Adsorption of arabinoxylan on cellulosic surfaces: influence of degree of substitution and substitution pattern on adsorption characteristics

Cereal dietary fiber regulates the quality of whole grain products: Interaction between composition, modification and processing adaptability

The coarse texture and difficulty in processing dietary fiber (DF) in cereal bran have become limiting factors for the development of the whole cereal grain (WCG) food industry. To promote the development of the WCG industry, this review comprehensively summarizes the various forms and structures of cereal DF, including key features such as molecular weight, chain structure, and substitution groups. Different modification methods for changing the chemical structure of DF and their effects on the modification methods on physicochemical properties and biological activities of DF are discussed systematically. Furthermore, the review focusses on exploring the interactions between DF and dough components and discusses the effects on the gluten network structure, starch gelatinization and retrogradation, fermentation, glass transition, gelation, and rheological and crystalline characteristics of dough. Additionally, opportunities and challenges regarding the further development of DF for the flour products are also reviewed. The objective of this review is to establish a comprehensive foundation for the precise modification of cereal DF, particularly focusing on its application in dough-related products, and to advance the development and production of WCG products.

Structural changes of hemicellulose during pulping process and its interaction with nanocellulose

It is believed that hemicellulose plays a crucial role in binding cellulose and lignin in plant cells. It may provide significant implications through figuring out the interaction between hemicellulose and microfibers and gaining insights how the structure of hemicellulose affects its association with cellulose nanofibers. Herein, the hemicellulose and nanocellulose fractions from pulps obtained by controlling the H-factors of kraft pulping process were quantitatively evaluated for their adsorption behavior using QCM-D. The results showed that harsher cooking (corresponding to high H-factor) significantly affected the chemical composition of hemicellulose, leading to a decrease of its molecular weight and gradually turning it into a linear structure. Hemicellulose possesses a strong natural affinity for CNC-coated sensors. The hemicellulose from the pulp cooked by high H-factor process decreases its ability to adsorb onto nanocellulose, the adsorption rate also slows down, and the conformation of the adsorbed layer changes which makes the binding weak and reversible. In conclusion, the pulping process in high H-factor significantly changed the structure of hemicellulose, leading to a variation in the strength of its interaction with nanocellulose.

Arabinoxylan in Water through SANS: Single-Chain Conformation, Chain Overlap, and Clustering

Using small-angle neutron scattering (SANS), we examine the structure and conformational behavior of wheat arabinoxylan (AX) prepared at various concentrations in a sodium phosphate aqueous buffer. As for another major hemicellulose, xyloglucan, we observe a small number of large clusters surrounded by AX chains that behave exactly as a polymer in good solvent with a Flory exponent ν = 0.588. The fit of the data at high q-values to a standard worm-like chain model gives the persistence length lp = 45 Å and cross section of the chains 2Rc = 11-12 Å. In addition, using a dedicated modeling approach, we extract from the SANS data at the intermediate q-range the correlation length ξ of the solutions in the semidilute regime. The decay of ξ with concentration follows a scaling law that further confirms the self-avoiding statistical behavior of the AX chains. This first comprehensive study about the properties of water-soluble AX at different length scales may help in the development of products and processes involving AX as a substitute for fossil carbon molecules.

Functional and Nutritional Characteristics of Natural or Modified Wheat Bran Non-Starch Polysaccharides: A Literature Review

Wheat bran (WB) consists mainly of different histological cell layers (pericarp, testa, hyaline layer and aleurone). WB contains large quantities of non-starch polysaccharides (NSP), including arabinoxylans (AX) and β-glucans. These dietary fibres have long been studied for their health effects on management and prevention of cardiovascular diseases, cholesterol, obesity, type-2 diabetes, and cancer. NSP benefits depend on their dose and molecular characteristics, including concentration, viscosity, molecular weight, and linked-polyphenols bioavailability. Given the positive health effects of WB, its incorporation in different food products is steadily increasing. However, the rheological, organoleptic and other problems associated with WB integration are numerous. Biological, physical, chemical and combined methods have been developed to optimise and modify NSP molecular characteristics. Most of these techniques aimed to potentially improve food processing, nutritional and health benefits. In this review, the physicochemical, molecular and functional properties of modified and unmodified WB are highlighted and explored. Up-to-date research findings from the clinical trials on mechanisms that WB have and their effects on health markers are critically reviewed. The review points out the lack of research using WB or purified WB fibre components in randomized, controlled clinical trials.

Tuning interfacial microstructure of alginate-based amphiphile by dynamic bonding for stabilizing Pickering emulsion

Polysaccharide-based soft colloidal particles mediated by the dynamic bonding-engineered interfacial self-assembly can regulate the properties of oil-water interfacial films, availing the stability of emulsions under a wide pH range. The amphiphilic phenylboronic alginate soft colloidal particles (Alg-PBA) were designed to stabilize pH-responsive Pickering emulsions (PEs). Combining stability analysis with quartz crystal microbalance and dissipation monitoring (QCM-D), the microstructure and viscoelasticity of Alg-PBA at the oil-water interface were determined. The results showed that PEs stabilized by Alg-PBA due to a thicker and stronger viscoelastic interface film induced by BO bonds and hydrogen bonds. The structure-function relationship of the Alg-PBA emulsifier driven by dynamic bonds was further elaborated at multiple scales by laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Meanwhile, the microstructure of aerogels templated by emulsion could be tuned by adjusting dynamic bonds, which provides a new idea for polysaccharide soft material engineering.

Covalent Bond Interfacial Recognition of Polysaccharides/Silica Reinforced High Internal Phase Pickering Emulsions for 3D Printing

Significant challenges remain in designing sufficient viscoelasticity polysaccharide-based high internal phase Pickering emulsions (HIPPEs) as soft materials for 3D printing. Herein, taking advantage of the interfacial covalent bond interaction between modified alginate (Ugi-OA) dissolved in the aqueous phase and aminated silica nanoparticles (ASNs) dispersed in oil, HIPPEs with printability were obtained. Using multitechniques coupling a conventional rheometer with a quartz crystal microbalance with dissipation monitoring, the correlation between interfacial recognition coassembly on the molecular scale and the stability of whole bulk HIPPEs on the macroscopic scale can be clarified. The results showed that Ugi-OA/ASNs assemblies (NPSs) were strongly retargeted into the oil-water interface due to the specific Schiff base-binding between ASNs and Ugi-OA, further forming thicker and more rigid interfacial films on the microscopic scale compared with that of the Ugi-OA/SNs (bared silica nanoparticles) system. Meanwhile, flexible polysaccharides also formed a 3D network that suppressed the motion of the droplets and particles in the continuous phase, endowing the emulsion with appropriately viscoelasticity to manufacture a sophisticated "snowflake" architecture. In addition, this study opens a novel pathway for the construction of structured all-liquid systems by introducing an interfacial covalent recognition-mediated coassembly strategy, showing promising applications.

Hemicellulolytic enzymes in lignocellulose processing

Lignocellulosic biomass is the most abundant source of carbon-based material on a global basis, serving as a raw material for cellulosic fibers, hemicellulosic polymers, platform sugars, and lignin resins or monomers. In nature, the various components of lignocellulose (primarily cellulose, hemicellulose, and lignin) are decomposed by saprophytic fungi and bacteria utilizing specialized enzymes. Enzymes are specific catalysts and can, in many cases, be produced on-site at lignocellulose biorefineries. In addition to reducing the use of often less environmentally friendly chemical processes, the application of such enzymes in lignocellulose processing to obtain a range of specialty products can maximize the use of the feedstock and valorize many of the traditionally underutilized components of lignocellulose, while increasing the economic viability of the biorefinery. While cellulose has a rich history of use in the pulp and paper industries, the hemicellulosic fraction of lignocellulose remains relatively underutilized in modern biorefineries, among other reasons due to the heterogeneous chemical structure of hemicellulose polysaccharides, the composition of which varies significantly according to the feedstock and the choice of pretreatment method and extraction solvent. This paper reviews the potential of hemicellulose in lignocellulose processing with focus on what can be achieved using enzymatic means. In particular, we discuss the various enzyme activities required for complete depolymerization of the primary hemicellulose types found in plant cell walls and for the upgrading of hemicellulosic polymers, oligosaccharides, and pentose sugars derived from hemicellulose depolymerization into a broad spectrum of value-added products.

Design of experiments as a tool to guide the preparation of tailor-made activated carbons

Activated carbon produced from biomass exhibits a high specific surface area due to the natural hierarchical porous structure of the precursor material. To reduce production costs of activated carbon, bio-waste materials receive more and more attention, which has led to a steep increase in the number of publications over the past decade. However, the characteristics of activated carbon are highly dependent on the properties of the precursor material used, making it difficult to draw assumptions about activation conditions for new precursor materials based on published work. Here, we introduce a Design of Experiment methodology with a Central Composite Design to better predict the properties of activated carbons from biomass. As a model precursor, we employ well-defined regenerated cellulose-based fibers which contain 25 wt.% chitosan as intrinsic dehydration catalyst and nitrogen donor. The use of the DoE methodology opens up the possibility to better identify the crucial dependencies between activation temperature and impregnation ratio on the yield, surface morphology, porosity and chemical composition of the activated carbon, independent of the used biomass. The use of DoE yields contour plots, which allows for more facile analysis on correlations between activation conditions and activated carbon properties, thus enabling its tailor-made manufacturing.

Adsorption and Assembly of Octenyl Succinic Anhydride Starch/Chitosan Electrostatic Complexes at Oil-Water Interface

Biopolymer electrostatic complexes are popular Pickering stabilizers whose structures greatly affect their interfacial properties. This study comprehensively demonstrated the interfacial adsorption and assembly of dissolved octenyl succinic anhydride (OSA) starch (OSA-D)/chitosan (CS) electrostatic complexes with different structures through complementary characterization methods. We found that compared with single-component systems, OSA-D/CS complexes exhibited significantly increased wetting stability and adsorption rate to the interface, which was reinforced by molecular dynamics simulations. Their soft structures and the entanglement of molecular chains led to the formation of thick and highly viscoelastic multilayer adsorbed films, which greatly resisted deformation against shearing forces. The adsorption and assembly of the complexes were strongly influenced by OSA-D/CS ratios and pH, which could be related to the different interfacial interaction strengths. Overall, the electrostatic complexation, structural characteristics, and interfacial properties of OSA-D/CS complexes were well related, thereby providing valuable information for the regulation of controlled interfaces and bulk system properties.

Enzymatic debranching is a key determinant of the xylan-degrading activity of family AA9 lytic polysaccharide monooxygenases

BACKGROUND

Previous studies have revealed that some Auxiliary Activity family 9 (AA9) lytic polysaccharide monooxygenases (LPMOs) oxidize and degrade certain types of xylans when incubated with mixtures of xylan and cellulose. Here, we demonstrate that the xylanolytic activities of two xylan-active LPMOs, TtLPMO9E and TtLPMO9G from Thermothielavioides terrestris, strongly depend on the presence of xylan substitutions.

RESULTS

Using mixtures of phosphoric acid-swollen cellulose (PASC) and wheat arabinoxylan (WAX), we show that removal of arabinosyl substitutions with a GH62 arabinofuranosidase resulted in better adsorption of xylan to cellulose, and enabled LPMO-catalyzed cleavage of this xylan. Furthermore, experiments with mixtures of PASC and arabinoglucuronoxylan from spruce showed that debranching of xylan with the GH62 arabinofuranosidase and a GH115 glucuronidase promoted LPMO activity. Analyses of mixtures with PASC and (non-arabinosylated) beechwood glucuronoxylan showed that GH115 action promoted LPMO activity also on this xylan. Remarkably, when WAX was incubated with Avicel instead of PASC in the presence of the GH62, both xylan and cellulose degradation by the LPMO9 were impaired, showing that the formation of cellulose-xylan complexes and their susceptibility to LPMO action also depend on the properties of the cellulose. These debranching effects not only relate to modulation of the cellulose-xylan interaction, which influences the conformation and rigidity of the xylan, but likely also affect the LPMO-xylan interaction, because debranching changes the architecture of the xylan surface.

CONCLUSIONS

Our results shed new light on xylanolytic LPMO9 activity and on the functional interplay and possible synergies between the members of complex lignocellulolytic enzyme cocktails. These findings will be relevant for the development of future lignocellulolytic cocktails and biomaterials.

Light-dimerization telechelic alginate-based amphiphiles reinforced Pickering emulsion for 3D printing

Functional Pickering emulsions that depend on the interparticle interactions hold promise for building template materials. A novel coumarin-grafting alginate-based amphiphilic telechelic macromolecules (ATMs) undergoing photo-dimerization enhanced particle-particle interactions and changed the self-assembly behavior in solutions. The influence of self-organization of polymeric particles on the droplet size, microtopography, interfacial adsorption and viscoelasticity of Pickering emulsions were further determined by multi-scale methodology. Results showed that stronger attractive interparticle interactions of ATMs (post-UV) endowed Pickering emulsion with small droplet size (16.8 μm), low interfacial tension (9.31 mN/m), thick interfacial film, high interfacial viscoelasticity and adsorption mass, and well stability. The high yield stress, outstanding extrudability (n₁ < 1), high structure maintainability, and well shape retention ability, makes them ideal inks for direct 3D printing without any additions. The ATMs provides an increased capacity to produce stable Pickering emulsions with tailoring their interfacial performances and, providing a platform for fabricating and developing alginate-based Pickering emulsion-templated materials.

Nutritional and Functional Roles of Phytase and Xylanase Enhancing the Intestinal Health and Growth of Nursery Pigs and Broiler Chickens

This review paper discussed the nutritional and functional roles of phytase and xylanase enhancing the intestinal and growth of nursery pigs and broiler chickens. There are different feed enzymes that are currently supplemented to feeds for nursery pigs and broiler chickens. Phytase and xylanase have been extensively studied showing consistent results especially related to enhancement of nutrient digestibility and growth performance of nursery pigs and broiler chickens. Findings from recent studies raise the hypothesis that phytase and xylanase could play functional roles beyond increasing nutrient digestibility, but also enhancing the intestinal health and positively modulating the intestinal microbiota of nursery pigs and broiler chickens. In conclusion, the supplementation of phytase and xylanase for nursery pigs and broiler chickens reaffirmed the benefits related to enhancement of nutrient digestibility and growth performance, whilst also playing functional roles benefiting the intestinal microbiota and reducing the intestinal oxidative damages. As a result, it could contribute to a reduction in the feed costs by allowing the use of a wider range of feedstuffs without compromising the optimal performance of the animals, as well as the environmental concerns associated with a poor hydrolysis of antinutritional factors present in the diets for swine and poultry.

Impact of Wheat Arabinoxylan with Defined Substitution Patterns on the Heat-Induced Polymerization Behavior of Gluten

To further depict the interaction mechanism of wheat arabinoxylan (AX) and gluten proteins upon thermal processing, AX was enzymatically tailored with defined substitution patterns and the impact on the heat-induced polymerization behavior of gluten was comparatively studied. The results showed that tailormade AX promoted the formation of glutenin-glutenin and glutenin-gliadin macrocrosslinks upon heating, with the optimal effect detected for AX depleted of Araf of disubstituted Xylp. The tailormade AX, especially AX depleted of monosubstituted Xylp, facilitated the polymerization ability of α-gliadin into glutenin compared with untailored AX. The unfolding process of gluten was partially impeded by AX upon heating, while the tailormade AX promoted the unfolding process. AX could bury Trp and Tyr upon polymerization of glutenin and gliadin and induced the change of the disulfide bridge conformation to a less-stable state, while the effect was alleviated with tailormade AX. The enhanced polymerization with tailormade AX strengthened the gluten network and induced more heterogeneously distributed large protein aggregates.

Optimization and Rheological Study of an Exopolysaccharide Obtained from Fermented Mature Coconut Water with Lipomyces starkeyi

The current research aimed to solve the environmental pollution of mature coconut water by Lipomyces starkeyi and provide a study of its high value utilization. The innovation firstly investigated the rheological properties and interface behavior of a crude exopolysaccharide and provided a technical support for its application in food. A response surface methodology was performed to ameliorate the fermentation factors of the new exopolysaccharide with mature coconut water as a substrate, and the consequences suggested that the maximum yield was 7.76 g/L under optimal conditions. Rotary shear measurements were used to study the influence of four variables on the viscosity of the exopolysaccharide solution. The results illustrated that the exopolysaccharide solution demonstrated a shear-thinning behavior and satisfactory thermal stability within the test range. The viscosity of the exopolysaccharide solution was significantly affected by ionic strength and pH; it reached the peak viscosity when the concentration of NaCl was 0.1 mol/L and the pH was neutral. The adsorption behavior of the exopolysaccharide at the medium chain triglyceride–water interface was investigated by a quartz crystal microbalance with a dissipation detector. The results demonstrated that the exopolysaccharide might form a multilayer adsorption layer, and the thickness of the adsorption layer was at its maximum at a concentration of 1.0%, while the interfacial film was the most rigid at a concentration of 0.4%. Overall, these results suggest that the exopolysaccharide produced by Lipomyces starkeyi is an excellent biomaterial for usage in drink, makeup and drug fabrications as a thickening and stabilizing agent.

Studies into interactions and interfacial characteristics between cellulose nanocrystals and bovine serum albumin

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Interactions between cellulose nanocrystal (CNC) and BSA were studied.

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BSA dominated the interface behavior in CNC/BSA complex.

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BSA and CNC formed viscoelastic layers at pH 3 driven by electrostatic attraction.

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Interactions mainly occurred between (1 0 0) surface of CNC and domain IIA of BSA.

This study investigates the interactions between cellulose nanocrystals (CNCs) and bovine serum albumin (BSA) under different pH conditions. A multiscale technique was employed to characterize the CNCs and BSA at pH 7 and pH 3. ζ-Potential measurement and UV–vis spectroscopy demonstrated strong interactions between CNCs and BSA at pH 3, whereat they have opposite charges. Interfacial tensiometry showed a deficiency in the surface activity of the CNCs and indicated that BSA dominated the interface behavior in their complex. Quartz crystal microbalance with dissipation revealed that the sequential adsorption of BSA and CNCs produced viscoelastic bilayers at pH 3, and the mass adsorbed was ∼ 28 times that adsorbed at pH 7. Molecular dynamics simulations indicated that the key interactions between the two materials were produced between the hydrophobic CNC surface and the BSA domain IIA region. These results provide interesting insights into the design of complex food emulsions and fluid interfaces.

Tailormade Wheat Arabinoxylan Reveals the Role of Substitution in Regulating Gelatinization and Retrogradation Behavior of Wheat Starch

To elucidate the role of substitution of arabinoxylan (AX) in the characteristics of wheat starch, this study prepared AX with a well-defined structure by targeted enzymatic hydrolysis and comparatively investigated the effects of AX with different degrees of substitution on gelatinization and retrogradation behavior of starch. Removal of major arabinofuranosyl (Araf) of mono- or disubstituted xylopyranosyl (Xylp) of both low-molecular-weight (Mw: 62.5 kDa, Araf/Xylp: 0.61) and high-molecular-weight AX (Mw: 401.2 kDa, Araf/Xylp: 0.61) reversed the decreased gelatinization viscosity and recrystallization of amylose induced by AX to a similar extent. Upon retrogradation for 30 days, the Araf of mono- and disubstituted Xylp contributed to the water distribution and the effect depended on the molecular chain length. The C3-linked Araf of disubstituted Xylp was more involved in prohibiting the retardation of recrystallization of amylopectin, while the presence of Araf of monosubstituted Xylp might hinder the interactions between AX and amylopectin.

Declining carbohydrate solubilization with increasing solids loading during fermentation of cellulosic feedstocks by Clostridium thermocellum: documentation and diagnostic tests

Background

For economically viable 2nd generation biofuels, processing of high solid lignocellulosic substrate concentrations is a necessity. The cellulolytic thermophilic anaerobe Clostridium thermocellum is one of the most effective biocatalysts for solubilization of carbohydrate harbored in lignocellulose. This study aims to document the solubilization performance of Clostridium thermocellum at increasing solids concentrations for two lignocellulosic feedstocks, corn stover and switchgrass, and explore potential effectors of solubilization performance.

Results

Monocultures of Clostridium thermocellum demonstrated high levels of carbohydrate solubilization for both unpretreated corn stover and switchgrass. However, fractional carbohydrate solubilization decreases with increasing solid loadings. Fermentation of model insoluble substrate (cellulose) in the presence of high solids lignocellulosic spent broth is temporarily affected but not model soluble substrate (cellobiose) fermentations. Mid-fermentation addition of cells (C. thermocellum) or model substrates did not significantly enhance overall corn stover solubilization loaded at 80 g/L, however cultures utilized the model substrates in the presence of high concentrations of corn stover. An increase in corn stover solubilization was observed when water was added, effectively diluting the solids concentration mid-fermentation. Introduction of a hemicellulose-utilizing coculture partner, Thermoanaerobacterium thermosaccharolyticum, increased the fractional carbohydrate solubilization at both high and low solid loadings. Residual solubilized carbohydrates diminished significantly in the presence of T. thermosaccharolyticum compared to monocultures of C. thermocellum, yet a small fraction of solubilized oligosaccharides of both C₅ and C₆ sugars remained unutilized.

Conclusion

Diminishing fractional carbohydrate solubilization with increasing substrate loading was observed for C. thermocellum-mediated solubilization and fermentation of unpretreated lignocellulose feedstocks. Results of experiments involving spent broth addition do not support a major role for inhibitors present in the liquid phase. Mid-fermentation addition experiments confirm that C. thermocellum and its enzymes remain capable of converting model substrates during the middle of high solids lignocellulose fermentation. An increase in fractional carbohydrate solubilization was made possible by (1) mid-fermentation solid loading dilutions and (2) coculturing C. thermocellum with T. thermosaccharolyticum, which ferments solubilized hemicellulose. Incomplete utilization of solubilized carbohydrates suggests that a small fraction of the carbohydrates is unaffected by the extracellular carbohydrate-active enzymes present in the culture.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02110-4.

Calcium Ion-Induced Structural Changes in Carboxymethylcellulose Solutions and Their Effects on Adsorption on Cellulose Surfaces

The adsorption of carboxymethylcellulose (CMC) on cellulose surfaces is one of the most studied examples of the adsorption of an anionic polyelectrolyte on a like-charged surface. It has been suggested that divalent ions can act as a bridge between CMC chains and the surface of cellulose and enhance the CMC adsorption: they can, however, also alter the structure of CMCs in the solution. In previous investigations, the influence of cations on solution properties has been largely overlooked. This study investigates the effect of Ca²⁺ ions on the properties of CMC solutions as well as the influence on cellulose nanofibers (CNFs), which was studied by dynamic light scattering and correlated with the adsorption of CMC on a cellulose surface probed using QCM-D. The presence of Ca²⁺ facilitated the multichain association of CMC chains and increased the hydrodynamic diameter. This suggests that the adsorption of CMCs at high concentrations of CaCl₂ is governed mainly by changes in solution properties rather than by changes in the cellulose surface. Furthermore, an entropy-driven mechanism has been suggested for the adsorption of CMC on cellulose. By comparing the adsorption of CMC from H₂O and D₂O, it was found that the release of water from the cellulose surface is driving the adsorption of CMC.

Kinetics and Thermodynamics of Hemicellulose Adsorption onto Nanofibril Cellulose Surfaces by QCM-D

The adsorption of hemicellulose derived from bagasse onto nanofibril cellulose has been studied in terms of kinetics and thermodynamics. In situ monitoring of bagasse hemicellulose with different molecular weights onto the nanofibril cellulose surfaces has been investigated using quartz crystal microbalance and dissipation. Then, the adsorption kinetics and thermodynamic properties were analyzed. Also, the sorption behavior and the adsorption layer properties were quantified in aqueous solutions. The maximum adsorption mass was 2.8314 mg/m2 at a concentration of 200 mg/L. Also, compared with that of the low-molecular-weight hemicellulose, the adsorption capacity of the high-molecular-weight hemicellulose was higher, and the adsorption rate changed faster and could reach an equilibrium in a shorter time. The intraparticle diffusion kinetic model represented the experimental data very well. Therefore, the kinetics of hemicellulose on the fiber adsorption was commonly described by a three-stage process: mass to transfer, diffusion, and equilibrium. The Gibbs energy change of the adsorption of hemicellulose was found to range from -20.04 to -49.75 kJ/mol at 25 °C. The entropy change was >0. It was found that the adsorption was spontaneous, and the adsorbed mass increased with the increase in temperature. This strengthened the conclusion that the adsorption process of the bagasse hemicellulose on the NFC was driven by the increase in entropy caused by the release of water molecules due to hydrophobic interaction or solvent reorganization.

Tuning Supramolecular Polymers' Amphiphilicity via Host-Guest Interfacial Recognition for Stabilizing Multiple Pickering Emulsions

Supramolecular host-guest chemistry bridging the adjustable amphiphilicity and macromolecular self-assembly is well advanced in aqueous media. However, the interfacial self-assembled behaviors have not been further exploited. Herein, we designed a β-cyclodextrin-grafted alginate/azobenzene-functionalized dodecyl (Alg-β-CD/AzoC12) supra-amphiphilic system that possessed tunable amphiphilicity by host-guest interfacial self-assembly. Especially, supra-amphiphilic aggregates could be utilized as highly efficient soft colloidal emulsifiers for stabilizing water-in-oil-water (W/O/W) Pickering emulsions due to the excellent interfacial activity. Meanwhile, the assembled particle structures could be modulated by adjusting the oil-water ratio, resulting from the tunable aggregation behavior of supra-amphiphilic macromolecules. Additionally, the interfacial adsorption films could be partially destroyed/reconstructed upon ultraviolet/visible irradiation due to the stimuli-altering balance of amphiphilicity of Alg-β-CD/AzoC12 polymers, further constructing the stimulus-responsive Pickering emulsions. Therefore, the supramolecular interfacial self-assembly-mediated approach not only technologically advances the continued development of creative templates to construct multifunctional soft materials with anisotropic structures but also serves as a creative bridge between supramolecular host-guest chemistry, colloidal interface science, and soft material technology.

"Bottom-Up" Assembly of Nanocellulose Microgels as Stabilizer for Pickering Foam Forming

Microgels assembled from bio-based nanomaterials are a promising soft stabilizer for a Pickering system. In this study, nanocellulose microgels with foaming properties were constructed by electrostatic assembly between nisin and 2,2,6,6-tetramethyl piperidine-1-oxyl-oxidized cellulose nanocrystals (TOCNC). Pickering wet foam was prepared by using the microgels as a foaming stabilizer. Nanocellulose microgels exhibited better foaming ability and foam stability than TOCNCs. Quartz crystal microbalance with dissipation and transmission electron microscopy analyses confirmed that the nanocellulose microgels prepared under different nisin concentrations demonstrated significant differences in morphology, conformation, and structural strength. Microgel particles prepared at 0.03 and 0.06 wt % nisin concentrations had a unique dendritic microstructure. Microgels containing 0.06 wt % nisin displayed better foaming ability and foam stability. It was possible that the soft dendritic structure of the microgels could endow bubbles with sufficient thickness and strength to prevent coalescence. This novelty nanocellulose microgel is expected to be used for expanding the application of nanocellulose in the functional interfacial design of Pickering foams.

Tailoring renewable materials via plant biotechnology

Plants inherently display a rich diversity in cell wall chemistry, as they synthesize an array of polysaccharides along with lignin, a polyphenolic that can vary dramatically in subunit composition and interunit linkage complexity. These same cell wall chemical constituents play essential roles in our society, having been isolated by a variety of evolving industrial processes and employed in the production of an array of commodity products to which humans are reliant. However, these polymers are inherently synthesized and intricately packaged into complex structures that facilitate plant survival and adaptation to local biogeoclimatic regions and stresses, not for ease of deconstruction and commercial product development. Herein, we describe evolving techniques and strategies for altering the metabolic pathways related to plant cell wall biosynthesis, and highlight the resulting impact on chemistry, architecture, and polymer interactions. Furthermore, this review illustrates how these unique targeted cell wall modifications could significantly extend the number, diversity, and value of products generated in existing and emerging biorefineries. These modifications can further target the ability for processing of engineered wood into advanced high performance materials. In doing so, we attempt to illuminate the complex connection on how polymer chemistry and structure can be tailored to advance renewable material applications, using all the chemical constituents of plant-derived biopolymers, including pectins, hemicelluloses, cellulose, and lignins.

Progress and challenges in the synthesis of sequence controlled polysaccharides

The sequence, length and substitution of a polysaccharide influence its physical and biological properties. Thus, sequence controlled polysaccharides are important targets to establish structure-properties correlations. Polymerization techniques and enzymatic methods have been optimized to obtain samples with well-defined substitution patterns and narrow molecular weight distribution. Chemical synthesis has granted access to polysaccharides with full control over the length. Here, we review the progress towards the synthesis of well-defined polysaccharides. For each class of polysaccharides, we discuss the available synthetic approaches and their current limitations.

Isolation, Physicochemical Properties, and Structural Characteristics of Arabinoxylan from Hull-Less Barley

Arabinoxylan (HBAX-60) was fractioned from alkaline-extracted arabinoxylan (HBAX) in the whole grain of hull-less barley (Hordeum vulgare L. var. nudum Hook. f. Poaceae) by 60% ethanol precipitation, which was studied for physicochemical properties and structure elucidation. Highly purified HBAX-60 mainly composed of arabinose (40.7%) and xylose (59.3%) was created. The methylation and NMR analysis of HBAX-60 indicated that a low-branched β-(1→4)-linked xylan backbone possessed un-substituted (1,4-linked β-Xylp, 36.2%), mono-substituted (β-1,3,4-linked Xylp, 5.9%), and di-substituted (1,2,3,4-linked β-Xylp, 12.1%) xylose units as the main chains, though other residues (α-Araf-(1→, β-Xylp-(1→, α-Araf-(1→3)-α-Araf-(1→ or β-Xylp-(1→3)-α-Araf-(1→) were also determined. Additionally, HBAX-60 exhibited random coil conformation in a 0.1 M NaNO3 solution. This work provides the properties and structural basis of the hull-less barley-derived arabinoxylan, which facilitates further research for exploring the structure-function relationship and application of arabinoxylan from hull-less barley.

Oxidized xylan additive for nanocellulose films - A swelling modifier

Polymeric wood hemicelluloses are depicted to join cellulose, starch and chitosan as key polysaccharides for sustainable materials engineering. However, the approaches to incorporate hemicelluloses in emerging bio-based products are challenged by lack of specific benefit, other than the biomass-origin, although their utilization would contribute to sustainable material use since they currently are a side stream that is not valorized. Here we demonstrate wood-xylans as swelling modifiers for neutral and charged nanocellulose films that have already entered the sustainable packaging applications, however, suffer from humidity sensitivity. The oxidative modification is used to modulate the water-solubility of xylan and hence enable adsorption in an aqueous environment. A high molecular weight grade, hence less water-soluble, adsorbed preferentially on the neutral surface while the adsorbed amount on a negatively charged surface was independent of the molecular weight, and hence, solubility. The adsorption of the oxidized xylans on a neutral cellulose surface resulted in an increase in the amount of water in the film while on the negatively charged cellulose the total amount of water decreased. The finding of synergy of two hygroscopic materials to decrease swelling in hydrophilic bio-polymer films demonstrates the oxidized macromolecule xylan as structurally functional component in emerging cellulose products.

Friend or Foe? Impacts of Dietary Xylans, Xylooligosaccharides, and Xylanases on Intestinal Health and Growth Performance of Monogastric Animals

This paper discusses the structural difference and role of xylan, procedures involved in the production of xylooligosaccharides (XOS), and their implementation into animal feeds. Xylan is non-starch polysaccharides that share a β-(1-4)-linked xylopyranose backbone as a common feature. Due to the myriad of residues that can be substituted on the polymers within the xylan family, more anti-nutritional factors are associated with certain types of xylan than others. XOS are sugar oligomers extracted from xylan-containing lignocellulosic materials, such as crop residues, wood, and herbaceous biomass, that possess prebiotic effects. XOS can also be produced in the intestine of monogastric animals to some extent when exogenous enzymes, such as xylanase, are added to the feed. Xylanase supplementation is a common practice within both swine and poultry production to reduce intestinal viscosity and improve digestive utilization of nutrients. The efficacy of xylanase supplementation varies widely due a number of factors, one of which being the presence of xylanase inhibitors present in common feedstuffs. The use of prebiotics in animal feeding is gaining popularity as producers look to accelerate growth rate, enhance intestinal health, and improve other production parameters in an attempt to provide a safe and sustainable food product. Available research on the impact of xylan, XOS, as well as xylanase on the growth and health of swine and poultry, is also summarized. The response to xylanase supplementation in swine and poultry feeds is highly variable and whether the benefits are a result of nutrient release from NSP, reduction in digesta viscosity, production of short chain xylooligosaccharides or a combination of these is still in question. XOS supplementation seems to benefit both swine and poultry at various stages of production, as well as varying levels of XOS purity and degree of polymerization; however, further research is needed to elucidate the ideal dosage, purity, and degree of polymerization needed to confer benefits on intestinal health and performance in each respective species.

Xyloglucan endotransglycosylase/hydrolase increases tightly-bound xyloglucan and chain number but decreases chain length contributing to the defense response that Glycine max has to Heterodera glycines

The Glycine max xyloglucan endotransglycosylase/hydrolase (EC 2.4.1.207), GmXTH43, has been identified through RNA sequencing of RNA isolated through laser microdissection of Heterodera glycines-parasitized root cells (syncytia) undergoing the process of defense. Experiments reveal that genetically increasing XTH43 transcript abundance in the H. glycines-susceptible genotype G. max[Williams 82/PI 518671] decreases parasitism. Experiments presented here show decreasing XTH43 transcript abundance through RNA interference (RNAi) in the H. glycines-resistant G. max[Peking/PI 548402] increases susceptibility, but it is unclear what role XTH43 performs. The experiments presented here show XTH43 overexpression decreases the relative length of xyloglucan (XyG) chains, however, there is an increase in the amount of those shorter chains. In contrast, XTH43 RNAi increases XyG chain length. The experiments show that XTH43 has the capability to function, when increased in its expression, to limit XyG chain extension. This outcome would likely impair the ability of the cell wall to expand. Consequently, XTH43 could provide an enzymatically-driven capability to the cell that would allow it to limit the ability of parasitic nematodes like H. glycines to develop a feeding structure that, otherwise, would facilitate parasitism. The experiments presented here provide experimentally-based proof that XTHs can function in ways that could be viewed as being able to limit the expansion of the cell wall.

Breeding Targets to Improve Biomass Quality in Miscanthus

Lignocellulosic crops are attractive bioresources for energy and chemicals production within a sustainable, carbon circular society. Miscanthus is one of the perennial grasses that exhibits great potential as a dedicated feedstock for conversion to biobased products in integrated biorefineries. The current biorefinery strategies are primarily focused on polysaccharide valorization and require severe pretreatments to overcome the lignin barrier. The need for such pretreatments represents an economic burden and impacts the overall sustainability of the biorefinery. Hence, increasing its efficiency has been a topic of great interest. Inversely, though pretreatment will remain an essential step, there is room to reduce its severity by optimizing the biomass composition rendering it more exploitable. Extensive studies have examined the miscanthus cell wall structures in great detail, and pinpointed those components that affect biomass digestibility under various pretreatments. Although lignin content has been identified as the most important factor limiting cell wall deconstruction, the effect of polysaccharides and interaction between the different constituents play an important role as well. The natural variation that is available within different miscanthus species and increased understanding of biosynthetic cell wall pathways have specified the potential to create novel accessions with improved digestibility through breeding or genetic modification. This review discusses the contribution of the main cell wall components on biomass degradation in relation to hydrothermal, dilute acid and alkaline pretreatments. Furthermore, traits worth advancing through breeding will be discussed in light of past, present and future breeding efforts.

Balanced Xylan Acetylation is the Key Regulator of Plant Growth and Development, and Cell Wall Structure and for Industrial Utilization

Xylan is the most abundant hemicellulose, constitutes about 25–35% of the dry biomass of woody and lignified tissues, and occurs up to 50% in some cereal grains. The accurate degree and position of xylan acetylation is necessary for xylan function and for plant growth and development. The post synthetic acetylation of cell wall xylan, mainly regulated by Reduced Wall Acetylation (RWA), Trichome Birefringence-Like (TBL), and Altered Xyloglucan 9 (AXY9) genes, is essential for effective bonding of xylan with cellulose. Recent studies have proven that not only xylan acetylation but also its deacetylation is vital for various plant functions. Thus, the present review focuses on the latest advances in understanding xylan acetylation and deacetylation and explores their effects on plant growth and development. Baseline knowledge about precise regulation of xylan acetylation and deacetylation is pivotal to developing plant biomass better suited for second-generation liquid biofuel production.

BdGT43B2 functions in xylan biosynthesis and is essential for seedling survival in Brachypodium distachyon

Xylan is the predominant hemicellulose in the primary cell walls of grasses, but its synthesis and interactions with other wall polysaccharides are complex and incompletely understood. To probe xylan biosynthesis, we generated CRISPR/Cas9 knockout and amiRNA knockdown lines of BdGT43B2, an ortholog of the wheat TaGT43-4 xylan synthase scaffolding protein in the IRX14 clade, in Brachypodium distachyon. Knockout of BdGT43B2 caused stunting and premature death in Brachypodium seedlings. Immunofluorescence labeling of xylans was greatly reduced in homozygous knockout BdGT43B2 mutants, whereas cellulose labeling was unchanged or slightly increased. Biochemical analysis showed reductions in digestible xylan in knockout mutant walls, and cell size was smaller in knockout leaves. BdGT43B2 knockdown plants appeared morphologically normal as adults, but showed slight reductions in seedling growth and small decreases in xylose content in isolated cell walls. Immunofluorescence labeling of xylan and cellulose staining was both reduced in BdGT43B2 knockdown plants. Together, these data indicate that BdGT43B2 functions in the synthesis of a form of xylan that is required for seedling growth and survival in Brachypodium distachyon.

Arabinoxylan/Cellulose Nanocrystal Hydrogels with Tunable Mechanical Properties

Hydrogels are three-dimensional networks of hydro-soluble polymers containing a large amount of water that have found a wide panel of applications in many sectors. The need for eco-friendly and nontoxic materials for the elaboration of sustainable hydrogels is obvious, and materials derived from biomass can easily meet these requirements. Cellulose nanocrystals (CNC) and arabinoxylans (AX) are abundant, biobased, hydrophilic, and renewable nanoparticles and polymers that interact together. In this study, we have built fully biobased hydrogels using CNC and AX. First, as revealed by Quartz Crystal Microbalance with Dissipation (QCM-D) experiments, AX adsorbs almost instantly on cellulosic surfaces in an irreversible manner. Nevertheless, gelation kinetics is not instantaneous and shows temperature dependence. The determination of phase diagrams using the inverted tube method leads to the conclusion that high AX/CNC ratios are needed for gel formation. The mechanical properties of CNC-AX hydrogels were investigated by measuring storage and loss moduli (G', G'') as a function of concentrations and hydrogel reformation after submission to high shear rates. Hydrogel properties were also tuned by increasing the ionic strength and the enzymatic removal of arabinose moieties from AX. In light of the obtained results, we hypothesize that gel formation occurs in two steps, i.e., AX adsorption followed by gelation of the complexes, and is due to the formation of reversible and tunable interactions between CNC/AX complexes interacting with each other, offering a wide panel of physicochemical tools to tune and trigger the final properties of hydrogels.

Structural characterization of hemicellulose released from corn cob in continuous flow type hydrothermal reactor

Hydrothermal reaction is known to be one of the most efficient procedures to extract hemicelluloses from lignocellulosic biomass. We investigated the molecular structure of xylooligosaccharides released from corn cob in a continuous flow type hydrothermal reactor designed in our group. The fraction precipitable from the extract with four volumes of ethanol was examined by ¹H-NMR spectroscopy and MALDI-TOF MS before and after enzymatic treatment with different purified enzymes. The released water-soluble hemicellulose was found to correspond to a mixture of wide degree of polymerization range of acetylarabinoglucuronoxylan fragments (further as corn cob xylan abbreviated CX). Analysis of enzymatic hydrolyzates of CX with an acetylxylan esterase, GH3 β-xylosidase, GH10 and GH11 xylanases revealed that the main chain contains unsubstituted regions mixed with regions of xylopyranosyl residues partially acetylated and occasionally substituted by 4-O-methyl-d-glucuronic acid and arabinofuranose esterified with ferulic or coumaric acid. Single 2- and 3-O-acetylation was accompanied by 2,3-di-O-acetylation and 3-O-acetylation of Xylp residues substituted with MeGlcA. Most of the non-esterified arabinofuranose side residues were lost during the hydrodynamic process. Despite reduced branching, the acetylation and ferulic acid modification of pentose residues contribute to high yields and high solubility of the extracted CX. It is also shown that different enzyme treatments of CX may lead to various types of xylooligosaccharides of different biomedical potential.

Action of a GH115 α-glucuronidase from Amphibacillus xylanus at alkaline condition promotes release of 4-O-methylglucopyranosyluronic acid from glucuronoxylan and arabinoglucuronoxylan

Glucuronic acid and/or 4-O-methyl-glucuronic acid (GlcA/MeGlcA) are substituents of the main xylans present in hardwoods, conifers, and many cereal grains. α-Glucuronidases from glycoside hydrolase family GH115 can target GlcA/MeGlcA from both internally and terminally substituted regions of xylans. The current study describes the first GH115 α-glucuronidase, AxyAgu115A, from the alkaliphilic organism Amphilbacillus xylanus. AxyAgu115A was active in a wide pH range, and demonstrated better performance in alkaline condition compared to other characterized GH115 α-glucuronidases, which generally show optimal activity in acidic conditions. Specifically, its relative activity between pH 5.0 and pH 8.5 was above 80%, and was 35% of maximum at pH 10.5; although the enzyme lost 30% and 80% relative residual activity after 24-h pre-incubation at pH 9 and pH 10, respectively. AxyAgu115A was also similarly active towards glucuronoxylan as well as comparatively complex xylans such as spruce arabinoglucurunoxylan. Accommodation of complex xylans was supported by docking analyses that predicted accessibility of AxyAgu115A to branched xylo-oligosaccharides. MeGlcA release by AxyAgu115A from each xylan sample was increased by up to 30% by performing the reaction at pH 11.0 rather than pH 4.0, revealing applied benefits of AxyAgu115A for xylan recovery and processing.