjugate structure and carboxylic groups, would significantly impact the lignin model compounds’ UV performance. Additionally, the antioxidant activities and UV absorbance of different model compounds and lignin preparations are closely related to their structures. These insights revealed the structure-activity relationship of lignin under UV radiation and will provide a theoretical basis for optimizing lignins or lignin derivatives as the sun-screening agents in sunscreens.

During the lignification of grass cell walls, ferulate acts like a nucleation site that can cross couple with monolignols, i.e. coniferyl alcohol and sinapyl alcohol, to form dimeric products. Here we investigated in detail the ferulate-sinapyl alcohol cross-coupling products in an effort on better understanding the nature and scope of lignin-ferulate interactions. In a biomimetic oxidative system, sinapyl alcohol (SA) reacted with ethyl ferulate (FA), a simplified model for feruloyl polysaccharides in plants, to give a mixture of dozens of dimeric products. We delineated the structure of each product by GC-MS and NMR characterizations. It was found that sinapyl alcohol readily reacts with ethyl ferulate producing various cross-coupled dimers including SA-(β–5)-FA (compound 6), SA-(β–8)-FA (both ester and lactones, compounds 7 and 9), and SA-(β–O–4)-FA (compound 8) cross-coupled products in addition to homo-coupled products from ethyl ferulate or sinapyl alcohol. SA-(β–O–4)-FA 8 was identified for the first time in a vitro free radical biomimetic system and the homo-coupled SA-(β–O–4)-SA 3 from sinapyl alcohol was accurately quantified as less than 5%, while the half-open syringaresinol 5 was discovered when dimerization of SA was catalyzed by peroxidase in a biomimetic buffer system. Moreover, one new compound 18 formed by the cross-coupled linkage SA-(β–5)-FA (de-protonated) was identified by GC-MS and NMR, and one possible FA-(8–β)-SA dimer 19* was proposed.

To protect forest resources and increase the value of agro-industrial residues, it would be helpful to produce paper-based materials from non-woody or recycled fiber resources. This study investigated the reinforcement mechanism of bacterial cellulose (BC) on paper sheets made from different sources including softwood, hardwood, sugarcane bagasse, bamboo, wheat straw, and recycled fiber, which represent a selection of high quality, medium quality, and low quality fibers. The results showed that by maintaining BC addition at a low level of 0.5–1.5% (total paper dry weight), the paper sheets made from high and medium quality fibers have the maximum tensile index improvement, with 5–25%. The tensile index of low quality fiber including wheat straw pulp and recycled fiber pulp increased slightly and gradually with the level of BC addition; at 5% BC addition, the tensile indexes increased by 9 and 40%, respectively. To investigate the BC reinforcement mechanism, different fiber characteristics, SEM images of BC reinforced paper, BC retention rate on paper, and the effects of dispersant addition were evaluated. It was found that high BC addition or retention rate in paper sheets do not necessarily result in good BC reinforcement effects but that proper dispersion of BC is important.

Poacic acid, a decarboxylated product from 8–5-diferulic acid that is commonly found in monocot lignocellulosic hydrolysates, has been identified as a natural antifungal agent against economically significant fungi and oomycete plant pathogens. Starting from commercially available or monocot-derivable ferulic acid, a three-step synthetic procedure has been developed for the production of poacic acid needed for field testing in a controlled agricultural setting. First, ferulic acid was esterified to produce ethyl ferulate in 92% yield. Second, peroxidase-catalyzed free radical dehydrodimerization of ethyl ferulate produced crude diferulates, mainly 8–5-diferulate, in 91% yield. Finally, crystalline poacic acid was obtained in 25% yield via alkaline hydrolysis of the crude diferulates after purification by flash-column chromatography. This new procedure offers two key improvements relevant to large-scale production: 1) bubbling air through the reaction mixture in the second step to remove acetone greatly improves the recovery efficiency of the crude diferulates; and 2) telescoping minor impurities directly into the alkaline hydrolysis step eliminates the need for additional column purifications, thus reducing the overall cost of production and removing a major impediment to process scale-up.

Bacterial cellulose (BC) was used to reinforce paper sheets made from non-woody fibers, e.g. sugarcane bagasse. BC produced from static and agitated fermentation methods was mixed with bleached sugarcane bagasse pulp (BSBP) to produce composite paper sheets. BC from static culture had a higher degree of polymerization, crystallinity, and crystallite width. Adding BC at a low ratio (

Hybrid poplars (Populus nigra L. × Populus maximowiczii A.) were genetically modified through antisense insertion of the 4-coumarate:coenzyme A ligase (4CL) gene. Compositional changes in response to this genetic change were measured in the field after 2 and 3 years of growth. The stem samples were treated with either green liquor or dilute acid pretreatments, representing alkaline and acid pretreatments. The enzymatic saccharification of the untreated and pretreated transgenic poplars were evaluated. After transgenic species were transplanted into the environment, they showed reduced recalcitrance to chemicals (i.e., pretreatments) and enzymes despite their lignin content and S/V ratio being comparable to those of the wild types. Compared to the field-grown poplars, the sugar yield increased up to 103% for untreated transgenic samples and increased 22% for acid- and green liquor-pretreated transgenic samples. This shows that field-grown transgenic hybrid poplars with modified lignin biosynthesis have imp...

Lignin structural studies play an essential role both in understanding the development of plant cell walls and for valorizing lignocellulosics as renewable biomaterials. Dimeric products released by selectively cleaving β–aryl ether linkages between lignin units reflect the distribution of recalcitrant lignin units, but have been neither absolutely defined nor quantitatively determined. Here, 12 guaiacyl‐type thioacidolysis dimers were identified and quantified using newly synthesized standards. One product previously attributed to deriving from β–1‐coupled units was established as resulting from β–5 units, correcting an analytical quandary. Another longstanding dilemma, that no β–β dimers were recognized in thioacidolysis products from gymnosperms, was resolved with the discovery of two such authenticated compounds. Individual GC response factors for each standard compound allowed rigorous quantification of dimeric products released from softwood lignins, affording insight into the various interunit‐linkage distributions in lignins and thereby guiding the valorization of lignocellulosics.

γ-valerolactone (GVL)/H2O/acid solvent mixtures has been used in chemical pretreatment of lignocellulosic biomass, it was claimed that GVL lignins were structurally close to proto (native) lignins, or having low molecular weight with narrow polydispersity, however, the structural changes of GVL lignins have not been investigated. In this study, β-O-4 (β-aryl ether, GG), β-5 (phenylcoumaran), and β-β (resinol) lignin model compounds were treated by an acidic GVL-H2O solvent system, a promising pretreatment of lignocellulose for biomass utilization, to investigate the structural changes possibly related to the lignin involved. NMR characterization of the products isolated from the treated GG indicated that a phenyl dihydrobenzofuran, having typical C-H correlations at δC/δH 50.74/4.50 and 93.49/4.60 ppm in its HSQC spectrum, was produced from GG. In the pretreatment, the released formaldehyde from GG reacted fast with GG to form a novel 1,3-dioxane intermediate whose characteristic HSQC signals were: δC/δH 94.15–94.48/4.81–5.18 ppm and 80.82–83.34/4.50–4.94 ppm. The β-5 model, dihydrodehydrodiconiferyl alcohol, was converted into phenylcoumarone and stilbene having benzaldehyde that resulted from the allyl alcohol side chain. The β-β model, syringaresinol, was isomerized to form a mixture of syringaresinol, epi-, and dia-syringaresinol although being degraded slightly.

Lignin is a major polymer in the secondary plant cell wall and composed of hydrophobic interlinked hydroxyphenylpropanoid units. The presence of lignin hampers conversion of plant biomass into biofuels; plants with modified lignin are therefore being investigated for increased digestibility. The bacterium Sphingomonas paucimobilis produces lignin-degrading enzymes including LigD, LigF and LigG involved in cleaving the most abundant lignin inter-unit linkage, the β-aryl ether bond. In this study, we expressed the LigD, LigF and LigG (LigDFG) genes in Arabidopsis thaliana to introduce post-lignification modifications into the lignin structure. The three enzymes were targeted to the secretory pathway. Phenolic metabolite profiling and 2D HSQC NMR of the transgenic lines showed an increase in oxidized guaiacyl and syringyl units without concomitant increase in oxidized β-aryl-ether units, showing lignin bond cleavage. Saccharification yield increased significantly in transgenic lines expressing LigDFG, showing the applicability of our approach. Additional new information on substrate specificity of the LigDFG enzymes is also provided. This article is protected by copyright. All rights reserved.

Linking lignin model compounds to carrier proteins is required either to raise antibodies to them or to structurally screen antibodies raised against lignins or models. This paper describes a flexible method to link phenolic compounds of interest to cationic bovine serum albumin (cBSA) without interfering with their important structural features. With the guaiacylglycerol-β-guaiacyl ether dimer, for example, the linking was accomplished in 89% yield with the number of dimers per carrier protein being as high as 50; NMR experiments on a 15N- and 13C-labeled conjugation product indicated that 13 dimers were added to the native lysine residues and the remainder (∼37) to the amine moieties on the ethylenediamine linkers added to BSA; ∼32% of the available primary amine groups on cBSA were therefore conjugated to the hapten. This loading is suitable for attempting to raise new antibodies to plant lignins and for screening.

Thioacidolysis is a method used to measure the relative content of lignin monomers bound by β‐O‐4 linkages. Current thioacidolysis methods are low‐throughput as they require tedious steps for reaction product concentration prior to analysis using standard GC methods. A quantitative thioacidolysis method that is accessible with general laboratory equipment and uses a non‐chlorinated organic solvent and is tailored for higher‐throughput analysis is reported. The method utilizes lignin arylglycerol monomer standards for calibration, requires 1–2 mg of biomass per assay and has been quantified using fast‐GC techniques including a Low Thermal Mass Modular Accelerated Column Heater (LTM MACH). Cumbersome steps, including standard purification, sample concentrating and drying have been eliminated to help aid in consecutive day‐to‐day analyses needed to sustain a high sample throughput for large screening experiments without the loss of quantitation accuracy. The method reported in this manuscript has been quantitatively validated against a commonly used thioacidolysis method and across two different research sites with three common biomass varieties to represent hardwoods, softwoods, and grasses.

Wet-storage is the most common way to maintain sugarcane bagasse in the paper-making industry, although there were few studies on the structural alteration of lignins caused by a wet-storage system. Lignin preparations isolated from wet-stored bagasse in a laboratory simulated wet storage system, corresponding pulps, and spent liquors of soda-oxygen pulping were characterized by various analytical techniques, including elemental analysis (EA), gel permeation chromatography (GPC), and heteronuclear single-quantum coherence (HSQC) NMR spectroscopy. The characteristics of these lignins were compared with those of lignin preparations isolated from fresh sugarcane bagasse samples. Eleven percent decrease of p-coumarate (p-CA) in the lignins from wet-stored raw materials were observed. p-Coumarate and tricin were completely removed during the pulping process. Results from this study suggested that syringyl units were more easily degraded and dissolved under low temperature soda-oxygen pulping conditions. Wet-st...