Wheat Bran Arabinoxylan Research Articles

Multi-omics insights into anti-colitis benefits of the synbiotic and postbiotic derived from wheat bran arabinoxylan and Limosilactobacillus reuteri

Exploring nutritional therapies that manipulate tryptophan metabolism to activate AhR signaling represents a promising approach for mitigating chronic colitis. Arabinoxylan is a bioactive constituent abundant in wheat bran. Here, we comprehensively investigated anti-colitis potentials of wheat bran arabinoxylan (WBAX), its synbiotic and postbiotic derived from WBAX and Limosilactobacillus reuteri WX-94 (i.e., a probiotic strain exhibiting tryptophan metabolic activity). WBAX fueled L. reuteri and promoted microbial conversion of tryptophan to AhR ligands during in vitro fermentation in the culture medium and in the fecal microbiota from type 2 diabetes. The WBAX postbiotic outperformed WBAX and its synbiotic in augmenting efficacy of tryptophan in restoring DSS-disturbed serum immune markers, colonic tight junction proteins and gene profiles involved in amino acid metabolism and FoxO signaling. The WBAX postbiotic remodeled gut microbiota and superiorly enhanced AhR ligands (i.e., indole metabolites and bile acids), alongside with elevation in colonic AhR and IL-22. Associations between genera and metabolites modified by the postbiotic and colitis in human were verified and strong binding capacities between metabolites and colitis-related targets were demonstrated by molecular docking. Our study advances the novel perspective of WBAX in manipulating tryptophan metabolism and anti-colitis potentials of WBAX postbiotic via promoting gut microbiota-dependent AhR signaling.

Feruloylation and Hydrolysis of Arabinoxylan Extracted from Wheat Bran: Effect on Dough Rheology and Microstructure.

Feruloylated arabinoxylan (AX) is a potential health-promoting fiber ingredient that can enhance nutritional properties of bread but is also known to affect dough rheology. To determine the role of feruloylation and hydrolysis of wheat bran AX on dough quality and microstructure, hydrolyzed and unhydrolyzed AX fractions with low and high ferulic acid content were produced, and their chemical composition and properties were evaluated. These fractions were then incorporated into wheat dough, and farinograph measurements, large and small deformation measurements and dough microstructure were assessed. AX was found to greatly affect both fraction properties and dough quality, and this effect was modulated by hydrolysis of AX. These results demonstrated how especially unhydrolyzed fiber fractions produced stiff doughs with poor extensibility due to weak gluten network, while hydrolyzed fractions maintained a dough quality closer to control. This suggests that hydrolysis can further improve the baking properties of feruloylated wheat bran AX. However, no clear effects from AX feruloylation on dough properties or microstructure could be detected. Based on this study, feruloylation does not appear to affect dough rheology or microstructure, and feruloylated wheat bran arabinoxylan can be used as a bakery ingredient to potentially enhance the nutritional quality of bread.

Wheat bran arabinoxylans: Chemical structure, extraction, properties, health benefits, and uses in foods.

Wheat bran (WB) is a well-known and valuable source of dietary fiber. Arabinoxylan (AX) is the primary hemicellulose in WB and can be isolated and used as a functional component in various food products. Typically, AX is extracted from the whole WB using different processes after mechanical treatments. However, WB is composed of different layers, namely, the aleurone layer, pericarp, testa, and hyaline layer. The distribution, structure, and extractability of AX vary within these layers. Modern fractionation technologies, such as debranning and electrostatic separation, can separate the different layers of WB, making it possible to extract AX from each layer separately. Therefore, AX in WB shows potential for broader applications if it can be extracted from the different layers separately. In this review, the distribution and chemical structures of AX in WB layers are first discussed followed by extraction, physicochemical properties, and health benefits of isolated AX from WB. Additionally, the utilization of AX isolated from WB in foods, including cereal foods, packaging film, and the delivery of food ingredients, is reviewed. Future perspectives on challenges and opportunities in the research field of AX isolated from WB are highlighted.

Effect of Damaged Starch and Wheat-Bran Arabinoxylans on Wheat Starch and Wheat Starch-Gluten Systems.

This study investigated the impact of damaged starch and arabinoxylans on the thermal and pasting behavior of mixtures containing starch and gluten. The mixtures containing starch, arabinoxylans, and gluten were dispersed in water and a 50% sucrose solution. When arabinoxylans were added to native starch in water, it did not modify the viscosity profiles. An increase in viscosity parameters was observed due to the addition of arabinoxylans to starch with a higher level of damage. Gluten did not influence the effects caused by arabinoxylans. In the sucrose solution, arabinoxylans caused an increase in the viscosity parameters of native starch and starch with higher damage content dispersions. Gluten caused greater viscosity increases when arabinoxylans were added. In water, the addition of arabinoxylans to native starch caused a decrease in the enthalpy of gelatinization and an increase in the onset temperature. Adding arabinoxylans to starch with a higher level of damage caused the opposite effects. In the presence of sucrose, arabinoxylans caused a decrease in the enthalpy of gelatinization. These results lay the foundations for studying the influence of damaged starch and arabinoxylans in water-rich systems characterized by the presence of substantial proportions of sucrose, such as batter formulations.

Wheat bran arabinoxylan-soybean protein isolate emulsion-filled gels as a β-carotene delivery carrier: Effect of polysaccharide content on textural and rheological properties

This study aimed to investigate the effects of different wheat bran arabinoxylan (WBAX) concentrations (1, 2, 3, and 4 wt%) on the structural and physicochemical properties of WBAX-soybean protein isolate (SPI) emulsion-filled gels (EFGs) prepared using laccase and heat treatment. The properties of the various gels as well as their microstructure, rheology, and in vitro digestion behaviors were investigated. Results showed that WBAX-SPI EFGs with a 3 wt% WBAX concentration had a smooth and uniform appearance, high water holding capacity (98.5 ± 0.2 %), and enhanced mechanical properties. Rheological experiments suggested that a stronger and closer gel network was formed at 3 wt% WBAX concentration. Fourier transform infrared spectroscopy showed that laccase and heat treatment not only catalyzed the intramolecular crosslinking of WBAX and SPI, respectively, but also promoted the interaction between WBAX and SPI. Confocal laser scanning microscopy revealed that the WBAX gel network was interspersed within the SPI network. The interactions contributing to the gelation analysis revealed that chemical (disulfide bond) and physical (hydrogen bond and hydrophobic) interactions promoted the formation of denser EFGs. Furthermore, the WBAX-SPI EFGs provided a β-carotene bioaccessibility of 21.8 ± 0.6 %. Therefore, our study suggests that WBAX-SPI EFGs hold promising potential for industrial applications in the delivery of β-carotene.

Arabinoxylan of varied structural features distinctively affects the functional and in vitro digestibility of wheat starch

This study explored the effects of wheat bran arabinoxylan (AX) of various molecular structures on the functional and in vitro digestibility of wheat starch. AX was separated with sequential ethanol precipitation into different fractions (L-Fra and H-Fra), followed by acidic treatment at varied time to convert L-Fra into different subfractions (H-Sub, M-Sub and L-Sub), and the structural features of AX and its subsequent fractions were compared. The Mw and branching degree of the fractions were decreased in the order of H-Fra (545 kDa, 1.15), L-Fra (86 kDa, 0.35), H-Sub (38 kDa, 0.16), M-Sub (21 kDa, 0.10) and L-Sub (7 kDa, 0.08). The functional properties, such as pasting properties, rheological properties, thermal properties, and their effect on the in vitro digestibility of wheat starch-AX combinations, were closely related to the molecular structures of AX. AX with higher Mw, higher branching degree and phenolic content could better inhibit the starch gelatinization and retrogradation, thus reducing the apparent viscosity and gelling properties of wheat starch. The possible mechanisms can be illustrated as 1) AX could compete for water with starch to inhibit granule expansion; 2) AX could not only adsorb on the surface of starch granules through hydrogen bonds but also entangle with the leached amylose and wrap on the surface of granules; 3) AX contained phenols, leading them to inhibit granule expansion through non-covalent interactions with starch molecules. Overall, this study provides a theoretical basis to improve the quality of wheat starch foods and extend the shelf life of wheat foods.

The role of feruloylation of wheat bran arabinoxylan in regulating the heat-evoked polymerization behavior of gluten

To further reveal the role of feruloylation of arabinoxylan (AX) in regulating the heat-evoked polymerization behavior of gluten, AX was extracted from wheat bran and in situ modified with lime to obtain AX with controlled ferulic acid (FA) content. The effects of AX with varied FA level on the heat-evoked polymerization of gluten were comparatively studied. The results suggested that AX postponed the disulfide bond mediated polymerization behavior of glutenins and enhanced polymerization degree of glutenin-glutenin and glutenin-gliadin crosslinks upon thermal treatment, while FA moiety suppressed the facilitated polymerization behavior compared with AX free of FA. iTARQ analysis demonstrated that FA moiety of AX mainly suppressed the polymerization of low molecular weight glutenin subunits and α/γ-gliadins in glutenin-gliadin crosslinks. The complete polymerization of glutenin and gliadin elevated the intermolecular β-sheet and ordered α-helix structures at the expense of other structures, while AX stabilized the transformation of secondary structures and was irrelevant with FA level. FA moiety of AX contributed to stabilizing the microenvironment of tryptophan, and evoked the disulfide bond conformation with reduced gauche-gauche-gauche conformation upon formation of glutenin-gliadin crosslinks. AX with the highest FA level exhibited the optimum elevation effect on the viscoelasticity of gluten, which might be attributed to the moderate polymerization of glutenin-gliadin and potential covalent linkage formed between the FA moiety of AX and gluten. This study could contribute to depicting the interacting mechanism of AX and gluten proteins, and further provide basis for exploiting nutritious high-fiber wheat-based products with superior organoleptic quality. • Arabinoxylan (AX) was in situ modified to control the ferulic acid (FA) content. • FA of AX contributed to suppressing the heat-evoked polymerization of gluten proteins. • Suppressed polymerized subunits of gluten upon heating by FA were identified. • FA moiety of AX contributed to stabilizing the microenvironment of tryptophan. • AX with high FA level exhibit optimum elevation effect on viscoelasticity of gluten.

Rational design cold-set interpenetrating network hydrogel based on wheat bran arabinoxylans and pea protein isolates for regulating the release of riboflavin in simulated digestion

Cold-set interpenetrating polymer network gels as riboflavin (RF) delivery vehicles based on wheat bran arabinoxylans (AX) and pea protein isolate (PPI) were developed via enzymatic-crosslinking. The impact of AX concentrations on the physicochemical property, in vitro digestion property and microstructure of IPN gels was explored. Increased concentrations of AX enhanced the viscoelasticity of IPN gels and resulted in a more compact microstructure. However, at a concentration of 5.0 % (w/v), the faster and stronger crosslinking of AX molecules caused separate network gel between PPI and AX. The IPN gel improved the encapsulation efficiency and release property of embedded RF as compared to PPI gel. SEM results showed that IPN gel maintained a complete network structure after gastric digestion. Particularly, the IPN gel with 1.0 % AX exhibited a homogeneous and complete network structure even after intestinal digestion, which explained the reason for the highest encapsulation efficiency and lowest release ratios of RF.

Design and structural characterization of edible double network gels based on wheat bran arabinoxylan and pea protein isolate

Double network (DN) gels based on wheat bran arabinoxylan (WBAX) and pea protein isolate (PPI) were fabricated by a two-step sequential gelation method with laccase catalyzed cross-linking followed by heating. The rheological properties, water holding capacity, microstructure and molecular structure of WBAX/PPI DN gels were investigated. Increasing the concentrations of WBAX and PPI contributed to an enhanced viscoelastic modulus of DN gel, which exhibited an interconnected, bicontinuous and compact structure with smaller pore sizes, as a result of higher cross-linking intensity of WBAX molecules. Low field nuclear magnetic resonance (LF-NMR) results showed that increasing the contents of PPI and WBAX could further restrict the water mobility within DN gel, which was beneficial for enhancing the water holding capacity of gel samples. The molecular structure analysis showed that the crosslinking of WBAX-WBAX, PPI-PPI and WBAX-PPI participated in the formation of WBAX-PPI DN gels.

Wheat bran arabinoxylan and bovine serum albumin conjugates: Enzymatic synthesis, characterization, and applications in O/W emulsions

Wheat bran arabinoxylan-bovine serum albumin (WBAX-BSA) conjugates were prepared via enzymatic synthesis using horseradish peroxidase (HRP) and H2O2 as catalysts. The conjugates were characterized by ultraviolet–visible spectroscopy (UV–vis), high-performance size exclusion chromatography (HPSEC), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The feasibility of its application in stable emulsions was also assessed. UV–vis results revealed that phenolic acid in WBAX and aromatic amino acids in BSA were implicated in the enzymatic synthesis of the WBAX-BSA conjugate with the optimal WBAX:BSA mass ratio of 3:2. HPSEC results confirmed the intermolecular interactions between WBAX and BSA and the molecular weight of WBAX-BSA (2673 ± 16 kg/mol) was higher than that of control groups. Compared with the WBAX/BSA physical complexes, the WBAX-BSA conjugates had higher apparent viscosity (0.08–0.24 Pa.s), denser structure, larger particle sizes (33.5 ± 5.7 nm), and improving emulsifying properties in oil in water (O/W) emulsion system under different environmental stresses. The preparation of the enzymatic conjugates not only provides novel O/W emulsion systems but also improves processed food manufacturing processes that require efficient emulsification.

Effect of wheat bran arabinoxylan on the gelatinization and long-term retrogradation behavior of wheat starch

The effect of wheat bran arabinoxylan (WBAX) with different molecular characteristics on the gelatinization and long-term retrogradation behavior of wheat starch (WS) have been evaluated. WBAXs with Mw of 280–754 kDa and Ara/Xyl of 0.45–0.62 were obtained through alkaline extraction with graded ethanol precipitation. WBAXs with larger Mw and branching degree could impede gelatinization process of wheat starch by effectively decreasing the water availability for starch gelatinization. The hydrogen-bonding interactions between WS and WBAX could enhance the gel strength of WS-WBAX mixed pastes. WBAXs with lower branching degree could inhibit the long-term retrogradation of starch through hindering the rearrangement of amylopectin and double-helical associations of amylose during long-term storage, due to hydrogen-bonding interaction between WBAX and starch. Low-field nuclear magnetic resonance (LF-NMR) relaxometry analysis confirmed that the addition of WBAXs could improve the water holding properties of retrograded starch gels.

Laccase‐induced wheat bran arabinoxylan hydrogels from different wheat cultivars: Structural, physicochemical, and rheological characteristics

The impact of three arabinoxylan (AX) cultivars (262, 44, 229) on the physicochemical, rheological, and microstructural characteristics of AX hydrogels was explored. The gelation of AX262 was faster and the viscoelastic modulus was higher. During the gelation process, the consumption of ferulic acids was 96%, 87%, and 69% for AX262, AX44, and AX229, respectively, indicating a higher oxidative cross-linking degree of AX262. The decline of adsorption intensity for AX262 hydrogel at 1,644 and 3,423 cm−1 was more pronounced, which might be related to a denser gel network as a result of higher oxidation degree of FA. Meanwhile, AX262 hydrogel was more capable of binding water molecules and exhibited better thermal stability. The difference in the gelation properties of varied AX cultivars lied in the molecular structure. AX262 had a higher ferulic acid content (0.23 μg/mg) and larger molecular weight with 1.17 × 106 Da, contributing to an enhanced oxidative cross-linking capacity. Novelty impact statement Wheat bran arabinoxylans extracted from strong gluten wheat cultivars with higher contents of FA were suitable to fabricate hydrogel system, due to their better oxidative cross-linking capacity. The prepared AX hydrogel had uniform honeycomb structure with enhanced thermal stability and mechanical properties, which could be potentially used as delivery system for bioactive compounds.

Gelatinization, Retrogradation and Gel Properties of Wheat Starch-Wheat Bran Arabinoxylan Complexes.

Gelatinization, retrogradation and gel properties of wheat starch–wheat bran arabinoxylan (WS–WBAX) complexes have been evaluated. The results of rapid viscosity analyzer (RVA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) confirmed that WBAX samples with larger Mw and branching degree (HWBAX) significantly impeded gelatinization process of starch by effectively reducing the amount of water available for starch gelatinization. DSC analysis showed that both molecular characteristics and additive amount of WBAX samples have an effect on the long-term retrogradation behavior of starch. For the rheological studies of WS–WBAX mixed gels, the elastic moduli (G’) and shear viscosity of WS–WBAX mixed gels increased with the increase in additive amount of WBAX. WS–HWBAX mixed gels exhibited the lower G’ compared with starch gels containing WBAX with lower Mw and branching degree (LWBAX) at the same amount. The scanning electron micrographs (SEM) revealed that the microstructures of WS–WBAX mixed gels were mainly affected by the amount of WBAX, but hardly by the molecular characteristics of WBAX. Texture profile analysis (TPA) showed that the cohesiveness of fresh WS–WBAX mixed gels became larger with an increase in the WBAX addition amount. The hardness of WS–WBAX mixed gels tended to increase over the 14-day storage.

Effects of emulsion concentration on the physicochemical properties of wheat bran arabinoxylan-soy protein isolate emulsion-filled gels used as β-carotene carriers

The application of natural polymers in emulsion-filled gels is an effective way to enhance the protective and controlled release properties of bioactive compounds. In this study, wheat bran arabinoxylan–soy protein isolate (WBAX-SPI) emulsion-filled gels were formed by embedding a WBAX emulsion containing 10 mL/100 mL soybean oil in a dispersion of WBAX and SPI polymer followed by gelation. The physicochemical properties of the emulsion-filled gels with different emulsion concentrations (9, 12, 15, 18, and 21 g/100 g) were evaluated. The WBAX-SPI emulsion-filled gels were self-supported gels with high water holding capacities (98 ± 0.5 g/100 g). Texture profile analysis showed that a highly integrated gel network was formed at the emulsion concentration of 15 g/100 g. Rheological measurements showed that the emulsion acted as an active filler in the WBAX-SPI emulsion-filled gels, leading to different rheological properties compared to the WBAX-SPI hydrogels. Confocal laser scanning microscopy observations indicated that the structure of the WBAX-SPI emulsion-filled gels was affected by the emulsion concentration. In vitro simulated digestion demonstrated that the WBAX-SPI emulsion-filled gels had better sustained release performance compared to the WBAX or SPI emulsion-filled gels.

In vitro Colon Fermentation of Soluble Arabinoxylan Is Modified Through Milling and Extrusion.

Dietary fibers such as arabinoxylan (AX) are promising food constituents to prevent particular diet-related chronic diseases because of their prebiotic properties. Arabinoxylan fermentation by the gut microbiota depends on the structural architecture of AX, which can be modified during food processing and consequently affect its prebiotic potential, but it is little investigated. Therefore, the aim of this study was to evaluate the effects of naturally occurring and processing-induced structural alterations of the soluble AX of wheat bran and rye flour on the in vitro human colon fermentation. It was found that fermentation behavior is strongly linked to the AX fine structure and their processing-induced modifications. The short-chain fatty acid (SCFA) metabolism, acidification kinetics, bacterial growth, and bacterial composition revealed that wheat bran AX (WBAX) was fermented faster than rye flour AX. Increased levels of bound phenolic acids resulting from processing were identified as the inhibiting factor for AX fermentation kinetics. Bacterial genera promoted by AX varied between AX source and processing type, but also between microbiota. Extruded WBAX promoted butyrate production and growth of butyrate-producing Faecalibacterium in the butyrogenic microbiota while it did not enhance fermentation and inhibited the growth of Prevotella in the propiogenic microbiota. We anticipate that the findings of this study are a starting point for further investigation on the impact of processing-induced changes on the prebiotic potential of dietary fibers prior to human studies.

Comparison of Alkaline/Oxidative and Hydrothermal Extraction of Wheat Bran Arabinoxylans.

The bran accounts for approximately 25% of the wheat kernel but is currently only a by-product, used as animal feed. However, due to its high arabinoxylan content it could be a valuable raw material for food production. Arabinoxylans cannot be digested in the human intestine but are intensely studied for their health-beneficial properties. These include glycemic control by formation of a highly viscous gel in the intestine, and hence delaying starch digestion, alongside an increase in short chain fatty acids. To apply sufficient amounts of arabinoxylan for health-beneficial effects, extraction and concentration is required. Alkaline/oxidative conditions are commonly used, but for potential food applications more cost-efficient methods, without hazardous chemicals, are required. Therefore, this study aimed to optimize the conditions for hydrothermal extraction (extraction time and temperature) at laboratory-scale and to compare the results to an established alkaline/oxidative method. The resulting extracts were characterized for yield, purity, arabinoxylan molecular mass, arabinose/xylose ratio, and viscosity to evaluate the quality of the method. For the hydrothermal extraction, an extraction time of 1 h at 160 °C and 6.5 bar gave the best results. However, even these optimized conditions resulted in lower extract purity and severely degraded arabinoxylans. Although further optimization of the hydrothermal process is required, the present work builds an important foundation for the development of an industrial hydrothermal extraction method.

Preparation and characterization of pH-responsive microgel using arabinoxylan from wheat bran for BSA delivery

Wheat bran arabinoxylan (AX) discard from wheat production was utilized to form pH-responsive microgels. AX was modified by carboxymethylation, and the carboxymethylated arabinoxylans (CMAX) were characterized by FT-IR, NMR, gel permeation chromatography (GPC), and rheological analysis. The CMAX microgel was cross-linked by Fe3+ using an inverse emulsification polymerization. The morphology, particle size, pH sensitivity, and mechanism of cross-linking between COO− and Fe3+ of the CMAX microgel was investigated. The CMAX microgel was used to be an oral protein drug carrier. The CMAX microgel particles exhibited a stable spherical structure. FT-IR spectral analysis of the CMAX microgel indicated that the microgel was crosslinked by bridging Fe3+ and COO− with unidentate binding. The CMAX microgel exhibited good pH sensitivity and high stability in acid condition. Additionally, BSA was used as the embedding protein, and the controlled release effect of CMAX microgel was explored in gastrointestinal tract simulation.

Relative abundance of the Prevotella genus within the human gut microbiota of elderly volunteers determines the inter-individual responses to dietary supplementation with wheat bran arabinoxylan-oligosaccharides

BackgroundThe human colon is colonised by a dense microbial community whose species composition and metabolism are linked to health and disease. The main energy sources for colonic bacteria are dietary polysaccharides and oligosaccharides. These play a major role in modulating gut microbial composition and metabolism, which in turn can impact on health outcomes.ResultsWe investigated the influence of wheat bran arabinoxylan oligosaccharides (AXOS) and maltodextrin supplements in modulating the composition of the colonic microbiota and metabolites in healthy adults over the age of 60. Male and female volunteers, (n = 21, mean BMI 25.2 ± 0.7 kg/m2) participated in the double-blind, cross over supplement study. Faecal samples were collected for analysis of microbiota, short chain fatty acids levels and calprotectin. Blood samples were collected to measure glucose, cholesterol and triglycerides levels. There was no change in these markers nor in calprotectin levels in response to the supplements. Both supplements were well-tolerated by the volunteers. Microbiota analysis across the whole volunteer cohort revealed a significant increase in the proportional abundance of faecal Bifidobacterium species (P ≤ 0.01) in response to AXOS, but not maltodextrin, supplementation. There was considerable inter-individual variation in the other bacterial taxa that responded, with a clear stratification of volunteers as either Prevotella-plus (n = 8; > 0.1% proportional abundance) or Prevotella-minus (n = 13; ≤0.1% proportional abundance) subjects founded on baseline sample profiles. There was a significant increase in the proportional abundance of both faecal Bifidobacterium (P ≤ 0.01) and Prevotella species (P ≤ 0.01) in Prevotella-plus volunteers during AXOS supplementation, while Prevotella and Bacteroides relative abundances showed an inverse relationship. Proportional abundance of 26 OTUs, including bifidobacteria and Anaerostipes hadrus, differed significantly between baseline samples of Prevotella-plus compared to Prevotella-minus individuals.ConclusionsThe wheat bran AXOS supplementation was bifidogenic and resulted in changes in human gut microbiota composition that depended on the initial microbiota profile, specifically the presence or absence of Prevotella spp. as a major component of the microbiota. Our data therefore suggest that initial profiling of individuals through gut microbiota analysis should be considered important when contemplating nutritional interventions that rely on prebiotics.Trial registrationClinical trial registration number: NCT02693782. Registered 29 February 2016 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02693782?term=NCT02693782&rank=1

Enzyme synergy for the production of arabinoxylo-oligosaccharides from highly substituted arabinoxylan and evaluation of their prebiotic potential

Wheat bran arabinoxylan can be converted by enzymatic hydrolysis into short arabinoxylo-oligosaccharides (AXOS) with prebiotic potential. Alkali extraction of arabinoxylan from wheat-bran offers advantages in terms of yield and results in arabinoxylan with highly-substituted regions which has been a challenge to hydrolyse using endoxylanases. We show that this hurdle can be overcome by selecting an arabinoxylanase that attacks these regions. The yield of AXOS can be increased by enzyme synergy, involving the hydrolysis of some arabinoxylan side groups. Thus, arabinoxylanase (CtXyl5At) from Clostridium thermocellum, belonging to subfamily 34 of glycoside hydrolase (GH) family 5 was investigated pertaining to its specificity for highly-substituted regions in the arabinoxylan-backbone. CtXyl5At preferentially hydrolysed the water-soluble fraction of alkali-extracted arabinoxylan. AXOS with DP 2–4 were determined as major products from CtXyl5At catalyzed hydrolysis. Increase in AXOS yield was observed with enzyme synergy, involving an initial treatment of soluble arabinoxylan with a GH43 α-l-arabinofuranosidase from Bifidobacterium adolescentis termed BaAXHd3 (30 °C, 6h), followed by hydrolysis with CtXyl5At (50 °C, 24h). The prebiotic potential of AXOS was shown by growth analysis using the human gut bacteria Bifidobacterium adolescentis ATCC 15703 and Roseburia hominis DSM 6839. Importantly, AXOS were utilized by the bacteria and short-chain fatty acids were produced.

Structural modifications to water-soluble wheat bran arabinoxylan through milling and extrusion

Feruloylated arabinoxylan (AX) is one of the most predominant dietary fiber in cereal grains. In recent decades, soluble AX has gained interest, as a result of its well-established health benefits. Apart from enzymatic degradation during cereal storage, food processing causes AX degradation. These reactions lead to structural modifications and influence both the AX functionalities and its health promoting effects. The aim of this study was to investigate the structural modifications and related property changes of health promoting water-extractable (WE) wheat bran AX through grain milling and extrusion. Multi-detector HPSEC revealed a correlation between Mw, conformational changes and the related viscosity behaviour depending on the processing type. Processing caused molecular degradation of insoluble high Mw AX, which increased the solubility significantly. Moreover, extrusion leaded to a more heterogenic AX fine structure. The detailed characterization of processed dietary fiber may help to facilitate the optimized incorporation of AX in health-promoting foods.