Lignin Degradation Products Research Articles

Effect of time series on the degradation of lignin by Trametes gibbosa: Products and pathways

Lignin is the third most abundant organic resource in nature. The utilization of white-rot fungi for wood degradation effectively circumvents environmental pollution associated with chemical treatments, facilitating the benign decomposition of lignin. Trametes gibbosa is a typical white-rot fungus with rapid growth and strong wood decomposition ability. The lignin content decreased from 23.62 mg/mL to 17.05 mg/mL, which decreased by 27 % in 30 days. The activity of manganese peroxidase increased steadily by 9.44 times. The activities of laccase and lignin peroxidase had the same trend of change and reached peaks of 49.88 U/L and 10.43 U/L on the 25th day, respectively. The change in H2O2 content in vivo was opposite to its trend. For FTIR and GC–MS analysis, the fungi attacked the side chain structure of lignin phenyl propane polymer and benzene ring to crack into low molecular weight aromatic compounds. The side chains of low molecular weight aromatic compounds are oxidized, and long-chain carboxylic acids are formed. Additionally, the absorption peak in the vibration region of the benzene ring skeleton became complex, and the structure of the benzene rings changed. In the beginning, fungal growth was inhibited. Fungal autophagy was aggravated. The metal cation binding proteins of fungi were active, and the genes related to detoxification metabolism were upregulated. The newly produced compounds are related to xenobiotic metabolism. The degradation peak focused on the redox process, and the biological function was enriched in the regulation of macromolecular metabolism, lignin metabolism, and oxidoreductase activity acting on diphenols and related substances as donors. Notably, genes encoding key degradation enzymes, including lcc3, lcc4, phenol-2-monooxygenase, 3-hydroxybenzoate-6-hydroxylase, oxalate decarboxylase, and acetyl-CoA oxidase were significantly upregulated. On the 30th day, the N-glycan biosynthesis pathway was significantly enriched in glycan biosynthesis and metabolism. Weighted correlation network analysis was performed. A total of 1452 genes were clustered in the coral1 module, which were most related to lignin degradation. The genes were significantly enriched in oxidoreductase activity, peptidase activity, cell response to stimulation, signal transduction, lignin metabolism, and phenylpropane metabolism, while the rest were concentrated in glucose metabolism. In this study, the lignin degradation process and products were revealed by T. gibbosa. The molecular mechanism of lignin degradation in different stages was explored. The selection of an efficient utilization time of lignin will help to increase the degradation rate of lignin. This study provides a theoretical basis for the biofuel and biochemical production of lignin. SynopsisTrametes gibbosa degrades lignin in a pollution-free way, improving the utilization of carbon resources in an environmentally friendly spontaneous cycle. The products are the new way towards sustainable development and low-carbon technology.

Sucrose-derived porous carbon catalyzed lignin depolymerization to obtain a product with application in type 2 diabetes mellitus

As the most important phenolic biopolymer in nature, lignin shows promising application potentialities in various bioactivities in vivo and in vitro, mainly including antioxidant, anti-inflammatory, hypolipidemic, and antidiabetic control. In this work, several carbon-based solid acids were synthesized to catalyze the fragmentation of organosolv lignin (OL). The generated lignin fragments, with controllable molecular weight and functional groups, were further evaluated for their application in the prevention and treatment of type 2 diabetes mellitus (T2DM). The results suggested that the urea-doped catalyst (SUPC) showed a more excellent catalytic performance in producing diethyl ether insoluble lignin (DEIL) and diethyl ether soluble lignin (DESL). In addition, the lignin fragments have a good therapeutic effect on the cell model of T2DM. Compared with the insulin resistance model, DEIL obtained by catalytic depolymerization of OL with SUPC could improve the glucose consumption of insulin-resistant cells. Moreover, low-concentration samples (50 μg/mL) can promote glucose consumption (19.7 mM) more than the traditional drug rosiglitazone (17.5 mM). This work demonstrates the prospect of depolymerized lignin for the prevention and treatment of T2DM and provides a new application field for lignin degradation products.

Uncovering the lignin-degrading potential of Serratia quinivorans AORB19: insights from genomic analyses and alkaline lignin degradation

BackgroundLignin is an intricate phenolic polymer found in plant cell walls that has tremendous potential for being converted into value-added products with the possibility of significantly increasing the economics of bio-refineries. Although lignin in nature is bio-degradable, its biocatalytic conversion is challenging due to its stable complex structure and recalcitrance. In this context, an understanding of strain's genomics, enzymes, and degradation pathways can provide a solution for breaking down lignin to unlock the full potential of lignin as a dominant valuable bioresource. A gammaproteobacterial strain AORB19 has been isolated previously from decomposed wood based on its high laccase production. This work then focused on the detailed genomic and functional characterization of this strain based on whole genome sequencing, the identification of lignin degradation products, and the strain’s laccase production capabilities on various agro-industrial residues.ResultsLignin degrading bacterial strain AORB19 was identified as Serratia quinivorans based on whole genome sequencing and core genome phylogeny. The strain comprised a total of 123 annotated CAZyme genes, including ten cellulases, four hemicellulases, five predicted carbohydrate esterase genes, and eight lignin-degrading enzyme genes. Strain AORB19 was also found to possess genes associated with metabolic pathways such as the β-ketoadipate, gentisate, anthranilate, homogentisic, and phenylacetate CoA pathways. LC–UV analysis demonstrated the presence of p-hydroxybenzaldehyde and vanillin in the culture media which constitutes potent biosignatures indicating the strain’s capability to degrade lignin. Finally, the study evaluated the laccase production of Serratia AORB19 grown with various industrial raw materials, with the highest activity detected on flax seed meal (257.71 U/L), followed by pea hull (230.11 U/L), canola meal (209.56 U/L), okara (187.67 U/L), and barley malt sprouts (169.27 U/L).ConclusionsThe whole genome analysis of Serratia quinivorans AORB19, elucidated a repertoire of genes, pathways and enzymes vital for lignin degradation that widens the understanding of ligninolytic metabolism among bacterial lignin degraders. The LC-UV analysis of the lignin degradation products coupled with the ability of S. quinivorans AORB19 to produce laccase on diverse agro-industrial residues underscores its versatility and its potential to contribute to the economic viability of bio-refineries.

Synthetic urushiols from biorenewable carbon resources: chemical conversion of enzymatic degradation products of wood lignin to an ancient yet future coating material

An artificial urushi coating material was developed by chemical conversion of bio-renewable carbon resources, such as phenylpropanoids obtained from enzymatic degradation of woody lignin and vegetable fat.

Degradation of the lignin in roasted sesame seed hull improves the oxidation stability of sesame oil

Sesame seed hulls are rich in lignin. Sesame oil extracted from roasted sesame seeds has a high oxidation stability. To investigate the influence of roasting on lignin and the oxidation stability of sesame oil, the degradation products (L190, L220, and L250) and solid residues were obtained from sesame seed hull lignin heated at three temperatures (190 °C, 220 °C, and 250 °C). The results showed that roasting caused partial degradation of lignin. The degree of lignin degradation became more severe with increasing roasting temperature. This degradation leads to the production of low-molecular-weight phenolic compounds, such as vanillin and 1-(4-hydroxy-3-methoxyphenyl)butan-1-one. As the roasting temperature increased, the kinds and amounts of phenolic compounds produced increased. These compounds were high in antioxidants, the increasing of roasting temperature correlated significantly with the decrease in peroxide value (rPOV = −0.977, p < 0.05) and p-anisidine value (rp-AnV = −0.988, p < 0.05) of sesame oils with added products of lignin degradation. The products of lignin degradation inhibited sesame oil oxidation, with L250 showing the strongest ability to improve the oxidative stability of sesame oil, similar to sesamol. This study demonstrated that the thermal degradation of lignin during roasting of sesame seed hulls enhanced the oxidative stability of sesame oil.

Strategies towards a green solvent biorefinery: Efficient delignification of lignocellulosic biomass residues by gamma-valerolactone/water catalyzed system

Biorefineries promote the integral use of lignocellulosic biomass by separating lignin, cellulose, and hemicelluloses, so environmentally friendly solvents with good efficiency in lignin removal at mild conditions (low temperatures and pressures) are under thorough research. This study evaluates the optimization of γ-Valerolactone (GVL) systems using a solvent complying with the principles of green chemistry as an efficient delignification strategy for lignocellulosic biomass residues such as sugarcane bagasse and pine sawdust. First, depithed sugarcane bagasse was delignified by a solvent system composed of GVL/water and a low concentration of sulfuric acid (SA), considering temperature, reaction time, GVL, and SA concentration in the liquor as variables, organized following a 4-factor Draper-Lin Central Composite Design (CCD). Milder treatments compared with literature were applied, with extreme points at 130–180 °C, 40–140 min, 43–77 wt% GVL, and 0–0.01 M SA, respectively. The experimental conditions involving pine sawdust were assessed at the highest delignification point of sugarcane bagasse. Delignification from 75% to 96% was obtained for sugarcane bagasse. In the same conditions, pine sawdust delignification was slightly lower. The solid fraction characterization involved yield, ISO brightness, crystallinity index, intrinsic viscosity in cupriethylenediamine, structural carbohydrates, and lignin content, whereas sugars, byproducts, and degradation products were analyzed in the liquid fraction. The study compares different properties combined into one single combined severity factor. The evaluation also involved optical properties relevant to some uses, such as dissolving pulps or nanocellulose.

Chlorinated organic compounds in concrete as specific markers for chlorine gas exposure

The formation of chlorinated organic compounds in concrete debris exposed to reactive chlorine was studied to search for markers specific to chlorine gas exposure. Concrete materials of different origins were exposed to a range of species of reactive chlorine including bleach, humid and dry chlorine gas at different concentrations. Chlorinated organic compounds in concrete extracts were analysed by targeted gas and liquid chromatography-tandem mass spectrometry (GC-MS/MS and LC-MS/MS) and by non-targeted screening using the corresponding high-resolution techniques (GC-HRMS and LC-HRMS). Overall, different levels and species of chlorinated organic compounds namely chlorophenols, chlorobenzenes, chloromethoxyphenols, chloromethylbenzenes and chloral hydrate were identified in these chlorinated concrete extracts; two examples of diagnostic markers for neat chlorine exposure were trichloromethylbenzene and tetrachlorophenol. The old concrete samples from the 1930s and 1950s had the most chlorinated organic compounds after exposure to neat chlorine gas. Lignin or lignin degradation products were identified as probable candidates for phenolic precursor molecules in the concrete samples. Multivariate data analysis (OPLS-DA) shows distinct patterns for bleach and chlorine exposure. The chlorinated chemicals and specific markers for chlorine gas discovered in our research assist other laboratories in forensic investigations of chlorine gas attacks.

CELLULOLYTIC MICROORGANISMS: AEROBIC, MICROAEROPHILIC, ANAEROBIC BACTERIA AND MICROBIAL CONSORTIA (Part II)

In nature, cellulose, lignocellulose and lignin are major sources of plant biomass therefore their recycling is indispensable for the carbon cycle. The synergistic action of a variety of microorganisms is needed for recycling lignocellulosic materials. The capacities of microorganisms to assimilate complex carbohydrates, such as cellulose, hemicellulose and lignin, depend on the ability to produce the enzymes that work synergically. Populations growing in compost piles consist mainly of bacteria (including actinobacteria) and fungi. Polymers such as hemicellulose, cellulose, and lignin are only degraded once the more easily degradable compounds have been consumed. Afterwards, the lignocellulosic materials are partly transformed into humus. In the present review, numerous studies on the isolation of cellulose-degrading bacteria and fungi, their identification, enzymatic activities, and their ability to grow in the presence of lignocellulose and components of these industrial waste streams (phenolic compounds, sulfides, and dyes are analyzed and discussed. This is of particular interest to design future studies to isolate those bacteria that can specifically degrade cellulose matrix and more recalcitrant components such as lignin and aromatic lignin degradation products. Cultivation and characterization of microorganisms alone is not adequate without preservation techniques that do not alter the morphology, physiology or genetics of pure strains. Careful preservation is imperative for future research, teaching and industrial applications.

Large scale production of vanillin using an eugenol oxidase from Nocardioides sp. YR527

Bacterial eugenol oxidases (EUGOs) entered recently the scientific spotlight as these versatile biocatalysts were reported to transform lignin degradation products into valuable platform chemicals. Here we describe the second member of the enzyme family, EUGO from Nocardioides sp. YR527 (NspEUGO) and investigated its biocatalytic potential in direct comparison with EUGO from Rhodococcus jostii RHA1. NspEUGO was found to be most active on vanillyl alcohol derivatives (up to 5.6 ± 0.3 s−1) while for eugenol the highest affinity was observed (KM: 33.1 ± 4.1 µM). For the catalyzed reactions, a high ambiguity was observed in dependency of the pH: The highest kcat of 16.0 ± 0.3 s−1 was found at pH 9.5 while the best long-term performance was detected at pH 6.0 (∼300,000 TTN). To stabilize the enzyme, immobilization on a total of 14 carrier materials was conducted and the performance was investigated in two reactor types for large scale application. This resulted in the successful production of vanillin at 1 g L−1 h−1 in a packed bed reactor.

Effect of solvent systems on the synergistic catalytic hydrogenolysis of alkaline lignin over Pd/C-NaOH

Solvents and catalysts are two of the most critical factors for the depolymerization of lignin. This paper investigated the effect of different pure solvents on the hydrogenolysis of the β-O-4 MC and one of the mixed solvents on the hydrogenolysis of alkaline lignin. It was found that MC had higher conversion (96.5% and 94.3%) and monophenol yield (83.4 wt% and 77.9 wt%) in ethanol and 1,4-dioxane. The effects of different ratios of mixed solvents (ethanol-H2O and 1,4-dioxane-H2O), reaction conditions (temperature, time, pressure), and the synergistic effect of alkali and Pd/C catalysts on the hydrogenolysis of alkaline lignin were investigated in this paper. The composition, structure, and distribution of the lignin degradation products were also analyzed by GC, GC–MS, GPC, FT-IR, and 2D-HSQC. The results showed that the optimum monomer yields were 37.5 wt% and 24.7 wt% for ethanol-H2O and 1,4-dioxane-H2O at 3:2 (v:v) and 2:3 (v:v), respectively. The optimum yields were obtained at 260 °C, 2 MPa H2, and 4 h. The properties of solvent (protic polar solvent, nonpolar aprotic solvent) could influence the hydrogenolysis greatly and selectively break bonds. The different ratios of solvents in the mixed solvent systems influenced the solubility of alkaline lignin and its hydrogenolysis results. In addition, the synergistic effect of Pd/C and NaOH could improve the monomer yield and inhibit the polymerization of intermediates in hydrogenolysis.

Biological decay by microorganisms in stems from the Upper Triassic Ischigualasto Formation (San Juan Province, Argentina): A striking microbial diversity in Carnian-Norian terrestrial ecosystems

We studied degradation patterns and microorganisms preserved in permineralized stems of Rhexoxylon piatnitzky, Protojuniperoxylon ischigualastense, and Agathoxylon argentinum from the Valle de la Luna Member of the Ischigualasto Formation (Upper Triassic, San Juan, Argentina). All three species show loss of middle lamella, thinning, and whitening of tracheid cell walls, and detachment of the S3 layer, consistent with selective delignification by white rot. This type of rot is the product of lignin and cellulosic degradation by Basidiomycetes and Ascomycetes. Rhexoxylon piatnitzkyi also shows small cavities, more or less circular in outline, on the wall of tracheids. This is known as soft rot and can be produced by some Ascomycetes, the anamorphic phases of diverse fungi, and tunneling bacteria. Additionally, abundant and diverse microorganisms were found. Rhexoxylon piatnitzkyi shows fragments of septate hyphae, evidence of bacterial activity, and structures of unknown affinity. Protojuniperoxylon ischigualastense presents structures common to anamorphic phases of diverse fungi, such as chlamydospores and conidiophores. Lastly, Agathoxylon argentinum bears coiled and septate hyphae, and a fan-shaped mycelium, whose significance is discussed. The microbiological study was complemented by the assessment of sedimentary and taphonomic data of the fossil-bearing beds. A gradual increment in humidity for the Valle de la Luna Member is interpreted, which concludes with a humidity peak in its upper section. This contribution represents the first detailed study of xylophagous and saprophyte micro-communities for the Ischigualasto Formation. The abundance and diversity of microorganisms described illustrate the complexity of wood-inhabiting micro-communities from the Carnian-Norian interval of Argentina.

Effect of Microbial Consortium Constructed with Lignolytic Ascomycetes Fungi on Degradation of Rice Stubble

Microbial degradation is an effective, eco-friendly and sustainable approach for management of the rice residue. After harvesting a rice crop, removal of stubble from the ground is a challenging task, that forces the farmers to burn the residue in-situ. Therefore, accelerated degradation using an eco-friendly alternative is a necessity. White rot fungi are the most explored group of microbes for accelerated degradation of lignin but they are very slow in growth. The present investigation focuses on degradation of rice stubble using a fungal consortium constructed with highly sporulating ascomycetes fungi, namely, Aspergillus terreus, Aspergillus fumigatus and Alternaria spp. All three species were successful at colonizing the rice stubble. Periodical HPLC analysis of rice stubble alkali extracts revealed that incubation with ligninolytic consortium released various lignin degradation products such as vanillin, vanillic acid, coniferyl alcohol, syringic acid and ferulic acid. The efficiency of the consortium was further studied at different dosages on paddy straw. Maximum lignin degradation was observed when the consortium was applied at 15% volume by weight of rice stubble. Maximum activity of different lignolytic enzymes such as lignin peroxidase, laccase and total phenols was also found with the same treatment. FTIR analysis also supported the observed results. Hence, the presently developed consortium for degrading rice stubble was found to be effective in both laboratory and field conditions. The developed consortium or its oxidative enzymes can be used alone or combined with other commercial cellulolytic consortia to manage the accumulating rice stubble effectively.

Preparation of Symmetrical Capacitors from Lignin-Derived Phenol and PANI Composites with Good Electrical Conductivity.

As a natural polymer, lignin is only less abundant in nature than cellulose. It has the form of an aromatic macromolecule, with benzene propane monomers connected by molecular bonds such as C-C and C-O-C. One method to accomplish high-value lignin conversion is degradation. The use of deep eutectic solvents (DESs) to degrade lignin is a simple, efficient and environmentally friendly degradation method. After degradation, the lignin is broken due to β-O-4 to produce phenolic aromatic monomers. In this work, lignin degradation products were evaluated as additives for the preparation of polyaniline conductive polymers, which not only avoids solvent waste but also achieves a high-value use of lignin. The morphological and structural characteristics of the LDP/PANI composites were investigated using 1H NMR, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and elemental analysis. The LDP/PANI nanocomposite provides a specific capacitance of 416.6 F/g at 1 A/g and can be used as a lignin-based supercapacitor with good conductivity. Assembled as a symmetrical supercapacitor device, it provides an energy density of 57.86 Wh/kg, an excellent power density of 952.43 W/kg and, better still, a sustained cycling stability. Thus, the combination of polyaniline and lignin degradate, which is environmentally friendly, amplifies the capacitive function on the basis of polyaniline.

Reaction kinetics, pyrolytic behavior and product characterization of dewatered solids from spent fermentation coir wastes using a fixed batch reactor

Solid residues after pretreatment and hydrolysis of coir pith and Bit fiber waste was dewatered, dried and pyrolyzed at 300, 350, and 400 °C using a fixed bed batch pyrolyzer. The products were characterized using ultimate analysis, FTIR and GCMS. Bit fiber yielded more bio-oil (26.3 %), rich in 4-Methoxy phenol (60.94 %) and a Higher Heating Value of 27.06 MJ kg−1. Coir pith bio-oil with Higher Heating Value of 27.16 MJ kg−1, was rich in 2-Methoxy Phenol, which are principal lignin degradation products. Non condensable gases included mixture of methane, carbon dioxide and isomers of butene. Activation energy for thermal decomposition was studied using Coats and Redfern model from thermogravimetric data at heating rates of 10 and 15 k min−1, which showed two major phases of decomposition. Activation energy was higher for devolatilization phase of bit fiber waste (132 kJ/ mol) owing to higher percentage of lignin than in coir pith waste (Ea = 114 kJ/ mol).

Investigation of pitch deposits throughout the fiber line of softwood pulp mill

The formation of detrimental pitch deposits can cause various problems at pulp and paper mills, as they can contribute to unscheduled shutdowns and even paralyze the operation of the entire mills. To understand, avoid and control of pitch deposits formation in pulp mills, we investigated the overall chemical composition of 16 pitch deposit samples collected from the fiber line of a softwood kraft pulp mill. Sodium salts were tentatively speculated as the dominant fractions of the pitch deposits in addition to the minor fractions of the extractives and carbohydrates. Low molar mass extractives from dichloromethane, acetone and water extracts were analysed by gas chromatography–mass spectrometry. The extractable fraction is chemically heterogeneous, representing the degradation products of carbohydrates, lignin, and woody extractives. Furthermore, new chlorinated stilbenes (monochloropinosylvin, dichloropinosylvin, trichloropinosylvin dimethyl ether, and dichlorinated pinosylvin monomethyl ether) and other chlorinated components (chloro-manoyl/epimanoyl oxide, 12- and 14-chlorodehydroabietic acids) were for the first time identified as part of pitch deposits in the fiber line. Moreover, significant amount of 3-hydroxy fatty acids was found from the drying stage, also representing novel pulp mill deposit compounds. Pinostilbene and pterostilbene are rarely identified from the industrial woody chips of Scotch pine. Overall, the investigation of extractive profile from pitch deposits may provide us with a new perspective to understand the formation mechanism of pitch deposits and study the binding behavior between the extractive and surfaces of the process equipment. The new findings may provide guidance for the pulp mills to design optimal strategies to avoid and control pitch deposits.

Bioconversion of ferulic acid and vanillin to vanillic acid by cold-adapted Paraburkholderia aromaticivorans AR20-38: impact of culture conditions

PurposeBiovalorization of lignin-derived aromatic monomers such as ferulic acid (FA) has attracted considerable interest. The cold-adapted strain Paraburkholderia aromaticivorans AR20-38 converts FA to the value-added product vanillic acid (VA), without further VA degradation. The efficiency of the bioconversion of FA to VA was optimized by studying culture conditions.MethodsVarious cultivation parameters (agitation, temperature, FA concentration, nutrient supplementation) were assessed to increase biomass production and shorten the cultivation time, while obtaining high VA production yields. The fate of the intermediate vanillin was also studied. Lignin monomers and degradation products (FA, vanillin, VA) were quantified via UV/Vis-HPLC.ResultFull bioconversion of 5 mM FA occurred over a broad temperature range of 5–30 °C. Concentrations up 30 mM FA were utilized as the sole carbon source at 20 °C. Molar VA yields (> 90%) produced from 5 to 12.5 mM FA and from 15 to 17.5 mM FA (82–87%) were not significantly different at 10 °C and 20 °C. The supplementation of the mineral medium with monosaccharides (glucose, fructose, mannose) and/or N-rich complex compounds (yeast extract, casamino acids) resulted in high biomass production, accelerated FA bioconversion, and high molar yields (96–100%). The presence of the N-rich compounds alone or in combination with glucose reduced the incubation time necessary to convert FA to VA. Vanillin, formed as an intermediate during FA degradation, was consumed and converted to VA before FA metabolization, when added in combination with FA. Vanillin bioconversion was significantly accelerated in the presence of glucose.ConclusionThe variation of culture conditions improved the efficiency of the studied strain to convert FA via vanillin to VA and demonstrated remarkable FA bioconversion under varying environmental conditions, especially temperature, substrate concentration, and nutrient availability, which is of importance for potential future application.

Lignin Valorization: Production of High Value-Added Compounds by Engineered Microorganisms

Lignin is the second most abundant polymer in nature, which is also widely generated during biomass fractionation in lignocellulose biorefineries. At present, most of technical lignin is simply burnt for energy supply although it represents the richest natural source of aromatics, and thus it is a promising feedstock for generation of value-added compounds. Lignin is heterogeneous in composition and recalcitrant to degradation, with this substantially hampering its use. Notably, microbes have evolved particular enzymes and specialized metabolic pathways to degrade this polymer and metabolize its various aromatic components. In recent years, novel pathways have been designed allowing to establish engineered microbial cell factories able to efficiently funnel the lignin degradation products into few metabolic intermediates, representing suitable starting points for the synthesis of a variety of valuable molecules. This review focuses on recent success cases (at the laboratory/pilot scale) based on systems metabolic engineering studies aimed at generating value-added and specialty chemicals, with much emphasis on the production of cis,cis-muconic acid, a building block of recognized industrial value for the synthesis of plastic materials. The upgrade of this global waste stream promises a sustainable product portfolio, which will become an industrial reality when economic issues related to process scale up will be tackled.

Synthesis, Curing and Thermal Behavior of Amine Hardeners from Potentially Renewable Sources.

Research into bio-based epoxy resins has intensified in recent decades. Here, it is of great importance to use raw materials whose use does not compete with food production. In addition, the performance of the newly developed materials should be comparable to that of conventional products. Possible starting materials are lignin degradation products, such as vanillin and syringaldehyde, for which new synthesis routes to the desired products must be found and their properties determined. In this article, the first synthesis of two amine hardeners, starting with vanillin and syringaldehyde, using the Smiles rearrangement reaction is reported. The amine hardeners were mixed with bisphenol A diglycidyl ether, and the curing was compared to isophorone diamine, 4-4'-diaminodiphenyl sulfone, and 4-Aminonbenzylamine by means of differential scanning calorimetry. It was found that the two amines prepared are cold-curing. As TG-MS studies showed, the thermal stability of at least one of the polymers prepared with the potentially bio-based amines is comparable to that of the polymer prepared with isophorone diamine, and similar degradation products are formed during pyrolysis.

Characterization of the degradation products of lignocellulosic biomass by using tandem mass spectrometry experiments, model compounds, and quantum chemical calculations.

Biomass-derived degraded lignin and cellulose serve as possible alternatives to fossil fuels for energy and chemical resources. Fast pyrolysis of lignocellulosic biomass generates bio-oil that needs further refinement. However, as pyrolysis causes massive degradation to lignin and cellulose, this process produces very complex mixtures. The same applies to degradation methods other than fast pyrolysis. The ability to identify the degradation products of lignocellulosic biomass is of great importance to be able to optimize methodologies for the conversion of these mixtures to transportation fuels and valuable chemicals. Studies utilizing tandem mass spectrometry have provided invaluable, molecular-level information regarding the identities of compounds in degraded biomass. This review focuses on the molecular-level characterization of fast pyrolysis and other degradation products of lignin and cellulose via tandem mass spectrometry based on collision-activated dissociation (CAD). Many studies discussed here used model compounds to better understand both the ionization chemistry of the degradation products of lignin and cellulose and their ions' CAD reactions in mass spectrometers to develop methods for the structural characterization of the degradation products of lignocellulosic biomass. Further, model compound studies were also carried out to delineate the mechanisms of the fast pyrolysis reactions of lignocellulosic biomass. The above knowledge was used to assign likely structures to many degradation products of lignocellulosic biomass.

Achieving efficient pretreatment of corn straw at elevated temperatures via constraining cellulose degradation

Greatly reducing the cellulose crystallinity and lignin content of lignocellulose can substantially improve the enzymatic hydrolysis efficiency, dramatically reducing the enzyme dosage; however, it is difficult to be simultaneously achieved. A solution was put forward - biomass pretreatment was carried out with the binary system consisted of 1-n-butyl-3-methylimidazole chloride (BMIMCl) and arginine (Arg) at temperatures higher than the glass transition temperature of lignin (Tg-lignin). The cellulose crystallinity decreased because of hydrogen bonding with BMIMCl. Delignification was promoted via raising the temperature higher than the Tg-lignin, while cellulose degradation was constrained by Arg. The delignification rate reached 90.36 %. The yield of cellulose remained at a level of 88.89 %, while the Crystallinity Index (CI) of cellulose decreased from 36.13 % (raw corn straw) to 13.50 % (regenerated material, RM). It was found that the average molecular weight (Mw) of lignin decreased from 1632 g/mol to 584 g/mol after pretreatment, indicating the lignin was depolymerized; the 2D-HSQC result showed the β-O-4′ bond of lignin was broken. Because the cellulose crystallinity and the lignin content of the regenerated material were reduced greatly at the same time, the RM was easily hydrolyzed by cellulase. The enzymatic hydrolysis glucose yield of the RM was 3.75 times that of raw corn straw when the enzyme dosage was only 0.41 FPU/g sample, reaching 99.5 %. The IL was successfully recycled four times, and the recovery rate was higher than 93 % each time. RM obtained in four cycles maintained high lignin removal rate and enzymatic hydrolysis glucose yield. The degradation products of hemicellulose and lignin were the main impurities in the recovered IL. This work may provide a new solution for green and efficient biomass pretreatment.