Lignin-like Material Research Articles

Ocean-atmosphere interactions: Different organic components across Pacific and Southern Oceans

Sea spray aerosol (SSA) particles strongly influence clouds and climate but the potential impact of ocean microbiota on SSA fluxes is still a matter of active research. Here–by means of in situ ship-borne measurements–we explore simultaneously molecular-level chemical properties of organic matter (OM) in oceans, sea ice, and the ambient PM2.5 aerosols along a transect of 15,000 km from the western Pacific Ocean (36°13′N) to the Southern Ocean (75°15′S). By means of orbitrap mass spectrometry and optical characteristics, lignin-like material (24 ± 5 %) and humic material (57 ± 8 %) were found to dominate the pelagic Pacific Ocean surface, while intermediate conditions were observed in the Pacific-Southern Ocean waters. In the marine atmosphere, we found a gradient of features in the aerosol: lignin-like material (31 ± 9 %) dominating coastal areas and the pelagic Pacific Ocean, whereas lipid-like (23 ± 16 %) and protein-like (11 ± 10 %) OM controlled the sympagic Southern Ocean (sea ice-influence). The results of this study showed that the OM composition in the ocean, which changes with latitude, affects the OM in aerosol compositions in the atmosphere. This study highlights the importance of the global-scale OM monitoring of the close interaction between the ocean, sea ice, and the atmosphere. Sympagic primary marine aerosols in polar regions must be treated differently from other pelagic-type oceans.

Hydrochar-derived fuels from waste walnut shell through hydrothermal carbonization: characterization and effect of processing parameters

The raw walnut shell was converted to hydrochar fuel through hydrothermal carbonization. The structural, morphological, and compositional analyses were carried out using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric and basic elemental analyses. The effect of the processing parameters including reaction temperature, residence time, and water:biomass ratio on the hydrothermal treatment was studied. The selected hydrochar has been produced at the optimized condition of T = 250 °C, t = 5 h, and water:biomass ratio = 6.0 mL/g. The H:C and O:C atomic ratios decreased from 1.51 and 0.73 to 0.91 and 0.26 for walnut shell and the selected hydrochar, respectively. The elemental reduction occurred through the carbonization process, which mainly includes dehydration, decarboxylation, and depolymerization reactions in liquid phase. The higher heating value increased from 18.85 for walnut shell to 27.95 for the selected hydrochar. The obtained walnut shell–based hydrochar presents a relatively homogenized structure consisting of microspherical particles with a mean diameter of 6 μm. This lignin-like material with high carbon content and low ash content shows high thermal stability. These promising results are relevant to the development of hydrochar products from waste biomass for fuel applications.

Sargassum angustifolium brown macroalga as a high potential substrate for alginate and ethanol production with minimal nutrient requirement

The brown macroalga, Sargassum angustifolium harvested from the Persian Gulf in the summer and winter was exploited within a biorefinery approach for valuable bioproducts and ethanol production. This alga mainly contained alginate (20.9–22.4%), glucan (36.2–43.1%), lignin-like materials (i.e., polyphenols; 11.8–25.8%), and ash (43.8–35.5%). The biomass protein content was highly depended on the harvesting season, where the biomass harvested in summer and winter comprised 11.9% and 19.7% protein, respectively. The alginate was first extracted in the form of sodium alginate. Then, the residual biomass obtained during alginate extraction was used for bioethanol production through the separate hydrolysis and fermentation. The results demonstrated that 44.5 (28.0) to 53.3 (32.5) kg of ethanol and 2.4 × 102 (2.2 × 102) kg of sodium alginate could be obtained from each tone of summer (winter) algal biomass. During the extraction of alginate, a nutrient-rich extract, “macroalgal extract”, was produced. This extract was successful substitute for yeast extract, which was necessary for the ethanolic fermentation. The results revealed the great potential of S. angustifolium for implementation as a source of sodium alginate, a nutrient-rich extract, and bioethanol.

Fractionation and DOSY NMR as Analytical Tools: From Model Polymers to a Technical Lignin

One key challenge hindering the valorization of lignin is its structural complexity. Artificial lignin-like materials provide a stepping stone between the simplicity of model compounds and the complexity of lignin. Here, we report an optimized synthesis of an all-G β-O-4 polymer 1 designed to model softwood lignin. After acetylation, the polymer Ac-1(V) was fractionated using a protocol that involved only volatile organic solvents, which left no insoluble residue. Using diffusion ordered spectroscopy NMR in combination with gel permeation chromatography, it was revealed that this fractionated material behaved like a flexible linear polymer in solution (average α > 0.5). Acetylated kraft lignin was subsequently processed using the same fractionation protocol. By comparison with the model polymer, we propose that the acetylated kraft lignin is composed of two classes of materials that exhibit contrasting physical properties. One is comparable to the acetylated all-G β-O-4 polymer Ac-1, and the second has a significantly different macromolecular structure.

Product yield, quality and energy in the hydrolysis of urban bio-waste compost from laboratory-scale runs

The valorisation of bio-waste is pursued to cope with the increasing amount of waste that results from human food consumption and also to find renewable feedstock for manufacturing fuel and chemicals, as an alternative to fossils. Bio-waste is currently processed using fermentation and thermo-chemical technologies, to produce bio-fuel, compost and small platform molecules. Commercial low temperature chemical processes to valorise the bio-waste lignin fractions as feedstock for value-added chemicals do not as yet exist. The present work addresses this technology gap showing that the low-temperature hydrolysis of municipal bio-waste compost is a safe eco-friendly, cost effective process for converting the lignin-like material from compost into value-added speciality chemicals. It is reported that the process produces a 30%–70% yield of soluble biopolymers (SBO) as temperature increases from 60 to 150 °C. The SBO at 150 °C exhibit the best surfactant properties, making them promising for multipurpose uses in the future. The reaction yield is limited by non-hydrolysable lignin-like matter present in the pristine compost. Energy changes occur due to endothermic and exothermic reaction during hydrolysis at different temperatures. The process allows most of the process water and reagent to be recycled and saves on reagents, water and processing energy. No secondary treatment of the process effluent is necessary. The data lead to the conclusion that it will be feasible to produce SBO at commercial level through low-temperature hydrolysis of compost or biomass from different sources.

In situ polymerisation of isoeugenol as a green consolidation method for waterlogged archaeological wood

Waterlogged archaeological wood is often in need of consolidation prior to drying to prevent shrinkage and cracking of the object. There is a need for new greener materials (than for example polyethylene glycol) and methods for consolidation to be developed. The use of wood-based components could provide good interaction between the consolidant and the remaining wood structure and would also support a shift away from fossil fuel-based materials to those with more sustainable sources. Based on this, lignin-like structures have been investigated for their ability to consolidate waterlogged archaeological wood. The in situ formation of a lignin-like material has been carried out using isoeugenol polymerised by horse radish peroxidase in aqueous solution. The formation of the oligomeric/polymeric materials within the wood following this reaction has been determined by Attenuated Total Reflectance Fourier Transform Infra Red (ATR-FTIR) spectroscopy. The oligomers remaining in solution have been characterised by ATR-FTIR and nuclear magnetic resonance (NMR) spectroscopy as well as analytical ultracentrifugation, showing that they have a weight average Mw of 0.4–0.9 kDa and a lignin-like structure rich in the β-5′ moiety. Therefore, this approach is proposed as a basis to further develop a green consolidation method for waterlogged archaeological wood.

Characterization of transformations of maize residues into soil organic matter.

An awareness of the transformation of plant residues returned to cultivated soils is vital for a better understanding of carbon cycles, the maintenance of soil fertility and the practice of a sustainable agriculture. The transformation of maize (Zea mays L) straw residues into soil organic matter (SOM) in a one year incubation experiment was studied in a soil that had been under long term cultivation with wheat (Triticum aestivum L) for >30years. A novel sequential exhaustive extraction and fractionation procedure isolated a series of fractions of SOM. The samples were characterized by elemental and δ13C analyses, by amino acids and neutral sugars analyses, by Fourier transformed infrared (FTIR) spectrometry, and by solid state 13C nuclear magnetic resonance (NMR) spectroscopy and with chemical shift anisotropy (CSA) -filter and dipolar dephasing (DD) spectral editing NMR techniques. The δ13C data indicated that 59% and 38% of the newly transformed organic carbon was in the humic and fulvic acid fractions, respectively, and in general a greater proportion of the transformed carbon was in the fractions isolated at the higher pH values. Results for SOM fractions from the amended soil indicate dominant contributions from carbohydrate and lignin-like material, and that can be clearly identified by FTIR, CP/TOSS, and spectral editing of CSA-filter and DD. The compositions of the fractions from the amended and non-amended soils fractions can be clearly differentiated using principal component analysis (PCA) for the data collected. The sequential extraction procedure showed that the hydrophilicity of humic fractions increased as the result of the maize amendment, and the aromaticity of the fraction decreased. The data may give some indications of transformations that take place during humification processes.

The MYB36 transcription factor orchestrates Casparian strip formation

The endodermis in roots acts as a selectivity filter for nutrient and water transport essential for growth and development. This selectivity is enabled by the formation of lignin-based Casparian strips. Casparian strip formation is initiated by the localization of the Casparian strip domain proteins (CASPs) in the plasma membrane, at the site where the Casparian strip will form. Localized CASPs recruit Peroxidase 64 (PER64), a Respiratory Burst Oxidase Homolog F, and Enhanced Suberin 1 (ESB1), a dirigent-like protein, to assemble the lignin polymerization machinery. However, the factors that control both expression of the genes encoding this biosynthetic machinery and its localization to the Casparian strip formation site remain unknown. Here, we identify the transcription factor, MYB36, essential for Casparian strip formation. MYB36 directly and positively regulates the expression of the Casparian strip genes CASP1, PER64, and ESB1. Casparian strips are absent in plants lacking a functional MYB36 and are replaced by ectopic lignin-like material in the corners of endodermal cells. The barrier function of Casparian strips in these plants is also disrupted. Significantly, ectopic expression of MYB36 in the cortex is sufficient to reprogram these cells to start expressing CASP1-GFP, correctly localize the CASP1-GFP protein to form a Casparian strip domain, and deposit a Casparian strip-like structure in the cell wall at this location. These results demonstrate that MYB36 is controlling expression of the machinery required to locally polymerize lignin in a fine band in the cell wall for the formation of the Casparian strip.

Chemical differences of aquatic humic substances extracted by XAD-8 and DEAE-cellulose

Chemical characteristics of dissolved organic matter (DOM) extracted from an ombrotrophic bog in northern Minnesota by two methods – XAD-8 and DEAE-cellulose – were compared using 13C NMR spectroscopy, excitation–emission matrix fluorescence spectroscopy (EEMS), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). DOM extracted with XAD-8, a relatively hydrophobic sorbent, had a larger 13C NMR signal in the aromatic carbon region, but DOM extracted by DEAE-cellulose, a weak anion exchanger, had a larger signal in the carboxylic carbon region. DOM extracts prepared by the two methods were similar in their overall chemical characteristics that serve as proxies for organic matter sources. For example, only small differences were observed in the fluorescence index (FI) values of the extracts, and all values were within the range expected for terrestrially-derived DOM. EEMS spectra of both extracts had “humic-like” peak A areas smaller than that of standard reference Suwannee River fulvic acid. Of 2801 distinct chemical formulas assigned during FT-ICR MS analysis of the two extracts, 66% were present in both; 15% were unique to the XAD-8 extract, and 19% were unique to the DEAE-cellulose extract. Van Krevelen plots showed that the DEAE-cellulose extract had more tannin-like and condensed aromatic entities and formulas with higher O/C ratios, whereas the XAD-8 extract had more lignin-like material and formulas with higher H/C ratios. Overall, differences in chemical characteristics of the extracts reflect the mechanisms by which the extractants operate.

Mechanisms of water interaction with pore systems of hydrochar and pyrochar from poplar forestry waste.

The aim of this study was to understand the water-surface interactions of two chars obtained by gasification (pyrochar) and hydrothermal carbonization (hydrochar) of a poplar biomass. The two samples revealed different chemical compositions as evidenced by solid state (13)C NMR spectroscopy. In fact, hydrochar resulted in a lignin-like material still containing oxygenated functionalities. Pyrochar was a polyaromatic system in which no heteronuclei were detected. After saturation with water, hydrochar and pyrochar were analyzed by fast field cycling (FFC) NMR relaxometry. Results showed that water movement in hydrochar was mainly confined in very small pores. Conversely, water movement in pyrochar led to the conclusion that a larger number of transitional and very large pores were present. These results were confirmed by porosity evaluation derived from gas adsorption. Variable-temperature FFC NMR experiments confirmed a slow-motion regime due to a preferential diffusion of water on the solid surface. Conversely, the higher number of large pores in pyrochar allowed slow movement only up to 50 °C. As the temperature was raised to 80 °C, water interactions with the pore surface became weaker, thereby allowing a three-dimensional water exchange with the bulk liquid. This paper has shown that pore size distribution was more important than chemical composition in affecting water movement in two chemically different charred systems.

Different diversity-functioning relationship in lake and stream bacterial communities

Biodiversity patterns have been successfully linked to many ecosystem functions, and microbial communities have been suspected to harbour a large amount of functionally redundant taxa. We manipulated the diversity of stream and lake water column bacterial communities and investigated how the reduction in diversity affects the activities of extracellular enzymes involved in dissolved organic carbon degradation. Dissimilar communities established in cultures inoculated with stream or lake bacteria and utilized different organic matter compounds as indicated by the different extracellular enzyme activities. Stream bacterial communities preferentially used plant-derived organic material such as cellulose and hemicellulose. Communities obtained from the lake, where the longer residence time might permit the organic matter to age, efficiently degraded lignin-like material and also showed higher peptide degradation capacities. The results highlight a stronger negative effect of decreasing diversity on ecosystem multifunctionality for stream than for lake bacterial communities. We found a relatively higher multifunctional redundancy in the lake as compared to the stream-derived cultures and suggest that community assembly might shape diversity-functioning relationships in freshwater bacterial communities.

Pseudo-lignin and pretreatment chemistry

The formation of pseudo-lignin by the combination of carbohydrate and lignin degradation products has been proposed to be responsible for the increased Klason lignin content in biomass pretreated under acidic conditions. Direct evidence for the presence of pseudo-lignin has never been presented. The formation of additional lignin-like material may be detrimental to enzymatic hydrolysis due to the non-productive binding of enzymes with lignin. To investigate the chemistry of pseudo-lignin formation, dilute acid pretreatments were performed on delignified hybrid poplar biomass under conditions of varying severity. The results show a progressive increase in the Klason lignin content of the acid pretreated material with increasing pretreatment severity. NMR and FT-IR spectroscopic characterization shows the development of aliphatic, unsaturated and carbonyl carbon functionalities in the samples pretreated at higher severities. Given the very low Klason lignin content of the starting material, acid catalyzed dehydration of carbohydrates is responsible for the formation of pseudo-lignin.

On the Reactions of Two Fungal Laccases Differing in Their Redox Potential with Lignin Model Compounds: Products and Their Rate of Formation

Laccases (EC 1.10.3.2) are multicopper oxidases able to oxidize phenolic compounds such as lignin-related polyphenols. Since the discovery that so-called mediators effectively extend the family of laccase substrates, direct interactions between lignin-like materials and laccase have gained much less attention. In this work, the aim was to characterize oxidation products formed in direct laccase-catalyzed oxidation of different guaiacylic and syringylic lignin model compounds with two different laccases: a low redox potential Melanocarpus albomyces laccase and a high redox potential Trametes hirsuta laccase. By following the formation of different, mainly biphenylic (5-5) and benzylic oxidation products, it was found that although both of these enzymes generated practically the same pattern of products with particular types of syringyl and guaiacyl compounds, in some cases a clear difference in the rates of their formation was observed. The results also confirm further to the suggestions that syringylic compounds are able to act as mediators in their own oxidation reactions and also that in some instances acetylation of phenolic material may produce altered, unexpected structures.

Accumulation of cell-wall bound phenolic compounds and phytoalexin in Arabidopsis thaliana leaves following inoculation with pathovars of Pseudomonas syringae

Here we have examined genetically well-defined interactions in leaves of Arabidopsis ecotype Col-5 during compatible and incompatible interactions with isogenic pairs of Pseudomonas syringae pathovars tomato ( Pst) DC3000 and phaseolicola ( Pph) 1448A strains differing only in the presence or absences of cloned avr genes that determine the compatibility and incompatibility of the reaction. Strain Pst DC3000 was virulent causing formation of a spreading lesion surrounded by a chlorotic halo. The bean pathogen Pph 1448A (as a non-host pathogen) caused no visible symptoms apart from very patchy discolouration after 3 days. The presence of the avirulence genes avrPpiA and avrPphB in Pph 1448A led to a rapid or slow HR owing to interaction with the resistance genes RPM1 and RPS5 respectively. The hrpL mutant of Pph failed to produce symptoms. Microscopical and biochemical studies were used for in situ localization of plant molecules involved in plant resistance such as autofluorescent phenolics, lignin and camalexin. A strong correlation was observed between the timing and extent of cell death and high levels of phenolic and lignin accumulation in cell-walls and cytoplasm of cells undergoing the HR, whereas no staining of lignin-like material was observed during the compatible interaction. Accumulation of phytoalexin, camalexin, was associated with tissue necrosis whether during the HR or a susceptible response. Although high levels of camalexin were found within tissues inoculated with the virulent strain DC3000, the earliest detection of camalexin occurred during HR following inoculation with avirulent strain. The results indicate that accumulation of phenolics but not camalexin may be involved in resistance against bacterial pathogens used in this study.

In-mill removal of TMP whitewater contaminants by biological treatment in an aerobic biokidney used in conjunction with microfiltration and laccase treatment

SUMMARY: The suitability of an aerobic in-mill biokidney for purification of TMP newsprint white water was investigated. The effects of microfiltration and laccase treatment on the quality of biologically treated white water were also studied. The biokidney showed high (71-92%) removal efficiency for COD, BOD, carbohydrates and lignans. The removal efficiency was moderate (50-66%) for TOC and TS, and low (25-35%) for lipophilic extractives and lignin-like material while the amount of suspended solids (SS) increased by 67% as some of the biomass from the biokidney went into the white water. Microfiltration of biologically treated white water removed a minor part of the remaining contaminants of TMP origin and the bulk of the biomass from the biokidney. The treatment of biologically treated white water with laccase before microfiltration gave a large improvement in removal efficiency for all contaminants originating from the TMP but the material present in the laccase solution caused an increase in COD, BOD and TS. The biomass-based SS from the biokidney and the dissolved material in the laccase solution had a more detrimental effect on the mechanical and optical properties of handsheets prepared with untreated and treated white water than the wood-based contaminants.

‘Defence lignin’ and hydroxycinnamyl alcohol dehydrogenase activities in wounded Eucalyptus gunnii

‘Defence lignin’ and hydroxycinnamyl alcohol dehydrogenase activities in wounded <i>Eucalyptus gunnii</i>

Preliminary characterization of race-specific elicitors fromPeronospora parasitica and their ability to elicit phenolic accumulation inArabidopsis

Intercellular washing fluid (IWF) obtained from the susceptibleArabidopsis accession Ws-eds1 inoculated withPeronospora parasitica isolate Emoy-2, contained an elicitor of necrosis with ecotype specificity towardsArabidopsis accessions with particular resistance genes. This elicitor caused necrosis on the highly resistant accessions La-er, Nd-1 and partly on Col-5, but not on the susceptible accessions Ws-eds1 and Oy-0. In resistant plants, injection of IWF caused hypersensitive reaction (HR)-like cell collapse which was associated with the accumulation of phenolics and lignin-like material in walls of cells undergoing cell death. The elicitor is sensitive to proteinase K and pronase enzymes, heating and autoclaving but insensitive to periodate oxidation, freezing and thawing, and is not dialyzable. Results suggest that the elicitor is a protein. Fractionation experiments using size-exclusion membranes revealed that elicitor activity has a molecular weight in excess of 100 kDa.

Effect of Ultraviolet (UV-B) Radiation on the Formation and Localization of Phenolic Compounds in Tea Plant Callus Cultures

The effect of ultraviolet (UV-B) radiation on the accumulation and tissue localization of phenolic compounds in two strains of callus cultures of tea plant (Camellia sinensisL.) were investigated. The strains differed in their morphological and physiological characteristics and biosynthetic capacity. UV-B radiation hampered culture growth, decreased the size of callus-forming cells and promoted the accumulation of soluble and, to a lesser extent, polymeric forms of phenolic compounds, such as lignin. This accumulation was accompanied by an increase in the phenolic compound deposition in cell walls and intercellular space and by deposition of a lignin-like material on the surface of callus cultures. The strain characterized by an increased formation of phenolic compounds was more resistant to UV-B radiation as compared to that with lower phenolic productivity.

Infection of tubercles of the parasitic weed Orobanche aegyptiaca by mycoherbicidal Fusarium species.

Progression of the infection by host-specific strains of Fusarium oxysporum and Fusarium arthrosporioides of Orobanche aegyptiaca (Egyptian broomrape) tubercles attached to tomato roots was tracked using light, confocal and electron microscopy. Mycelia transformed with the gene for green fluorescent protein were viewed using a confocal microscope. Fungal penetration was preceded by a rapid loss of starch, with approx. 10 % remaining at 9 h and no measurable starch at 24 h. Penetration into the Orobanche tubercles began by 12 h after inoculation. Hyphae penetrated the outer six cell layers by 24 h, reaching the centre of the tubercles by 48 h and infecting nearly all cells by 72 h. Most of the infected tubercles were dead by 96 h. Breakdown of cell walls and the disintegration of cytoplasm in and around the infected cells occurred between 48 and 96 h. Lignin-like material increased in tubercle cells of infected tissues over time, but did not appear to be effective in limiting fungal penetration or spread. Callose, suberin, constitutive toxins and phytoalexins were not detected in infected tubercles, suggesting that there are no obvious defence mechanisms to overcome. Both Fusarium spp. pathogenic on Orobanche produced fumonisin-like ceramide synthase inhibitors, while fusaric acid was produced only by F. oxysporum in liquid culture. The organisms do not have sufficient virulence for field use (based on glasshouse testing), suggesting that virulence should be transgenically enhanced or additional isolates sought.

Studies on the phloroglucinol–HCl reactive material produced by squash fruit elicited with pectinase: Isolation using hydrolytic enzymes and release of p -coumaryl aldehyde by water reflux

Pathological tissues from a variety of plants turn red when treated with the histochemical reagent phloroglucinol (PG)–HCl. This induced PG–HCl reacting material has been termed both wound gum and, more recently, induced lignin or lignin-like material. We are exploring alternative approaches to better identify this induced material. In this report, we describe methods for purifying the PG–HCl reactive material from solvent-washed tissue preparations and measuring the amount of p -coumaryl aldehyde released from the purified material by boiling in water. Acorn squash fruit wall tissue was sliced, sprayed with pectinase to elicit the formation of PG–HCl reactive material and incubated up to 72 h at 27°C. Sampled tissue was washed extensively with water and organic solvents. Insoluble residues were treated with cell wall degrading enzymes to remove cell wall materials, and dimethyl sulfoxide was used to dissolve starch. Yields of residual material increased from 7.5% in the time zero samples to 29.7% after 72 h. Refluxing the purified material in water released <6 μ g p -coumaryl aldehyde g −1 from preparations of tissue at time zero and 8100 μ g p -coumaryl aldehyde g −1 from samples incubated for 48 h. These results suggest that the function of the material is to sequester phytoalexins, but are not consistent with the material being lignin. Published by Elsevier Science Ltd.