Amorphous Polysaccharides Research Articles

Effect of Moisture Content on Ion Diffusion and Glass Transition Temperature in Wood Cell Walls.

Understanding and controlling the diffusion of ions and chemicals within the secondary plant cell walls are pivotal in various applications of biomasses. Recent studies have shown that inorganic ion diffusion through secondary cell walls is controlled by a moisture-induced glass transition in amorphous polysaccharides, including amorphous cellulose and hemicelluloses. Understanding the diffusion of ions in these structures has been the subject of numerous recent experiments; however, a deep understanding of the underlying mechanisms of interactions between ion atoms and water/hemicellulose molecules is still lacking. This study uses molecular dynamics simulations to elucidate the diffusion mechanisms of potassium and chloride ions in the cell walls under varying moisture content. The results reveal that a higher moisture content leads to the formation of solvent layers around the ions and reduces the charge interaction between the functional groups of wood polymers and ions. Hence, a higher moisture content results in an improved diffusion rate of ions within the domain. The simulation results also show that higher moisture content lowers the glass transition temperature, promoting diffusion of ions in the system. In contrast, increases in the ion concentration increase the glass transition temperature of the system and degrade the diffusion of ions in the system.

Comparison on thermally modified beech wood in different mediums: Morphology, chemical change and water-related properties

Thermal modification has been proved to be an effective approach to improve the dimensional stability of wood, while different processes of thermal modification often resulted in various efficacy. In this study, the morphology, chemical structure, crystallinity, pore size distribution, and some water-related properties were investigated in order to explore the effect of different mediums (vacuum, nitrogen, steam and air) on thermally modified wood (TMW). It was found that heating medium plays an important role in thermal modification of wood. At both 180 and 210 ℃, the general severity of thermal modification is in the following order: air > steam > nitrogen > vacuum. Accordingly, the highest dimensional stability appeared in air TMW, and then steam, nitrogen, and vacuum. It seemed that the water-related properties were primarily affected by the extent of decomposition of the amorphous polysaccharides, but showed no direct relationship with the pore structure. Lignin changed greatly for TMW treated in steam at 180 ℃ and all TMW treated at 210 ℃, by showing more uniform distribution in all cell wall layers. It might be resulted from the migration of lignin fragments after depolymerization, the formation of pseudo lignin from holocellulose, and the increased relative lignin content in secondary wall. The changes on pore structure and lignin structure might have significant effect on other wood properties.

Enhancing enzymatic saccharification of sunflower straw through optimal tartaric acid hydrothermal pretreatment

Sunflower straw, a usually neglected and abundant agricultural waste, has great potential for contributing to environmental protection realizing its high-value of valorization if utilizing properly. Because hemicellulose contains amorphous polysaccharide chains, relatively mild organic acid pretreatment can effectively reduce its resistance. Through hydrothermal pretreatment, sunflower straw was pretreated in tartaric acid (1 wt%) at 180 °C for 60 min to enhance its reducing sugar recovery. After tartaric acid-assisted hydrothermal pretreatment, 39.9% of lignin and 90.2% of xylan were eliminated. The reducing sugar recovery increased threefold, while the solution could be effectively reused for four cycles. The properties of more porous surface, improved accessibility, and decreased surface lignin area of sunflower straw were observed through various characterizations, which explained the improved saccharide recovery and provided a basis for the mechanism of tartaric acid-assisted hydrothermal pretreatment. Overall, this tartaric acid hydrothermal pretreatment strategy greatly provided new impetus for the biomass refinery.

Characterization and biological activity of acidic sugarcane leaf polysaccharides by microwave-assisted hot alkali extraction

As a waste of sugarcane, the added value of sugarcane leaves has not been fully utilized, and sugarcane leaf polysaccharide is an important active component of sugarcane leaves. Using new extraction methods to study the structure and biological activity of polysaccharides from sugarcane leaves is of great significance for the development and application of sugarcane leaves. To determine the structural characteristics and biological activities of different acidic sugarcane leaf polysaccharides (ASLPs) extracted by microwave-assisted hot alkali extraction (MALE), three new acidic sugarcane leaf polysaccharides (ASLP-50, ASLP-70 and ASLP-90) were precipitated by ethanol. The structure of ASLPs extracted by MALE contains protein, sulfate and uronic acid. ASLP-50 (195.88 kDa), ASLP-70 (94.62 kDa) and ASLP-90 (16.37 kDa) were acidic polysaccharides composed of mannose, galacturonic acid, glucose, arabinose and fucose. The results of XRD and NMR showed that ASLPs were amorphous polysaccharides composed of α-L-Araf-(1→ main chain, and its branching points were composed of Arap and GalpA residues. In addition, ASLPs showed significant antioxidant, hypoglycemic, hypolipidemic and antibacterial activities in vitro. The research and application of ASLPs provide a reference for the recycling of sugarcane leaves, which is conducive to the development of food, agriculture and pharmaceutical industries.

Cell compensatory responses of fungi to damage of the cell wall induced by Calcofluor White and Congo Red with emphasis on Sporothrix schenckii and Sporothrix globosa. A review.

The cell wall (CW) of fungi exhibits a complex structure and a characteristic chemical composition consisting almost entirely of interacting crystalline and amorphous polysaccharides. These are synthesized by a number of sugar polymerases and depolymerases encoded by a high proportion of the fungal genome (for instance, 20% in Saccharomyces cerevisiae). These enzymes act in an exquisitely coordinated process to assemble the tridimensional and the functional structure of the wall. Apart from playing a critical role in morphogenesis, cell protection, viability and pathogenesis, the CW represents a potential target for antifungals as most of its constituents do not exist in humans. Chitin, β-glucans and cellulose are the most frequent crystalline polymers found in the fungal CW. The hexosamine biosynthesis pathway (HBP) is critical for CW elaboration. Also known as the Leloir pathway, this pathway ends with the formation of UDP-N-GlcNAc after four enzymatic steps that start with fructose-6-phosphate and L-glutamine in a short deviation of glycolysis. This activated aminosugar is used for the synthesis of a large variety of biomacromolecules in a vast number of organisms including bacteria, fungi, insects, crustaceans and mammalian cells. The first reaction of the HBP is catalyzed by GlcN-6-P synthase (L-glutamine:D-fructose-6-phosphate amidotransferase; EC 2.6.1.16), a critical enzyme that has been considered as a potential target for antifungals. The enzyme regulates the amount of cell UDP-N-GlcNAc and in eukaryotes is feedback inhibited by the activated aminosugar and other factors. The native and recombinant forms of GlcN-6-P synthase has been purified and characterized from both prokaryotic and eukaryotic organisms and demonstrated its critical role in CW remodeling and morphogenesis after exposure of some fungi to agents that stress the cell surface by interacting with wall polymers. This review deals with some of the cell compensatory responses of fungi to wall damage induced by Congo Red and Calcofluor White.

Characterization and Antibacterial Activity of a Polysaccharide Produced From Sugarcane Molasses by Chaetomium globosum CGMCC 6882.

As a by-product of the sugar industry containing many sugars, proteins, nitrogenous materials, and heavy metals, molasses is rarely used for polysaccharide production. In the present work, a Chaetomium globosum CGMCC 6882 polysaccharide was produced from sugarcane molasses (CGP-SM) was successfully produced from sugarcane molasses. The yield of CGP-SM was 5.83 ± 0.09 g/l and its protein content was 2.41 ± 0.12% (w/w). Structural analysis showed that CGP-SM was a crystalline and amorphous polysaccharide containing rhamnose, glucosamine, galactose, glucose, mannose, fructose, and glucuronic acid in the molar ratio of 10.31: 1.14: 2.07: 59.55: 42.65: 1.92: 9.63. Meanwhile, weight-average molecular weight (Mw), number-average molecular weight (Mn), and polydispersity (Mw/Mn) of CGP-SM were 28.37 KDa, 23.66 KDa, and 1.199, respectively. Furthermore, the bacteriostatic assay indicated that CGP-SM inhibited the growth of Escherichia coli and Staphylococcus aureus in a concentration-dependent manner, and its inhibitory effect on S. aureus was higher than that of E. coli. Above all, this work provides a green method for the production of bioactive polysaccharide from sugarcane molasses.

Modification of xylan via an oxidation–reduction reaction

Xylan is a biopolymer readily available from forest resources. Various modification methods, including oxidation with sodium periodate, have been shown to facilitate the engineering applications of xylan. However, modification procedures are often optimized for semicrystalline high molecular weight polysaccharide cellulose rather than for lower molecular weight and amorphous polysaccharide xylan. This paper elucidates the procedure for the periodate oxidation of xylan into dialdehyde xylan and its further reduction into a dialcohol form and is focused on the modification work up. The oxidation–reduction reaction decreased the molecular weight of xylan while increased the dispersity more than 50%. Unlike the unmodified xylan, all the modified grades could be solubilized in water, which we see essential for facilitating the future engineering applications of xylan. The selection of quenching and purification procedures and pH-adjustment of the reduction step had no significant effect on the degree of oxidation, molecular weight and only a minor effect on the hydrodynamic radius in water. Hence, it is possible to choose the simplest oxidation-reduction route without time consuming purification steps within the sequence.

Bioinspired manufacturing of oriented polysaccharides scaffolds for strong, optical haze and anti-UV/bacterial membranes

Here, biomimetic dual esterification strategy was proposed on natural polysaccharides cellulose nanocrystals (CNCs) and galactomannan (GM) in combination with tartaric acid (TA) and benzoic anhydride (BA) respectively. Evaporation-induced self-assembly (EISA) formed the oriented quasinematic structure of the nanocomposites membranes. The CNCs crystallites were modified by TA and intercalated by amorphous polysaccharides, building a complex supramolecular network. Thus, it presents excellent light scattering property with the optical haze of ~90%, which was rarely reported previously. TA and BA simultaneously contributed to satisfying UV adsorption capability for the membranes, showing almost whole-spectra UVA/UVB blocking. Super high mechanical strength (>150 MPa) and toughness (~8 kJ/m3) were revealed by the membranes with high addition amount of BA, together with the efficient antibacterial capability on both Gram-positive and negative bacteria. The diverse optical, mechanical and biological functions displayed by the polysaccharides membranes, propose new horizons on application for packaging, optoelectronic and biomonitoring sensors.

Influence of biological origin on the tensile properties of cellulose nanopapers

Cellulose nanopapers provide diverse, strong and lightweight templates prepared entirely from sustainable raw materials, cellulose nanofibers (CNFs). Yet the strength of CNFs has not been fully capitalized in the resulting nanopapers and the relative influence of CNF strength, their bonding, and biological origin to nanopaper strength are unknown. Here, we show that basic principles from paper physics can be applied to CNF nanopapers to illuminate those relationships. Importantly, it appeared that ~ 200 MPa was the theoretical maximum for nanopapers with random fibril orientation. Furthermore, we demonstrate the contrast in tensile strength for nanopapers prepared from bacterial cellulose (BC) and wood-based nanofibrillated cellulose (NFC). Endemic amorphous polysaccharides (hemicelluloses) in NFC act as matrix in NFC nanopapers, strengthening the bonding between CNFs just like it improves the bonding between CNFs in the primary cell wall of plants. The conclusions apply to all composites containing non-woven fiber mats as reinforcement.Graphic abstract

Chiral Cellulose Nanocrystals with Intercalated Amorphous Polysaccharides for Controlled Iridescence and Enhanced Mechanics

AbstractA unique case of combined enhanced mechanical performance and tunable structural color for chiral composites from cellulose nanocrystals (CNCs) arises by adding nanofibrillar wood‐derived polymers with similar chemical compositions. When amorphous polysaccharides (pullulan, dextran, and xylan) are added, they intercalate seamlessly into the original helicoidal organization via interstitial volumes within nanocrystals and between nematic monolayers. The polysaccharides fill the available free volume in between packed nanocrystals until 40 wt% content is reached, with no phase separation occurring. Due to the inter‐nanocrystal intercalation, these natural polysaccharide–cellulose composites show a nearly twofold increase in toughness and modulus. Beyond improved mechanics, the preserved iridescence shows a dramatic red shift from blue to near‐infrared region, expanding the initial pitch length without disturbing the long‐range chiral ordering. In the mechanistic model suggested here, the individual backbones first form intercalated morphologies in the interstitial volumes between tightly packed nanocrystals. After this, the polysaccharides form a monolayer, and eventually double layer, between nanocrystal monolayers, thus incrementally “unwinding” initial chiral organization. The resulting CNC–polysaccharide films maintain their vivid iridescence with broad color appearance and are among the first entirely biobased composites to maintain iridescence with improved mechanics.

Measurement of moisture-dependent ion diffusion constants in wood cell wall layers using time-lapse micro X-ray fluorescence microscopy

Our future bioeconomy depends on increased utilization of renewable lignocellulosic biomass. Controlling the diffusion of chemicals, such as inorganic ions, within secondary plant cell walls is central to many biomass applications. However, insufficient understanding of intra-cell-wall diffusion within secondary plant cell walls is hindering the advancement of many lignocellulosic biomass applications. In this work, X-ray fluorescence microscopy was used to measure diffusion constants of K+, Cu2+, and Cl− diffusing through loblolly pine (Pinus taeda) cell wall layers under 70%, 75%, or 80% relative humidity (RH). Results revealed that diffusion constants increased with RH, the larger Cu2+ diffused more slowly than the K+, and the Cl− diffusion constant was the same as that for the counter cation, indicating cations and anions diffused together to maintain charge neutrality. Comparison with electrical conductivity measurements showed that conductivity is being controlled by ion mobility over these RH. The results further support that intra-cell-wall diffusion of inorganic ions is a Fickian diffusion process occurring through rubbery amorphous polysaccharides, which contradicts previous assertions that intra-cell-wall diffusion is an aqueous process occurring through water pathways. Researchers can now utilize polymer science approaches to engineer the molecular architecture of lignocellulosic biomass to optimize properties for specific end uses.

Zwitterionic Polypeptides: Chemoenzymatic Synthesis and Loosening Function for Cellulose Crystals.

A polypeptide with a GlyHisGly repeating sequence containing zwitterionic structures that effectively interact with cellulose was synthesized for dissociation of cellulose crystals. Polypeptide with the GlyHisGly sequence was synthesized by chemoenzymatic polymerization and postfunctionalization of the His residues was performed to afford imidazolium butyrate on the side chains. The resulting zwitterionic polypeptide effectively dissociated bundles of tunicate cellulose nanocrystals, even when the conditions were mild and the concentration of the polypeptide was as low as 1-2 mg mL-1. Polypeptide treatment also affected the morphology of the cell walls in cultured plant cells, and the cellulose microfibril networks and amorphous polysaccharide layer were dissociated according to atomic force microscopy (AFM). The zwitterionic polypeptide treatment did not change the crystal structure of the cellulose nanocrystals. Analysis of the mechanical properties of the cellulose nanocrystals by force curve measurements using AFM revealed that the elastic modulus of the cellulose nanocrystals increased after treatment with the zwitterionic polypeptide, indicating that the amorphous part of the cellulose nanocrystals was removed by interactions with the polypeptide. At a concentration of the polypeptide that enabled the dissociation of the cellulose network, the zwitterionic polypeptide showed negligible cytotoxicity to the plant cells. The mild and noncytotoxic technique for loosening cellulose microfibrils/nanocrystals that was developed in this study has tremendous significance for the modification of cellulose in terms of polymer chemistry, material science, and plant biotechnology.

Hydrothermal treatments to promote surface inactivation and increased flexibility in three hardwoods

In the present study, three juvenile hardwoods (namely sycamore, pecan and london plane) were treated by boiling, steaming and microwave. Trees from Platanus x acerifolia (sycamore), Carya illinoinensis (pecan) and Luehea divaricata (london plane) were selected in homogeneous forests located in southern Brazil. Each hydrothermal treatment was performed for 60 min. In general, the hydrothermal treatments caused a certain surface inactivation effect, which was marked by decreased surface roughness, increased hydrophobic charac-ter and darkened colour patterns. Also, both decreased stiffness and strength, as well as increased deflectibility were obtained. These mechanisms were attributed to degradation in fine segments from amorphous polysac-charides, leaching of some organic extractives and fragmentation of lignin, as indirectly indicated by infrared spectra

Encapsulation of poorly soluble drugs in yeast glucan particles by spray drying improves dispersion and dissolution properties.

In this work, novel amorphous solid dispersions based on yeast glucan particles were produced. Yeast glucan particles are hollow and porous, and they are mainly composed of amorphous polysaccharides. We hypothesized that these particles are suitable candidates for the amorphization of drugs with low water solubility. Model drugs ibuprofen and curcumin were successfully encapsulated in glucan particles by spray drying. Different spray-drying parameters were tested to evaluate the influence of atomizing droplet size and initial solid content on encapsulation efficiency. It was shown that higher solid content and, more significantly, larger droplet sizes lead to higher encapsulation efficiencies. The encapsulation efficiency of ibuprofen (10wt%) into glucan particles was considerably improved from 41.3±0.5% to 64.3±0.2% by increasing initial solid content and droplet size with the two-fluid nozzle. The spray drying process was further optimized by using the ultrasonic nozzle and it was possible to achieve complete encapsulation of ibuprofen and curcumin without any precipitation of the active compound outside of the glucan particles. Overall, it was possible to produce completely amorphous composites with outstanding wettability and dispersion properties, and with significantly faster dissolution rates when compared to the micronized crude drug.

Effects of Moisture on Diffusion in Unmodified Wood Cell Walls: A Phenomenological Polymer Science Approach

Despite the importance of cell wall diffusion to nearly all aspects of wood utilization, diffusion mechanisms and the detailed effects of moisture remain poorly understood. In this perspective, we introduce and employ approaches established in polymer science to develop a phenomenological framework for understanding the effects of moisture on diffusion in unmodified wood cell walls. The premise for applying this polymer-science-based approach to wood is that wood polymers (cellulose, hemicelluloses, and lignin) behave like typical solid polymers. Therefore, the movement of chemicals through wood cell walls is a diffusion process through a solid polymer, which is in contrast to previous assertions that transport of some chemicals occurs via aqueous pathways in the cell wall layers. Diffusion in polymers depends on the interrelations between free volume in the polymer matrix, molecular motions of the polymer, diffusant dimensions, and solubility of the diffusant in the polymer matrix. Because diffusion strongly depends on whether a polymer is in a rigid glassy state or soft rubbery state, it is important to understand glass transitions in the amorphous wood polymers. Through a review and analysis of available literature, we conclude that in wood both lignin and the amorphous polysaccharides very likely have glass transitions. After developing and presenting this polymer-science-based perspective of diffusion through unmodified wood cell walls, suggested directions for future research are discussed. A key consideration is that a large difference between diffusion through wood polymers and typical polymers is the high swelling pressures that can develop in unmodified wood cell walls. This pressure likely arises from the hierarchical structure of wood and should be taken into consideration in the development of predictive models for diffusion in unmodified wood cell walls.

Effect of mercerization on the physico-chemical properties of matured and seasoned Cocos nucifera fibers for making sustainable composites

This study is mainly focused to exploit the potential of the leftover Cocos nucifera fibers that remains after taking the fruit. These fibers are extracted and are seasoned under sunlight for 120 days before using them for the study. Alkaline treatment on the fibers and its effect on the moisture content, density and chemical composition are studied by conducting characterization techniques. Characterization studies such as Fourier Transform Infrared spectroscopy, x-ray diffraction and Thermo-gravimetric studies are conducted to determine to the micro-structural characterization changes that have taken place as a result of mercerization on the matured and seasoned fibers. It is seen from the FTIR studies that the hydrogen bond energy of the untreated fibers doubled from 3.938 kJ to 7.875 kJ along with corresponding increase in hydrogen bond distance upon mercerization. Removal of amorphous components in fibers guarantee improved adhesion between fibers and matrix during composite fabrication. X-ray diffraction studies and thermogravimetric analysis show 16.75% increase in crystalline index and enhanced thermal stability respectively upon mercerization. Removal of gummy amorphous polysaccharides after mercerization causes reduction in decomposition temperature to a lower temperature of 462 °C from 485 °C. This study thus concludes that matured and seasoned Cocos nucifera fibers can be potentially used as polymeric reinforcements and their properties can be enhanced after mercerization to produce relatively stronger, light weight sustainable composites like automobile interiors, packaging cases and mobile phone covers.

Mechanism for Diffusion through Secondary Cell Walls in Lignocellulosic Biomass.

The future bioeconomy depends on the increased utilization of renewable lignocellulosic resources from trees and other bioenergy crops. However, considering that the diffusion of ions, chemicals, and enzymes into secondary cell walls is critical to effectively utilize lignocellulosic biomass, the unidentified mechanisms underpinning this diffusion have hindered progress. Here, nanomechanical spectroscopy was used to measure changes in moisture-dependent relaxations of amorphous polysaccharides inside loblolly pine ( Pinus taeda) cell wall layers. The comparison with recent ion mobility measurements made in similar cell wall layers revealed that the mineral ion diffusion occurs via interconnecting nanoscale pathways of rubbery amorphous polysaccharides. This result contradicts previous assertions of cell wall transport being an aqueous process occurring through simple interconnecting water pathways. Because polymer diffusion and aqueous transport via water channels are such different phenomena, the identification of the diffusion mechanism in this manuscript opens up a new paradigm in lignocellulosic research. The utilization of lignocellulosic resources is expected to be accelerated because the extensive polymer science literature can now be used to design the molecular architecture of lignocellulosic biomass to optimize diffusion properties for specific uses, including biorefinery feedstocks, advanced materials, and wood-based construction materials.

β-Glucan as an immune activator and a carrier in the construction of a synthetic MUC1 vaccine.

We describe the preparation of a cancer vaccine candidate by conjugating a MUC1 peptide antigen to the β-glucan polysaccharide, which serves both as a carrier and an immune activator. In contrast to amorphous polysaccharides, peptide-β-glucan conjugates form uniform nanoparticles that facilitate the delivery of antigens and binding to myeloid cells, thus leading to the activation of both innate and adaptive immunity.

Effect of structure features of polysaccharides on properties of dialdehyde polysaccharide tanning agent

Sodium alginate (SA), tara gum (TG), starch (ST) and cyclodextrin (CD) were oxidized to dialdehyde polysaccharides (DAPs) using equivalent sodium periodate. The effects of polysaccharide structure features on aldehyde group content, molecular size and tanning performance of DAPs were investigated. Each DAP had abundant aldehyde groups (>7 mmol/g) for fur tanning in the experimental conditions, and DAP with higher aldehyde group content was obtained when polysaccharide with lower molecular weight and linear chain was used. Lower crystallinity and β-(1→4) glycosidic linkage of polysaccharide benefited its degradation. Compared with dialdehyde ST (Mw>150,000) and dialdehyde CD (Mw<500), DAPs prepared from β-(1→4)-linked amorphous SA and TG had moderate molecular sizes (Mw 15,000–30,000) and exhibited satisfactory penetrability and crosslinking reactivity in collagen fiber network, and thus performed more favorable tanning properties in terms of higher shrinkage temperature and whiteness of fur. This suggests the suitability of β-(1→4)-linked amorphous polysaccharides for preparing dialdehyde tanning agents.

Comparison of chemical treatment methods for loblolly pine to utilize as enzyme hydrolyzate feedstock

The ground pine wood chips (GPWC) were examined through chemical treatment methods employing alkaline hydrogen peroxide treatment (AHP, consisted of 50 g L−1 potassium hydroxide, and 50 g L−1 hydrogen peroxide with added water at 78 °C for 24 h), and ethyl-hydro-oxides treatment (EHOs, consisted of 60% ethanol (of total solution), 50 g L−1 potassium hydroxide, and 50 g L−1 hydrogen peroxide with added water at 78 °C for 24 h). The effects of chemical treatments on GPWC were examined through combination of chemical composition followed by enzymatic hydrolysis (using Accellerase® 1500). The application of EHOs treatment removes the foaming issue that currently occurs due to AHP treatment at the elevated temperature. A removal of the foaming phenomenon increased the enzymatic glucan conversion (>70%) which is important in increasing the efficiency of biorefinery. The interaction of different variables in EHOs solvent formulations including ethanol concentration (0–60%), potassium hydroxide concentration (0–50 g L−1), hydrogen peroxide concentration (0–50 g L−1), and processing temperature (38 °-78 °C) were analyzed through four variables response surface methodology using glucan conversion and total polysaccharide conversion as responses. The glucan conversion and total polysaccharide conversion were analyzed to determine the specific and overall effects of Accellerase® 1500 on the amorphous polysaccharide contents of GPWC resulted through EHOs treatment formulations, respectively. The implications of all these findings are discussed with the available literature.