Explore the vast range of titles available.

Red alga dulse possesses a unique xylan, which is composed of a linear β-(1→3)/β-(1→4)-xylosyl linkage. We previously prepared characteristic xylooligosaccharide (DX3, (β-(1→3)-xylosyl-xylobiose)) from dulse. In this study, we evaluated the prebiotic effect of DX3 on enteric bacterium. Although DX3 was utilized by Bacteroides sp. and Bifidobacterium adolescentis, Bacteroides Ksp. grew slowly as compared with β-(1→4)-xylotriose (X3) but B. adolescentis grew similar to X3. Therefore, we aimed to find the key DX3 hydrolysis enzymes in B. adolescentis. From bioinformatics analysis, two enzymes from the glycoside hydrolase family 43 (BAD0423: subfamily 12 and BAD0428: subfamily 11) were selected and expressed in Escherichia coli. BAD0423 hydrolyzed β-(1→3)-xylosyl linkage in DX3 with the specific activity of 2988 mU/mg producing xylose (X1) and xylobiose (X2), and showed low activity on X2 and X3. BAD0428 showed high activity on X2 and X3 producing X1, and the activity of BAD0428 on DX3 was 1298 mU/mg producing X1. Cooperative hydrolysis of DX3 was found in the combination of BAD0423 and BAD0428 producing X1 as the main product. From enzymatic character, hydrolysis of X3 was completed by one enzyme BAD0428, whereas hydrolysis of DX3 needed more than two enzymes.

Xylanolytic enzyme systems in ascomycetous yeasts remain underexplored, despite the presence of yeasts in various xylan-rich ecological niches. In this study, we investigated the secreted xylanolytic machineries of three Blastobotrys species— B. mokoenaii , B. illinoisensis , and B. malaysiensis —by integrating genome annotation, bioinformatics, and secretome analyses of cultures grown on beechwood glucuronoxylan. Our findings demonstrate that these yeasts effectively hydrolyze xylan through the secretion of xylanases from the glycoside hydrolase (GH) family 11, which play a central role in cleaving the xylan backbone. Additionally, the yeasts produce a diverse array of other CAZymes, including members of GH families 3, 5, and 67, with putative roles in xylan degradation. We also report on the heterologous expression and functional characterization of the GH30_7 xylanase Bm Xyn30A from B. mokoenaii , which exhibits both glucuronoxylanase and xylobiohydrolase activities. We demonstrate additive effects between GH family 30 Bm Xyn30A and GH family 11 Bm Xyn11A during the hydrolysis of beechwood glucuronoxylan, where the enzymes exhibit complementary roles that enhance the deconstruction of this complex hemicellulose substrate. These findings broaden our understanding of the xylanolytic systems in yeasts and underscore the potential of Blastobotrys species as cell factories and natural xylanase producers. The enzymes they produce hold promise for biorefining applications, enabling efficient utilization of renewable xylan-rich plant biomass resources. Key points • Extracellular GH11 xylanases dominate glucuronoxylan degradation in Blastobotrys yeasts. • Yeast GH30_7 enzyme shows multifaceted activity, supporting complex xylan breakdown. • Blastobotrys yeasts show promise as cell factories for industrial biotechnology applications.

Cell wall degradation is a crucial process within the malting process of barley. Therefore, the haplotype diversity of genes for two cell wall degrading enzymes, (1 → 3),(1 → 4)-β-d-Glucan-4-glucanohydrolase and (1 → 4)-β-Xylan-endohydrolase 1, was investigated and associations to malting quality parameters were performed. The (1 → 3),(1 → 4)-β-d-Glucan-4-glucanohydrolase gene glb2 had two major haplotypes defined by three SNPs and one INDEL, which explained 8.9 and 9.5% of the total variation of malt extract content and viscosity in the spring barley gene pool, respectively. The most significant associations of (1 → 4)-β-Xylan-endohydrolase 1 gene X-1 were found for diastatic power, saccharification VZ45 and soluble nitrogen with 18, 12 and 8% of the total variation explained by SNP3 in the spring barleys. High-throughput markers were developed for both genes which can be used for marker assisted selection.

Barley endosperm begins development as a syncytium where numerous nuclei line the perimeter of a large vacuolated central cell. Between 3 and 6 days after pollination (DAP) the multinucleate syncytium is cellularized by the centripetal synthesis of cell walls at the interfaces of nuclear cytoplasmic domains between individual nuclei. Here we report the temporal and spatial appearance of key polysaccharides in the cell walls of early developing endosperm of barley, prior to aleurone differentiation. Flowering spikes of barley plants grown under controlled glasshouse conditions were hand-pollinated and the developing grains collected from 3 to 8 DAP. Barley endosperm development was followed at the light and electron microscope levels with monoclonal antibodies specific for (1 to 3)-β-d-glucan (callose), (1to3,1to4)-β-d-glucan, hetero-(1to4)-β-d-mannans, arabino-(1to4)-β-d-xylans, arabinogalactan-proteins (AGPs) and with the enzyme, cellobiohydrolase II, to detect (1to4)-β-d-glucan (cellulose). Callose and cellulose were present in the first formed cell walls between 3 and 4 DAP. However, the presence of callose in the endosperm walls was transient and at 6 DAP was only detected in collars surrounding plasmodesmata. (1to3,1to4)-β-d-Glucan was not deposited in the developing cell walls until approximately 5 DAP and hetero-(1to4)-β-d-mannans followed at 6 DAP. Deposition of AGPs and arabinoxylan in the wall began at 7 and 8 DAP, respectively. For arabinoxylans, there is a possibility that they are deposited earlier in a highly substituted form that is inaccessible to the antibody. Arabinoxylan and heteromannan were also detected in Golgi and associated vesicles in the cytoplasm. In contrast, (1to3,1to4)-β-d-glucan was not detected in the cytoplasm in endosperm cells; similar results were obtained for coleoptile and suspension cultured cells.

The structure of the human gut microbiota is controlled primarily through the degradation of complex dietary carbohydrates, but the extent to which carbohydrate breakdown products are shared between members of the microbiota is unclear. We show here, using xylan as a model, that sharing the breakdown products of complex carbohydrates by key members of the microbiota, such as Bacteroides ovatus, is dependent on the complexity of the target glycan. Characterization of the extensive xylan degrading apparatus expressed by B. ovatus reveals that the breakdown of the polysaccharide by the human gut microbiota is significantly more complex than previous models suggested, which were based on the deconstruction of xylans containing limited monosaccharide side chains. Our report presents a highly complex and dynamic xylan degrading apparatus that is fine-tuned to recognize the different forms of the polysaccharide presented to the human gut microbiota.

Colorectal cancer (CRC) therapy efficiency can be influenced by the microbiota in the gastrointestinal tract. Compared with traditional intervention, prebiotics delivery into the gut is a more controllable method for gut microbiota modulatory therapy. Capecitabine (Cap), the first-line chemotherapeutic agent for CRC, lacks a carrier that can prolong its half-life. Here, we construct a Cap-loaded nanoparticle using the prebiotic xylan-stearic acid conjugate (SCXN). The oral administration of SCXN delays the drug clearance in the blood and increases the intra-tumoral Cap concentration in the CRC mouse model. SCXN also facilitates the probiotic proliferation and short chain fatty acid production. Compared with free Cap, SCXN enhances the anti-tumor immunity and increases the tumor inhibition rate from 5.29 to 71.78%. SCXN exhibits good biocompatibility and prolongs the median survival time of CRC mice from 14 to 33.5 d. This prebiotics-based nanoparticle provides a promising CRC treatment by combining gut microbiota modulation and chemotherapy. Gut microbiota regulates colorectal cancer (CRC) progression and respond to therapy. Here the authors generate nanoparticles using prebiotic micelles and loaded with the chemo drug capecitabine that boost gastrointestinal probiotic response, increase anti-tumour immunity and improve survival when provided orally in CRC preclinical murine models.

A genetic locus from the gut symbiont Bacteroides ovatus is identified and described that encodes a cohort of enzymes and carbohydrate-binding proteins necessary for the metabolism of xyloglucans—a predominant component of dietary fibre. Niche bacteria central to digestion of plant fibre We can derive energy from dietary fibre thanks largely to the ability of the gut microbiota to digest and ferment complex polysaccharides. The mechanism of degradation of one ubiquitous family of branched plant cell wall polysaccharides, the xyloglucans, has been unclear. Here Harry Brumer and colleagues report the identification and molecular characterization of an archetypal genetic locus from the gut symbiont Bacteroides ovatus encoding enzymes dedicated to xyloglucan utilization. The ability to utilize xyloglucan is shown not to be universal among the Bacteroidetes but rather is carried out by a few specialists. The importance of a niche species of bacteria in the utilization of such an abundant form of dietary fibre is of relevance to the design of dietary strategies for the treatment of intestinal disease and highlights the need for careful strain selection and monitoring for achieving a healthy, balanced microbiota. A well-balanced human diet includes a significant intake of non-starch polysaccharides, collectively termed ‘dietary fibre’, from the cell walls of diverse fruits and vegetables 1 . Owing to the paucity of alimentary enzymes encoded by the human genome 2 , our ability to derive energy from dietary fibre depends on the saccharification and fermentation of complex carbohydrates by the massive microbial community residing in our distal gut 3 , 4 . The xyloglucans (XyGs) are a ubiquitous family of highly branched plant cell wall polysaccharides 5 , 6 whose mechanism(s) of degradation in the human gut and consequent importance in nutrition have been unclear 1 , 7 , 8 . Here we demonstrate that a single, complex gene locus in Bacteroides ovatus confers XyG catabolism in this common colonic symbiont. Through targeted gene disruption, biochemical analysis of all predicted glycoside hydrolases and carbohydrate-binding proteins, and three-dimensional structural determination of the vanguard endo -xyloglucanase, we reveal the molecular mechanisms through which XyGs are hydrolysed to component monosaccharides for further metabolism. We also observe that orthologous XyG utilization loci (XyGULs) serve as genetic markers of XyG catabolism in Bacteroidetes, that XyGULs are restricted to a limited number of phylogenetically diverse strains, and that XyGULs are ubiquitous in surveyed human metagenomes. Our findings reveal that the metabolism of even highly abundant components of dietary fibre may be mediated by niche species, which has immediate fundamental and practical implications for gut symbiont population ecology in the context of human diet, nutrition and health 9 , 10 , 11 , 12 .

Purpose Specific combinations of dietary fiber (DF) have been observed to result in improved glucose tolerance at a subsequent standardized breakfast. Arabinoxylan oligosaccharides (AXOS) are considered as DF with prebiotic potential, but so far no studies have investigated their metabolic effects in humans. This randomized cross-over study evaluated the overnight impact of breads containing AXOS-rich wheat bran extract and resistant starch (RS, Hi-Maize), separately or combined, on glucose tolerance, related metabolic parameters and markers of gut fermentation in healthy subjects. Methods Evening reference and test products were: (1) reference white wheat flour bread (WWB), WWB supplemented with (2) AXOS and RS (WWB + AXOS + RS), (3) an increased content of either AXOS (WWB +  hi AXOS) or (4) RS (WWB +  hi RS). At the subsequent standardized breakfast, blood was sampled for 3 h to monitor glucose, insulin, nonesterified fatty acids, glucagon-like peptide (GLP)-1 and GLP-2. Breath hydrogen (H 2 ) and short chain fatty acids (SCFA) were measured as markers of gut fermentation, and subjective appetite was rated using visual analog scales. Results Dose-dependent decreases in glucose responses were observed with increased AXOS over the duration of 3 h. Insulin sensitivity index was improved in the morning after the WWB +  hi AXOS evening meal. An increase in breath H 2 concentration and circulating SCFA was observed in the morning after both evening meals containing AXOS. Conclusion The present study indicates that AXOS have the potential of improving glucose tolerance in an overnight perspective and suggested mechanisms are improved insulin sensitivity and increased gut fermentation.

Root-knot nematodes ( Meloidogyne spp.) are an important group of plant parasitic nematodes that induce within host plant roots unique feeding site structures, termed giant cells, which supply nutrient flow to the nematode. A comparative in situ analysis of cell wall polysaccharides in the giant cells of three host species (Arabidopsis, maize and aduki bean) infected with Meloidogyne incognita has been carried out. Features common to giant cell walls of all three species include the presence of high-esterified pectic homogalacturonan, xyloglucan and pectic arabinan. The species-specific presence of xylan and mixed-linkage glucan (MLG) epitopes in giant cell walls of maize reflected that host’s taxonomic group. The LM5 galactan and LM21 mannan epitopes were not detected in the giant cell walls of aduki bean but were detected in Arabidopsis and maize giant cell walls. The LM2 arabinogalactan-protein epitope was notable for its apparent global variations in root cell walls as a response to infection across the three host species. Additionally, a set of Arabidopsis cell wall mutants were used to determine any impacts of altered cell wall structures on M . incognita infection. Disruption of the arabinogalactan-protein 8 gene had the greatest impact and resulted in an increased infection rate.

Background/objectives: Several studies emphasise that arabinoxylan and β-glucan have more beneficial effects on glucose metabolism than low-dietary fibre (DF) meals. Less attention has been paid to the effects of concentrated DF compared with whole grain. We compared the effects of DF and whole grain on glucose, hormone responses and appetite in subjects with the metabolic syndrome (MetS). Subjects/methods: Fifteen subjects with MetS participated in this acute, randomised, cross-over intervention study. The test breads provided 50 g of digestible carbohydrate: wheat bread with concentrated arabinoxylan (AX) or β-glucan (BG), rye bread with kernels (RK) and wheat bread (WB) as control. Blood samples were drawn for 270 min to determine glucose, insulin, glucagon-like peptide-1, glucose-dependent insulinotropic peptide (GIP) and ghrelin. Appetite score was addressed every 30 min. Ad libitum energy intake (EI) was measured 270 min after test meals. Results: Compared with WB, BG and RK induced lower initial glycaemic responses ( P <0.001), whereas AX only reduced the glucose peak value ( P <0.001). RK reduced insulin ( P <0.001) and GIP responses ( P <0.001) compared with the other breads. BG lowered insulin responses more than AX ( P <0.001). AX, BG and RK increased satiety feeling ( P <0.001) more than WB, but did not differ significantly in terms of subsequent EI ( P =0.089). Conclusion: BG and RK had beneficial impact on the glucose response, whereas AX had only effect on the postprandial glucose peak. The impact of the AX bread was influenced by higher protein content. Whether the metabolic effects of the breads are still present to mixed meals remains to be tested.