Utilization Of Lignocellulosic Biomass Research Articles

Performance of combined hydrochemo-mechanical pretreatment of rice straw for bioethanol production

Pretreatment was an inevitable process in the biorefinery process of lignocellulosic biomass utilization. Generally, biomass was considered an essential carbon source that could be converted into several bio-based products such as biofuels and biochemicals. This study aimed to evaluate the performance of combined hydrochemo-mechanical pretreatment of rice straw for bioethanol production. Rice straw was pretreated with autoclave followed by ball-milling pretreatment. The hydrochemical pretreatment was performed in an autoclave with different concentrations of NaOH (1 and 10%) at 121 °C for two different durations (30, 60 min). The pretreated biomasses were then subjected to ball-milling pretreatment for size reduction and subsequently hydrolyzed via enzymatic and bioethanol fermentation. The obtained results indicated that the highest reducing sugars were 0.4513 kg reducing sugar/kg biomass obtained by 1% of NaOH at 121 °C, 30 min, which provided the highest energy efficiency and the lowest waste generation was 0.1423 kg reducing sugar/kWh and 0.2570 kg of waste/kg reducing sugar respectively. Moreover, the highest bioethanol yield was 0.0491 kg/kg biomass obtained from a similar condition. Additionally, the combined pretreatment suggested that it could be an alternative pretreatment for a lignocellulosic biorefinery in industrial applications.

A Review on Advanced Processes of Biohydrogen Generation from Lignocellulosic Biomass with Special Emphasis on Thermochemical Conversion

The utilization of lignocellulosic biomass as an alternative energy source presents a promising opportunity to achieve a future energy system that is clean and free from CO2 emissions. To realize this potential, it is crucial to develop effective techniques for converting biomass and organic solid waste into secondary energy sources. Among the available options, hydrogen production stands out due to its numerous advantages, including its cleanliness, versatility in conversion and utilization technologies, high energy efficiency, and dense energy content per unit weight. This article offers a comprehensive overview of different conversion pathways and important technologies for generating hydrogen from biomass and organic solid waste. It specifically focuses on the thermochemical conversion process, which shows promise as an economically viable approach. While certain thermochemical conversion processes are still in the developmental phase, utilizing organic biomass for hydrogen production is widely recommended due to its ability to yield higher amounts of end products and its compatibility with existing facilities. However, it should be noted that this method necessitates a substantial amount of energy due to its endothermic nature. This article also explores alternative hydrogen conversion technologies and their potential for utilizing organic biomass as a feedstock, while addressing the challenges and limitations associated with these methods.

Utilization of lignocellulosic biomass by glycerol organosolv pretreatment for biobutanol production integrated with bioconversion of residual glycerol into value-added products

Glycerol organosolv pretreatment (GOP) is considered an efficient method to deconstruct lignocellulose for producing fermentable sugars. Herein, the liquid fraction containing glycerol after GOP was utilized for recycled pretreatment of corn stover (CS) for four cycles. Enzymatic yield of glucose after recycled pretreatment was enhanced by 2.4–3.5 folds compared with untreated CS. Meanwhile, residual glycerol was used as carbon source for cultivation of Pichia pastoris to obtain high cell-density, and a final titer of 1.3 g/L human lysozyme was produced by P. pastoris under low temperature methanol induction strategy. Additionally, the pretreated CS was mixed with cassava as fermentable substrates for butanol production by wild-type Clostridium acetobutylicum ATCC 824. Final butanol production of 13.9 g/L was obtained from mixed substrates (25%:75% of CS/cassava) at 10% solids loading by simultaneous saccharification and fermentation. Overall, integration of residual glycerol utilization and butanol production by microbial fermentation provided an efficient strategy for biorefinery.

Polyoxometalates-modified and facets-engineered TiO2 nanocomposites for selective photocatalytic cleavage of C–C bond of lignin models

Selective cleavage of C-C bond of lignin derivatives and models via oxidation is vital to realize value-added utilization of lignocellulosic biomass. Herein, based on the strategy of facet engineering and pseudo-heterojunction construction, a series of P2W17V/{001}-TiO2 heterogenous photocatalysts were constructed by loading monovanadium-substituted Dawson-type polyoxometalates P2W17V onto TiO2 with exposed {001} facets. The morphologies, structures, photoelectrical properties, and photocatalytic performances of the nanocomposites were researched. P2W17V/{001}-TiO2 could effectively photocatalyze the transformation of 2-phenoxy-1-phenylethanol, the lignin model compound with characteristic β-O-4 structure, to benzaldehyde and phenol. Photogenerated electrons and O2•- were disclosed critical to lignin model conversion that could induce C-C bond cleavage, with a selectivity above 85%, through a Cβ-centered radical. Neither pure O2 nor precious metal was required in the photocatalysis. P2W17V acted as electron pools. The engineered facets of TiO2 and the pseudo-heterojunction between P2W17V and TiO2 suppressed electron-hole recombination, facilitated charge transfer, and promoted photocatalytic performance. This work paved a new avenue to convert lignin and lignin derivatives to high-value chemicals by selectively breaking C-C bond under mild conditions.

The novel properties of Kluyveromyces marxianus glucose sensor/receptor repressor pathway and the construction of glucose repression-released strains

BackgroundGlucose repression in yeast leads to the sequential or diauxic utilization of mixed sugars and reduces the co-utilization of glucose and xylose from lignocellulosic biomasses. Study of the glucose sensing pathway helps to construct glucose repression-released yeast strains and enhance the utilization of lignocellulosic biomasses.ResultsHerein, the glucose sensor/receptor repressor (SRR) pathway of Kluyveromyces marxianus which mainly consisted of KmSnf3, KmGrr1, KmMth1, and KmRgt1 was studied. The disruption of KmSNF3 led to a release of glucose repression, enhanced xylose consumption and did not result in deficient glucose utilization. Over-expression of glucose transporter gene restored the mild decrease of glucose utilization ability of Kmsnf3 strain to a similar level of the wildtype strain but did not restore glucose repression. Therefore, the repression on glucose transporter is parallel to glucose repression to xylose and other alternative carbon utilization. KmGRR1 disruption also released glucose repression and kept glucose utilization ability, although its xylose utilization ability was very weak with xylose as sole carbon source. The stable mutant of KmMth1-ΔT enabled the release of glucose repression irrespective that the genetic background was Kmsnf3, Kmmth1, or wildtype. Disruption of KmSNF1 in the Kmsnf3 strain or KmMTH1-ΔT overexpression in Kmsnf1 strain kept constitutive glucose repression, indicating that KmSNF1 was necessary to release the glucose repression in both SRR and Mig1-Hxk2 pathway. Finally, overexpression of KmMTH1-ΔT released the glucose repression to xylose utilization in S. cerevisiae.ConclusionThe glucose repression-released K. marxianus strains constructed via a modified glucose SRR pathway did not lead to a deficiency in the utilization ability of sugar. The obtained thermotolerant, glucose repression-released, and xylose utilization-enhanced strains are good platforms for the construction of efficient lignocellulosic biomass utilization yeast strains.

Effective conversion of corn stalk into ethyl levulinate and crude lignin catalyzed by ionic liquids

The chemical transformation of lignocellulosic biomass into platform chemicals is one of the most efficient utilization methods for agricultural wastes. In this work, a one-pot strategy for the conversion of corn stalk to ethyl levulinate and further extraction of valorizable lignin catalyzed by ILs was proposed. With the optimized catalyst of [C3H6SO3Hmim]HSO4, corn stalk of 92.45% was transformed into ethyl levulinate with a favorable yield of 24.72% at 200 °C for 90 min. Furthermore, the lignin extraction was substantially influenced by co-solution system. A high lignin yield of 79.94% was achieved with ethanol content of 75% (v/v) in the ethanol-water system. The analysis on morphology, thermal stability and functional group showed that condensation of lignin occurred during the liquefaction process, the two-dimensional heteronuclear single quantum correlation (2D-HSQC) investigation demonstrated that the stable structure of lignin provides a favorable foundation for its valorization. Overall, this work proposed a feasible biorefinery strategy for effective conversion and utilization of lignocellulosic biomass.

Maximizing the utilization of lignocellulosic biomass: Process development and analysis

Herein, an innovative strategy is proposed for the manufacture of biochemicals (dissolving pulp, furfural, high-purity lignin, and acetic acid) from lignocellulosic biomass. Utilizing sulfuric acid as the catalyst and a mixture of water and γ-valerolactone (GVL) as the solvent, the biomass was successfully fractionated into four major components: 1) cellulose, which was converted into dissolving pulp for fiber production; 2) hemicellulose, which was decomposed into furfural, a valuable platform chemical; 3) lignin, which was purified intensively for the production of carbon foams or battery anodes; and 4) acetate, which was converted into acetic acid, a chemical that is potentially useful as a H2 carrier and in H2 production. Separation subsystems were developed to recover the water and GVL mixture effectively for reuse in biomass fractionation and to separate cellulose, hemicellulose, lignin, and acetate for further treatment. To reduce the energy requirements, a heat pump was introduced and heat integration was conducted. The integrated process achieved a positive NPV ($19.9 million), making our process economically viable against initial uncertainties and high risks related to the project. Furthermore, dissolving pulp production was found to be the major environmental contributor accounting for 47.1% of fossil depletion and 36.4% of climate change.

Structure investigation of light-colored lignin extracted by Lewis acid-based deep eutectic solvent from softwood

Lignin is the most abundant natural phenolic polymer. However, the severe condensations of industrial lignin resulted in an undesirable apparent morphology and darker color, which hindered its application in the field of daily chemicals. Therefore, a ternary deep eutectic solvent is used to obtain lignin with light-color and low condensations from softwood. The results showed that the brightness value of lignin extracted from aluminum chloride-1,4-butanediol-choline chloride at 100 °C and 1.0 h was 77.9, and the lignin yield was 32.2 ± 0.6%. It is important that 95.8% of β-O-4 linkages (β-O-4 and β-O-4′) was retained. Lignin is used to prepare sunscreens and is added to physical sunscreens at 5%, with SPF up to 26.95 ± 4.20. Meanwhile, enzyme hydrolysis experiments and reaction liquid composition tests were also conducted. In conclusion, a systematic understanding of this efficient process could facilitate high-value utilization of lignocellulosic biomass in industrial processes.

Self-Hydrogen Supplied Catalytic Fractionation of Raw Biomass into Lignin-Derived Phenolic Monomers and Cellulose-Rich Pulps.

Lignocellulosic biomass is one of the most well-studied and promising green carbon sources. The fullest utilization of lignocellulosic biomass in hydrogen-free and mild conditions to produce phenolic monomers while preserving cellulose-rich pulps is challenging and has far-reaching significance. Here, we report an innovative strategy to convert lignocellulosic biomass into lignin oils and cellulose-rich pulps without exogenous hydrogen under mild conditions over a Pt/NiAl2O4 catalyst. In this process, the structural hydrogens in hemicellulose acted as a hydrogen source to realize the fractionation and depolymerization of lignin into phenolic monomers while keeping the cellulose intact, which is named self-hydrogen supplied catalytic fractionation (SCF). By using water as a solvent, the theoretical yield of phenolic monomers (46.6 wt %, with propyl(ethyl) end-chained syringol and guaiacol as main products) is achieved at 140 °C for 24 h, with 90% cellulose intact in birch sawdust. This H2-free process can be extended to other biomass (hardwood, softwood, and grass) and can be scaled up. The Pt/NiAl2O4 catalyst also shows good stability in recycling as well as regeneration treatment. This work provides a new strategy to achieve high utilization of lignocellulosic biomass for sustainable biorefinery by using water as a solvent without exogenous hydrogen under mild conditions.

Polylactic Acid/Lignin Composites: A Review

With the gradual depletion of petroleum resources and the increasing global awareness of environmental protection, biodegradable plastics are receiving more and more attention as a green substitute for traditional petroleum-based plastics. Poly (lactic acid) is considered to be the most promising biodegradable material because of its excellent biodegradability, biocompatibility, and good processability. However, the brittleness and high cost limit its application in more fields. Lignin, as the second largest renewable biopolymer in nature after cellulose, is not only rich in reserves and low in cost, but it also has an excellent UV barrier, antioxidant activity, and rigidity. The molecular structure of lignin contains a large number of functional groups, which are easy to endow with new functions by chemical modification. Currently, lignin is mostly treated as waste in industry, and the value-added utilization is insufficient. The combination of lignin and poly (lactic acid) can on the one hand solve the problems of the high cost of PLA and less efficient utilization of lignin; on the other hand, the utilization of lignocellulosic biomass in compounding with biodegradable synthetic polymers is expected to afford high-performance wholly green polymer composites. This mini-review summarizes the latest research achievements of poly (lactic acid)/lignin composites. Emphasis was put on the influence of lignin on the mechanical properties of its composite with poly (lactic acid), as well as the compatibility of the two components. Future research on these green composites is also prospected.

Valorization of Boehmeria nivea stalk towards multipurpose fractionation: furfural, pulp, and phenolic monomers

BackgroundAs one of the most abundant bioresource in nature, the value-added utilization of lignocellulosic biomass is limited due to its inherent stubbornness. Pretreatment is a necessary step to break down the recalcitrance of cell walls and achieve an efficient separation of three main components (cellulose, hemicelluloses, and lignin).ResultsIn this study, hemicelluloses and lignin in Boehmeria nivea stalks were selectively extracted with a recyclable acid hydrotrope, an aqueous solution of P-toluenesulfonic acid (p-TsOH). 79.86% of hemicelluloses and 90.24% of lignin were removed under a mild pretreatment condition, C80T80t20, (acid concentration of 80 wt%, pretreatment temperature and time of 80 °C and 20 min, respectively). After ultrasonic treatment for 10 s, the residual cellulose-rich solid was directly converted into pulp. Subsequently, the latter was utilized to produce paper via mixing with softwood pulp. The prepared handsheets with a pulp addition of 15 wt% displayed higher tear strength (8.31 mN m2/g) and tensile strength (8.03 Nm/g) than that of pure softwood pulp. What’s more, the hydrolysates of hemicelluloses and the extracted lignin were transformed to furfural and phenolic monomers with yields of 54.67% and 65.3%, respectively.ConclusionsThe lignocellulosic biomass, Boehmeria nivea stalks, were valorized to pulp, furfural, and phenolic monomers, successfully. And a potential solution of comprehensive utilization of Boehmeria nivea stalks was provided in this paper.Graphical

Modification of lignin composition by ectopic expressing wheat TaF5H1 led to decreased salt tolerance in transgenic Arabidopsis plants

Lignin is an important cell wall component that provides plants with mechanical support and improved tolerance to pathogen attacks. Previous studies have shown that plants rich in S-lignin content or with a higher S/G ratio always exhibit higher efficiency in the utilization of lignocellulosic biomass. Ferulate 5-hydroxylase, or coniferaldehyde 5-hydroxylase (F5H, or CAld5H), is the critical enzyme in syringyl lignin biosynthesis. Some F5Hs have been characterized in several plant species, e.g., Arabidopsis, rice, and poplar. However, information about F5Hs in wheat remains unclear. In this study, a wheat F5H gene, TaF5H1, together with its native promoter (pTaF5H1), was functionally characterized in transgenic Arabidopsis. Gus staining results showed that TaF5H1 could be expressed predominantly in the highly lignified tissues in transgenic Arabidopsis plants carrying pTaF5H1:Gus. qRT-PCR results showed that TaF5H1 was significantly inhibited by NaCl treatment. Ectopic expression of TaF5H1 driven by pTaF5H1 (i.e., pTaF5H1:TaF5H1) could increase the biomass yield, S-lignin content, and S/G ratio in transgenic Arabidopsis plants, which could also restore the traces of S-lignin in fah1-2, the Arabidopsis F5H mutant, to an even higher level than the wild type (WT), suggesting that TaF5H1 is a critical enzyme in S lignin biosynthesis, and pTaF5H1:TaF5H1 module has potential in the manipulation of S-lignin composition without any compromise on the biomass yield. However, expression of pTaF5H1:TaF5H1 also led to decreased salt tolerance compared with the WT. RNA-seq analysis showed that many stress-responsive genes and genes responsible for the biosynthesis of cell walls were differentially expressed between the seedlings harboring pTaF5H1:TaF5H1 and the WT, hinting that manipulation of the cell wall components targeting F5H may also affect the stress adaptability of the modified plants due to the interference to the cell wall integrity. In summary, this study demonstrated that the wheat pTaF5H1: TaF5H1 cassette has the potential to modulate S-lignin composition without any compromise in biomass yield in future engineering practice. Still, its negative effect on stress adaptability to transgenic plants should also be considered.

Preparation and characterization of starch-based composite films reinforced by quinoa (Chenopodium quinoa Willd.) straw cellulose nanocrystals

The development of green and biodegradable nanomaterials is significant for the sustainable utilization of renewable lignocellulosic biomass. This work aimed to obtain the cellulose nanocrystals from quinoa straws (QCNCs) by acid hydrolysis. The optimal extraction conditions were investigated by response surface methodology, and the physicochemical properties of QCNCs were evaluated. The maximum yield of QCNCs (36.58 ± 1.42 %) was obtained under the optimal extraction conditions of 60 % (w/w) sulfuric acid concentration, 50 °C reaction temperature, and 130 min reaction time. The characterization results of QCNCs showed that it is a rod-like material with an average length of 190.29 ± 125.25 nm, an average width of 20.34 ± 4.69 nm, excellent crystallinity (83.47 %), good water dispersibility (Zeta potential = −31.34 mV) and thermal stability (over 200 °C). The addition of 4–6 wt% QCNCs could significantly improve the elongation at break and water resistance of high-amylose corn starch films. This study will pave the route for improving the economic value of quinoa straw, and provide relevant proof of QCNCs for the preliminary application in starch-based composite films with the best performance.

One-pot conversion of glucose to 5-hydroxymethylfurfural under aqueous conditions using acid/base bifunctional mesoporous silica catalyst

One-pot conversion of carbohydrate-derived biomass compounds to 5-hydroxymethylfurfural (HMF) using an environmentally green solvent such as water is meritorious, yet challenging, which requires the strategic design of catalysts. We prepare an ordered bifunctional organocatalyst (MS-AB) containing 3-aminopropylacetic acid grafted within the silica nanocage that converts glucose-to-HMF, exhibiting the highest HMF yield (60 wt.%/85.7 mol%) in water and under microwave conditions. Moreover, the calculated activation energies (150–170 °C) for glucose isomerization to fructose, vis-à-vis dehydration to HMF were 59.06 and 138.05 kJ mol−1, respectively which can even be comparable with the metal-catalyzed reactions. Further evidence was shown from the rate constant values, indicating fructose dehydration is faster (rate constant: k2: 1.92 x 10−2 to 1.13 x 10−1 min−1) than glucose isomerization (rate constant: k1: 2.5 to 5.3 x 10−3 min−1). Considering the advantages associated with MS-AB, the results might showcase the potential of organocatalyst for sustainable utilization of lignocellulosic biomass to platform chemicals.

Co-production of 5-hydroxymethyl furfural and furfural from holocellulose over UiO-66-derived acid-base catalysts

UiO-66-derived H2N-UiO-66-SO3H with acid-base active sites was used for the co-production of 5-hydroxymethyl furfural (5-HMF) and furfural (FUR) in the direct conversion of holocellulose composed of cellulose and hemicellulose. The prepared catalyst was further characterized by various techniques, confirming its formation, structure, and composition. H2N-UiO-66-SO3H displayed excellent performance for the selective conversion of holocellulose to 5-HMF and FUR, achieving yields of 39.1 % and 28.2 %, respectively. The reusability of the catalyst was also investigated by direct use after recycling without any pretreatment. The results indicated that H2N-UiO-66-SO3H had good stability, and after four cycles, the yields of 5-HMF and FUR decreased only slightly to 37.2 % and 27.1 %, respectively. The recyclable catalyst H2N-UiO-66-SO3H for the effective conversion of holocellulose to 5-HMF and FUR demonstrated application potential for the utilization of lignocellulosic biomass.

Reduction of fossil CO2 emissions of engine fuels by integration of stabilized bio-oil distillation residue to a crude-oil refinery hydrocracking process

Utilization of waste lignocellulosic biomass to produce high-quality fuels with renewable carbon content using existing refinery infrastructure is an important step towards carbon neutrality. Direct hydroprocessing of pyrolysis bio-oil to liquid biofuels is technically challenging due to its wide fractional and complex chemical composition that requires harsh reaction conditions associated with extensive biocarbon loss to the gaseous products. We have proposed a novel bio-oil hydroprocessing strategy based on 1) bio-oil hydrotreatment (stabilization), 2) fractionation of the stabilized bio-oil and 3) co-processing of the fractions in appropriate refinery processes. In this work, we focus on the co-processing of the stabilized bio-oil distillation residue (SBDR, b.p. 360+°C) with vacuum gas-oil (VGO) in a hydrocracking fixed bed reactor under conventional conditions. This allowed us to maximize biogenic carbon content (92%) in the liquid transportation fuels as confirmed by the distribution of 14C (obtained by Accelerator Mass Spectrometry) into the corresponding fractions. i.e. gases, naphtha, kerosene, diesel and distillation residue. Reduction of the fossil CO2 emission was 3 times higher for the naphtha fraction compared with E10 gasoline; 2.4 times higher for the diesel fraction compared with B7 diesel (7 vol% FAME). Detailed analysis of the products via GC × GC-TOFMS, 13C NMR, and FTIR together with the standardized methods demonstrated that fuel distillates met requirements for conventional fuels with only negligible effect of the SBDR on physicochemical properties of products and catalyst stability. This shows that the co-hydrocracking of SBDR is a suitable process to maximize liquid fuel production with increased biogenic carbon content.

Effectiveness of ruminal xylanase with an extra proline-rich C-terminus on lignocellulosic biomass degradation

The efficient degradation of plant polysaccharides in agricultural waste requires xylanases with high catalytic activity. In this study, the C-terminal proline-rich GH10 xylanase XynA from sheep rumen was investigated using product analysis, structural characterization, truncated and site-directed mutagenesis, molecular dynamics simulation, and application evaluation, revealing that the proline-rich C-terminus contributes to the interaction at the substrate-binding pocket to reduce the binding free energy. Compared to the C-terminally truncated enzyme XynA-Tr, XynA has a more favorable conformation for proton transfer and affinity attack, facilitating the degradation of oligomeric and beechwood xylan without altering the hydrolysis pattern. Moreover, both the reduced sugar yield and weight loss of the pretreated wheat bran, corn cob, and corn stalk hydrolyzed by XynA for 12 h increased by more than 30 %. These findings are important to better understand the relationship between enzyme activities and their terminal regions and suggest candidate materials for lignocellulosic biomass utilization.

Durable composites by vulcanization of oleyl-esterified lignin.

Productive utilization of lignocellulosic biomass is critical to the continued advancement of human civilization. Whereas the cellulose component can be efficiently upconverted to automotive fuel-grade ethanol, the lack of upconversion methods for the lignin component constitutes one of the grand challenges facing science. Lignin is an attractive feedstock for structural applications, in which its highly-crosslinked architecture can endow composite structures with high strengths. Prior work suggests that high-strength composites can be prepared by the reaction of olefin-modified lignin with sulfur. Those studies were limited to ≤5 wt% lignin, due to phase-separation of hydrophilic lignin from hydrophobic sulfur matrices. Herein we report a protocol to increase lignin hydrophobicity and thus its incorporation into sulfur-rich materials. This improvement is affected by esterifying lignin with oleic acid prior to its reaction with sulfur. This approach allowed preparation of esterified lignin-sulfur (ELS) composites comprising up to 20 wt% lignin. Two reaction temperatures were employed such that the reaction of ELS with sulfur at 180 °C would only produce S-C bonds at olefinic sites, whereas the reaction at 230 °C would produce C-S bonds at both olefin and aryl sites. Mechanistic analyses and microstructural characterization elucidated two ELS composites having compressive strength values (>20 MPa), exceeding the values observed with ordinary Portland cements. Consequently, this new method represents a way to improve lignin utilization to produce durable composites that represent sustainable alternatives to Portland cements.

Lignin-First Biorefinery for Converting Lignocellulosic Biomass into Fuels and Chemicals

Driven by the excessive consumption of fossil resources and environmental pollution concerns, a large amount of biorefinery research efforts have been made for converting lignocellulosic biomass into fuels and chemicals. Recently, a strategy termed “lignin-first,” which allows for realizing high-yield and high-selectivity aromatic monomers, is regarded as one of the best prospective strategies. This review summarizes recent research advances in lignin-first biorefinery, starting from the raw lignocellulose through lignin-first processing and moving to downstream processing pathways for intermediate compounds. In particular, for the core purpose of producing liquid fuels, the corresponding downstream processing strategies are discussed in detail. These are based on the structural properties of the intermediates derived from lignin-first biorefinery, including the catalytic conversion of lignin and its derivatives (aqueous phase system and pyrolysis system) and the cascade utilization of carbohydrate residues (fermentation, pyrolysis, and hydrothermal liquefaction). We conclude with current problems and potential solutions, as well as future perspectives on lignin-first biorefinery, which may provide the basis and reference for the efficient utilization of lignocellulosic biomass.

Rapid and massive fractionation of hemicelluloses for purifying cellulose at room temperature by tetramethylammonium hydroxide

The fractionation of hemicelluloses is a promising method to improve the comprehensive utilization of lignocellulosic biomass. However, the effective fractionation of hemicelluloses is always limited by the structural complexity and easy degradability. In this study, tetramethylammonium hydroxide (TMAH) was developed to fractionate hemicelluloses from poplar holocellulose with high molecular weights and high yields at room temperature. Approximately 90% of hemicelluloses could be dissolved at room temperature in 1 h, and the yield was up to 81.9%. Compared with the fractionation using NaOH solution, the hemicelluloses isolated by TMAH solvent showed a more complete structure and higher purity. Meanwhile, the retention rate of cellulose after treatment with TMAH was up to 90.2%, and the crystal structure of cellulose in the residues was practically unchanged. Moreover, the TMAH solvent could be recycled to fractionate hemicelluloses. The work provides an elegant and significantly efficient method towards hemicelluloses fractionation and cellulose purification.