Pectin-like heteroxylans in the early-diverging charophyte Klebsormidium fluitans.

BACKGROUND AND AIMS: The cell walls of charophytic algae both resemble and differ from those of land plants. Cell walls in early-diverging charophytes (e.g. Klebsormidiophyceae) are particularly distinctive, in ways that may enable survival in environments that are incompatible with land-plant polymers. This study therefore investigates the structure of Klebsormidium polysaccharides. METHODS: The 'pectin' fraction (defined by extractability) of Klebsormidium fluitans, solubilised by various buffers from alcohol-insoluble residues (AIRs), was digested with several treatments that (partially) hydrolyse land-plant cell-wall polysaccharides. Products were analysed by gel-permeation and thin-layer chromatography. KEY RESULTS: The Klebsormidium pectic fraction made up ~30-50% of its AIR, was optimally solubilised at pH 3-4 at 100°C, and contained residues of xylose ≈ galactose > rhamnose > arabinose, fucose, mannose, glucose. Uronic acids were undetectable and the pectic fraction was more readily solubilised by formate than by oxalate, suggesting a lack of chelation. Some land-plant-targeting hydrolases degraded the Klebsormidium pectic fraction: digestion by α-l-arabinanase, endo-ß-(1⟶4)-d-xylanase, and α-d-galactosidase suggests the presence of ß-(1⟶4)-xylan with terminal α-l-arabinose, α-d-galactose and (unexpectedly) rhamnose. 'Driselase' released oligosaccharides of xylose and rhamnose (~1:1) and graded acid hydrolysis of these oligosaccharides indicated a 'rhamnoxylan' with rhamnose side-chains. Partial acid hydrolysis of Klebsormidium pectic fraction released rhamnose plus numerous oligosaccharides, one of which comprised xylose and galactose (~1:2 Gal/Xyl), suggesting a galactoxylan. Lichenase was ineffective, as were endo-ß-(1⟶4)-d-galactanase, endo-ß-(1⟶4)-d-mannanase, ß-d-xylosidase and ß-d-galactosidase. CONCLUSIONS: Klebsormidium pectic fraction possesses many land-plant-like linkages but is unusual in lacking uronic acid residues and in containing rhamnoxylan and galactoxylan domains. Uronic acids allow land-plant and late-diverging charophyte pectins to form Ca2+-bridges, facilitating cell-wall polymer association; their absence from Klebsormidium suggests that neutral heteroxylans rely on alternative cross-linking mechanisms. This lack of dependency on Ca2+-bridges may confer Klebsormidium's ability to grow in the acidic, metal-rich environments which it tolerates.

Wood inspired biobased nanocomposite films composed of xylans, lignosulfonates and cellulose nanofibers for active food packaging.

The growing concerns on environmental pollution and sustainability have raised the interest on the development of functional biobased materials for different applications, including food packaging, as an alternative to the fossil resources-based counterparts, currently available in the market. In this work, functional wood inspired biopolymeric nanocomposite films were prepared by solvent casting of suspensions containing commercial beechwood xylans, cellulose nanofibers (CNF) and lignosulfonates (magnesium or sodium), in a proportion of 2:5:3 wt%, respectively. All films presented good homogeneity, translucency, and thermal stability up to 153 °C. The incorporation of CNF into the xylan/lignosulfonates matrix provided good mechanical properties to the films (Young's modulus between 1.08 and 3.79 GPa and tensile strength between 12.75 and 14.02 MPa). The presence of lignosulfonates imparted the films with antioxidant capacity (DPPH radical scavenging activity from 71.6 to 82.4 %) and UV barrier properties (transmittance ≤19.1 % (200-400 nm)). Moreover, the films obtained are able to successfully delay the browning of packaged fruit stored over 7 days at 4 °C. Overall, the obtained results show the potential of using low-cost and eco-friendly resources for the development of sustainable active food packaging materials.

Leucine rich repeat-malectin receptor kinases IGP1/CORK1, IGP3 and IGP4 are required for arabidopsis immune responses triggered by ß-1,4-D-Xylo-oligosaccharides from plant cell walls.

Pattern-Triggered Immunity (PTI) in plants is activated upon recognition by Pattern Recognition Receptors (PRRs) of Damage- and Microbe-Associated Molecular Patterns (DAMPs and MAMPs) from plants or microorganisms, respectively. An increasing number of identified DAMPs/MAMPs are carbohydrates from plant cell walls and microbial extracellular layers, which are perceived by plant PRRs, such as LysM and Leucine Rich Repeat-Malectin (LRR-MAL) receptor kinases (RKs). LysM-RKs (e.g. CERK1, LYK4 and LYK5) are needed for recognition of fungal MAMP chitohexaose (ß-1,4-D-(GlcNAc)6, CHI6), whereas IGP1/CORK1, IGP3 and IGP4 LRR-MAL RKs are required for perception of ß-glucans, like cellotriose (ß-1,4-D-(Glc)3, CEL3) and mixed-linked glucans. We have explored the diversity of carbohydrates perceived by Arabidopsis thaliana seedlings by determining PTI responses upon treatment with different oligosaccharides and polysaccharides. These analyses revealed that plant oligosaccharides from xylans [ß-1,4-D-(xylose)4 (XYL4)], glucuronoxylans and α-1,4-glucans, and polysaccharides from plants and seaweeds activate PTI. Cross-elicitation experiments of XYL4 with other glycans showed that the mechanism of recognition of XYL4 and the DAMP 33-α-L-arabinofuranosyl-xylotetraose (XA3XX) shares some features with that of CEL3 but differs from that of CHI6. Notably, XYL4 and XA3XX perception is impaired in igp1/cork1, igp3 and igp4 mutants, and almost not affected in cerk1 lyk4 lyk5 triple mutant. XYL4 perception is conserved in different plant species since XYL4 pre-treatment triggers enhanced disease resistance in tomato to Pseudomonas syringae pv tomato DC3000 and PTI responses in wheat. These results expand the number of glycans triggering plant immunity and support IGP1/CORK1, IGP3 and IGP4 relevance in Arabidopsis thaliana glycans perception and PTI activation. Significance Statement: The characterization of plant immune mechanisms involved in the perception of carbohydrate-based structures recognized as DAMPs/MAMPs is needed to further understand plant disease resistance modulation. We show here that IGP1/CORK1, IGP3 and IGP4 LRR-MAL RKs are required for the perception of carbohydrate-based DAMPs ß-1,4-D-(xylose)4 (XYL4) and 33-α-L-arabinofuranosyl-xylotetraose (XA3XX), further expanding the function of these LRR-MAL RKs in plant glycan perception and immune activation.

Recent Advances in Biomedical Applications of Mannans and Xylans.

Plant-based phytochemicals, including flavonoids, alkaloids, tannins, saponins, and other metabolites, have attracted considerable attention due to their central role in synthesizing nanomaterials with various biomedical applications. Hemicelluloses are the second most abundant among naturally occurring heteropolymers, accounting for one-third of all plant constituents. In particular, xylans, mannans, and arabinoxylans are structured polysaccharides derived from hemicellulose. Mannans and xylans are characterized by their linear configuration of ß-1,4-linked mannose and xylose units, respectively. At the same time, arabinoxylan is a copolymer of arabinose and xylose found predominantly in secondary cell walls of seeds, dicotyledons, grasses, and cereal tissues. Their widespread use in tissue engineering, drug delivery, and gene delivery is based on their properties, such as cell adhesiveness, cost-effectiveness, high biocompatibility, biodegradability, and low immunogenicity. Moreover, it can be easily functionalized, which expands their potential applications and provides them with structural diversity. This review comprehensively addresses recent advances in the field of biomedical applications. It explores the potential prospects for exploiting the capabilities of mannans and xylans in drug delivery, gene delivery, and tissue engineering.

Immunomodulation by xylan and carrageenan-type polysaccharides from red seaweeds: Anti-inflammatory, wound healing, cytoprotective, and anticoagulant activities.

The immunomodulatory properties of the polysaccharides (carrageenan, xylan) from Chondrus crispus (CC), Ahnfeltiopsis devoniensis (AD), Sarcodiotheca gaudichaudii (SG) and Palmaria palmata (PP) algal species were studied. Using RAW264.7 macrophages, we investigated the proliferation and migration capacity of different extracts along with their immunomodulatory activities, including nitric oxide (NO) production, phagocytosis, and secretion of pro-inflammatory cytokines. Polysaccharides from C. crispus and S. gaudichaudii effectively mitigated inflammation and improved scratch-wound healing. Polysaccharide fractions extracted under cold conditions (25 °C), including CC-1A, SG-1A and SG-1B stimulated cell proliferation, while fractions extracted under hot conditions (95 °C), including CC-3A, CC-2B and A. devoniensis (AD-3A), inhibited cell proliferation after 48 h. Furthermore, RAW264.7 cells treated with the fractions CC-3A, AD-1A, and SG-2A significantly reduced LPS-stimulated NO secretion over 24 h. Phagocytosis was significantly improved by treatment with C. crispus (CC-2B, CC-3B) and A. devoniensis (AD-3A) fractions. RAW264.7 cells treated with the CC-2A and SG-1A fractions showed elevated TGF-ß1 expression without affecting TNF-α expression at 24 h. Polysaccharide fractions of A. devoniensis (ι/κ hybrid carrageenan; AD-2A, AD-3A) showed the highest anti-coagulation activity. CC-2A and SG-1A fractions enhanced various bioactivities, suggesting they are candidates for skin-health applications. The carrageenan fractions (CC-3A: λ-, µ-carrageenan, SG-2A: ν-, ι-carrageenan) tested herein showed great potential for developing anti-inflammatory and upscaled skin-health applications.

Structural and functional investigation of a fungal member of carbohydrate esterase family 15 with potential specificity for rare xylans.

In plant cell walls, covalent bonds between polysaccharides and lignin increase recalcitrance to degradation. Ester bonds are known to exist between glucuronic acid moieties on glucuronoxylan and lignin, and these can be cleaved by glucuronoyl esterases (GEs) from carbohydrate esterase family 15 (CE15). GEs are found in both bacteria and fungi, and some microorganisms also encode multiple GEs, although the reason for this is still not fully clear. The fungus Lentithecium fluviatile encodes three CE15 enzymes, of which two have previously been heterologously produced, although neither was active on the tested model substrate. Here, one of these, LfCE15C, has been investigated in detail using a range of model and natural substrates and its structure has been solved using X-ray crystallography. No activity could be verified on any tested substrate, but biophysical assays indicate an ability to bind to complex carbohydrate ligands. The structure further suggests that this enzyme, which possesses an intact catalytic triad, might be able to bind and act on more extensively decorated xylan chains than has been reported for other CE15 members. It is speculated that rare glucuronoxylans decorated at the glucuronic acid moiety may be the true targets of LfCE15C and other CE15 family members with similar sequence characteristics.

Xylans extracted from branches and leaves of Protium puncticulatum: antioxidant, cytotoxic, immunomodulatory, anticoagulant, antitumor, prebiotic activities and their structural characterization.

This work aimed to isolate and characterize xylans from branches and leaves of Protium puncticulatum, in addition to evaluating its in vitro biological and prebiotic potential. The results showed that the chemical structure of the obtained polysaccharides is similar being classified as homoxylans. The xylans presented an amorphous structure, in addition to being thermally stable and presenting a molecular weight close to 36 g/mol. With regard to biological activities, it was observed that xylans were able to promote low antioxidant activity (< 50%) in the different assays evaluated. The xylans also showed no toxicity against normal cells, in addition to being able to stimulate cells of the immune system and showing promise as anticoagulant agents. In addition to presenting promising antitumor activity in vitro. In assays of emulsifying activity, xylans were able to emulsify lipids in percentages below 50%. Regarding in vitro prebiotic activity, xylans were able to stimulate and promote the growth of different probiotics. Therefore, this study, in addition to being a pioneer, contributes to the application of these polysaccharides in the biomedical and food areas. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03506-1.

Potential of Wood Hemicelluloses and Their Derivates as Food Ingredients.

A holistic utilization of all lignocellulosic wood biomass, instead of the current approach of using only the cellulose fraction, is crucial for the efficient, ecological, and economical use of the forest resources. Use of wood constituents in the food and feed sector is a potential way of promoting the global economy. However, industrially established food products utilizing such components are still scarce, with the exception of cellulose derivatives. Hemicelluloses that include xylans and mannans are major constituents of wood. The wood hemicelluloses are structurally similar to hemicelluloses from crops, which are included in our diet, for example, as a part of dietary fibers. Hence, structurally similar wood hemicelluloses have the potential for similar uses. We review the current status and future potential of wood hemicelluloses as food ingredients. We include an inventory of the extraction routes of wood hemicelluloses, their physicochemical properties, and some of their gastrointestinal characteristics, and we also consider the regulatory route that research findings need to follow to be approved for food solutions, as well as the current status of the wood hemicellulose applications on that route.

Enhanced Furfural Production in Deep Eutectic Solvents Comprising Alkali Metal Halides as Additives.

The addition of alkali metal halide salts to acidic deep eutectic solvents is here reported as an effective way of boosting xylan conversion into furfural. These salts promote an increase in xylose dehydration due to the cation and anion interactions with the solvent being a promising alternative to the use of harsh operational conditions. Several alkali metal halides were used as additives in the DES composed of cholinium chloride and malic acid ([Ch]Cl:Mal) in a molar ratio of 1:3, with 5 wt.% of water. These mixtures were then used as both solvent and catalyst to produce furfural directly from xylan through microwave-assisted reactions. Preliminary assays were carried out at 150 and 130 °C to gauge the effect of the different salts in furfural yields. A Response Surface Methodology was then applied to optimize the operational conditions. After an optimization of the different operating conditions, a maximum furfural yield of 89.46 ± 0.33% was achieved using 8.19% of lithium bromide in [Ch]Cl:Mal, 1:3; 5 wt.% water, at 157.3 °C and 1.74 min of reaction time. The used deep eutectic solvent and salt were recovered and reused three times, with 79.7% yield in the third cycle, and the furfural and solvent integrity confirmed.

Hemicellulose-remodelling transglycanase activities from charophytes: towards the evolution of the land-plant cell wall.

Transglycanases remodel cell-wall polymers, having a critical impact on many physiological processes. Unlike xyloglucan endotransglucosylase (XET) activity, widely studied in land plants, very little is known about charophyte wall-modifying enzymes - information that would promote our understanding of the 'primordial' wall, revealing how the wall matrix is remodelled in the closest living algal relatives of land plants, and what changed during terrestrialisation. We conducted various in-vitro assays for wall-remodelling transglycosylases, monitoring either (a) polysaccharide-to-[3 H]oligosaccharide transglycosylation or (b) non-radioactive oligosaccharide-to-oligosaccharide transglycosylation. We screened a wide collection of enzyme extracts from charophytes (and early-diverging land plants for comparison) and discovered several homo- and hetero-transglycanase activities. In contrast to most land plants, charophytes possess high trans-ß-1,4-mannanase activity, suggesting that land plants' algal ancestors prioritised mannan remodelling. Trans-ß-1,4-xylanase activity was also found, most abundantly in Chara, Nitella and Klebsormidium. Exo-acting transglycosidase activities (trans-ß-1,4-xylosidase and trans-ß-1,4-mannosidase) were also detected. In addition, charophytes exhibited homo- and hetero-trans-ß-glucanase activities (XET, mixed-linkage glucan [MLG]:xyloglucan endotransglucosylase and cellulose:xyloglucan endotransglucosylase) despite the paucity or lack of land-plant-like xyloglucan and MLG as potential donor substrates in their cell walls. However, trans-α-xylosidase activity (which remodels xyloglucan in angiosperms) was absent in charophytes and early-diverging land plants. Transglycanase action was also found in situ, acting on endogenous algal polysaccharides as donor substrates and fluorescent xyloglucan oligosaccharides as acceptor substrates. We conclude that trans-ß-mannanase and trans-ß-xylanase activities are present and thus may play key roles in charophyte walls (most of which possess little or no xyloglucan and MLG, but often contain abundant ß-mannans and ß-xylans), comparable to the roles of XET in xyloglucan-rich land plants.

Molecular modification, structural characterization, and biological activity of xylans.

The differences in the source and structure of xylans make them have various biological activities. However, due to their inherent structural limitations, the various biological activities of xylans are far lower than those of commercial drugs. Currently, several types of molecular modification methods have been developed to address these limitations, and many derivatives with specific biological activity have been obtained. Further research on structural characteristics, structure-activity relationship and mechanism of action is of great significance for the development of xylan derivatives. Therefore, the major molecular modification methods of xylans are introduced in this paper, and the primary structure and conformation characteristics of xylans and their derivatives are summarized. In addition, the biological activity and structure-activity relationship of the modified xylans are also discussed.

Hevea brasiliensis coniferaldehyde-5-hydroxylase (HbCAld5H) regulates xylogenesis, structure and lignin chemistry of xylem cell wall in Nicotiana tabacum.

KEY MESSAGE: The HbCAld5H1 gene cloned from Hevea brasiliensis regulates the cambial activity, xylem differentiation, syringyl-guaiacyl ratio, secondary wall structure, lignification pattern and xylan distribution in xylem fibres of transgenic tobacco plants. Molecular characterization of lignin biosynthesis gene coniferaldehyde-5-hydroxylase (CAld5H) from Hevea brasiliensis and its functional validation was performed. Both sense and antisense constructs of HbCAld5H1 gene were introduced into tobacco through Agrobacterium-mediated genetic transformation for over expression and down-regulation of this key enzyme to understand its role affecting structural and cell wall chemistry. The anatomical studies of transgenic tobacco plants revealed the increase of cambial activity leading to xylogenesis in sense lines and considerable reduction in antisense lines. The ultra-structural studies showed that the thickness of secondary wall (S2 layer) of fibre had been decreased with non-homogenous lignin distribution in antisense lines, while sense lines showed an increase in S2 layer thickness. Maule color reaction revealed that syringyl lignin distribution in the xylem elements was increased in sense and decreased in antisense lines. The immunoelectron microscopy revealed a reduction in LM 10 and LM 11 labelling in the secondary wall of antisense tobacco lines. Biochemical studies showed a radical increase in syringyl lignin in sense lines without any significant change in total lignin content, while S/G ratio decreased considerably in antisense lines. Our results suggest that CAld5H gene plays an important role in xylogenesis stages such as cambial cell division, secondary wall thickness, xylan and syringyl lignin distribution in tobacco. Therefore, CAld5H gene could be considered as a promising target for lignin modification essential for timber quality improvement in rubber.

Activity and Action of Cell-Wall Transglycanases.

Transglycanases (endotransglycosylases) are enzymes that "cut and paste" polysaccharide chains. Several transglycanase activities have been discovered which can cut (i.e., use as donor substrate) each of the major hemicelluloses [xyloglucan, mannans, xylans, and mixed-linkage ß-glucan (MLG)], and, as a recent addition, cellulose. These enzymes may play interesting roles in adjusting the wall's physical properties, influencing cell expansion, stem strengthening, and fruit softening.Activities discussed include the homotransglycanases XET (xyloglucan endotransglucosylase, i.e., xyloglucan-xyloglucan endotransglycosylase), trans-ß-mannanase (mannan -mannan endotransglycosylase), and trans-ß-xylanase (xylan -xylan endotransglucosylase), plus the heterotransglycanases MXE (MLG -xyloglucan endotransglucosylase) and CXE (cellulose -xyloglucan endotransglucosylase).Transglycanases acting on polysaccharide donor substrates can utilize small, labeled oligosaccharides as acceptor substrates, generating easily recognizable polymeric labeled products. We present methods for extracting transglycanases from plant tissues and assaying them in vitro, either quantitatively in solution assays or by high-throughput dot-blot screens. Both radioactively and fluorescently labeled substrates are mentioned. A general procedure (glass-fiber blotting) is illustrated by which proposed novel transglycanase activities can be tested for.In addition, we describe strategies for detecting transglycanase action in vivo. These methods enable the quantification of, separately, XET and MXE action in Equisetum stems. Related methods enable the tissue distribution of transglycanase action to be visualized cytologically.

Alkaline conditions better extract anti-inflammatory polysaccharides from winemaking by-products.

Winemaking generates large amounts of by-products, a well recognized source of phenolic compounds. However, less attention has been paid to the polysaccharide-rich fraction (PRF) and effects of fractionation techniques on its potential bioactivity. Therefore, PRFs from Syrah and Tempranillo winemaking by-products were extracted under aqueous (neutral pH conditions), acidic and alkaline conditions. PRFs were screened for their monosaccharide composition, uronic acid content, homogeneity and molecular weight. Anti-inflammatory activity of PRFs were evaluated on stimulated RAW 264.7 macrophages. PRF obtained in water and/or under acidic conditions showed heterogeneous profiles. As like as in the others, a heterogeneous and complex profile was detected in extracts procured under alkaline conditions. A high content of uronic acid was found in aqueous extracts, thus indicating the presence of pectin. Pectin and hemicellulose were present in PRFs procured under acidic conditions. Alkaline conditions rendered extracts containing a complex mixture of monosaccharides, mainly xylose. This latter PRF was the only one exhibiting anti-inflammatory potential (at 100 µg/mL) by reducing the release of TNF-α and activation of NF-κB in LPS-activated RAW 264.7 macrophages, with no effect on cell viability. Regardless of the grape variety, PRFs obtained under alkaline conditions were the best option to obtain bioactive polysaccharides with potential application as a source of anti-inflammatory compounds. A complex mixture of polymers may be responsible for the anti-inflammatory effects. Finally, according to results procured by NMR, it is possible to suggest that bioactive fractions are composed of a chain of α-L-Araf-(1 → 3) linked, ß-D-Xylp- (1 → 4), α-D-Glcp-(1 → 4) linked, α-D-GalpA-(1 → 4), α-D-Gal-(1 → 2) forming possible RG I and RG II and xylan chains.

Xylans of Red and Green Algae: What Is Known about Their Structures and How They Are Synthesised?

Xylans with a variety of structures have been characterised in green algae, including chlorophytes (Chlorophyta) and charophytes (in the Streptophyta), and red algae (Rhodophyta). Substituted 1,4-ß-d-xylans, similar to those in land plants (embryophytes), occur in the cell wall matrix of advanced orders of charophyte green algae. Small proportions of 1,4-ß-d-xylans have also been found in the cell walls of some chlorophyte green algae and red algae but have not been well characterised. 1,3-ß-d-Xylans occur as triple helices in microfibrils in the cell walls of chlorophyte algae in the order Bryopsidales and of red algae in the order Bangiales. 1,3;1,4-ß-d-Xylans occur in the cell wall matrix of red algae in the orders Palmariales and Nemaliales. In the angiosperm Arabidopsis thaliana, the gene IRX10 encodes a xylan 1,4-ß-d-xylosyltranferase (xylan synthase), and, when heterologously expressed, this protein catalysed the production of the backbone of 1,4-ß-d-xylans. An orthologous gene from the charophyte green alga Klebsormidium flaccidum, when heterologously expressed, produced a similar protein that was also able to catalyse the production of the backbone of 1,4-ß-d-xylans. Indeed, it is considered that land plant xylans evolved from xylans in ancestral charophyte green algae. However, nothing is known about the biosynthesis of the different xylans found in chlorophyte green algae and red algae. There is, thus, an urgent need to identify the genes and enzymes involved.

Deep Eutectic Solvent Aqueous Solutions as Efficient Media for the Solubilization of Hardwood Xylans.

This work contributes to the development of integrated lignocellulosic-based biorefineries by the pioneering exploitation of hardwood xylans by solubilization and extraction in deep eutectic solvents (DES). DES formed by choline chloride and urea or acetic acid were initially evaluated as solvents for commercial xylan as a model compound. The effects of temperature, molar ratio, and concentration of the DES aqueous solutions were evaluated and optimized by using a response surface methodology. The results obtained demonstrated the potential of these solvents, with 328.23 g L-1 of xylan solubilization using 66.7 wt % DES in water at 80 °C. Furthermore, xylans could be recovered by precipitation from the DES aqueous media in yields above 90 %. The detailed characterization of the xylans recovered after solubilization in aqueous DES demonstrated that 4-O-methyl groups were eliminated from the 4-O-methylglucuronic acids moieties and uronic acids (15 %) were cleaved from the xylan backbone during this process. The similar Mw values of both pristine and recovered xylans confirmed the success of the reported procedure. DES recovery in four additional extraction cycles was also demonstrated. Finally, the successful extraction of xylans from Eucalyptus globulus wood by using aqueous solutions of DES was demonstrated.

Preparation of new ß-D-xyloside- and ß-D-xylobioside-based ionic liquids through chemical and/or enzymatic reactions.

Several tetraalkylphosphonium and tetraalkylammonium salts containing xyloside- and xylobioside-based anionic moieties have been prepared. Two stereoselective routes have been developed: i) a chemical pathway in four steps from D-xylose, and ii) a chemoenzymatic pathway directly from biomass-derived xylans. These salts displayed interesting properties as ionic liquids. Their structures have been correlated to their thermal properties (melting, glass transition and decomposition temperatures).

Characterization of structural cell wall polysaccharides in cattail (Typha latifolia): Evaluation as potential biofuel feedstock.

Second generation bioethanol produced from lignocellulosic biomass is attracting attention as an alternative energy source. In this study, a detailed knowledge of the composition and structure of common cattail (Typha latifolia L.) cell wall polysaccharides, obtained from stem or leaves, has been conducted using a wide set of techniques to evaluate this species as a potential bioethanol feedstock. Our results showed that common cattail cellulose content was high for plants in the order Poales and was accompanied by a small amount of cross-linked polysaccharides. A high degree of arabinose-substitution in xylans, a high syringyl/guaiacyl ratio in lignin and a low level of cell wall crystallinity could yield a good performance for lignocellulose saccharification. These results identify common cattail as a promising plant for use as potential bioethanol feedstock. To the best of our knowledge, this is the first in-depth analysis to be conducted of lignocellulosic material from common cattail.

Size-exclusion chromatography of xylan derivatives-the critical evaluation of macromolecular data.

Hydroxypropyl xylans with varying degrees of substitution were characterized by size-exclusion chromatography. Molar masses of the samples were determined using two approaches: by conventional calibration with molar mass standards and by a multi-detection method that utilizes the combination of static light scattering, viscometry, and differential refractive index detection. The molar mass results obtained by the multi-detection method were accurate, but required the determination of separate refractive index increments for each structurally different sample. The column calibration approach with standard pullulan samples gave biased results due to the differences in hydrodynamic volumes between pullulans and hydroxypropyl xylans with similar molar masses. The degree of hydroxypropylation affected the chain conformation and compactness of the polymer chains. Mark-Houwink parameters and persistence length values suggested that the hydroxypropyl substituents reduced the flexibility of the xylan chain and made the polymer chain more extended.

GH115 α-glucuronidase and GH11 xylanase from Paenibacillus sp. JDR-2: potential roles in processing glucuronoxylans.

Paenibacillus sp. JDR-2 (Pjdr2) has been studied as a model for development of bacterial biocatalysts for efficient processing of xylans, methylglucuronoxylan, and methylglucuronoarabinoxylan, the predominant hemicellulosic polysaccharides found in dicots and monocots, respectively. Pjdr2 produces a cell-associated GH10 endoxylanase (Xyn10A1) that catalyzes depolymerization of xylans to xylobiose, xylotriose, and methylglucuronoxylotriose with methylglucuronate-linked α-1,2 to the nonreducing terminal xylose. A GH10/GH67 xylan utilization regulon includes genes encoding an extracellular cell-associated Xyn10A1 endoxylanase and an intracellular GH67 α-glucuronidase active on methylglucuronoxylotriose generated by Xyn10A1 but without activity on methylglucuronoxylotetraose generated by a GH11 endoxylanase. The sequenced genome of Pjdr2 contains three paralogous genes potentially encoding GH115 α-glucuronidases found in certain bacteria and fungi. One of these, Pjdr2_5977, shows enhanced expression during growth on xylans along with Pjdr2_4664 encoding a GH11 endoxylanase. Here, we show that Pjdr2_5977 encodes a GH115 α-glucuronidase, Agu115A, with maximal activity on the aldouronate methylglucuronoxylotetraose selectively generated by a GH11 endoxylanase Xyn11 encoded by Pjdr2_4664. Growth of Pjdr2 on this methylglucuronoxylotetraose supports a process for Xyn11-mediated extracellular depolymerization of methylglucuronoxylan and Agu115A-mediated intracellular deglycosylation as an alternative to the GH10/GH67 system previously defined in this bacterium. A recombinantly expressed enzyme encoded by the Pjdr2 agu115A gene catalyzes removal of 4-O-methylglucuronate residues α-1,2 linked to internal xylose residues in oligoxylosides generated by GH11 and GH30 xylanases and releases methylglucuronate from polymeric methylglucuronoxylan. The GH115 α-glucuronidase from Pjdr2 extends the discovery of this activity to members of the phylum Firmicutes and contributes to a novel system for bioprocessing hemicelluloses.