Miscanthus giganteus lignin was extracted by an organosolv process under reflux conditions (4 h) with varying concentrations of ethanol (65%, 75%, 85%, 95%) and 0.2 M hydrochloric acid as catalyst. The resulting lignin was extensively characterized by size exclusion chromatography (SEC), Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR), and chemical analysis (residual sugars, Klason lignin, ash). The predominant linkage units present were β-O-4' (82-84%), resinol (6-7%), and phenylcoumaran (10-11%). The 65% ethanol solvent system gave the lowest lignin yield (14% of starting biomass) compared to 29-32% of the other systems. Increasing ethanol concentration resulted in decreasing carbohydrate content of the lignins (3.6-1.1%), a higher solubility in tetrahydrofuran (THF), a slight reduction of the molecular weight (M(w) 2.72-2.25 KDa), an increasing α-ethoxylation, and an increase in ethoxylated phenylpropenoic compounds (p-coumaric and ferulic acid), but the S/G ratio of the monolignols (0.63, GC/MS) and Klason lignin content (86-88%) were unaffected. An extraction method for these ethyl-esterified phenylpropenoids and smaller molecular weight lignin compounds was developed. The effect of reaction time (2, 4, and 8 h) was investigated for the 95% ethanol solvent system. Besides increased lignin yield (13-43%), a slight increase in M(w) (2.21-2.38 kDa) and S/G ratio (0.53-0.68, GC-MS) was observed. Consecutive extractions suggested that these changes were not from lignin modifications (e.g., condensations) but rather from extraction of lignin of different composition. The results were compared to similar solvent systems with 95% acetone and 95% dioxane.

Lignocellulosic biomass is composed of the polysaccharides cellulose and hemicellulose and the polyphenol lignin. Many current methods for analyzing the structure of lignocelluloses involve a sequential extraction of the material and subsequent analysis of the resulting fractions, which is labor-intensive and time-consuming. The work presented here assesses the dissolution of whole lignocellulosic material, focusing on biomass derived from the perennial bioenergy grass Miscanthus. The solvent dimethylsulfoxide (DMSO)-d6 containing 1-ethyl-3-methylimidazolium acetate ([Emim]OAc) was able to dissolve lignocellulosic material completely and gave high-resolution 2D heteronuclear single quantum coherence (HSQC) NMR spectra of the entire array of wall polymers. Extrapolated time-zero HSQC was applied using DMSO-d6/[Emim]OAc-d14 and enabled quantitative analysis of structural traits of lignocellulose components.

Lignin samples isolated from Miscanthus giganteus using organosolv processes were treated with vanadium catalysts that were previously developed in our group. We demonstrate that the catalyst with high β-O-4′ bond-cleaving activity in dimeric lignin models was also effective in depolymerizing actual lignin. Molecular weight-lowering was evidenced by gel permeation chromatography (GPC), whereas 2D NMR experiments showed that β-O-4′ linkages were selectively cleaved in the degradation process, just as in the case of lignin models. Monophenolic degradation products were also formed, and the individual molecules were identified and quantified by GC/MS.

We report the reagentless cleavage of prevalent β-O-4 linkages in lignin model compounds, as well as the cleavage of several types of organosolv lignins, catalyzed by commercially available Pd/C. Such lignin fragmentation occurred without added reagent if the indigenous double bonds were reduced first or it occurred under conditions in which just 1 atm of hydrogen was added to the system to reduce CC bonds of the original lignin sample in situ prior to fragmentation. A detailed view of the sites of cleavage of lignin samples from various sources was gained by HSQC NMR experiments. Complex model compounds were prepared and shown to form simpler arenes and substituted phenols under catalytic conditions without added reagents. The hydrogen generated in situ from alcohol functionalities provides the reductant for concomitant hydrogenolysis of C−O bonds in β aryl ethers. Decarbonylation of primary alcohols also occurred, and this process resulted in significant amounts of aromatic products containing substituents bearing one fewer carbon atom than the original linkages in lignin. The fragmentations of synthetic lignin and several organosolv lignins derived from Miscanthus giganteus and pine tree were conducted. Because the lignins contain alkenes that accept the hydrogen, two procedures involving reduction of the alkenes prior to C−O bond cleavage were developed. The first procedure involves reduction of the alkenes, followed by catalytic cleavage of C−O bonds after saturation of the C−C bonds; a second involves cleavage of lignin samples in the presence of 1 atm of hydrogen to saturate the alkenes before cleavage in situ. These protocols convert solid lignin to monomeric phenolic compounds with 20 mol % catalyst or to an oil (with 5 mol % Pd/C loading) having favorable viscosity parameters upon blending with a renewable organic solvent.

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(C.R.S.).In order to understand factors controlling the synthesis and deposition of cellulose, we have studied the Arabidopsis (Arabidopsis thaliana) double mutant shaven3 shaven3-like1 (shv3svl1), which was shown previously to exhibit a marked cellulose deficiency. We discovered that exogenous sucrose (Suc) in growth medium greatly enhances the reduction in hypocotyl elongation and cellulose content of shv3svl1. This effect was specific to Suc and was not observed with other sugars or osmoticum. Live-cell imaging of fluorescently labeled cellulose synthase complexes revealed a slowing of cellulose synthase complexes in shv3svl1 compared with the wild type that is enhanced in a Suc-conditional manner. Solid-state nuclear magnetic resonance confirmed a cellulose deficiency of shv3svl1 but indicated that cellulose crystallinity was unaffected in the mutant. A genetic suppressor screen identified mutants of the plasma membrane Suc/H + symporter SUC1, indicating that the accumulation of Suc underlies the Suc-dependent enhancement of shv3svl1 phenotypes. While other cellulose-deficient mutants were not specifically sensitive to exogenous Suc, the feronia (fer) receptor kinase mutant partially phenocopied shv3svl1 and exhibited a similar Suc-conditional cellulose defect. We demonstrate that shv3svl1, like fer, exhibits a hyperpolarized plasma membrane H + gradient that likely underlies the enhanced accumulation of Suc via Suc/H + symporters. Enhanced intracellular Suc abundance appears to favor the partitioning of carbon to starch rather than cellulose in both mutants. We conclude that SHV3-like proteins may be involved in signaling during cell expansion that coordinates proton pumping and cellulose synthesis.

Sn‐BEA zeolite is known to catalyze the aldose‐to‐ketose isomerization of xylose and glucose; however, the selectivity to pentose and hexose isomers is not stoichiometric, suggesting the formation of other products. In the present study, we have observed near‐complete conversion of all pentose and hexose isomers when xylose and glucose were reacted in the presence of Sn‐BEA at 140 °C and 200 °C, respectively. The previously unidentified products were identified by nuclear magnetic resonance and mass spectrometry to be hydroxyalkanoic acids and their derivatives. The hydroxyl‐rich acids comprise a significant fraction of the converted sugars and are potential monomers for the synthesis of hyper‐crosslinked, biodegradable polymers.

Background:The COBRA gene is highly coexpressed with cellulose synthase genes, but its function remains unclear. Results: COBRA localizes at the plasma membrane and binds glucan chains. NMR studies indicate structural defects in cellulose in the mutant despite normal polymerization rate. Conclusion: COBRA functions downstream of cellulose biosynthesis. Significance: This work suggests that alignment of glucan chains into cellulose fibrils is facilitated by one or more proteins.