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Ionic liquids (ILs) can be used to sustainably convert lignocellulosic feedstocks into renewable bio-based materials and chemicals. To improve the prospects of commercialization, it is essential to investigate the fate of lignocellulosic biomass during IL-based processing and develop tools for designing and optimizing this "green" technology. In situ characterization during pretreatment and dissolution processes have shown that ILs reduced the inherent recalcitrance of lignocellulosic biomass via swelling of cellulose bundles and formation of fissures in the secondary cell wall layers. It subsequently enhanced the penetration of ILs into the plant cell wall leading to depolymerization and solubilization of matrix polysaccharides, mainly hemicellulose via deacetylation. Lignin also underwent dehydration or reduction reactions, depending on the IL type, with different mechanisms leading to the cleavage of inter-unit linkages. Following this process, the accessibility to cellulose microfibrils increased and induced delamination. Complementary X-ray diffraction analyses have elucidated that ILs also reduced cellulose crystallinity and altered cellulose polymorphs. High throughput in situ analyses, namely bright-field optical microscopy, nuclear magnetic resonance and Fourier transform infrared spectroscopies, have aided in monitoring the degree of swelling and chemical structural changes in lignocellulosic biomass during IL-based processing. Development of novel in situ analytical tools like IL-based gel permeation chromatography and rheometry will further shed light on molecular level changes in lignocellulose. Thus, an overall understanding of physico-chemical changes underwent by lignocellulosic biomass will help develop tools for monitoring and improving IL-based engineering of renewable materials and chemicals. [ABSTRACT FROM AUTHOR]

The wide-scale production of renewable fuels from lignocellulosic feedstocks continues to be hampered by the natural recalcitrance of biomass. Therefore, there is a need to develop robust and reliable methods to characterize and quantify components that contribute to this recalcitrance. In this study, we utilized a method that incorporates pyrolysis with successive gas chromatography and mass spectrometry (Py-GC/MS) to assess lignification in cell suspension cultures. This method was compared with other standard techniques such as acid-catalyzed hydrolysis, acetyl bromide lignin determination, and nitrobenzene oxidation for quantification of cell wall bound phenolic compounds. We found that Py-GC/MS can be conducted with about 250 µg of tissue sample and provides biologically relevant data, which constitutes a substantial advantage when compared to the 50–300 mg of tissue needed for the other methods. We show that when combined with multivariate statistical analyses, Py-GC/MS can distinguish cell wall components of switchgrass (Panicum virgatum) suspension cultures before and after inducing lignification. The deposition of lignin precursors on uninduced cell walls included predominantly guaiacyl-based units, 71% ferulic acid, and 5.3% p-coumaric acid. Formation of the primary and partial secondary cell wall was supported by the respective ~15× and ~1.7× increases in syringyl-based and guaiacyl-based precursors, respectively, in the induced cells. Ferulic acid was decreased by half after induction. These results provide the proof-of-concept for quick and reliable cell wall compositional analyses using Py-GC/MS and could be targeted for either translational genomics or for fundamental studies focused on understanding the molecular and physiological mechanisms regulating plant cell wall production and biomass recalcitrance. [ABSTRACT FROM AUTHOR]

Fast pyrolysis of pine wood was carried out to yield a liquid bio-oil mixture that was separated into organic and aqueous phases. The organic phase (ORG-bio-oil) was characterized by gas chromatography–mass spectroscopy, 31P-nuclear magnetic resonance spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. It was further used as a raw material for producing a mixture of biphenolic compounds (ORG-biphenol). ORG-bio-oil, ORG-biphenol, and bisphenol-A were reacted with cyanogen bromide to yield cyanate ester monomers. Cyanate esters were characterized using FTIR spectroscopy and were thermally cross-linked to develop thermoset materials. Thermomechanical properties of cross-linked cyanate esters were assessed using dynamic mechanical analysis and compared with those of cross-linked bisphenol-A-based cyanate ester. ORG-biphenol cyanate ester was observed to have a superior glass transition temperature (350–380°C) as compared to bisphenol-A cyanate ester (190–220°C). Cyanate esters derived from bio-oil have the potential to be a sustainable alternative to the bisphenol-A-derived analog. [ABSTRACT FROM AUTHOR]

Materials generated from renewable resources are promising and attractive substitutes for petroleum-based materials. Recently, regeneration of cellulose fibers using ionic liquids (ILs) as green solvents has been a topic of interest to both industrial and academic sectors. However, extraction of cellulose from lignocellulosic biomass requires numerous energy intensive processing steps. Additionally, the deconstruction and removal of lignin and hemicellulose components from lignocellulosic biomass usually involve corrosive pretreatment and the solvation of specific biomass components. Instead, utilization of the whole biomass—particularly woody residues—to manufacture high-performance materials offers an attractive value-proposition. In this study, we demonstrated fiber regeneration of whole hybrid poplar (HP) biomass by a sustainable method. We developed an environmentally friendly approach by partially auto-hydrolyzing the biomass with water before its dissolution in 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) ionic liquid, for large-scale, roll-to-roll production of fibers by solution spinning. We report, for the first time, a fundamental understanding of the inter- and intramolecular interactions in HP biomass–IL solutions, as well as their corresponding spinnability, structural reformation, and mechanical performance of the regenerated fibers. Particularly, the molecular alignment, recrystallization, and crystallinity of the spun fibers were correlated to the chain entanglement, molecular relaxation, and rheological properties of the HP biomass–IL solutions. A window of entangled concentration (4–6.5 wt%) of biomass in the IL was determined to be favorable for fiber spinning. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) is a leading lignocellulosic bioenergy feedstock. Cellulose is a major component of the plant cell walls and the primary substrate for saccharification. Accessibility of cellulose to enzymatic breakdown into fermentable sugars is limited by the presence of lignin in the plant cell wall. In this study, putatively novel switchgrass secondary cell wall cellulose synthase PvCesA4 and primary cell wall PvCesA6 genes were identified and their functional role in cellulose synthesis and cell wall composition was examined by overexpression and knockdown of the individual genes in switchgrass. The endogenous expression of PvCesA4 and PvCesA6 genes varied among including roots, leaves, stem, and reproductive tissues. Increasing or decreasing PvCesA4 and PvCesA6 expression to extreme levels in the transgenic lines resulted in decreased biomass production. PvCesA6-overexpressing lines had reduced lignin content and syringyl/guaiacyl lignin monomer ratio accompanied by increased sugar release efficiency, suggesting an impact of PvCesA6 expression levels on lignin biosynthesis. Cellulose content and cellulose crystallinity were decreased, while xylan content was increased in PvCesA4 and PvCesA6 overexpression or knockdown lines. The increase in xylan content suggests that the amount of non-cellulosic cell wall polysaccharide was modified in these plants. Taken together, the results show that the manipulation of the cellulose synthase genes alters the cell wall composition and availability of cellulose as a bioprocessing substrate. [ABSTRACT FROM AUTHOR]

Abstract: Fractionation of lignocellulosic biomass is an attractive solution to develop an economically viable biorefinery by providing a saccharide fraction to produce fuels and a lignin stream that can be converted into high value products such as carbon fibers. In this study, the analysis of ionic liquid-activated biomass demonstrates that in addition of decreasing crystallinity, the selected ILs (1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium acetate) deacetylate Yellow poplar under mild conditions (dissolution at 60–80°C), and lower the degradation temperature of each biomass polymeric component, thereby reducing the recalcitrance of biomass. Among the three tested ILs, 1-ethyl-3-methylimidazolium acetate performed the best, providing a strong linear relationship between the level of deacetylation and the rate of enzymatic saccharification for Yellow poplar. [Copyright &y& Elsevier]

The article discusses research regarding the stability and activity of ionic liquid cellulases and glucosidase systems in the presence of 1-ethyl-3-methylimiazolium acetate. The latter was selected for several factors including its low viscosity and melting temperature. The various concentrations used to determine the enzymatic stability of cellulase mixtures are described. Details concerning the enzymatic saccharification of both pretreated and activated Avicel solutions are also presented.

The article discusses a study which examined the thermal decomposition behavior of lignocellulosic biomass using near infrared (NIR) spectroscopy. It notes that different chemical compositions have contributed to the different thermal degradation behaviors of the woody and herbaceous biomass. Results of the study showed similarity in the data predicted by the wavelet partial least squares (PLS) model and thermogravimetric analysis (TGA).

Background: Lignocellulosic biomass requires either pretreatment and/or fractionation to recover its individual components for further use as intermediate building blocks for producing fuels, chemicals, and products. Numerous ionic liquids (ILs) have been investigated for biomass pretreatment or fractionation due to their ability to activate lignocellulosic biomass, thereby reducing biomass recalcitrance with minimal impact on its structural components. In this work, we studied and compared 1-allyl-3-methylimidazolium formate ([AMIM][HCOO]) to the commonly used 1-ethyl-3-methylimidazolium acetate ([EMIM][CH3COO]) for its potential to activate hybrid poplar biomass and enable high cellulose and hemicellulose enzymatic conversion. Although [EMIM][CH3COO] has been widely used for activation, [AMIM][HCOO] was recently identified to achieve higher biomass solubility, with an increase of 40% over [EMIM][CH3COO]. Results: Since IL activation is essentially an early stage of IL dissolution, we assessed the recalcitrance of [EMIM][CH3COO] and [AMIM][HCOO]-activated biomass through a suite of analytical tools. More specifically, Fourier transform infrared spectroscopy and X-ray diffraction showed that activation using [AMIM][HCOO] does not deacetylate hybrid poplar as readily as [EMIM][CH3COO] and preserves the crystallinity of the cellulose fraction, respectively. This was supported by scanning electron microscopy and enzymatic saccharification experiments in which [EMIM][CH3COO]-activated biomass yielded almost twice the cellulose and hemicellulose conversion as compared to [AMIM][HCOO]-activated biomass. Conclusion: We conclude that the IL [AMIM][HCOO] is better suited for biomass dissolution and direct product formation, whereas [EMIM][CH3COO] remains the better IL for biomass activation and fractionation. [ABSTRACT FROM AUTHOR]

Inorganic elements present in lignocellulosic biomass and introduced during harvesting and handling of the feedstock negatively affect biomass conversion to fuels and products. In particular, alkali and alkaline earth metals act as catalysts during thermochemical conversion, contribute to reactor degradation, and decrease the yield and quality of the reaction products. In this study, we investigated an approach to reduce ash content of switchgrass. Several reagents (chelating agents ethylenediaminetetraacetic acid (EDTA) and citric acid, as well as acetic acid, sulfuric acid, and water) under various extraction times (5, 10, 15, and 20 min) were tested using a microwave-assisted extraction method. After the extraction, mass loss, total ash, individual inorganics, and concentration of sugars in the hydrolyzates were measured. EDTA afforded the highest inorganics removal, with near complete extraction of alkali and alkaline earth metals K, Ca, and Mg, and high removal of S and Si. Citric acid and sulfuric acid removed similarly high amounts of K, Ca, and Mg as EDTA, but less Mg, P, S, and Fe. Additionally, extraction with water resulted in near complete removal of K; however, more modest removal of other inorganics was observed compared to other treatments. The mass loss was significantly higher in the sulfuric acid extractions due to hydrolysis of the structural carbohydrates, while EDTA resulted in little carbohydrate degradation due to the more neutral pH conditions. This study illustrated the benefits of extracting with chelating agents, as opposed to mineral acids, to remove inorganics and improve biomass quality. [ABSTRACT FROM AUTHOR]