Experimental and Theoretical Evaluation of the Solubility/Insolubility of Spruce Xylan (Arabino Glucuronoxylan)

Xylooligosaccharides from lignocellulosic biomass and their applications as nutraceuticals: a review on their production, purification, and characterization

Xylooligosaccharides (XOS) are considered a potent source of prebiotics for humans. The global prebiotic market is expanding in size, was valued at USD 6.05 billion in 2021, and is expected to grow at a 14.9% compound annual growth rate between 2022 and 2030, indicating a huge demand. These XOS are non-digestible pentose sugar oligomers comprising mainly xylose. Xylose is naturally present in the lignocellulosic biomass (LCB), fruits and vegetables. Apart from the prebiotic effect, these XOS have been reported to reduce blood cholesterol, possess antioxidant effects, increase calcium absorption, reduce colon cancer risk, and benefit diabetic patients. The primary use of XOS is reported in the feed industry followed by health, medical use, food and drinks. LCB mainly contains glucan, xylan and lignin. After glucan, xylan is the second-highest available sugar on the globe composed of xylose. Therefore, the xylan fraction of LCB has great significance in producing food, feed and energy. Glucan has been exploited for the commercial production of ethanol, xylitol, furfural, hydroxymethyl furfural and glucose. As of now, xylan has limited applications. Therefore, xylan can be exploited to convert to XOS. The production of XOS from LCB fraction not only helps to produce these at a very low price, but also helps in the reduction of greenhouse gases. Its use in food and drinks is increasing as it can be derived from the abundantly and cheaply available LCB. The article provides a review on the production, purification and characterization of XOS in view of their use as nutraceuticals. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Encapsulation of Polyphenolic Compounds Based on Hemicelluloses to Enhance Treatment of Inflammatory Bowel Diseases and Colorectal Cancer

Inflammatory bowel diseases (IBD) and colorectal cancer (CRC) are difficult to cure, and available treatment is associated with troubling side effects. In addition, current therapies have limited efficacy and are characterized by high costs, and a large segment of the IBD and CRC patients are refractive to the treatment. Moreover, presently used anti-IBD therapies in the clinics are primarily aimed on the symptomatic control. That is why new agents with therapeutic potential against IBD and CRC are required. Currently, polyphenols have received great attention in the pharmaceutical industry and in medicine due to their health-promoting properties. They may exert anti-inflammatory, anti-oxidative, and anti-cancer activity, via inhibiting production of pro-inflammatory cytokines and enzymes or factors associated with carcinogenesis (e.g., matrix metalloproteinases, vascular endothelial growth factor), suggesting they may have therapeutic potential against IBD and CRC. However, their use is limited under both processing conditions or gastrointestinal interactions, reducing their stability and hence their bioaccessibility and bioavailability. Therefore, there is a need for more effective carriers that could be used for encapsulation of polyphenolic compounds. In recent years, natural polysaccharides have been proposed for creating carriers used in the synthesis of polyphenol encapsulates. Among these, hemicelluloses are particularly noteworthy, being characterized by good biocompatibility, biodegradation, low immunogenicity, and pro-health activity. They may also demonstrate synergy with the polyphenol payload. This review discusses the utility and potential of hemicellulose-based encapsulations of polyphenols as support for treatment of IBD and CRC.

Morphology and swelling of thin films of dialcohol xylan

Polysaccharides are excellent network formers and are often processed into films from water solutions. Despite being hydrophilic polysaccharides, the typical xylans liberated from wood are sparsely soluble in water. We have previously suggested that an additional piece to the solubilization puzzle is modification of the xylan backbone via oxidative cleavage of the saccharide ring. Here, we demonstrate the influence of the degree of modification, i.e., degree of oxidation (DO) on xylan solubilization and consequent film formation and stability. Oxidized and reduced wood xylans (i.e., dialcohol xylans) with the highest DO (77 %) within the series exhibited the smallest hydrodynamic diameter (d_h) of 60 nm in dimethylsulfoxide (DMSO). We transferred the modified xylans into films credit to their established solubility and then quantified the film water interactions. Dialcohol xylans with intermediate DOs (42 and 63 %) did not form continuous films. The films swelled slightly when subjected to humidity. However, the film with the highest DO demonstrated a significant moisture uptake that depended on the film mass and was not observed with the other modified grades or with unmodified xylan.

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.

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.

Recent patents on water-soluble polysaccharides for advanced drug delivery, tissue engineering and regenerative medicine

Water-soluble polysaccharides have unique properties and have found wide application in the design of advanced drug-delivery systems and the biofabrication of tissue engineered scaffolds in regenerative medicine. This patent review provides a concise incursion into the mechanisms that define the key properties of water-soluble polysaccharides that have found embodiment within active patents recently granted (2020-2021). In addition, the relationship between their solubility and structural features such as molecular weight, ionic profile, degree of branching/crosslinking, side-chain flexibility and the presence/modification of functional groups that have been discusses. An assimilation of patents in which water-soluble polysaccharides are central to the design of therapeutic interventions applied to specialized treatments in oncology, infectious diseases and neuronal disorders is provided.

Functional Lignin Nanoparticles with Tunable Size and Surface Properties: Fabrication, Characterization, and Use in Layer-by-Layer Assembly

Lignin is the richest source of renewable aromatics and has immense potential for replacing synthetic chemicals. The limited functionality of lignin is, however, challenging for its potential use, which motivates research for creating advanced functional lignin-derived materials. Here, we present an aqueous-based acid precipitation method for preparing functional lignin nanoparticles (LNPs) from carboxymethylated or carboxypentylated lignin. We observe that the longer grafted side chains of carboxypentylated lignin allow for the formation of larger LNPs. The functional nanoparticles have high tolerance against salt and aging time and well-controlled size distribution with R_h ≤ 60 nm over a pH range of 5-11. We further investigate the layer-by-layer (LbL) assembly of the LNPs and poly(allylamine hydrochloride) (PAH) using a stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). Results demonstrate that LNPs made of carboxypentylated lignin (i.e., PLNPs with the adsorbed mass of 3.02 mg/m²) form a more packed and thicker adlayer onto the PAH surface compared to those made of carboxymethylated lignin (i.e., CLNPs with the adsorbed mass of 2.51 mg/m²). The theoretical flux, J, and initial rate of adsorption, (dΓ/dt)₀, analyses confirm that 22% of PLNPs and 20% of CLNPs arriving at the PAH surface are adsorbed. The present study provides a feasible platform for engineering LNPs with a tunable size and adsorption behavior, which can be adapted in bionanomaterial production.

Entropy drives the adsorption of xyloglucan to cellulose surfaces - A molecular dynamics study

The adsorption of nonionic polymers to cellulose is of large importance both in the plant cell wall during synthesis and for the development of sustainable materials from wood. Here, the thermodynamics of adsorption of the polysaccharide xyloglucan (XG) to both native and chemically modified cellulose with carboxyl groups was investigated using molecular dynamics simulations. The free energy of adsorption was calculated as the potential of mean force between an XG oligomer and model cellulose surfaces in a range of temperatures from 298 K to 360 K. It was found that the adsorption near room temperature is an endothermic process dominated by the entropy of released interfacial water molecules. This was corroborated by quantitative assessment of the absolute entropy per water molecule both at the interface and in the bulk. In the case of native cellulose, the adsorption became exothermic at higher temperatures, while the relatively strong interactions between water and the charged groups of the oxidized cellulose impede such a transition. The results also indicate that the extraction of strongly associated hemicelluloses would be facilitated by low temperature.

Wood hemicelluloses exert distinct biomechanical contributions to cellulose fibrillar networks

Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interactions with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of wood xylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties.

Hemicelluloses are an essential constituent of plant cell walls, but the individual biomechanical roles remain elusive. Here the authors report on the interaction of wood hemicellulose with bacterial cellulose during deposition and explore the resultant fibrillar architecture and mechanical properties.

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.