Phenolic Lignin Research Articles

Trends in Sustainable Green Synthesis of Silver Nanoparticles Using Agri‐Food Waste Extracts and Their Applications in Health

Currently, silver nanoparticles have boomed in food and medicine due to their potential applications, such as antibacterial and anticancer activity. These nanoparticles have been synthesized by several techniques; however, green synthesis has taken on greater importance due to the non‐generation of toxic residues. Green synthesis has been constructed from plant parts; however, the new trend comprises the use of agri‐food waste extracts, known as sustainable green synthesis. The use of agri‐food waste reduces environmental pollution and confers on its added value. The main waste generated is found in agricultural crops and industry from fruits and vegetables, cereal, bagasse from the food industry, and alcoholic beverages, oil cake of the oil industry, among others. The main biomolecules in agri‐food waste extracts include phenolic compounds, alkaloids, terpenes, cellulose, hemicellulose, lignin, and proteins, whose function is to reduce the agents of the silver ion. Therefore, the objective of this review was to promote the use of agri‐food waste for the sustainable green synthesis of silver nanoparticles and its application as antibacterial and anticancer agents.

BIOLOGICAL ACTIVITY OF RICE STRAW-DERIVED MATERIALS: AN OVERVIEW

RS (RS) waste has been the most widely recognised pollutant in the world for several years. Therefore, it is critical to develop a simple process for converting rice straw (RS) into a useful products. RS is a rich source of phenolic acids (PAs), lignin, condensed tannins, flavonoids, and momilactone that can be extracted using conventional and environmentally friendly methods. These bioactive components of RS have various biological activities such as antibacterial, antifungal, pesticide, antioxidant, etc. Recently, RS-derived fluorescent nitrogen-doped carbon dots (NCDs) were developed for the detection and monitoring of diabetic ketoacidosis in diabetic patients. Herein, various straightforward and non-polluting method for reprocessing RS into value-added materials are discussed.

Structural characterization using 2D NMR spectroscopy and TMAH-GC × GC-MS: Application to humic acids from soils of an integrated agricultural system and an Atlantic native forest

Understanding the chemical make-up of soils and their structure is critical for constraining the role of soil organic matter (SOM) into the global biogeochemical cycles, as well as to understand the capability of SOM to sequester carbon and mitigate greenhouse gas emissions. Here, we use two-dimensional 1H-13C heteronuclear single quantum coherence nuclear magnetic resonance (2D 1H-13C HSQC NMR) spectroscopy to structurally characterize the most refractory component of SOM, the humic acid (HA). The observations from 2D 1H-13C HSQC NMR were coupled with lignin phenol and fatty acid measurements using tetramethylammonium hydroxide (TMAH) thermochemolysis – two-dimensional gas chromatography – mass spectrometry (TMAH-GC × GC-MS). We studied humic acids extracted from an integrated Crop – Livestock – Forest System (CLFS) agricultural area and an undisturbed Atlantic Native Forest (NF) area. We evaluated soils from two different depths: the topsoil (0–20 cm) and subsoil (60–100 cm) layers, and reveal the presence of oxidized ligninaceous phenols as we had previously hypothesized. Collectively, our results indicate that there are significant oxidative processes with increasing soil depth which are more pronounced in the CLFS relative to the NF area. Degradation of stearic acid with increasing depth in the CLFS soils indicated that the CLFS is more microbiologically active than NF. Therefore, CLFS is less biochemically stable than we originally perceived. The enhanced bio-reactivity of CLFS is likely driving the enhanced carbon sequestration in the CLFS soils. This is perhaps due to the diversity of biomass remnants available at the CLFS soil rhizosphere which allows for more different types of biomass to be sequestered as oxidized ligninaceous phenols. Our results employing structural characterization with 2D 1H-13C HSQC NMR and TMAH-GC × GC-MS provide a new layer of knowledge about the practice of integrated agricultural systems and allow us to understand the structure and fate of sequestered carbon in soils from different soil environments.

Plant secondary cell wall proteome analysis with an inducible system for xylem vessel cell differentiation.

Plant cell walls are typically composed of polysaccharide polymers and cell wall proteins (CWPs). CWPs account for approximately 10% of the plant cell wall structure and perform a wide range of functions. Previous studies have identified approximately 1000 CWPs in the model plant Arabidopsis thaliana; however, the analyses mainly targeted primary cell walls, which are generated at cell division. In contrast, little is known about CWPs in secondary cell walls (SCWs), which are rigid and contain the phenolic polymer lignin. Here, we performed a cell wall proteome analysis to obtain novel insights into CWPs in SCWs. To this end, we tested multiple methods for cell wall extraction with cultured Arabidopsis cells carrying the VND7-VP16-GR system, with which cells can be transdifferentiated into xylem-vessel-like cells with lignified SCWs by dexamethasone treatment. We then subjected the protein samples to in-gel trypsin digestion followed by LC-MS/MS analysis. The different extraction methods resulted in the detection of different cell wall fraction proteins (CWFPs). In particular, centrifugation conditions had a strong impact on the extracted CWFP species, resulting in the increased number of identified CWFPs. We successfully identified 896 proteins as CWFPs in total, including proteases, expansins, purple phosphatase, well-known lignin-related enzymes (laccase and peroxidase), and 683 of 896 proteins were newly identified CWFPs. These results demonstrate the usefulness of our CWP analysis method. Further analyses of SCW-related CWPs could be expected to produce information useful for understanding the roles of CWPs in plant cell functions.

Organic matter processing through an estuarine system: Evidence from stable isotopes (δ13C and δ15N) and molecular (lignin phenols) signatures

This study unraveled the origin, fate and accumulation of organic matter (OM) of surface sediments, spread between the fresh and marine end members of Guaratuba Bay (SE- Brazil). Sedimentation rates were obtained through the 210Pb sediment dating method, biogenic element accumulation (C-organic carbon, N-nitrogen, P-phosphorus, and lignin phenols) and stable isotopes of organic carbon (δ13C) and nitrogen (δ15N) were measured along the well-defined salinity gradient (0–35). The higher C:N ratios and lower δ13C values signatures indicate major terrestrial contribution in regions dominated by fluvial inputs, while the contributions from autochthonous primary production and mangrove forests were greater in the middle and outer estuarine sectors. A stable isotope mixing model showed that the material contribution from rivers and mangroves in surface sediments ranged from 80 to 90% in the upstream sector, 50–70% in the central sector and 25–50% at the outer region, whereas this contribution decreased to 15–20% in the adjacent ocean. Ratios between phenolic groups indicated material deposited from predominantly woody angiosperms. Vertical CNP deposition, accumulation rates and lignin phenol concentrations along the sedimentary profiles indicated three phases: Phase I, the more recently deposited sediments, which contained the highest CNP sedimentary fluxes; Phase II, dated to be from 1960s to 1990s, was characterized by changes related with increasing deforestation associated to fires; Phase III from the 1920s–1960s, exhibited four-fold lower C, N and P concentrations compared the more recent rates. Along the estuarine gradient, the C accumulation was found to be related to specific sources as indicated by the lignin's, stable isotopes as well as C:N ratios. Furthermore, the vertical accumulation of OM in sediments concomitantly with geochronology showed the recent anthropogenic perturbations in the estuary. This study highlights the land-ocean sedimentary continuum of which are poorly studied with respect to the transport of C, N and P in estuarine systems, reinforcing the presence of a marked land-ocean gradient. Knowledge of isotopic fractions, as well as lignin phenols, for different areas along the estuarine gradient is important as sampling along coastal areas can represent a bias in understanding the transport and cycling of OM to the sea if gradients and specific regions are not taken into account.

A well-defined diamine from lignin depolymerization mixtures for constructing bio-based polybenzoxazines

The demand for high-performance materials is increasing, and most of these materials are petrol based. Therefore, the development of highly efficient and selective catalytic methods that allow access to industrially relevant polymer building blocks from complex biomass depolymerization mixtures is essential. Here, we report on a robust catalytic strategy to obtain the industrially relevant 4,4′-methylenebiscyclohexanamine (MBCA) from lignin oxidation mixtures and its use for constructing fully bio-based polybenzoxazines. The strategy consists of two challenging catalytic steps: 1) the funneling of lignin-derived bisphenol mixtures into 4,4′-methylenebiscyclohexanol (MBC) and 2) the highly selective amination of MBC with ammonia to obtain MBCA. The renewable polybenzoxazines were prepared from MBCA and phenolic lignin platform chemicals. The most promising, cured poly (S-MBCA), shows high glass transition temperature Tg of 315°C, outstanding thermal stability (T10% = 400°C), and good storage modulus (E′25°C = 3.8 GPa), which is competitive with commercial resins.

Valorization of lignins from energy crops and agro-industrial byproducts as antioxidant and antibacterial materials.

Developing eco-friendly antioxidant and antimicrobial substances originating from biomass residues has recently attracted considerable interest. In this study, two lignosulfonates and various oxidized water-soluble lignins were investigated for their antioxidant properties, as assessed by ABTS, DPPH and Folin-Ciocalteu methods, and their antimicrobial activity against some bacterial strains responsible for human pathologies. The lignosulfonates showed the largest antiradical/antimicrobial capacity, whereas the other substrates were less effective. The observed antioxidant/antibacterial properties were positively correlated with lignin aromatic/phenolic content. The positive correlation between antiradical and antimicrobial activities suggests that lignin scavenging capacity was also involved in its antibacterial activity. A greater antimicrobial performance was generally observed against Gram-positive bacterial strains, and it was attributed to the intrinsic larger susceptibility of Gram-positive bacteria to lignin phenols. A significant though lesser inhibitory activity was also found against Escherichia coli. Our results confirmed the dependence of lignin antioxidant/antibacterial power on its extraction method and chemical structure, as well as on the type of bacterial strains. Identifying the relationship between lignin molecular composition and its antioxidant/antibacterial features represents an advance on the potential future use of renewable and eco-compatible lignin materials in nutraceutical, pharmaceutical and cosmetic sectors. © 2021 Society of Chemical Industry.

Adaptive Responses of Citrusgrandis Leaves to Copper Toxicity Revealed by RNA-Seq and Physiology.

Copper (Cu)-toxic effects on Citrus grandis growth and Cu uptake, as well as gene expression and physiological parameters in leaves were investigated. Using RNA-Seq, 715 upregulated and 573 downregulated genes were identified in leaves of C. grandis seedlings exposed to Cu-toxicity (LCGSEC). Cu-toxicity altered the expression of 52 genes related to cell wall metabolism, thus impairing cell wall metabolism and lowering leaf growth. Cu-toxicity downregulated the expression of photosynthetic electron transport-related genes, thus reducing CO2 assimilation. Some genes involved in thermal energy dissipation, photorespiration, reactive oxygen species scavenging and cell redox homeostasis and some antioxidants (reduced glutathione, phytochelatins, metallothioneins, l-tryptophan and total phenolics) were upregulated in LCGSEC, but they could not protect LCGSEC from oxidative damage. Several adaptive responses might occur in LCGSEC. LCGSEC displayed both enhanced capacities to maintain homeostasis of Cu via reducing Cu uptake by leaves and preventing release of vacuolar Cu into the cytoplasm, and to improve internal detoxification of Cu by accumulating Cu chelators (lignin, reduced glutathione, phytochelatins, metallothioneins, l-tryptophan and total phenolics). The capacities to maintain both energy homeostasis and Ca homeostasis might be upregulated in LCGSEC. Cu-toxicity increased abscisates (auxins) level, thus stimulating stomatal closure and lowering water loss (enhancing water use efficiency and photosynthesis).

Structure of dye-decolorizing peroxidase from Bacillus subtilis in complex with veratryl alcohol

Dye-decolorizing peroxidases (DyPs) are heme-containing peroxidases, which have promising application in biodegradation of phenolic lignin compounds and in detoxification of dyes. In this study, the crystal structure of BsDyP- veratryl alcohol (VA) complex delves deep into the binding of small substrate molecules within the DyP heme cavity. The biochemical analysis shows that BsDyP oxidizes the VA with a turnover number of 0.065 s−1, followed by the oxidation of 2,6-dimethoxyphenol (DMP) and guaiacol with a comparable turnover number (kcat) of 0.07 s−1 and 0.07 s−1, respectively. Moreover, biophysical and computational studies reveal the comparable binding affinity of substrates to BsDyP and produce lower-energy stable BsDyP-ligand(s) complexes. All together with our previous findings, we are providing a complete structural description of substrate-binding sites in DyP. The structural insight of BsDyP helps to modulate its engineering to enhance the activity towards the oxidation of a wide range of substrates.

Organic carbon composition and microbial transformation of seagrass meadow and its responses to eutrophication

<p indent="0mm">Carbon neutrality is an important concept in global climate change governance. Seagrass beds rank among the most productive autotrophic ecosystems on the planet, and are receiving increasing attention as globally-significant hotspots of organic carbon (“blue carbon”) sequestration. The blue carbon stored in seagrass beds has important implications for climate change mitigation. The protection of seagrass beds will also protect their organic carbon sequestration potential, consequently helping to achieve the goal of carbon neutrality. Unfortunately, about 29% of the world’s seagrass beds have been destroyed, with a loss rate of 7% a⁻¹ since 1990, mostly due to eutrophication. The organic carbon sequestration potential of seagrass beds could be influenced by the subsequent changes in organic carbon composition, and microbial transformation processes. We systematically reviewed the relevant local and international research to summarize the composition and microbial transformation of organic carbon and its responses to eutrophication. Organic carbon is present in various forms in seagrass beds, and can be roughly divided into primary producer living biomass carbon, litter organic carbon, water organic carbon, and sediment organic carbon according to its storage area. Organic carbon can also be divided into labile organic carbon (LOC), which is susceptible to microbial decomposition, and recalcitrant organic carbon (ROC), which is resistant to microbial decomposition. The total ROC (cellulose and lignin) content in seagrass is present in the range of <sc>153−561 mg/g,</sc> and accounts for more than 28.7% of the organic carbon in the seagrass plants. The ROC content of seagrass plants is affected by the species, morphology, tissue and organ types, and climatic zones. In the water column, color dissolved organic matter (CDOM) and neutral sugars are indicators of LOC, while the lignin phenol and humic-like fractions of fluorescent dissolved organic matter (FDOM) are potential tracers of ROC. The DOM in water can be divided into dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved organic phosphorus (DOP). The DOC/DON and DOC/DOP ratios are used to reflect DOC lability and microbial bioavailability, with high DON and DOP concentrations indicating high DOC lability. In sediments, extractable organic carbon and microbial biomass carbon are important indicators of LOC, while aromatic hydrocarbons and alkanes are indicative of recalcitrant components. There are significant differences in the sediment organic carbon contents of temperate and tropical regions. Microorganisms play a vital role in the transformation of organic carbon. There are geographic differences in microbial composition, which are mainly influenced by the available habitats and climate zones, but there are no differences between seagrass species within a fine-scale seagrass bed. Different microorganisms have different decomposition capacities. <italic>R</italic>-strategist microbes, including Clostridiales<italic> </italic>and<italic> </italic>Gammaproteobacteria, are able to rapidly decompose LOC, while <italic>k</italic>-strategists, such as Verrucomicrobiae<italic> </italic>and Anaerolinae, can break down the more recalcitrant compounds. There is a succession of <italic>r</italic>- to <italic>k</italic>-strategists microbes during the decomposition of fresh organic matter (including fresh seagrass litter, DOC, and SOC). Eutrophication may lead to the transformation of the community structure of primary producers in seagrass beds from seagrass to macroalgae, which will increase the input of labile carbon. This consequently causes an increase in LOC in the plant biomass, water column, and sediments, but a decrease in ROC. The nutrient loading can affect the microbial community structure and enzyme activity, which will affect the microbial transformation of organic carbon. Furthermore, nutrient and LOC inputs may induce a “priming effect” that promotes the remineralization of stored organic carbon. Several future research directions for determining the transformation of seagrass beds and their organic carbon were proposed. (1) Extensive studies of the organic carbon components (LOC and ROC) in seagrass beds are required. (2) There is a need to better understand the composition, function, and gene expression of microbial communities in seagrass beds. (3) The eutrophication mechanisms in microbial communities and the related extracellular enzyme activities need to be determined. (4) The response of the organic matter decomposition process to nutrient loading and the interaction of nutrients and algae need to be studied. There is also a need to strengthen local research on the carbon storage potential of seagrass beds to mitigate global climate change and provide theoretical support for achieving carbon neutrality.

Characteristics of Dissolved Organic Matter and Dissolved Lignin Phenols in Tropical Forest Soil Solutions during Rainy Seasons and Their Responses to Nitrogen Deposition

Characteristics of Dissolved Organic Matter and Dissolved Lignin Phenols in Tropical Forest Soil Solutions during Rainy Seasons and Their Responses to Nitrogen Deposition

A Comparison among Lignin Modification Methods on the Properties of Lignin-Phenol-Formaldehyde Resin as Wood Adhesive.

The research aim of this work is to determine the influence of lignin modification methods on lignin–phenol–formaldehyde (LPF) adhesive properties. Thus, glyoxal (G), phenol (P), ionic liquid (IL), and maleic anhydride (MA) were used to modify lignin. The modified lignins were used for phenol substitution (50 wt%) in phenol–formaldehyde adhesives. The prepared resins were then used for the preparation of wood particleboard. These LPF resins were characterized physicochemically, namely by using standard methods to determine gel time, solids content, density, and viscosity, thus the physicochemical properties of the LPF resins synthesized. The panels dimensional stability, formaldehyde emission, bending modulus, bending strength, and internal bond (IB) strength were also measured. MA-modified lignin showed by differential scanning calorimetry (DSC) the lowest temperature of curing than the resins with non-modified lignin and modified with IL, phenolared lignin, and glyoxal. LPF resins with lignin treated with maleic anhydride presented a shorter gel time, higher viscosity, and solids content than the resins with other lignin modifications. Equally, the particleboard panels prepared with LPF resins with maleic anhydride or with ionic liquid had the lowest formaldehyde emission and the highest mechanical strength among all the synthesized resins. The dimensional stability of all panels bonded with modified lignin LPF resins presented no difference of any significance.

Demethylation, phenolation, and depolymerization of lignin for the synthesis of lignin-based epoxy resin via a one-pot strategy

A one-pot method to synthesize demethylated-phenolated lignin (DPL) and demethylated-phenolated lignin-based epoxy resin (DPLINP) using phenol as a phenolic reagent and polymerization inhibitor was proposed in this study. This method avoids the occurrence of polycondensation caused by demethylation and simplifies the synthesis of lignin-based epoxy resins. Phenolated lignin (PL)-based epoxy resin (PLINP) and demethylated lignin (DL)-based epoxy resin (DLINP) were prepared to investigate the effects of different modification methods on the resulting lignin and epoxy resin. The results of 1H nuclear magnetic resonance (NMR), Fourier transform infrared, and gel permeation chromatography analyses indicated that the introduction of phenol could significantly reduce the occurrence of polycondensation while also decreasing the molecular weight and increasing the content of phenolic hydroxyl in DPL compared with DL and PL. 2D heteronuclear single quantum coherence NMR analysis was used to further investigate the structural changes of lignin during the modification process. The results obtained via dynamic mechanical analysis, flexural test, and impact test demonstrated that demethylated-phenolated lignin-based epoxy network (DPLIEN) possessed an improved cross-linking density, glass transition temperature, and mechanical performance compared with all other epoxy resins. Moreover, the polycondensation of DL caused by demethylation deteriorated the mechanical performance of demethylated lignin-based epoxy network (DLIEN). The thermal stability of DPLIEN was decreased compared with phenolated lignin-based epoxy network (PLIEN), as the removal of methoxy groups may have reduced the protective char layer formation in DPLIEN. This study provides a novel method for the modification of lignin and synthesis of lignin-based epoxy resins.

Resistance of genotypes and defence compounds against bacterial halo blight of coffee

AbstractBacterial halo blight of coffee (BHB), caused by Pseudomonas syringae pv. garcae, is one of the main coffee diseases and is economically important mainly in regions of higher altitudes and mild temperatures. The use of resistant cultivars in the management of diseases is the most efficient and least costly technology for producers. The Coffee Germplasm Bank of Minas Gerais State has genotypes with great genetic variability, some of which are sources of resistance to several diseases and pests. Thus, the objective of this study was to evaluate the potential of 34 genotypes from the Coffee Germplasm Bank of Minas Gerais State and five cultivars with resistance to BHB. We evaluated the expression of three plant defence genes (phenylalanine ammonia liase‐PAL, peroxidase‐POX, and cinnamyl alcohol dehydrogenase‐CAD) and quantified the content of total soluble phenolic compounds, lignin, caffeine, trigonelline, and chlorogenic acid in coffee leaves showing different levels of resistance to BHB. The cultivar IPR 102 (resistant control to BHB), the Catimor UFV 7158, Caturra Vermelho × CIFC H 79/1 UFV 339‐34, Catiguá MG2, Volutifolia Vermelho, Caturra Vermelho, Híbrido de Timor UFV 432‐02, Caturra Vermelho × CIFC H 288/14 UFV 319‐04, and Caturra Vermelho × CIFC H 79/1 UFV 339‐02 genotypes showed low disease severity. The UFV 7158 genotype showed higher PAL and POX expression levels than Mundo Novo 376/4 cultivar. The IPR 102 cultivar and UFV 7158 genotype showed high chlorogenic acid content and low caffeine and trigonelline contents.

Deep Eutectic Solvents (DESs) as Green Extraction Media of Beneficial Bioactive Phytochemicals

Deep eutectic solvents (DES) are a mixture of two or more components and are classified as ionic solvents with special properties such as low volatility, high solubility, low melting points, low-cost materials and are less toxic to humans. Using DES has been suggested as an eco-friendly, green method for extraction of bioactive compounds from medicinal plants and are a safe alternative for nutritional, pharmaceutical and various sector applications. Conventional solvent extraction methods present drawbacks such as long extraction period, safety issues, harmful to the environment, costly and large volume of solvents required. The extraction method with DES leads to higher extraction yield and better bioactivity results as compared to the conventional solvents. This review provides a summary of research progress regarding the advantages of using DES to extract bioactive compounds such as phenolic acid, flavonoids, isoflavones, catechins, polysaccharides, curcuminoids, proanthocyanidin, phycocyanin, gingerols, ginsenosides, anthocyanin, xanthone, volatile monoterpenes, tannins, lignin, pectin, rutin, tert-butyl hydroquinone, chlorogenic acids, resveratrol and others, as opposed to using conventional solvents. The bioactivity of the extracts is determined using antioxidant, antibacterial and antitumor activities. Hence, DESs are considered potential green media with selective and efficient properties for extracting bioactive ingredients from medicinal plants.

The vertical distribution pattern of microbial- and plant-derived carbon in the rhizosphere in alpine coniferous forests

Although the quantitative assessment of plant- and microbial-derived carbon (C) chemical composition in soil profiles has been initially explored, the vertical distribution pattern of these two C sources and their relative contribution in SOC formation based on the insights related to the rhizosphere are still lacking. We quantified the divergent accumulation of microbial-derived C (i.e., microbial residues), plant-derived C (i.e., lipids and lignin phenols) and SOC in the rhizosphere at various depths (0–10 cm, 10–20 cm and 20–30 cm) in the upper mineral soil and analyzed its control factors in an alpine coniferous forest (Picea asperata. Mast). We further revealed the relative contribution of plant- or microbial-derived C to rhizosphere SOC in the soil profile. The contents of microbial- and plant-derived C and SOC in the rhizosphere decreased with soil depth and were mainly regulated by root biomass and microbial biomass. Moreover, the contribution of microbial-derived C dominated by fungal residues to rhizosphere SOC at each soil depth (more than 62%) was much higher than that of plant-derived C (less than 6%), implying that the soil microbial C pump was intensely stimulated in the rhizosphere. These results indicated that microbial-derived C was the main contributor of rhizosphere SOC at various depths in the upper mineral soil. Our findings provide direct experimental evidence for assessing the relative contribution of microbial- or plant-derived C to SOC in the soil profile from the perspective of the rhizosphere.

Lignin-phenol monomers govern the pyrolytic conversion of natural biomass from lignocellulose to products

The effect of the interaction between lignin-phenol monomers and holocellulose in natural biomass on the distribution of pyrolysis products remains unknown. The results of this study showed that the interaction between lignin and holocellulose during the pyrolysis of natural biomass became more pronounced as the pyrolysis temperature increased. The interaction between lignin and holocellulose in the natural crosslinked structure promoted the generation of CO and inhibited the generation of CO2 at 750 °C. Lignin inhibited the decarboxylic reaction of hemicellulose during pyrolysis but was important for the generation of levoglucosan during cellulose pyrolysis. Holocellulose slowed the demethoxyreaction of lignin guaiacol but promoted the removal of aliphatic hydrocarbon substituents from the aromatic ring. The cinnamyl phenol monomers of lignin increased the rates of change of biomass pyrolysis products with the lignin mass fraction at 400 °C. However, when the pyrolysis temperature increased to 750 °C, all types of lignin phenol monomers increased the rates of change of the biomass pyrolysis products. Our results provide new insights that have implications for the development of pyrolysis techniques for the resource recycling of various types of biomass for the preparation of high-grade gaseous and liquid fuels.

Anatomical and histochemical characterization of leaves of Spondias purpurea L.

The Anacardiaceae family has species rich in secondary metabolites. They are widely used in popular medicine. Among them, Spondias purpurea L. stands out for containing several secondary metabolites with important biological activities. To aid in the precise identification of the species, this work aims to perform an anatomical and histochemical characterization of leaves of S. purpurea. Microscope slides containing cross-sections of the petiolule and leaflets, in addition to paradermal sections of the leaflets, were prepared and analyzed in an optical and polarized microscope. Histochemical tests were performed on fresh leaflets. Through microscopic analysis, it was possible to identify the anatomical structures that allow the diagnosis of the studied species, such as petiolule with concave-convex shape, non-glandular and glandular trichomes, druses in phloem; leafletsamphistomatic, with non-glandular trichomes on the adaxial face and glandular trichomes on the abaxial face, midrib with concave-convex shape, two collateral vascular bundles, one layer of palisade parenchyma, druses in phloem and mesophyll. Through histochemistry, the presence of phenolic compounds, alkaloids, tannins, triterpenes, steroids, lipophilic compounds, essential oils, lignin, starch and calcium oxalate crystals were evidenced in the leaflets. The results are important for the quality control of plant material.

Agaricales Mushroom Lignin Peroxidase: From Structure-Function to Degradative Capabilities.

Lignin biodegradation has been extensively studied in white-rot fungi, which largely belong to order Polyporales. Among the enzymes that wood-rotting polypores secrete, lignin peroxidases (LiPs) have been labeled as the most efficient. Here, we characterize a similar enzyme (ApeLiP) from a fungus of the order Agaricales (with ~13,000 described species), the soil-inhabiting mushroom Agrocybe pediades. X-ray crystallography revealed that ApeLiP is structurally related to Polyporales LiPs, with a conserved heme-pocket and a solvent-exposed tryptophan. Its biochemical characterization shows that ApeLiP can oxidize both phenolic and non-phenolic lignin model-compounds, as well as different dyes. Moreover, using stopped-flow rapid spectrophotometry and 2D-NMR, we demonstrate that ApeLiP can also act on real lignin. Characterization of a variant lacking the above tryptophan residue shows that this is the oxidation site for lignin and other high redox-potential substrates, and also plays a role in phenolic substrate oxidation. The reduction potentials of the catalytic-cycle intermediates were estimated by stopped-flow in equilibrium reactions, showing similar activation by H2O2, but a lower potential for the rate-limiting step (compound-II reduction) compared to other LiPs. Unexpectedly, ApeLiP was stable from acidic to basic pH, a relevant feature for application considering its different optima for oxidation of phenolic and nonphenolic compounds.

A molecular biomarker for end-Permian plant extinction in South China

Abstract To help resolve current controversies surrounding the fundamental question of synchrony between end-Permian mass extinction on land and in the sea, we examined the marine Permian–Triassic reference section at Meishan (southeastern China) for land-derived molecular degradation products of pentacyclic triterpenoids with oleanane carbon skeletons, diagnostic for the Permian plant genus Gigantopteris. We identified a continuous quantitative record of mono-aromatic des-A-oleanane, which abruptly ends in the main marine extinction interval just below the Permian-Triassic boundary. This taxon-specific molecular biomarker, therefore, reveals in unmatched detail the timing and tempo of the demise of one of the most distinctive Permian plants and provides evidence of synchronous extinction among continental and marine organisms. Parallel reduction in the relative abundance of lignin phenols confirms that aridity-driven extinction was not restricted to Gigantopteris but likely affected the entire wetland flora of the equatorial South China microcontinent.