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Sustainable production of 1,4-pentanediol (1,4-PDO) from biomass is of great importance because 1,4-PDO is a monomer of degradable polyesters and plastics. This paper reviews the conversion of biomass-derived levulinic acid (LA) and furfural as well as their derivatives alkyl levulinate, γ-valerolactone (GVL) and furfuryl alcohol (FAL) into 1,4-PDO. MoOx or ReOx modified noble metal catalysts and non-noble metal catalysts with core–shell and alloy structures show a high 1,4-PDO yield and stability in LA hydrogenation under severe hydrothermal conditions. The conversion of furfural to 1,4-PDO involves the initial C＝O bond hydrogenation to form FAL, the consecutive acid-catalyzed ring-opening and the final hydrogenation. Therefore, it needs a bifunctional catalyst composed of metallic species and acid sites to improve the 1,4-PDO yield. Efforts are made here to highlight the employed catalysts, structure–performance relationship, reaction pathway and reaction mechanism in detail. The current challenges for large-scale applications of conversion of LA and furfural to 1,4-PDO have been proposed, including process development, catalyst cost, solvent and active site distribution. We believe that this review will provide new opportunities and expand the options for the production of 1,4-PDO via biorefining processes. [ABSTRACT FROM AUTHOR]

When attempting to obtain light-color lignin from lignocellulosic biomass or industrial lignin, the available options based on chemical or morphological modification suffer from low yield, high cost, and lack of availability at the required scales. In this study, we adopted a polyhydric-alcohol-based deep eutectic solvent (PA-DES) to directly extract light-color lignin from natural biomass, which is even whiter than native cellulolytic enzyme lignin (CEL). The isolated lignin possessed a high recovery yield (97.36%), regular micro-spherical morphology, enriched β-ether linkage of 58/100Ar, low phenolic hydroxyl content of 1.25 mmol g−1, minimal carbonyl content of 0.70 mmol g−1, and less condensed structures, thus yielding a lower content of chromophores. This lignin showed excellent sunscreen effects, which could enhance the SPF of a commercial sunscreen from 15 to 40 with only 5 wt% addition. This study can provide essential guidance for the scale-up production of light-color lignin and obtaining near-complete digestible cellulose for further saccharification. [ABSTRACT FROM AUTHOR]

Lignocellulose biorefining has great potential to replace the use of petrochemical resources in the production of fuels and chemicals. However, the full use of lignocellulose, which is depolymerized to yield mainly glucose, xylose, and lignin-derived phenolics, remains challenging. Here, we developed a glucose–xylose–phenolics (GXP) system to fully use lignocellulose for the production of L-tyrosine and its analogues in minimal medium. First, we engineered an Escherichia coli–Escherichia coli consortium carrying a CRISPR/dCas9 interference system to simultaneously use glucose and xylose to support cell growth and produce pyruvate, obtaining 34.3 g L−1 pyruvate with a yield of 0.68 g g−1 sugar. Then, we introduced tyrosine phenol lyase and other biocatalytic enzymes into this consortium to generate the GXP system, which could convert pyruvate and lignin-derived phenolics to L-tyrosine and its analogues. Using this GXP system, 20.8 g L−1L-tyrosine was produced from 12.5 g L−1 phenol with a yield of 86.4%. Using the hydrolysate of the raw material sorghum pith, 0.94 g L−1L-tyrosine was produced from 0.96 g L−1p-coumaric acid with a yield of 88.7%, and 8.1 g L−1 pyruvate remained, corresponding to an overall yield of 0.163 g product g−1 sorghum pith. The development of this GXP system illustrates a strategy for fully utilizing lignocellulosic biomass for the synthesis of value-added chemicals. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) and ionic liquids (ILs) are potential solvents for lignocellulosic biomass fractionation. In this study, the rice straw pretreatment efficiency of four cholinium-based solvents (DESs and ILs) prepared from the same sources (lactic acid and lysine) were comparatively investigated at 110 °C for 4 h. The lignin removal rate correlated well with the saccharification efficiency of the pulps. Quantum chemical (QC) calculations and molecular dynamics (MD) simulations focused on the microscopic structure and non-covalent interactions of the solvents and lignin model molecules (guaiacylglycerol-β-guaiacyl ether, GG) were carried out, and the results indicate that anions of the solvent systems play a leading role (through strong hydrogen bonds or electrostatic interactions) in establishing interactions with GG, supported by cations (via van der Waals interactions). There were clear positive relationships between the total interaction energies (IEs) and lignin removal, cellulose digestibility and glucose yields. In particular, [Ch][Lys] with a low self-interaction energy is able to free some active sites to form strong hydrogen bonds and electrostatic interactions with lignin, thus resulting in lignin dissolution and excellent delignification. For cholinium cations, an ideal partner system provides low self-IEs for solvent molecules and strong IEs between solvents and lignin, which are determined by the type and number of functional groups and the alkyl chain length of the partner components. This work provides ideas about tailoring suitable partner systems for cholinium cations to build solvents for efficient biomass deconstruction. [ABSTRACT FROM AUTHOR]

In the context of promoting a circular bioeconomy, the development of green and efficient lignocellulosic biomass pretreatment technologies so as to realize high value-added biomass utilization is of intense interest. We demonstrated the potential of the bio-based green solvent dimethyl isosorbide (DMI) for the fractionation of Eucalyptus biomass with excellent performance. Here, to investigate the mechanisms involved in biomass fractionation, microimaging and microspectroscopic techniques were employed together with molecular dynamics (MD) simulation and COSMO-RS quantum chemical calculations to derive multiscale information. Both the microstructure and regional chemistry of the cell wall vary significantly with the volume ratio of DMI/H2O. The strongest effects were found at DMI/H2O = 9 : 1 and showed visible cell wall tearing cracks and cell wall deformation and collapse as well as the lowest values of cell wall thickness and circularity. From the MD simulations, lignin exhibits collapsed-like structure in pure H2O with low solvent accessibility surface area (SASA) and radius of gyration (Rg). In contrast, lignin in DMI/H2O shows extended structure with high SASA and solvent interactions dominated by van der Waals forces, with maximal contact in the 9 : 1 (v/v) system. Further, the COSMO-RS calculated sigma (σ-) potential suggests the intermolecular interactions in DMI and DMI/H2O co-solvent are weak, leading to stronger interaction with lignin and correspondingly higher lignin dissolution. The radial distribution functions and σ-potential all show that again DMI/H2O at 9 : 1 is an optimal volume ratio for high lignin dissolution. This study provides a solvent-ratio dependent mechanism for the action of polar aprotic solvents in the deconstruction of biomass. [ABSTRACT FROM AUTHOR]

Extraction of native-like lignin from lignocellulose is crucial for maximizing the value of all three major components of biomass. In this study, molecular dynamics was employed to reveal the essence of lignin condensation during the pretreatment of biomass with a promising acidic hydrotropic solution (AHS) at the molecular level. Diols were discovered to effectively suppress the excessive acidity of p-toluenesulfonic acid (pTsOH) in AHS while maintaining its solubilizing effect below a minimal hydrotropic concentration (MHC). The experimental results confirmed that the combined use of 1,4-butanediol and pTsOH can extract native-like lignin under mild conditions. The retention of lignin's β-O-4 linkages can exceed 90%, and the lignin extraction rate was over 80%. The obtained lignin can enhance the efficacy of chemical sunscreens, doubling the sun protection factor (SPF). Simultaneously, the residual cellulose was readily hydrolyzed into glucose by cellulase. This strategy demonstrates excellent adaptability to various biomass sources, including herbaceous species, hardwoods, and highly recalcitrant softwoods. The work lays the theoretical foundation for the precise control of biomass component separation using AHS, contributing to the development of mild and efficient component separation technologies in the future. [ABSTRACT FROM AUTHOR]

When we look for a poster child of green chemistry 'in action', we do not need to look further than the deconstruction of lignocellulose using ionic liquids (IL) to valorize this renewable resource into useful chemicals. However, there is a caveat: successful development of new chemistries cannot be achieved without systems-based design tools that consider performance in conjunction with potential toxicity. Here, we show that a combination of computational approaches, based on quantum mechanics (QM) calculations and Monte Carlo (MC) simulations, can be leveraged to construct a useful framework for screening existing and designing new ILs capable of safe and selective dissolution of lignocellulosic biomass. With the overwhelming number of IL cation–anion combinations, in silico methods are uniquely suited for this challenge so long as they retain mechanistic relevance to the underlying processes. Our computational approach ensures this criterion by relying on well-correlated linear models of interaction energetics between IL and key biomass building blocks. Functional considerations are supplemented with frontier molecular orbital calculations to determine safety toward aquatic species based on previously established and broadly validated guidelines. [ABSTRACT FROM AUTHOR]

Dilute acid (DA) pretreatment of biomass generates multiple inhibitory compounds within the pretreated hydrolysates. These compounds subsequently contribute to the formation of pseudo-lignin on the surface of the substrate, consequently impeding the efficiency of enzymatic digestibility. To detoxify the DA pretreated hydrolysates, post-incubation with non-catalytic proteins (amaranth protein, AP; soy protein, SP; bovine serum albumin, BSA) was performed in the present study. The enzymatic digestibility of DA-pretreated substrates was increased from 40.0% (without non-catalytic proteins) to 64.9, 53.8, and 56.4%, respectively, in the presence of AP (50 mg g−1), SP (65 mg g−1), and BSA (50 mg g−1). The post-incubation of pretreated substrates with non-catalytic proteins led to high hydrophobicity, contact angle, and accessibility, likely due to less formation of pseudo-lignin. Furthermore, gas chromatography/mass spectrometry analysis revealed that AP, SP, and BSA could lower the inhibitor concentrations in the pretreated hydrolysates by 39–100%, 5–100%, and 3–100%, respectively. The detoxification of the pretreated hydrolysates by AP demonstrated superior effectiveness compared to SP and BSA. To assess the affinity between inhibitors and non-catalytic proteins, surface plasmon resonance analysis was conducted, revealing the following affinity rates: AP (18.65 nM) > SP (17.04 nM) > BSA (16.87 nM). Additionally, molecular docking analysis revealed numerous molecular binding sites (i.e., hydrogen, polar, acidic, basic, and greasy contacts) with strong binding affinity ranging from −36.17 to −76.98 kcal mol−1 between the inhibitors and the amino acids of AP. Thus, this study highlights the potential application of AP as a cost-effective strategy for achieving a viable biorefinery. Also, the findings provide valuable insights that can be utilized to advance the development of (hemi)cellulases that exhibit enhanced resistance to lignin and inhibitors. [ABSTRACT FROM AUTHOR]

Dissolution of lignocellulose is of significant importance for its utilization and transformation. However, it remains a great challenge to efficiently and rapidly dissolve lignocellulose under mild conditions owing to the significant lack of efficient solvents for lignocellulose dissolution. Herein, robust solvent systems were designed by a combination of ionic liquids (ILs), ethanolamine (EA), and organic superbases for the dissolution of lignocellulose. It was observed that the prepared solvents (denoted as the IL/EA-superbase) could efficiently dissolve lignocellulose at mild temperatures (below 100 °C). In particular, the EmimOAc/EA-DBN system showed the best performance, and the solubility values of Populus tomentosa, sugarcane bagasse and Miscanthus giganteus at 90 °C could reach up to 3.8%, 9.5% and 20% (g per 100 g solvent), respectively. It was revealed that EA-superbase effectively participated in the interaction between ILs and lignocellulose, thus promoting the dissolution process. A systematic study revealed that the good performance of the developed solvents toward lignocellulose dissolution resulted from the synergistic effect of the three constructed components to make the solvent have a suitable capacity for the formation of hydrogen-bonding and an appropriate microstructure. [ABSTRACT FROM AUTHOR]

This study investigated a high-solid diol deep eutectic solvent (DES) pretreatment using a wet substrate as the starting material. This pretreatment led to a remarkable glucan saccharification of 94.8% with efficient lignin and xylan removal (as high as 63.1% and 73.0%, respectively). The chemical structures of the substrates were analyzed comprehensively to reveal the impact of the pretreatment. In addition, over 90% of the removed lignin was recovered from the pretreated liquid, which exhibited a well-preserved β-O-4 structure (46–56/100Ar). The protection mechanism of our DES was investigated by 2D HSQC NMR, GPC, and 31P NMR analysis. This study emphasized that diol-based DES pretreatment of undried lignocellulosic biomass at a high-solid loading can significantly utilize both carbohydrates and lignin fractions with high saccharification yields and high-quality lignin as a co-product. [ABSTRACT FROM AUTHOR]

Clean and efficient biofuels sourced from lignocellulosic biomass can play a significant role in achieving carbon neutrality. Enzymatic hydrolysis is regarded as a vital step in this process. In this study, inspired by the digestion process of termites, a two-stage microreactor system loaded with enzymes was proposed, for the first time, to hydrolyze wheat straw into monosaccharides efficiently. The two-stage microreactor system is composed of sections loaded with xylanase and cellulase sequentially. When 2.5% (w/w) wheat straw was reacted in the first stage for 24 h, hemicellulose was degraded by 16.8%, leading to an increase in cellulose accessibility by 8.1%. During this process, the specific surface area and porosity of wheat straw also increased, which enabled the cellulase in the second stage to degrade cellulose more efficiently, thereby increasing the glucose production by 89.7% in the second stage within 6 h as compared with the control. The total sugar yield obtained at a total hydrolysis time of 36 h in the two-stage microreactor was 3.0 times that obtained using the microreactor loaded with cellulase only. Therefore, the two-stage microreactor system loaded with enzymes was demonstrated as an effective means for enhancing lignocellulosic conversion under mild conditions. [ABSTRACT FROM AUTHOR]

Ethanol (EtOH)–water (H2O) mixture, as an environmentally friendly organic solvent, has been widely used in green textile dyeing technologies to reduce water consumption. However, it is essential to develop a sustainable and energy-saving approach for the recovery of the EtOH–H2O mixture to mitigate the global energy crisis. Herein, inspired by the transpiration process of a tree, we designed a bilayer structured solar energy-driven recovery device composed of a solar absorption layer and a liquid transport layer using the lignocellulosic biomass Juncus effusus (JE) and carbon nanotubes (CNTs). Benefiting from the structural design and distinct properties of the 3D hierarchically porous JE fibres, the as-prepared device exhibited an excellent light absorbability (>95.90%) and photothermal conversion capability, and was further used to purify the dye-contaminated EtOH–H2O mixture by steam generation from solar energy. By using this stable recovery device, the evaporation rate towards the EtOH–H2O mixture was up to 2.43 kg m−2 h−1 under one-sun illumination, which is approximately 3.6 times that of natural evaporation. Furthermore, we fabricated a large-scale steam evaporator with a total area of 900 cm2 for the recovery of the EtOH–H2O mixture, which was placed in an outdoor environment for one whole day (0:00–24:00) to evaluate the real-world evaporation and recovery performance. The EtOH content of the collected mixture remained almost invariable after evaporation, showing great potential in industrial production. The lignocellulosic JE-based evaporation device may be a promising solar energy-driven system for the highly efficient recovery of the EtOH–H2O mixture. [ABSTRACT FROM AUTHOR]

A novel ammonia-based pretreatment for densified lignocellulosic biomass was developed to reduce ammonia usage and integrate with viable biomass logistics scenarios. The COmpacted Biomass with Recycled Ammonia (COBRA) pretreatment performed at 100 °C allows >95% conversion of sugarcane bagasse (SCB) carbohydrates into soluble monomeric and oligomeric sugars (glucose and xylose) using industrially relevant 6% glucan loading (∼21% solids loading) enzymatic hydrolysis conditions at reduced enzyme loadings. Pretreatment via COBRA with simultaneous lignin extraction (COBRA-LE) improved Saccharomyces cerevisiae 424A(LNH-ST) metabolic yield from 89% to 97.5% relative to COBRA without delignification, allowing a process ethanol yield of 71.6%. A technoeconomic analysis on SCB biorefining to ethanol in the state of São Paulo, Brazil, compared COBRA to other mature technologies, such as AFEX and steam-explosion. Amongst all scenarios studied, biorefineries based on COBRA-LE pretreatment offered the lowest average minimum ethanol selling price of US$1.45 per gallon ethanol. COBRA pretreatment was subsequently tested on perennial grasses and hardwoods, and >80% total sugar yields were achieved for all cases. [ABSTRACT FROM AUTHOR]

The fractionation of lignocellulose in its three main components, hemicellulose, lignin and cellulose pulp can be achieved in a biphasic system comprising water and bio-based 2-methyltetrahydrofuran (2-MeTHF) as solvents and oxalic acid as catalyst at mild temperatures (up to 140 °C). This so-called OrganoCat concept relies on selective hemicellulose depolymerization to form an aqueous stream of the corresponding carbohydrates, whereas solid cellulose pulp remains suspended and the disentangled lignin is to a large extent extracted in situ with the organic phase. In the present paper, it is demonstrated that biomass loadings of 100 g L−1 can be efficiently fractionated within 3 h whereby the mild conditions assure that no significant amounts of by-products (e.g. furans) are formed. Removing the solid pulp by filtration allows to re-use the water and organic phase without product separation in repetitive batch mode. In this way, (at least) 400 g L−1 biomass can be processed in 4 cycles, leading to greatly improved biomass-to-catalyst and biomass-to-solvent ratios. Economic analysis of the process reveals that the improved biomass loading significantly reduces capital and energy costs in the solvent recycle, indicating the importance of process integration for potential implementation. The procedure was successfully scaled-up from the screening on bench scale to 3 L reactor. The feedstock flexibility was assessed for biomasses containing moderate-to-high hemicellulose content. [ABSTRACT FROM AUTHOR]

An efficient and sustainable pretreatment, such as organosolv pretreatment that produces high-quality lignin and highly digestible carbohydrates, could enable the potential complete utilization of lignocellulosic biomass. Demand for bio-based solvents with a high boiling point, low viscosity, and negligible toxicity is increasing. Herein, we report the use of dimethyl isosorbide (DMI) as a solvent to fractionate lignocellulosic biomass into its main components for the first time. High lignin removal efficiency (91.2%) with good cellulose retention (around 80%) could be achieved during the pretreatment of Eucalyptus by DMI/H2O co-solvents under a mild conditions. A near-complete cellulose conversion to its monosaccharide could be realized at a relatively low enzyme loading of 20 FPU g−1 glucan. The addition of water could suppress the condensation of lignin, yielding lignin with high purity (92.9%), a good fraction of β-O-4 linkages reserved (24.8%) and homogeneous molecular weight (Đ < 2). Besides its highly digestible nature, the high quality of the cellulose-rich residue is also demonstrated from a material perspective. A more efficient fibrillation of obtained pulp to nanocellulose was developed, leading to a promising potential of energy saving compared to the traditional bleaching pathway. Overall, this work developed a mild pretreatment technology as a potential basis for a green and closed-loop biorefinery concept for converting lignocellulosic biomass to multiple products (high purity lignin, fermentable sugars, or functional materials). [ABSTRACT FROM AUTHOR]

The quantitation of lignin is essential for the evaluation, conversion, and utilization of lignocellulosic biomass. However, the existing lignin quantitation methods like the widely used Klason method still have some disadvantages, such as requiring hazardous reagents, complicated steps, heating, introducing interfering substances, and low sensitivity. In this study, a novel green method for lignin quantitation based on the completely dissolved solution of lignocellulosic biomass in LiCl/DMSO and UV spectrophotometry (LiCl/DMSO CDS-UV method) was developed. The process does not require complex chemical pretreatment and separation of lignin from lignocellulosic biomass. The biomass samples extracted with benzene/ethanol (v/v 2 : 1) can be completely dissolved in an 8% LiCl/DMSO solvent system at room temperature (25 °C) and atmospheric pressure after short-time ball milling (3 h). For the chemical delignified samples with a low lignin content, the completely dissolved solution can be obtained only by heating the solution to 60 °C and stirring at atmospheric pressure for 2 h. Then the lignin content of the solution was determined by UV spectrophotometry. Different species of biomass including herbage (wheat straw), hardwood (black poplar), softwood (redwood), bark (eucalyptus bark and redwood bark), and above biomass treated by different delignification methods and degrees were applied to establish the LiCl/DMSO CDS-UV method and extend the applicability of this method. The results quantified by the LiCl/DMSO CDS-UV method were compared with the total lignin content measured by the Klason method and a good correlation was observed. The LiCl/DMSO CDS-UV method only requires trace samples (0.1 g) to achieve a precise determination of the lignin content, the conditions are mild, no hazardous reagents are used and no interfering substances are produced in the process. [ABSTRACT FROM AUTHOR]

The conversion of lignocellulose into a value-added chemical with high selectivity is of great significance but is a big challenge due to the structural diversities of biomass components. Here, we have reported an efficient approach for the one-step conversion of raw lignocellulose into diethyl maleate by the polyoxometalate ionic liquid [BSmim]CuPW12O40 in ethanol under mild conditions. The results reveal that all of the fractions in biomass, i.e., cellulose, lignin and hemicellulose, were simultaneously converted into diethyl maleate (DEM), achieving a 329.6 mg g−1 yield and 70.3% selectivity from corn stalk. Importantly, the performance of the ionic liquid catalyst [BSmim]CuPW12O40 was nearly twice that of CuHPW12O40, which can be attributed to the lower incorporation of the Cu2+ site in [BSmim]CuPW12O40. Hence, this process opens a promising route for producing bio-based bulk chemicals from raw lignocellulose without any pretreatment. [ABSTRACT FROM AUTHOR]

This work demonstrates the feasibility of applying dual functional solvents called alkanolamines towards the conversion of biomass into biofuels. Alkanolamines have the potential to serve as effective pretreatment solvents that promote a low energy intensity, process intensification, and downstream conversion via a cost-effective route. Several key factors were considered to effectively integrate the pretreatment technology into a biorefinery, including solvent screening (both experimentally and computationally), feedstock screening (capturing the effectiveness on softwood, hardwood, and grasses), fractionation of lignocellulose components (lignin removal), bioconversion efficacy, and a sustainability impact assessment. After a thorough and systematic optimization, the following conditions emerged for optimal process economics (i.e., shortest time, lowest temperature, and highest solid loading): pretreatment of sorghum biomass via ethanolamine (25% solvent in water) with temperature 100 °C, time 1 h and solid loading 40%. These conditions generated yields of 90% glucose, 76% xylose, 59% lignin removal, and 73% solid recovery. The pretreated biomass and recovered lignin were studied using PXRD/TGA/FTIR/NMR analyses, revealing that the morphology and crystallinity of biomass does not change after pretreatment, and recovered lignin is dominated by guaiacyl groups, which are suitable for lignin valorization. Subsequently the process was consolidated and scaled up (40X) to generate >99% sugar yields followed by a test of bioconversion using the omnivorous host R. toruloides, which converted >97% C5, C6 and phenolic into the biofuel precursor bisabolene at a titer of 1155 mg L−1. The TEA revealed that the cost of biomass deconstruction was severely reduced (up to 50%) compared to similar pretreatment methods, including ethanolamine acetate and cholinium lysinate, evaluated under the same modeling assumptions. This study has demonstrated the effectiveness and robustness of alkanolamines towards biomass processing and presents a new solvent group to be considered for biomass pretreatment within a commercial biorefinery for the deconstruction of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Recyclable biocatalysts and high-efficiency lignocellulose deconstruction are the crucial factors for cost-effective conversion of biomass into biofuels and bioproducts. Acetic acid-based catalytic hydrolysis of grassy lignocellulosic biomass presents a promising application because of its effectivity, recyclability, and other environmentally friendly features. However, this treatment is not as effective on woody biomass, such as poplar. One way to improve conversion performance of this process is to integrate it with other effective processes, such as pretreating biomass with protic ionic liquids (PILs) that have been shown to effectively solubilize lignin in reducing the recalcitrance of biomass to enzymatic deconstruction. In this work, an integrated acetic acid based one-pot ethanolamine acetate pretreatment (HAc–[EOA][OAc]) was developed for the efficient depolymerization of poplar polysaccharides. The configuration simultaneously removed ∼88% hemicellulose and selectively extracted up to ∼46% of the lignin from lignocellulosic biomass. HAc–[EOA][OAc] pretreated poplar yielded over 80% enzyme-hydrolyzed glucose that was attributed to an increase in the accessible surface area of cellulose to the hydrolytic enzymes. Analysis of the cellulose crystallinity and thermal decomposition profiles revealed that all pretreated samples have a higher cellulose crystallinity, indicating that amorphous cellulose had been removed during pretreatment. Conductor like screening model for real solvents (COSMO-RS) and Hansen solubility parameters (HSP) were used to provide insights into the mechanism of biomass pretreatment efficacy using both HAc and [EOA][OAc]. We found that a strong hydrogen-bonding and electrostatic misfit interaction between hemicellulose and HAc may explain the higher removal of hemicellulose during HAc pretreatment. Further, the close HSP values and COSMO-RS analysis indicate that [EOA][OAc] is a good lignin solvent, which leads to the higher delignification of biomass. This study demonstrates that the integration of IL with acid pretreatment is a promising strategy for conducting effective pretreatment on woody lignocellulose. [ABSTRACT FROM AUTHOR]

Pretreatment of lignocellulosic biomass to specifically depolymerise lignin moieties without the loss of carbohydrates as well as to minimize the generation of harmful intermediates during the process is a major challenge in the biofuel production process. In the present study, a nanoparticle mediated pretreatment strategy was developed to specifically depolymerise lignin from corn cob biomass. The synthesized nanoparticles possessed unique enzyme mimicking characteristics that can be exploited for the deconstruction of lignin moieties. The maximum delignification was 44% using cerium doped iron oxide nanoparticles within 24 h of incubation time, at 25 °C and a high solid loading of 20% (w/v). Gas chromatography-mass spectrometry study revealed the production of various lignin degraded compounds in pretreated liquids such as fatty acid methyl esters, which are the major components of fuel biodiesel. Aromatic alcohols and aldehydes were also observed during lignin degradation that has industrial importance. The remaining pretreated solid residues rich in carbohydrates can be further utilized in the generation of reducing sugars and in turn biofuels such as bioethanol, biobutanol, and biohydrogen. The value of the crystallinity index increased from 0.39 to 0.46 by delignification, indicating a total increase in biomass crystallinity. Moreover, the increase in biomass porosity indicates good biomass digestibility and in turn high reducing sugar yield. After enzymatic hydrolysis of 50 g L−1 pretreated biomass, 18.1 g L−1 of glucose and 9.12 g L−1 of xylose were released at 24 h, while the control (untreated biomass) showed a negligible amount of sugar release after hydrolysis. The recovery of nanoparticles after delignification was almost 50% of the initial concentration. The recovered catalyst was further recycled and reused, providing 37.1% delignification in the second run and 30.8% in the third run. Therefore, the obtained results in the current study substantiate the feasibility of the employed enzyme mimicking nanoparticles in the process of lignin degradation and fermentable sugar release in an eco-friendly manner. [ABSTRACT FROM AUTHOR]

In deconstructing lignocellulosic biomass, processing solvents directly and indirectly influence the process efficiency by reducing recalcitrance, fractionating target components, preserving/modifying biomass components, etc. Hydrotropic solvents have shown effective biomass fractionation performance due to their unique amphiphilic structure. In particular, these hydrotropes effectively separate lignin from the cellulose-rich fraction with minimum modification and maximum recovery, which aligns well with the biorefinery strategy by enhancing the recovered lignin quality and quantity. Hydrotropic solvent functions as a catalyst in biomass fractionation/degradation and also as a solvent via aggregation and clustering for the dissolution of target components such as lignin. Moreover, this solvent approach has great potential in eco-friendly manufacturing in plant biomass utilization because of aqueous processing. In this review, chemical structure, amphiphilicity, roles and mechanism of hydrotropic solvents are discussed along with their recent applications in plant biomass utilization. Current challenges in their industrial applications and perspectives on the direction of future research directions are presented. [ABSTRACT FROM AUTHOR]

Lignin, a renewable polymer derived from the lignocellulosic biomass represents more than 20% of the total mass of the Earth's biosphere. However, 98% of lignin is burned as a source of energy in the pulp and paper industry, essentially due to its complex structure. Today, the valorization of lignin into the production of value-added chemicals represents a real challenge in terms of both sustainability and environmental protection. The present contribution aims to provide a critical discussion on the crucial choice of the starting material to study lignin valorization. Next, a comparison between the different oxidation routes investigated by chemists over the past several years is presented, with emphasis on the major difficulties encountered. The main current challenges regarding the heterogeneous catalytic oxidation of lignin and its derivatives are also highlighted. Particular focus is given to innovative strategies favoring mild reaction conditions. Finally, we provide some recommendations and routes worthy of interest in this studied area of research in order to generate value-added chemicals from lignin oxidation through the use of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Biomass conversion to alcohols using supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHO) with CuMgAl mixed metal oxide is a promising process for biofuel production. We demonstrate how maple wood can be converted at high weight loadings and product concentrations in a batch and a semi-continuous reactor to a mixture of C2–C10 linear and cyclic alcohols. Maple wood was solubilized semi-continuously in supercritical methanol and then converted to a mixture of C2–C9 alcohols and aromatics over a packed bed of CuMgAlOx catalyst. Up to 95 wt% of maple wood can be solubilized in the methanol by using four temperature holds at 190, 230, 300, and 330 °C. Lignin was solubilized at 190 and 230 °C to a mixture of monomers, dimers, and trimers while hemicellulose and cellulose solubilized at 300 and 330 °C to a mixture of oligomeric sugars and liquefaction products. The hemicellulose, cellulose, and lignin were converted to C2–C10 alcohol fuel precursors over a packed bed of CuMgAlOx catalyst with 70–80% carbon yield of the entire maple wood. The methanol reforming activity of the catalyst decreased by 25% over four beds of biomass, which corresponds to 5 turnovers for the catalyst, but was regenerable after calcination and reduction. In batch reactions, maple wood was converted at 10 wt% in methanol with 93% carbon yield to liquid products. The product concentration can be increased to 20 wt% by partially replacing the methanol with liquid products. The yield of alcohols in the semi-continuous reactor was approximately 30% lower than in batch reactions likely due to degradation of lignin and cellulose during solubilization. These results show that solubilization of whole biomass can be separated from catalytic conversion of the intermediates while still achieving a high yield of products. However, close contact of the catalyst and the biomass during solubilization is critical to achieve the highest yields and concentration of products. [ABSTRACT FROM AUTHOR]

Several deep eutectic solvents (DESs) have been demonstrated to be highly effective for lignocellulosic biomass pretreatment, combining the advantages of simple synthesis, relatively low chemical cost and better biocompatibility. However, low biomass loading that is usually involved with DES pretreatment hinders its practical use. In this study, a twin-screw extruder was used for pretreating biomass sorghum bagasse at solid loadings up to 50%, mediated by a neutral-pH DES, choline chloride : glycerol (ChCl : Gly). This continuous extrusion process led to high glucose and xylose yields of >85% from enzymatic saccharification of the pretreated sorghum. A combination of microscopic, spectroscopic, and X-ray diffraction analyses demonstrate a high degree of defibration and disruption of the biomass cell wall structures; however, little or no change in chemical compositions. Further results from gel permeation chromatographic (GPC) and nuclear magnetic resonance (NMR) spectroscopic analyses indicate that ChCl : Gly-mediated extrusion preserved the basic lignin structural characteristics with no significant differences between extruded biomass at a solid loading of 30% and 50%. This study demonstrates the potential of DES-mediated extrusion as a highly effective continuous high-solid biomass pretreatment technology for industrially relevant applications. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is addressed as potential sustainable feedstock for green fuels and chemicals. (Hemi)cellulose is the largest constituent of the material. Conversion of these polysaccharides to bio-based platform chemicals is important in green chemical/fuel production and biorefinery. Hydroxymethyl furfural, furfural and levulinic acid are substantial building blocks from (poly)saccharides. Synthesis of these molecules involves acid catalysed hydrolysis/dehydration reactions which leads large formation of insoluble by-products, called humins. Humin obtained from dehydration of glucose is used in this study. Fractionisation of humin was investigated using various solvents (e.g., acetone, H2O, and NaOH 1%). Characterisation of humin using various techniques including ATR-IR, HR-SEM, solid state NMR, elemental analysis, Raman spectroscopy, pyrolysis, etc. confirms its furan rich structure with aliphatic oxygenate linkages. The influence of thermal treatment on humin was investigated. Humin undergoes a lot of changes both in morphology and structure. Humin loses ca. 45 wt% when preheated to 700 °C (prior to the gasification temperature) and contains above 92 wt% C in mainly aromatic/graphitic structures. Valorisation of humin via dry reforming was studied. Non-catalytic dry reforming of humin is very difficult; however, alkali catalysts (e.g. Na2CO3) can enhance the reaction rate tremendously. [ABSTRACT FROM AUTHOR]

Despite only recently becoming available in the quantities required for solvent usage, the cellulose-derived solvent, named Cyrene, has gained significant attention in green chemistry in recent years. To fulfill the sustainability criteria of future biorefineries, a novel renewable biomass pretreatment using Cyrene and water was developed for the first time. Results showed that Cyrene has high potential as a green pretreatment solvent in terms of lignin fractionation/recovery and sugar release in the follow-up enzymatic hydrolysis. The mechanism of this pretreatment was revealed by investigating the structural characteristics of pretreated biomass, and the recovered lignin was also fully characterized to assess its valorization potential. Results indicated that Cyrene pretreatment could be performed at a mild condition (120 °C) to reduce the lignin condensation and the cleavage of β-O-4 linkages without compromising lignin removal and the following sugar platform. The successful utilization of this cellulose-derived solvent in pretreatment will further contribute to the realization of a "closed-loop" biorefinery process. [ABSTRACT FROM AUTHOR]

Sustainable production of fine chemicals and biofuels from renewable biomass offers a potential alternative to the continued use of finite geological oil reserves. However, in order to compete with current petrochemical refinery processes, alternative biorefinery processes must overcome significant costs and productivity barriers. Herein, we demonstrate the biocatalytic production of the versatile chemical building block, coniferol, for the first time, directly from lignocellulosic biomass. Following the biocatalytic treatment of lignocellulose to release and convert ferulic acid with feruloyl esterase (XynZ), carboxylic acid reductase (CAR) and aldo-keto reductase (AKR), this whole cell catalytic cascade not only achieved equivalent release of ferulic acid from lignocellulose compared to alkaline hydrolysis, but also displayed efficient conversion of ferulic acid to coniferol. This system represents a consolidated biodegradation–biotransformation strategy for the production of high value fine chemicals from waste plant biomass, offering the potential to minimize environmental waste and add value to agro-industrial residues. [ABSTRACT FROM AUTHOR]

Levoglucosan has significant potential in commercial applications for the synthesis of polymers, solvents and pharmaceuticals. It is currently overlooked for commercial applications due to its high cost of synthesis and purification. We have developed a system to produce pure crystals of levoglucosan based on the fast pyrolysis of lignocellulosic biomass. A novel bio-oil recovery system concentrated levoglucosan along with other anhydrosugars, sugars and phenolic compounds in a non-aqueous "heavy ends" fraction. Liquid–liquid water extraction separated sugar-rich solubilized carbohydrates from non-soluble phenolic compounds. The solubilized carbohydrate fraction, contaminated with partially soluble phenolic monomers, was filtered through Sepabeads SP207 adsorption resin to produce clarified juice. The composition of the clarified juice on a dry basis after resin filtration and rotary evaporation was 81.2% sugars, 4.45–4.60% volatile non-sugar, 1.71% carboxylic acids and 12.5–12.6% unidentified compounds, which was sufficiently pure to crystallize the sugars by evaporation. A cold solvent rinse of the crystal mass separated and purified levoglucosan from other sugars. Levoglucosan purity was 102.5% ± 3.109% at the 99% confidence level. Techno-economic analysis of a plant pyrolyzing 250 tonne per day of pretreated biomass to produce cellulosic sugars indicated a minimum selling price (MSP) for pure levoglucosan crystals of $1333 per MT, which is less than one-tenth its current average market price. Operating hours of the plant, fermentable syrup yield and fixed capital are the most significant parameters affecting MSP. [ABSTRACT FROM AUTHOR]

This paper reviews the application of ionic liquids to the deconstruction and fractionation of lignocellulosic biomass, in a process step that is commonly called pretreatment. It is divided into four parts: the first gives background information on lignocellulosic biomass and ionic liquids; the second focuses on the solubility of lignocellulosic biomass (and the individual biopolymers within it) in ionic liquids; the third emphasises the deconstruction effects brought about by the use of ionic liquids as a solvent; the fourth part deals with practical considerations regarding the design of ionic liquid based deconstruction processes. [ABSTRACT FROM AUTHOR]

To date, information on biomass deconstruction and advanced biofuels production using pilot-scale pretreatments is scarce and typically derived from single feedstocks, making comparisons complicated. This work evaluates the effect of subjecting four different feedstocks (agave bagasse [AG], corn stover [CS], sugarcane bagasse [SC] and wheat straw [WS]) to pretreatment at 180 °C for 20 min in a 200 kg day−1 pilot-scale continuous tubular reactor constituted by three sequential stages (compression, autohydrolysis and steam explosion). Correlations between the structural changes and differences in digestibility on pretreated biomass were determined. It was determined that xylan removal by pretreatment generated more crystalline and energy dense materials, with higher lignin content and S/G ratio. Optimal reaction conditions for enzymatic saccharification of pretreated feedstocks at lower enzyme doses generated glucose conversions up to 80%. Finally, it was demonstrated that the yeast Rhodosporidium toruloides was able to grow in all hydrolysates, exhibiting simultaneous C5 and C6 sugar consumption and bisabolene production. [ABSTRACT FROM AUTHOR]

Oleaginous microbes are promising platform strains for the production of renewable diesel and fatty-acid derived chemicals given their innate capacity to produce high lipid yields from lignocellulose-derived sugars. Substantial efforts have been conducted to engineer model oleaginous yeasts primarily on model feedstocks, but to enable lipid production from biomass, judicious strain selection based on phenotypes beneficial for processing, performance on realistic feedstocks, and process integration aspects from sugars to fuels should be examined holistically. To that end, here we report the bench-scale production of diesel blendstock using a biological-catalytic hybrid process based on oleaginous yeast. This work includes flask screening of 31 oleaginous yeast strains, evaluated based on baseline lipid profiles and sugar consumption with corn stover hydrolysate. Three strains were down-selected for bioreactor performance evaluation. The cultivation results reveal that Cryptococcus curvatus ATCC 20509 and Rhodosporodium toruloides DSM-4444 exhibit equivalent fatty acid methyl ester (FAME) yield (0.24 g g−1), whereas the highest overall FAME productivity (0.22 g L−1 h−1) was obtained with C. curvatus, and R. toruloides displayed the highest final FAME titer (23.3 g L−1). Time-resolved lipid profiling (including neutral and polar lipid classing) demonstrated triacylglycerol accumulation as the predominant lipid class in all strains. When evaluating tolerance mechanisms to inhibitory compounds, all strains could reduce and oxidize 5-(hydroxymethyl)furfural, illustrating parallel detoxification mechanisms. The R. toruloides strain was also capable of growth on four aromatic compounds as a sole carbon source, suggesting its use as a strain for simultaneous sugar and lignin conversion. Lipids from R. toruloides were recovered using a mild acid treatment and extraction, hydrogenated, and isomerized to produce a renewable diesel blendstock. The blendstock exhibited a cloud point of −14.5 °C and simulated distillation showed that approximately 75% of the product was in the diesel range with a T90 consistent with no. 2 diesel fuel. Taken together, these results demonstrate an integrated process for renewable diesel production, identify oleaginous strains for further development, and highlight opportunities for improvements to an oleaginous microbial platform for the production of renewable diesel blendstock. [ABSTRACT FROM AUTHOR]

The commercialisation of the biorefinery approach involving the integration of the multi-step valorisation of low value biomass feedstock into a variety of chemicals, fuels and bioproducts is still very limited. In this context, the present work proposes an advanced methodology that comprises a cascaded approach towards wheat straw valorisation. The studied concept lies in the employment of an aqueous solution of the acidic 1-ethyl-3-methylimidazolium hydrogen sulfate ionic liquid in a selective and efficient hydrolysis of the hemicellulose fraction of wheat straw into pentoses, namely xylose and arabinose. An experimental design was utilised to search for the optimisation parameters, resulting in a maximum 80.5 wt% pentose yield in the liquor. Furthermore, the remaining solid, which contained practically all of the initial cellulose and lignin, was processed by considering two scenarios: (i) a direct enzymatic hydrolysis of the reaction solid, which yielded 75.8 mol% glucose; or (ii) a preceding extraction of lignin followed by enzymatic saccharification of the cellulose pulp, which yielded 91.3 mol% glucose. For both scenarios, lignin-rich solid fractions were obtained with distinct purities and yields. Additionally, the second scenario allowed producing a stream of value-added aromatic (phenolic) compounds. This work also overcame the challenges in IL recycling and reuse, with a simultaneous recovery of the pentoses from the reaction liquor as high as 88.6 mol%. [ABSTRACT FROM AUTHOR]

The complexity and recalcitrance of lignocellulosic biomass seriously hinder its subsequent conversion to liquid fuels. To achieve high-value utilization of lignocellulosic biomass, the physical–chemical barrier should be overcome through appropriate pretreatment techniques to improve the accessibility of cellulose for efficient enzymatic hydrolysis. With the rapid emergence of novel pretreatment solvents, biphasic solvent pretreatments represent a nascent and green pretreatment method that has shown outstanding advantages and broad application prospects in the biorefinery of lignocellulosic substrates due to its ability to provide economically viable biomass upgrading, the separation process for products in the solvent phase, and the reutilization of solvents. Herein, different types of biphasic solvents (e.g., 2-methyltetrahydrofuran, methyl isobutyl ketone, 1-butanol, phenoxyethanol, ionic liquids, and deep eutectic solvents) were reviewed systematically, including the fundamental designs of biphasic solvents for biomass pretreatment, their effect on the fractionation of individual biomass components (e.g., carbohydrate and lignin) and the enzymatic hydrolysis performance, and the coproduction of furan and hydroxymethylfurfural. Finally, the main pros and cons of these different biphasic solvent systems are summarized, and the future development direction is also proposed. This review can provide a reference for designing and selecting effective biphasic pretreatment methods for various types of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Cost-effective fractionation (pretreatment) of lignocellulosic biomass is necessary to enable its large-scale use as a source of liquid fuels, bio-based materials and bio-derived chemicals. While a number of ionic liquids (ILs) have proven capable of highly effective pretreatment, their high cost presents a barrier to commercial viability. In this study, we investigate in detail the application of the low-cost (ca. $1 kg−1) ionic liquid triethylammonium hydrogen sulfate for the fractionation of the grass Miscanthus x giganteus into a cellulose rich pulp, a lignin and a distillate. We found that up to 85% of the lignin and up to 100% of the hemicellulose were solubilized into the IL solution. The hemicellulose dissolved mainly in monomeric form, and pentoses were partially converted into furfural. Up to 77% of the glucose contained in the biomass could be released by enzymatic saccharification of the pulp. The IL was successfully recovered and reused four times. A 99% IL recovery was achieved each time. Effective lignin removal and high saccharification yields were maintained during recycling, representing the first demonstration that repeated IL use is feasible due to the self-cleaning properties of the non-distillable solvent. We further demonstrate that furfural and acetic acid can be separated quantitatively from the non-volatile IL by simple distillation, providing an easily recoverable, valuable co-product stream, while IL degradation products were not detected. We further include detailed mass balances for glucose, hemicellulose and lignin, and a preliminary techno-economic estimate for the fractionation process. This is the first demonstration of an efficient and repeated lignocellulose fractionation with a truly low-cost IL, and opens a path to an economically viable IL-based pretreatment process. [ABSTRACT FROM AUTHOR]

Here, we report on the ability of the biomass derived solvents ethanol and, in particular, n-butanol to fractionate lignocellulose into its main components. An organosolv system consisting of n-butanol containing 5% water and 0.2 M HCl at reflux was found to remove effectively the lignin and hemicellulose components of lignocellulosic biomass leaving a cellulose pulp suitable for enzymatic hydrolysis to simple sugars. Using a hardwood beech pulp as an example, essentially complete conversion of the cellulose component to reducing sugars was achieved with a cellulase loading of 22 FPU per g. Analysis of the solubilised hemicellulose fractions revealed that they consist almost exclusively of alkyl xylosides and mannosides which could serve as valuable synthetic building blocks. Additionally, the mild conditions (＜120 °C) and high alcohol content of the pre-treatment solvent suppressed lignin degradation reactions and allowed for the isolation of high quality lignins in good yields. Detailed HSQC NMR analysis of the isolated lignins revealed that they still contained large amounts of β-aryl ether units, especially α-ethoxylated and α-butoxylated β-O-4 units, making them particularly suitable for depolymerisation to mono-aromatic chemicals. This was demonstrated using a recently reported acidolysis method utilizing ethylene glycol which gave monomer yields of between 7.4 and 18 wt%. The yields for n-butanol lignins were at least four fold higher than those obtained from a current generation technical organosolv lignin under comparable conditions. [ABSTRACT FROM AUTHOR]

The catalytic fast pyrolysis (CFP) of pine was investigated over 10 wt% MoO3/TiO2 and MoO3/ZrO2 at 500 °C and H2 pressures ≤0.75 bar. The product distributions were monitored in real time using a molecular beam mass spectrometer (MBMS). Both supported MoO3 catalysts show different levels of deoxygenation based on the cumulative biomass to MoO3 mass ratio exposed to the catalytic bed. For biomass to MoO3 mass ratios ＜1.5, predominantly olefinic and aromatic hydrocarbons are produced with no detectable oxygen-containing species. For ratios ≥1.5, partially deoxygenated species comprised of furans and phenols are observed, with a concomitant decrease of olefinic and aromatic hydrocarbons. For ratios ≥5, primary pyrolysis vapours break through the bed, indicating the onset of catalyst deactivation. Product quantification with a tandem micropyrolyzer–GCMS setup shows that fresh supported MoO3 catalysts convert ca. 27 mol% of the original carbon into hydrocarbons comprised predominantly of aromatics (7 C%), olefins (18 C%) and paraffins (2 C%), comparable to the total hydrocarbon yield obtained with HZSM-5 operated under similar reaction conditions. Post-reaction XPS analysis on supported MoO3/ZrO2 and MoO3/TiO2 catalysts reveal that ca. 50% of Mo surface species exist in their partially reduced forms (i.e., Mo5+ and Mo3+), and that catalyst deactivation is likely associated to coking. [ABSTRACT FROM AUTHOR]

While current biorefinery processes use lignin only for its heat value, the conversion of lignin to high value chemicals is an area of increasing interest. Herein we present a detailed mechanistic study of the hydrodeoxygenation (HDO) of lignin by using a synergistic Pd/C and ZnII catalyst through use of both lignin model compounds and lignocellulosic biomass. Spectroscopic data coupled with the study of lignin model compounds suggest that ZnII activates and facilitates removal of the hydroxyl group at the Cγ position of the β-O-4 ether linkage. Activation is proposed to occur through formation of a six-membered ring complex of ZnII coordinated to the oxygen atoms at Cα and Cγ of the lignin model compound guaiacylglycerol-β-guaiacyl. [ABSTRACT FROM AUTHOR]

Acetoin (AC) is regarded as one of the top potential sugar-derived chemical building blocks that can be used as food additives, precursors in chemical synthesis, and plant growth promoting molecules. In this study, a low-cost lignocellulosic resource of pretreated corn stover was used as a carbon source to produce AC. After redirecting the metabolic flux, fine tuning reducing power, and eliminating carbon catabolite repression in Enterobacter cloacae SDM, a systematically engineered strain SDM 53 was constructed, which is able to utilize glucose and xylose efficiently and simultaneously. Using fed-batch fermentation of SDM 53, 45.6 g L−1 AC was produced at a rate of 1.52 g L−1 h−1 using the lignocellulosic hydrolysate. Biotechnological synthesis of AC has various advantages such as being sustainable and environment-friendly. With its desirable properties, the engineered strain SDM 53 may be a potential choice for the industrial production of AC. [ABSTRACT FROM AUTHOR]

Most valorization processes for biomass waste require dry raw material or at least a relatively low amount of residual humidity. In contrast, hydrothermal carbonization (HTC) is a valorization process for lignocellulosic biomass which uses water as a reaction medium. The product, hydrochar, can be used as dry solid fuel making the post-process drying procedure much more energy-efficient. Herein, three lignocellulosic biomass waste feedstocks, i.e. the organic fraction of municipal solid waste (OFMSW), orange peel waste (OPW) and the residues of a pepper plantation, were processed by HTC on a ton scale and the product evaluated as solid fuel in form of pellets for domestic use (EN ISO 17225). A critical property of the product is the ash content which has to be adjusted by post-treatment. Ash content below the established limit was achieved by acid treatment with sulfuric acid. An implementation of the treatment into the pilot plant is straightforward. An organic liquid fraction was obtained as an additional effluent in the pilot plant depending on the biomass feedstock. For instance, limonene in a mixture with other monoterpenes was separated when orange peel waste was processed, constituting approximately 3 wt% of the dry matter. It is further shown at laboratory scale that the monoterpene mixture can be directly used or can easily be transformed into para-cymene, a fragrance compound, by catalytic dehydrogenation. Therefore, the HTC process can be considered as a source for valuable apolar platform molecules derived from lignocellulosic biomass waste in addition to the production of hydrochar. [ABSTRACT FROM AUTHOR]

The selective oxidation of complex, water-insoluble and wet biomass from second and third generation to formic acid including effective catalyst recycling is reported. Additionally, the relevance and limits of potential contaminants are illustrated by different experimental approaches. By using a very robust homogeneous polyoxometalate catalyst in aqueous solution, molecular oxygen as an oxidant and an acid as a solubilizer, it is possible to convert different lignocellulosic and algae feedstock into formic acid and pure carbon dioxide. The applied green oxidation system benefits from its low reaction temperature (below 100 °C) and its very selective nature. Furthermore, catalyst recycling over three batches has been successfully carried out. [ABSTRACT FROM AUTHOR]

A novel pathway was investigated to produce jet fuel range cycloalkanes from intact biomass. The consecutive processes for converting lignocellulosic biomass into jet fuel range cycloalkanes principally involved the use of the well-promoted ZSM-5 in the process of catalytic microwave-induced pyrolysis and RANEY® nickel catalysts in the hydrogen saving process. Up to 24.68% carbon yield of the desired C8–C16 aromatics was achieved by catalytic microwave pyrolysis at 500 °C. We observed that solvents could assist in the hydrogenation reaction of naphthalene; and the optimum result for maximizing the carbon selectivity (99.9%) of decalin was obtained from the reaction conducted in the n-heptane medium. The recovery of organics could reach ∼94 wt% after the extraction process. These aromatics in the n-heptane medium were eventually hydrogenated into jet fuel range cycloalkanes. Various factors were analyzed to determine the optimal result under mild conditions. An increased catalyst loading, reaction temperature, and prolonged time could enhance the hydrogenation reactions to improve the selectivity of jet fuel range cycloalkanes. Three types of hydrogenation catalysts (NP Ni, RANEY® Ni 4200, home-made RANEY® Ni) were chosen to evaluate the catalytic performance. The results indicated that the home-made RANEY® nickel is the optimal catalyst to obtain the highest selectivity (84.59%) towards jet fuel range cycloalkanes. These cycloalkanes obtained can be directly used as additives to synthesize the desired jet fuels by blending with other hydrocarbons. Hence integration of catalytic processes and conversion of lignocellulosic biomass paved a new avenue for the development of green bio-jet fuels over inexpensive catalysts under mild conditions. [ABSTRACT FROM AUTHOR]

The catalytic conversion of lignocellulosic biomass to renewable and valuable chemicals has attracted global interest. Given the abundance of this renewable raw material and its reduced impact on the food chain, it is an attractive source for replacing fossil fuels and obtaining chemicals or fuels in the context of a sustainable economy. In this work, a catalyst (Ru/AC) was developed to perform, in a single step, hydrolysis and hydrogenation of cellulose to sorbitol. An activated carbon supported ruthenium catalyst was examined for the one-pot hydrolytic hydrogenation of cellulose and it has shown to be very active and selective for the conversion of cellulose into sorbitol. When microcrystalline cellulose was used, a conversion of 36% was reached after 5 hours of reaction, with a selectivity to sorbitol of 40%. On the other hand, ball-milled cellulose allowed attaining conversions close to 90%, with a selectivity to sorbitol of 50%. Moreover, if the catalyst was ball-milled together with cellulose, the selectivity to sorbitol could be further increased to almost 80%. The catalyst showed excellent stability after repeated use. In this work we combined hydrolysis and hydrogenation in one-pot (using heterogeneous catalysts instead of homogeneous), in the presence of a Ru/AC catalyst (without any support pre-treatment with acids) and pre-treated cellulose just by ball-milling (instead of using acids). For this reason, the results obtained in this work are one of the best values achieved when using supported metal catalysts to convert cellulose by an environmentally friendly process. [ABSTRACT FROM AUTHOR]

Biomass pretreatment with certain ionic liquids (IL) can be highly effective at generating a substrate that can be easily saccharified into fermentable sugars with high yields. In order to improve overall process economics, using mixtures of these ILs with water are more favored over the use of anhydrous IL; however, the solvent property of IL-water mixtures and correlations between cellulose digestibility, cellulose solvation and lignin depolymerization during IL-water pretreatment of lignocellulosic biomass are not well understood. We investigated pretreatment of switchgrass with mixtures of 1-ethyl-3-methylimidazolium acetate, [C2mim][OAc], and water at 160 °C. Results indicate that the chemical composition and crystallinity of the pretreated biomass, and the corresponding lignin dissolution and depolymerization, were dependent on [C2mim][OAc] concentration that correlated strongly with cellulose digestibility. In addition, the hydrogen bond basicity of the [C2mim][OAc]-water mixtures was found to be a good indicator of cellulose dissolution, lignin depolymerization, and sugar yields. Molecular dynamics simulations provided molecular level explanations on cellulose Iβ dissolution at different [C2mim][OAc]-water loadings. The knowledge gained from this study provides a better understanding of the duality of water as a co-solvent/anti-solvent in dissolving cellulose and serves as a design basis for the targeted design of IL- water mixtures that are effective at biomass pretreatment. [ABSTRACT FROM AUTHOR]

As one of the substitutes for traditional fossil energy, biomass resource has attracted extensive attention. Methyl levulinate (ML) is a short chain fatty acid ester, which is an important green and high value-added chemical derived from biomass. Starting from a few different model compounds, this review summarized a variety of process methods for preparing ML, pointed out the best reaction conditions and parameters in the current research progress, and explained the key reaction mechanism for ML formation. In addition, this review further discussed the research progress of converting real lignocellulosic biomass with more complex structure into ML with a particular emphasis on the selection of applicable biomass species. At the same time, the development of catalysts in this field was introduced. What's more, the conversion and utilization of ML to produce other fine platform chemicals were stressed. Subsequently, the advanced technologies and existing issues in the current research progress were presented, and finally the research directions in this field were prospected. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is a potential sustainable feedstock to replace fossil fuels. However, the complex structure of biomass makes it difficult to convert into high-value products. Utilization of lignocellulosic biomass in a green and effective way is of great significance for sustainable development. Based on the analysis of different options, we proposed that cascade utilization according to its composition, characteristics, and nature is the best way to utilize the lignocellulosic biomass. To promote the cascade utilization of lignocellulosic biomass, this article provides a review of the latest research results from the aspect of cascade utilization of lignocellulosic biomass covering the whole chain from pretreatment to high-value products, and the research on the non-conventional pretreatments including microwave irradiation, supercritical fluids, ultrasonic irradiation, electric field, hydrodynamic cavitation, and ionic liquids are presented in detail and evaluated by 4 proposed levels, and the newly developed high-value applications were further overviewed for lignin (carbon/graphene/carbon nano-tubes, dye dispersants, bioplastics, and aerogels), cellulose (cellulose-based ionic liquids, functional composites, adsorbent materials, carbon, and aerogels), and hemicellulose (films and pharmaceutical carriers), respectively. Finally, perspectives on the future research on the cascade utilization of lignocellulosic biomass are highlighted. [ABSTRACT FROM AUTHOR]

Despite the rapid progress in the field of biomass fractionation and lignin valorization, no industrial process for chemical utilization of lignin has yet been established. One major step in that direction has been made with the advent of biorefineries and new biomass fractionation methods that deliver a relatively clean lignin stream, allowing a more efficient recovery and utilization of this fraction. However, the transfer of lignin from the fractionation solvent to a different medium for subsequent valorization has been largely disregarded so far. In this work, we demonstrate the use of a green liquid/liquid-extraction to transfer lignin from the organic phase of the OrganoCat process into differently concentrated alkaline solutions for further utilization. We show that alkaline solutions of pH 13 and 14 are able to almost completely extract the OrganoCat lignin from the organic phase but that this extraction might be accompanied by changes in the molecular structure of lignin, here shown by a change in the apparent molecular weight distribution. [ABSTRACT FROM AUTHOR]

Here we report that γ-valerolactone (GVL), a biomass-derived solvent, can be used to facilitate the mild pretreatment of lignocellulosic biomass. An 80% GVL, 20% water solvent system was used to pretreat hardwood at the mild temperature of 120 °C with an acid loading of 75 mM H2SO4. Up to 80% of original lignin was removed with 96–99% of original cellulose retained in the pretreated substrates. The use of a mild temperature and low acid concentrations caused negligible degradation of sugars. Up to 99% of the original glucan and 96% of the original xylan could be recovered after pretreatment. The pretreated substrate was quantitatively converted to sugars (99% and 100% total glucose and xylose yield) with an enzyme loading of 15 FPU g−1 glucan. These digestibilities were three times higher than those obtained when using other organic solvents such as tetrahydrofuran or ethanol, and 20 times higher than when pure water was used during pretreatment. Over 99.5% of GVL could be recovered by liquid–CO2 extraction of the pretreated slurries while removing less than 1% of the sugars. This approach produced pretreatment slurries that could easily undergo high-solids (30% w/v) enzymatic hydrolysis without any substrate washing or drying. We obtained glucose and xylose yields of up to 90% and 97%, respectively, and generated sugar streams with sugar concentrations up to 182 g L−1. [ABSTRACT FROM AUTHOR]

This review presents an overview of the initial targeted chemical processing stages for conversion of lignocellulosic biomass to platform molecules that serve as intermediates for the production of carbonbased fuels and chemicals. We identify four classes of platform molecules that can be obtained in an initial chemical processing step: (i) sugars, (ii) dehydration products, (iii) polyols and (iv) lignin monomers. Special emphasis is placed on reporting and comparing parameters that affect process economics and/or sustainability, including product yields, amount of catalyst used, processing conditions, and product concentrations. We discuss the economic trade-offs associated with choices related to these parameters, depending on the product that is targeted. We also address the effects of real biomass on the ability to recover, recycle, and potentially regenerate catalysts and solvents used in the biomass conversion processes. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass, a potentially important renewable organic source of energy and chemical feedstock, resists degradation to glucose in industrial hydrolysis processes and thus requires expensive thermochemical pretreatments. Understanding the mechanism of biomass breakdown during these pretreatments will lead to more efficient use of biomass. By combining multiple probes of structure, sensitive to different length scales, with molecular dynamics simulations, we reveal two fundamental processes responsible for the morphological changes in biomass during steam explosion pretreatment: cellulose dehydration and ligninhemicellulose phase separation. We further show that the basic driving forces are the same in other leading thermochemical pretreatments, such as dilute acid pretreatment and ammonia fiber expansion. [ABSTRACT FROM AUTHOR]

Lignocellulose is the most abundant non-food biomass and is used as a feedstock for the production of chemicals. Lignocellulose consists of cellulose, hemicellulose and lignin, in which the sugar polymers account for a large portion of the biomass. Sugar compounds obtained from non-food biomass can be the first platform chemicals in the biorefinery. From this viewpoint, this review article mainly deals with the catalytic synthesis and utilisation of sugar derivatives produced from cellulose and hemicellulose using various methodologies from fundamental science to practical use. [ABSTRACT FROM AUTHOR]