Grain-associated xylanases: occurrence, variability, and implications for cereal processing

Upcycling soybean meal through enzymatic conversion of insoluble fiber into soluble dietary fiber enhanced by ball milling

Insoluble dietary fiber (IDF) in soybean meal, due to the insolubility, is one of the major impediments to upcycle the soybean meal for its value-added use. This study converted IDF to soluble dietary fiber (SDF) using ball milling and enzymatic hydrolysis of the IDF. The impact of ball milling and enzymatic hydrolysis on the physicochemical and functional properties of SDF was evaluated. Cellulase, hemicellulase, xylanase, galacturonase, and arabinofuranosidase were employed for hydrolyzing IDF. The results showed that ball milling significantly reduced the particle size of IDF, facilitating enhanced enzymatic hydrolysis and resulting in SDF with lower molecular weight and varied monosaccharide composition. The synergistic effect of ball milling and enzymatic processes with combination of cellulase-xylanase-galacturonase was evident by the improved conversion rates (69.8%) and altered weight-averaged molecular weight (<5900 Da) of the resulting SDF. Rheological and microstructural analyses of the SDF gel indicated that specific enzyme combinations led to SDF gels with distinct viscoelastic properties, pore sizes, and functional capabilities, suitable for varied applications in the food and pharmaceutical sectors. This comprehensive evaluation demonstrates the potential of optimized physical bioprocessing techniques in developing functional ingredients with tailored properties for industrial use.

Cereal-Derived Water-Unextractable Arabinoxylans: Structure Feature, Effects on Baking Products and Human Health

Arabinoxylans (AXs) are non-starch polysaccharides with complex structures naturally occurring in grains (i.e., barley, corn, and others), providing many health benefits, especially as prebiotics. AXs can be classified as water-extractable (WEAX) and water-unextractable (WUAX) based on their solubility, with properties influenced by grain sources and extraction methods. Numerous studies show that AXs exert an important health impact, including glucose and lipid metabolism regulation and immune system enhancement, which is induced by the interactions between AXs and the gut microbiota. Recent research underscores the dependence of AX physiological effects on structure, advocating for a deeper understanding of structure-activity relationships. While systematic studies on WEAX are prevalent, knowledge gaps persist regarding WUAX, despite its higher grain abundance. Thus, this review reports recent data on WUAX structural properties (chemical structure, branching, and MW) in cereals under different treatments. It discusses WUAX applications in baking and the benefits deriving from gut fermentation.

Co-immobilization of β-xylosidase and endoxylanase on zirconium based metal-organic frameworks for improving xylosidase activity at high temperature and in acetone

Improving the activity of β-xylosidase at high temperature and organic solvents is important for the conversion of xylan, phytochemicals and some hydroxyl-containing substances to produce xylose and bioactive substances. In this study, a β-xylosidase R333H and an endoxylanase were simultaneously co-immobilized on the metal-organic framework UiO-66-NH₂. Compared with the single R333H immobilization system, the co-immobilization enhanced the activity of R333H at high temperature and high concentration of acetone, and the relative activities at 95°C and 50% acetone solution were > 95%. The K_m value of co-immobilized R333H towards p-Nitrophenyl-β-D-xylopyranoside (pNPX) shifted from 2.04 to 0.94 mM, which indicated the enhanced affinity towards pNPX. After 5 cycles, the relative activities of the co-immobilized enzymes towards pNPX and corncob xylan were 52% and 70% respectively, and the accumulated amount of reducing sugars obtained by co-immobilized enzymes degrading corncob xylan in 30% (v/v) acetone solution was 1.7 times than that with no acetone.

Structures, Biochemical Characteristics, and Functions of β-Xylosidases

The complete degradation of abundant xylan derived from plants requires the participation of β-xylosidases to produce the xylose which can be converted to xylitol, ethanol, and other valuable chemicals. Some phytochemicals can also be hydrolyzed by β-xylosidases into bioactive substances, such as ginsenosides, 10-deacetyltaxol, cycloastragenol, and anthocyanidins. On the contrary, some hydroxyl-containing substances such as alcohols, sugars, and phenols can be xylosylated by β-xylosidases into new chemicals such as alkyl xylosides, oligosaccharides, and xylosylated phenols. Thus, β-xylosidases shows great application prospects in food, brewing, and pharmaceutical industries. This review focuses on the molecular structures, biochemical properties, and bioactive substance transformation function of β-xylosidases derived from bacteria, fungi, actinomycetes, and metagenomes. The molecular mechanisms of β-xylosidases related to the properties and functions are also discussed. This review will serve as a reference for the engineering and application of β-xylosidases in food, brewing, and pharmaceutical industries.

Characterization of Two Wheat-Derived Glycoside Hydrolase Family-10 Xylanases Resistant to Xylanase Inhibitors

Xylanase inhibitors inhibit the activities of microbial xylanases and seriously compromise the efficacy of microbial xylanases added to modify cereals. Cereal endogenous xylanases are unaffected by these xylanase inhibitors, but little information is available regarding their effects in improving cereal quality, a neglected potential application. As a strategy for circumventing the negative effects of xylanase inhibitors, the objective of this study was to use genetic engineering to obtain sufficient amounts of active endo-1,4-β-D-xylanase from wheat to analyze the characteristics of its structure. The endo-1,4-β-D-xylanase from wheat was heterologously expressed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), western blotting, MALDI-TOF/TOF (MS) analyses, and enzyme activity determination confirmed 2 active endo-1,4-β-D-xylanases (EXY3 and EXY4) were successfully obtained. The molecular weights (MW) and isoelectric point (pI) of EXY3 were 36.108 kDa and 5.491, while those of the EXY4 protein were 41.933 kDa and 5.726. They both contained the same catalytic domain of GH10 xylanases from G266 to V276 and have the same catalytic site, Glu273. They shared the same putative N-glycosylation sites (N62-T63-S64 and N280–V281–S282) and 3 putative O-glycosylation sites (Ser8, Ser9, and Thr21), but EXY4 had an additional O-glycosylation site (Thr358). EXY3 was smaller than EXY4 by 51 amino acids because of a nonsense mutation and premature termination. They both had the 8-fold beta/alpha-barrel (TIM-barrel) fold. The specific activities of EXY3 and EXY4 were 152.0891 and 67.2928 U/mg, respectively. This work demonstrates a promising way to obtain wheat xylanases by genetic engineering; the properties of the enzymes indicate their potential application in cereal-based industries.

Microwave-assisted enzymatic hydrolysis to produce xylooligosaccharides from rice husk alkali-soluble arabinoxylan

The prebiotic properties of xylooligosaccharides (XOS) and arabino-xylooligosaccharides (AXOS) produced from rice husk (RH) using microwave treatment combined with enzymatic hydrolysis were evaluated. The RH was subjected to microwave pretreatment at 140, 160 and 180 °C for 5, 10 and 15 min to obtain crude arabinoxylan (AX). Increasing microwave pretreatment time increased sugar content. Crude AX was extracted with 2% (w/v) sodium hydroxide at 25 °C for 24 h and used as a substrate for XOS production by commercial xylanases. Results showed that oligosaccharides produced by Pentopan Mono BG and Ultraflo Max provided xylobiose and xylotriose as the main products. AXOS was also present in the oligosaccharides that promoted growth of Lactobacillus spp. and resisted degradation by over 70% after exposure to simulated human digestion.

Biological Functions and Activities of Rice Bran as a Functional Ingredient: A Review

Rice bran (RB) is a nutrient-rich by-product of the rice milling process. It consists of pericarp, seed coat, nucellus, and aleurone layer. RB is a rich source of a protein, fat, dietary fibers, vitamins, minerals, and phytochemicals (mainly oryzanols and tocopherols), and is currently mostly used as animal feed. Various studies have revealed the beneficial health effects of RB, which result from its functional components including dietary fiber, rice bran protein, and gamma-oryzanol. The health effects of RB including antidiabetic, lipid-lowering, hypotensive, antioxidant, and anti-inflammatory effects, while its consumption also improves bowel function. These health benefits have drawn increasing attention to RB in food applications and as a nutraceutical product to mitigate metabolic risk factors in humans. This review therefore focuses on RB and its health benefits.

Micronized whole wheat flour and xylanase application: dough properties and bread quality

The micronization process by jet mill of whole wheat flour in addition to xylanase application may be used to improve dough properties and baking quality. This study aimed to evaluate the dough formation and bakery performance of whole wheat flour micronized using jet mill and having different particle sizes and xylanase content A decrease in particle size increased water absorption and increased dough stability by 3.7 units. Increase in xylanase content decreased the dough stability and mixture tolerance, resulting in reduced strength. Although the dough quality reduced, this was not evident in bread quality. In bread, the increase in xylanase content increased the specific volume and improved the texture profile. The 158 and 261 μm particle sizes with 60 and 100 mg kg^-1 xylanase content reduced the undesirable effects of fibers in the dough, which may lead to improved bread making, thus enhancing improved consumer acceptance.

Biochemical characterization of a GH10 xylanase from the anaerobic rumen fungus Anaeromyces robustus and application in bread making

Anaeromyces robustus is an anaerobic rumen microorganism which can produce plant cell wall degrading enzymes. In this study, a new GH10 xylanase gene xylAr10 from A. robustus was identified, cloned and expressed in Pichia pastoris GS115. The recombinant protein ArXyn10 was characterized after being purified by Ni-NTA. The optimal pH and temperature of ArXyn10 was determined at 5.5 and 40 °C, respectively. ArXyn10 was stable at the pH range of 4.0-8.0, and could maintain high stability from 35 to 45 °C. The hydrolysis products released from beechwood xylan by ArXyn10 showed chromatographic mobility similar to xylobiose and xylotriose according to thin-layer chromatography analysis. It was shown that the addition of 7.5 mg of ArXyn10 in 100 g high-gluten wheat flour during bread making could increase the reducing sugar content by 10.80%, indicating that xylo-oligosaccharides were produced. With the addition of ArXyn10, the hardness and chewiness of the bread decreased and the quality was improved. The new discovered xylanase ArXyn10 have potential application prospect in bread making.

Effect of Bran Pre-Treatment with Endoxylanase on the Characteristics of Intermediate Wheatgrass (Thinopyrum intermedium) Bread

Previous work indicated that bran removal promotes network formation in breads prepared from intermediate wheatgrass (IWG) flour. However, refinement reduces yields as well as contents of nutritionally beneficial compounds such as fiber. This study evaluated xylanase pretreatment of IWG bran as a processing option to enhance the properties of bread made with half of the original bran content. Xylanase pretreatment did not affect stickiness but significantly reduced hardness and increased specific loaf volumes compared to negative (without xylanase) and positive controls (with xylanase but without pretreatment). However, the surface of breads with pretreated bran was uneven due to structural collapse during baking. Fewer but larger gas cells were present due to pretreatment. Addition of ascorbic acid modulated these effects, but did not prevent uneven surfaces. Accessible thiol concentrations were slightly but significantly increased by xylanase pretreatment, possibly due to a less compact crumb structure. Endogenous xylanases (apparent activity 0.46 and 5.81 XU/g in flour and bran, respectively) may have been activated during the pretreatment. Moreover, Triticum aestivum xylanase inhibitor activity was also detected (193 and 410 InU/g in flour and bran). Overall, xylanase pretreatment facilitates incorporation of IWG bran into breads, but more research is needed to improve bread appearance.

Impact of Xylanase and Glucanase on Oligosaccharide Formation, Carbohydrate Fermentation Patterns, and Nutrient Utilization in the Gastrointestinal Tract of Broilers

This study aimed at determining how the degradation of cereal non-starch polysaccharides (NSP) by dietary enzymes during feed digestion can influence nutrient digestibility and NSP fermentability in broilers. Ninety-six one-day-old male broilers were assigned to 4 different treatments: control and enzyme-supplemented wheat-based (WC, WE) or maize-based (MC, ME) treatments. Enzyme supplementation with endo-xylanase and endo-glucanase occurred from day 20 onwards. On day 28, digesta samples were collected. Nutrient digestibility, NSP recovery, oligosaccharide profile, and short-chain fatty acids (SCFA) content were determined. Enzyme supplementation in WE resulted in a higher starch (3%; p = 0.004) and protein (5%; p = 0.002) digestion in the ileum compared to WC. Xylanase activity in WE led to in situ formations of arabinoxylan-oligosaccharides consisting of 5 to 26 pentose units in the ileum. This coincided with decreased arabinose (p = 0.059) and xylose (p = 0.036) amounts in the ceca and higher acetate (p = 0.014) and butyrate (p = 0.044) formation in WE compared to WC. Conversely, complete total tract recovery of arabinoxylan in MC and ME suggested poor maize NSP fermentability. Overall, enzyme action improved nutrient digestibility and arabinoxylan fermentability in the wheat-based diet. The lower response of the maize-based diet to enzyme treatment may be related to the recalcitrance of maize arabinoxylan as well as to the high nutritive value of maize.

Not All Fibers Are Born Equal; Variable Response to Dietary Fiber Subtypes in IBD

Diet provides a safe and attractive alternative to available treatment options in a variety of diseases; however, research has only just begun to elucidate the role of diet in chronic diseases, such as the inflammatory bowel diseases (IBD). The chronic and highly debilitating IBDs, Crohn disease and ulcerative colitis, are hallmarked by intestinal inflammation, immune dysregulation, and dysbiosis; and evidence supports a role for genetics, microbiota, and the environment, including diet, in disease pathogenesis. This is true especially in children with IBD, where diet-based treatments have shown excellent results. One interesting group of dietary factors that readily links microbiota to gut health is dietary fibers. Fibers are not digested by human cells, but rather fermented by the gut microbes within the bowel. Evidence has been mounting over the last decade in support of the importance of dietary fibers in the maintenance of gut health and in IBD; however, more recent studies highlight the complexity of this interaction and importance of understanding the role of each individual dietary fiber subtype, especially during disease. There are roughly ten subtypes of dietary fibers described to date, categorized as soluble or insoluble, with varying chemical structures, and large differences in their fermentation profiles. Many studies to date have described the benefits of the byproducts of fermentation in healthy individuals and the potential health benefits in select disease models. However, there remains a void in our understanding of how each of these individual fibers affect human health in dysbiotic settings where appropriate fermentation may not be achieved. This review highlights the possibilities for better defining the role of individual dietary fibers for use in regulating inflammation in IBD.

Dietary Fibre from Whole Grains and Their Benefits on Metabolic Health

The consumption of whole grain products is often related to beneficial effects on consumer health. Dietary fibre is an important component present in whole grains and is believed to be (at least partially) responsible for these health benefits. The dietary fibre composition of whole grains is very distinct over different grains. Whole grains of cereals and pseudo-cereals are rich in both soluble and insoluble functional dietary fibre that can be largely classified as e.g., cellulose, arabinoxylan, β-glucan, xyloglucan and fructan. However, even though the health benefits associated with the consumption of dietary fibre are well known to scientists, producers and consumers, the consumption of dietary fibre and whole grains around the world is substantially lower than the recommended levels. This review will discuss the types of dietary fibre commonly found in cereals and pseudo-cereals, their nutritional significance and health benefits observed in animal and human studies.

Advance diversity of enzymatically modified arabinoxylan from wheat chaff

Hydrolysates of arabinoxylan extracted from wheat chaff were prepared using different enzymatic treatments with an emphasis on improvements in their anti-diabetic, antioxidant and functional characteristics. The extracted arabinoxylan was subjected to enzymatic hydrolysis using individual xylanase, arabinofuranosidase, and feruloyl esterase, and their combinations. In all obtained hydrolysates, peaks corresponding to molecular weight lower than 38 kDa were noticed, while non-hydrolysed arabinoxylan had only peaks corresponding to 580 and 38 kDa. Results indicated that applied enzymes could hydrolyse polymeric arabinoxylan while their synergistic actions successfully modified its structure reflecting in lowered viscosity. Besides, it has been observed that the synergistic actions of enzymes improved the biological activities of arabinoxylan more than twice. Chemometric classification analysis showed that synergistic enzymes' actions were predominantly responsible for the improvement of biological activities. It indicated that they might be a useful tool for diversification and enhancement of biological activities of arabinoxylan from wheat chaff.

Purification, Identification, and Characterization of an Endo-1,4-β-Xylanase from Wheat Malt

In this study, an endo-1,4-β-xylanase was purified from wheat malt following the procedures of ammonium sulfate precipitation, cation-exchange chromatography, and two-step anion-exchange chromatography. The purified endo-1,4-β-xylanase had a specific activity of 3.94 u/mg, demonstrating a weight average molecular weight (Mw) of approximately 58,000 Da. After LC-MS/MS (Liquid chromatography-tandem mass spectrometry) identification, the purified enzyme had the highest matching degree with a GH10 (Glycoside Hydrolase 10) domain-containing protein from wheat, there were 23 match peptides with a score above the threshold and the prot-cover was 45.5%. The resulting purified enzyme was used to investigate its degradation ability on high viscosity wheat-derived water-extractable arabinoxylan (WEAX). Degradation experiments confirmed that the purified enzyme was a true endo-acting enzyme, which could degrade large WEAX into smaller WEAX. The average degree of polymerization (avDP) and the viscosity of WEAX decreased with the increasing reaction time. The enzyme could degrade a small amount of WEAX into arabinoxylan-oligosaccharides (AXOS) with a degree of polymerization of 2-6, but no monosaccharide was produced. The degradation occurred rapidly in the first 3.5 h and decreased with the further prolongation of reaction time.

Procedures for Breadmaking Quality Assessment of Rye Wholemeal Flour

The aim of this study was to evaluate the baking value of rye flours from industrial mills and to indicate which rye flour quality parameters are the most important predictors of wholemeal rye bread quality for commercially milled rye grains. Ten wholemeal rye flours, which were characterized by ash content ranging from 1.43% to 2.42% d.m. (dry mass), were used for the study. The parameters that characterize the flour properties and the baking test were assessed. The study revealed that for the analyzed commercial rye flours, the falling number test and the amylograph properties are insufficient parameters for predicting the quality of wholemeal rye bread. The manufacture of good quality wholemeal bread requires the use of rye flour with superior quality, such as fine granulation, low protein content, low total and insoluble pentosans content, and, in particular, a high percentage of water-soluble pentosans content. Breads with a higher volume were obtained from rye flours that were generally characterized by lower protein content, lower total and insoluble pentosans content, and higher water-soluble pentosans content. Flour granulation and the percentage of water-soluble pentosans content especially, had a significant impact on bread’s hardness of crumb and the hardness of crumb’s increase during bread storage.

Husks of Zea mays as a potential source of biopolymers for food additives and materials' development

Maize husks, an agricultural and industrial residue generated in a large volume, were investigated as a potential source of useful biopolymers. Thus, their chemical composition was firstly studied, after which two biopolymer products were obtained and characterized. Maize husks were dried and milled, obtaining a 210 μm-main particle size powder (MHP). It contained carotenes (4 mg/100 g), and exhibited antioxidant capacity (≈195 mg ascorbic acid/100 g MHP) coming also from extractable coumaric and cinnamic acids-derivatives (14 mg/100 g). A 31% of the MPH was water-soluble at room temperature, mainly constituted by fructose, glucose, and sorbitol of mesophylls' intracellular origin. The water insoluble fiber (WIF, ≈70%), which showed antioxidant capacity (≈25-33 mg ascorbic acid/100 g WIF), was almost entirely constituted by the cell wall biopolymers or alcohol insoluble residue (AIR) of the MPH, mostly arabinoxylans (≈26%) crosslinked by ferulic residues (18.6 mg/100 g MPH), and cellulose (26%). Low levels of pectins (5.5%) and lignin (7%) were found. Hence, a 1.25%-sulfur nanocellulose (NCC) was directly obtained with sulfuric acid (-15 mV Zeta-potential; 147 °C onset of thermal-degradation) without the necessity of previous delignification. On the other hand, a water soluble arabinoxylan enriched fraction (AX-EF) with pseudoplastic behavior in water and sensibility to calcium ions (≈3 Pa⋅s initial Newtonian-viscosity) was isolated by alkaline hydrolysis of diferulate bridges. Despite a 56% of crystallinity, NCC showed the highest water absorption capacity when compared to that of the AX-EF and AIR. Maize husks constitute an important source of biopolymers for development of materials and food additives/ingredients with relevant hydration and antioxidant properties.

Effect of glucose oxidase and pentosanase on the prebiotic potentials of wheat arabinoxylans in anin vitrofermentation system

GOX and Pn + GOX modification increased the prebiotic potential of WEAX. Pn + GOX treated WEAXs had higher prebiotic potentials than WEAXs treated with GOX. The prebiotic potential of the weak gel was higher than that in the strong gel.

Arabinoxylan hydrolyzates as immunomodulators in Caco-2 and HT-29 colon cancer cell lines

The use of plant derived polysaccharides as health promoters has gained immense interest in the past few years. Arabinoxylan (AX) is the predominant non-starch polysaccharide in cereals and grasses including wheat. The current research aimed to investigate the structure-function relationship of arabinoxylan hydrolyzates (AXH), obtained by the enzymatic hydrolysis of AX using xylanase and arabinofuranosidase as immunomodulators in two colon cancer cell lines: Caco-2 and HT-29. Fine structural details had a strong correlation with the immunological properties of the wheat AXH. As a general trend, as the presence of arabinose substitution increased in the AXH, the production of proinflammatory cytokines, IL-8 and TNF-α, decreased in both cell lines. Thus, AXH with a higher degree of arabinose substitution might be better adept in lowering inflammation in colon cancer cells.

Superior Growth Rates in Broilers Fed Wheat with Low In Vitro Feed-Xylanase Inhibition

Grain-batch variation in xylanase-inhibitor levels may account for variations in the efficacy of feed xylanase supplementation. This would make inhibition an important quality parameter in the routine analysis of feedstuffs. Two analytical procedures for testing feedstuffs against specific xylanases were researched: the high-throughput viscosity-pressure assay (ViPr) and the extraction-free remazol-brilliant-blue-beechwood-xylan (RBBX) assay. Thirty-two wheat cultivars were analyzed for inhibition of a commercial xylanase, Ronozyme WX. Four cultivars were selected for a feeding experiment in which the growth of 1440 broilers from ages 7-33 days was monitored. The treatments resulted up to 7 % difference (day 14) in broiler weight . The cultivar choice had an effect throughout the experiment ( p < 0.05). The performance ranking of the treatments corresponded better to xylanase inhibition than to crude-protein content or nonstarch-polysaccharide content. Wheat-grain xylanase-inhibitor content is therefore a highly relevant quality parameter when broiler diets are supplemented with feed xylanase.

Variation in levels of non-starch polysaccharides and endogenous endo-1,4-β-xylanases affects the nutritive value of wheat for poultry

1. Endo-1,4-β-xylanase is known to improve the nutritive value of wheat-based diets for poultry by degrading dietary arabinoxylans. However, broilers' response to supplementation of wheat-based diets with exogenous endo-1,4-β-xylanase is not always observed. 2. In this study, 108 different wheat lots were analysed for levels of extract viscosity as well as for endogenous endo-1,4-β-xylanase activity, and the impact of these two variables in animal performance was tested. 3. Results revealed that endogenous endo-1,4-β-xylanase activity and extract viscosity content varied widely among different wheat lots. Thus, a trial was conducted to evaluate the efficacy of exogenous enzyme supplementation in broiler diets using wheats with different levels of extract viscosity and endogenous endo-1,4-β-xylanase activity. 4. The data revealed that exogenous enzyme supplementation was only effective when the wheat present in the diet had high levels of extract viscosity (14.8 cP) with low endogenous endo-1,4-β-xylanase activity (347.0 U/kg). Nevertheless, it is apparent that exogenous microbial xylanases reduce digesta extract viscosity and feed conversion ratio independently of the endogenous properties presented by different wheat lots. 5. The data suggest that extract viscosity and/or endogenous endo-1,4-β-xylanase activity affect the response to enzyme supplementation by poultry fed on wheat-based diets.

Evolution and Distribution of Hydrolytic Enzyme Activities during Preharvest Sprouting of Wheat (Triticum aestivum) in the Field

To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed knowledge of the evolution of hydrolytic enzyme activities in PHS wheat (Triticum aestivum), a broad collection of samples from three varieties was obtained by harvesting before, at, and after maturity. Delaying harvest time coupled with periods of heavy rainfall caused sprouting in the kernels, observed as a drop in Falling Number and an increase in α-amylase activity. The appearance of α- and β-amylase, peptidase, and endoxylanase activity during field sprouting was independent from each other. Consequently, Falling Number could not be used to predict activity of other hydrolytic enzymes. When differentiating endogenous from kernel-associated microbial enzymes, results showed that α- and β-amylase and peptidase activity of PHS kernels were predominantly of endogenous origin, whereas endoxylanase activity was largely from microbial origin.

Arabinoxylan hydrolyzates as immunomodulators in lipopolysaccharide-induced RAW264.7 macrophages

The immunomodulatory effects of arabinoxylan (AX) have been demonstrated before. However, these effects could be structure driven. Thus, we indicate the relationship between fine structural details and immunomodulatory properties of AX.

Arabinoxylans, gut microbiota and immunity

Arabinoxylan (AX) is a non-starch polysaccharide found in many cereal grains and is considered as a dietary fiber. Despite their general structure, there is structural heterogeneity among AX originating from different botanical sources. Furthermore, the extraction procedure and hydrolysis by xylolytic enzymes can further render differences to theses AX. The aim of this review was to address the effects of AX on the gut bacteria and their immunomodulatory properties. Given the complex structure of AX, we also aimed to discuss how the structural heterogeneity of AX affects its role in bacterial growth and immunomodulation. The existing literature indicates the role of fine structural details of AX on its potential as polysaccharides that can impact the gut associated microbial growth and immune system.

Use of an extruder for pre-mixing enhances xylanase action on wheat bran at low water content

The aim of the work was to test the hypothesis that at low water content enzyme action on biomass is enhanced when the raw material is in the form of a continuous mass instead of powder/granular form. Effects of two pre-mixing methods, blade-mixing and extrusion, on xylanase action were studied during stationary incubation of wheat bran of different particle sizes, also in comparison with incubation at high water content with continuous stirring. The use of an extruder enhanced arabinoxylan (AX) solubilisation at low water content (<54%), as compared to blade-mixing. AX solubilisation was highest in the high-water stirring treatment, but based on molecular weight, xylanase action on solubilised AX was similar as in the extrusion-aided process. Pre-mixing by extrusion enabled efficient enzyme action at low water content without the requirement for continuous mixing, probably due to the enhanced diffusion by the formation of a continuous mass in the extruder.

Rye flour enriched with arabinoxylans in rye bread making

The aim of the study was to investigate physical and chemical properties of preparations of water soluble arabinoxylans (arabinoxylan-enriched flour) obtained by industrial method and their derivatives (obtained by hydrolysis and cross-linking of aranbinoxylans), as well as their impact on baking properties of rye flours. Additionally, these results were compared with highly purified arabinoxylans prepared by laboratory method and well characterized in the literature. Flour enriched with arabinoxylans was obtained by industrial method involving air separation of flour particles. It was characterized by 8.6% arabinoxylan content, lack of insoluble material and substantial residue (67%) of starch and dextrins. The addition of all industrial method preparations in amount of 10% (i.e. approx. 1% water soluble arabinoxylans), to rye flours resulted in an increase in water absorption, bread volume and decrease in hardness of the bread crumb and the effect was especially strong in the case of flour type 720. Due to the easiness of isolation procedure, industrial method preparation could be advised as an improver for rye bread making.

Mode of endosperm and wholemeal arabinoxylans solubilisation during rye breadmaking: genotypic diversity in the level, substitution degree and macromolecular characteristics

Insight into solubilisation mechanisms of rye arabinoxylans during breadmaking is important for understanding the biochemical processes that affect bread attributes. Purified ethanol precipitated water-extractable arabinoxylans (WE-AX) and residual unextractable counterparts (WU-AX) were isolated from rye flours and resulting breads. While the endosperm flours had lower endoxylanase activities and higher arabinose-to-xylose ratios of WU-AX than those of corresponding wholemeals, there were not any significant differences between them in the mean amounts of WU-AX hydrolysed during breadmaking. Nevertheless, they were highly affected by rye cultivar used for breadmaking. On average, 42% and 36% of WU-AX were recovered in bread WE-AX fraction, causing its 11% and 8% increase, respectively for endosperm and wholemeal breads. Bread WE-AX, however, had lower molecular weights than those of starting flours, implying chains depolymerisation. Degree of AX solubilisation depends mainly on rye genotype used, determining combined effect of enzymatic and acid hydrolyses, associations and fine structure of AX.

Secondary substrate binding strongly affects activity and binding affinity of Bacillus subtilis and Aspergillus niger GH11 xylanases

The secondary substrate binding site (SBS) of Bacillus subtilis and Aspergillus niger glycoside hydrolase family 11 xylanases was studied by site-directed mutagenesis and evaluation of activity and binding properties of mutant enzymes on different substrates. Modification of the SBS resulted in an up to three-fold decrease in the relative activity of the enzymes on polymeric versus oligomeric substrates and highlighted the importance of several amino acids in the SBS forming hydrogen bonds or hydrophobic stacking interactions with substrates. Weakening of the SBS increased K(d) values by up to 70-fold in binding affinity tests using natural substrates. The impact that modifications in the SBS have both on activity and on binding affinity towards polymeric substrates clearly shows that such structural elements can increase the efficiency of these single domain enzymes on their natural substrates.