Constituent Monosaccharides Research Articles

Molecular Modeling of Glycosylated Catalytic Domain of Human Carbonic Anhydrase IX.

Glycans exhibit significant structural diversity due to the flexibility of glycosidic bonds linking their constituent monosaccharides and the formation of numerous hydrogen bonds. The present work searches a simulated ensemble of glycan chain conformations attached to the catalytic domain of N-glycosylated human carbonic anhydrase IX (HCA IX-c) to identify conformations pointed away or back-folded toward the protein surface guided by different amino acid residues. A series of classical molecular dynamics (MD) simulation studies for a total of 30 μs followed by accelerated MD simulations for a total of 2 μs have been performed using two different force fields to capture varying degrees of fluctuations of both glycan chain and HCA IX. From the underlying free energy profile and kinetics derived using hidden Markov state model, several stable glycan orientations are identified that extend away from the protein surface and convert among each other with rate constants of the order 107-1010 S-1. Most importantly, we have identified a rare glycan conformation which reaches close to a catalytically important amino acid residue, Glu-106. We further enlist the protein residues that couple such less frequent event of the glycan chain back-folding toward the surface of the protein.

Analysis of Glycan Recognition by Concanavalin A Using Absolute Binding Free Energy Calculations.

Carbohydrates are key biological mediators of molecular recognition and signaling processes. In this case study, we explore the ability of absolute binding free energy (ABFE) calculations to predict the affinities of a set of five related carbohydrate ligands for the lectin protein, concanavalin A, ranging from 27-atom monosaccharides to a 120-atom complex-type N-linked glycan core pentasaccharide. ABFE calculations quantitatively rank and estimate the affinity of the ligands in relation to microcalorimetry, with a mean signed error in the binding free energy of -0.63 ± 0.04 kcal/mol. Consequently, the diminished binding efficiencies of the larger carbohydrate ligands are closely reproduced: the ligand efficiency values from isothermal titration calorimetry for the glycan core pentasaccharide and its constituent trisaccharide and monosaccharide compounds are respectively -0.14, -0.22, and -0.41 kcal/mol per heavy atom. ABFE calculations predict these ligand efficiencies to be -0.14 ± 0.02, -0.24 ± 0.03, and -0.46 ± 0.06 kcal/mol per heavy atom, respectively. Consequently, the ABFE method correctly identifies the high affinity of the key anchoring mannose residue and the negligible contribution to binding of both β-GlcNAc arms of the pentasaccharide. While challenges remain in sampling the conformation and interactions of these polar, flexible, and weakly bound ligands, we nevertheless find that the ABFE method performs well for this lectin system. The approach shows promise as a quantitative tool for predicting and deconvoluting carbohydrate-protein interactions, with potential application to design of therapeutics, vaccines, and diagnostics.

Model-Assisted Optimization of Xylose, Arabinose, Glucose, Mannose, Galactose and Real Hemicellulose Streams Dehydration To (Hydroxymethyl)Furfural and Levulinic Acid.

Conversion of hemicellulose streams and the constituent monosaccharides, xylose, arabinose, glucose, mannose, and galactose, was conducted to produce value-added chemicals, including furfural, hydroxymethylfurfural (HMF), levulinic acid and anhydrosugars. The study aimed at developing a kinetic model relevant for direct post-Organosolv hemicellulose conversion. Monosaccharides served as a tool to in detail describe the kinetic behavior and segregate contribution of hydrothermal decomposition and acid catalyzed dehydration at the temperature range of 120-190 °C. Catalyst free aqueous media demonstrated enhanced formation of furanics, while elevated temperatures led to significant saccharide isomerization. The introduction of sulfuric and formic acids maximized furfural yield and significantly reduced HMF concentration by facilitating its rehydration into levulinic acid (46 mol%). Formic acid additionally substantially enhanced formation of anhydrosaccharides. An excellent correlation between modeled and experimental data enabled process optimization to maximize furanic yield in two distinct hemicellulose streams. Sulfuric acid-containing hemicellulose stream achieved the highest furfural yield after 30 minutes at 238 °C, primarily due to the high Ea for pentose dehydration (150-160 kJ mol-1). Contrarily, formic acid-containing hemicellulose stream enabled maximal furfural yield at more moderate temperature and extended reaction time due to its lower Ea for the same reaction step (115-125 kJ mol-1).

Effects of acetic acid fermentation product and its components on defense signaling in rice.

Acetic acid fermentation product made from isomalto-oligosaccharide as the main raw material is composed of isomalto-oligosaccharide and acetic acid. In this paper, we have shown that the fermentation product enhanced the expression of disease resistance genes in rice, and that its main functional component was acetic acid. It has been reported so far that acetic acid enhances the jasmonic acid signaling pathway, while the role of isomalto-oligosaccharide in plant defense signaling remains unclear. In this study, we demonstrated the possibility that isomalto-oligosaccharide shifted part of the jasmonic acid signaling pathway, which is enhanced by acetic acid, to the salicylic acid signaling pathway, which is the other major defense pathway. Furthermore, glucose, a constituent monosaccharide of isomalto-oligosaccharide, and a disaccharide maltose had little effect on the signaling pathway, but a trisaccharide maltotriose tended to have a similar effect to isomalto-oligosaccharide on the defense signaling pathway.

Polysaccharides from Seedless Chestnut Rose (Rosa sterilis) Fruits: Insights into Innovative Drying Technologies and Their Structural Characteristics, Antioxidant, Antiglycation, and α-Glucosidase Inhibitory Activities.

The selection of an optimal drying method is essential for extending the shelf life and enhancing the quality of Rosa sterilis fruits. This study investigated the effects of both innovative (microwave vacuum drying and infrared drying) and traditional (freeze-drying and hot air drying) techniques on the structural characteristics and bioactivities of polysaccharides from R. sterilis fruits (RSPs). Four different RSPs were obtained from fruits dried using these methods. Results demonstrated that the structural characteristics and bioactivities of RSPs varied significantly with the drying method. Notable differences were observed in extraction yield, total sugar, uronic acid content, monosaccharide molar ratios, molecular weight distribution, particle size, thermal stability, and microstructures of RSPs. Despite these variations, the types of constituent monosaccharides and major glycosidic linkages remained consistent across all methods. Notably, RSPs obtained via microwave vacuum drying (RSPs-MVD) showed a higher uronic acid content and lower molecular weight, and exhibited stronger in vitro antioxidant, α-glucosidase inhibitory, and antiglycation activities. These findings suggest that microwave vacuum drying is an effective pre-drying technique for extracting RSPs, making them suitable as bioactive ingredients in functional foods and pharmaceuticals for managing diabetes mellitus and its complications.

A novel N-acetylglucosamine-6-phosphate deacetylase that is essential for chitin utilization in the chitinolytic bacterium, Chitiniphilus shinanonensis.

We aimed to investigate the function of an unidentified gene annotated as a PIG-L domain deacetylase (cspld) in Chitiniphilus shinanonensis SAY3. cspld was identified using transposon mutagenesis, followed by negatively selecting a mutant incapable of growing on chitin, a polysaccharide consisting of N-acetyl-d-glucosamine (GlcNAc). We focused on the physiological role of CsPLD protein in chitin utilization. Recombinant CsPLD expressed in Escherichia coli exhibited GlcNAc-6-phosphate deacetylase (GPD) activity, which is involved in the metabolism of amino sugars. However, SAY3 possesses two genes (csnagA1 and csnagA2) in its genome that code for proteins whose primary sequences are homologous to those of typical GPDs. Recombinant CsNagA1 and CsNagA2 also exhibited GPD activity with 23 and 1.6% of catalytic efficiency (kcat/Km), respectively, compared to CsPLD. The gene-disrupted mutant, Δcspld was unable to grow on chitin or GlcNAc, whereas the three mutants, ΔcsnagA1, ΔcsnagA2, and ΔcsnagA1ΔcsnagA2 grew similarly to SAY3. The determination of GPD activity in the crude extracts of each mutant revealed that CsPLD is a major enzyme that accounts for almost all cellular activities. Deacetylation of GlcNAc-6P catalyzed by CsPLD (but not by typical GPDs) is essential for the assimilation of chitin and its constituent monosaccharide, GlcNAc, as a carbon and energy source in C. shinanonensis.

Functional dissection of the spike glycoprotein S1 subunit and identification of cellular cofactors for regulation of swine acute diarrhea syndrome coronavirus entry.

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a novel porcine enteric coronavirus, and the broad interspecies infection of SADS-CoV poses a potential threat to human health. This study provides experimental evidence to dissect the roles of distinct domains within the SADS-CoV spike S1 subunit in cellular entry. Specifically, we expressed the S1 and its subdomains, S1A and S1B. Cell binding and invasion inhibition assays revealed a preference for the S1B subdomain in binding to the receptors on the cell surface, and this unknown receptor is not utilized by the porcine epidemic diarrhea virus. Nanoparticle display demonstrated hemagglutination of erythrocytes from pigs, humans, and mice, linking the S1A subdomain to the binding of sialic acid (Sia) involved in virus attachment. We successfully rescued GFP-labeled SADS-CoV (rSADS-GFP) from a recombinant cDNA clone to track viral infection. Antisera raised against S1, S1A, or S1B contained highly potent neutralizing antibodies, with anti-S1B showing better efficiency in neutralizing rSADS-GFP infection compared to anti-S1A. Furthermore, depletion of heparan sulfate (HS) by heparinase treatment or pre-incubation of rSADS-GFP with HS or constituent monosaccharides could inhibit SADS-CoV entry. Finally, we demonstrated that active furin cleavage of S glycoprotein and the presence of type II transmembrane serine protease (TMPRSS2) are essential for SADS-CoV infection. These combined observations suggest that the wide cell tropism of SADS-CoV may be related to the distribution of Sia or HS on the cell surface, whereas the S1B contains the main protein receptor binding site. Specific host proteases also play important roles in facilitating SADS-CoV entry.IMPORTANCESwine acute diarrhea syndrome coronavirus (SADS-CoV) is a novel pathogen infecting piglet, and its unique genetic evolution characteristics and broad species tropism suggest the potential for cross-species transmission. The virus enters cells through its spike (S) glycoprotein. In this study, we identify the receptor binding domain on the C-terminal part of the S1 subunit (S1B) of SADS-CoV, whereas the sugar-binding domain located at the S1 N-terminal part of S1 (S1A). Sialic acid, heparan sulfate, and specific host proteases play essential roles in viral attachment and entry. The dissection of SADS-CoV S1 subunit's functional domains and identification of cellular entry cofactors will help to explore the receptors used by SADS-CoV, which may contribute to exploring the mechanisms behind cross-species transmission and host tropism.

Ulvans are not equal - Linkage and substitution patterns in ulvan polysaccharides differ with Ulva morphology

Ulva are hardy green seaweeds that contain the sulfated polysaccharide ulvan and grow in two distinct morphologies: foliose and tubular. The authors hypothesise that ulvan from tubular species are more structurally complex than ulvans from foliose species. Herein, using standardised methods, the glycosyl linkage positions and sulfate ester substitutions of constituent monosaccharides of ulvan isolated from foliose (U. lacinulata and U. stenophylloides) and tubular (U. prolifera and U. ralfsii) species of Ulva were investigated. Comparison of native ulvans with 80 and 100 °C desulfated counterparts indicated that 4-linked rhamnose is predominantly 3-O-sulfated in all four ulvans. Ulvans from the foliose species predominantly contained →3,4)-Rhap-(1→, →4)-GlcAp-(1→ and →4)-IdoAp-(1→, collectively accounting for 67 to 81 mol% of the total linkages. In contrast, these same linkages in ulvans from the tubular species only collectively accounted for 29 to 36 mol%. Instead, ulvan from tubular species contained a combination of →2,3,4)-Rhap-(1→, terminal Rhap-(1→, →4)-GlcAp-(1→, →4)-Xylp-(1→, and/or →4)-Galp-(1→ in high proportions; some of the latter three residues were also likely O-2 sulfated. The results presented here suggest that ulvan from foliose species are predominantly unbranched polysaccharides composed of repeat disaccharides while ulvans from tubular species contain a greater diversity of branch and sulfate substitution locations.

Effects of different extraction methods on the structural and biological properties of Hericium coralloides polysaccharides

In current study, polysaccharides from Hericium coralloides were extracted by heat reflux, acid-assisted, alkali-assisted, enzyme-assisted, ultrasonic-assisted, cold water, pressurized hot water, hydrogen peroxide/ascorbic acid system and acid-chlorite delignification methods, which were named as HRE-P, ACE-P, AAE-P, EAE-P, UAE-P, CWE-P, PHE-P, HAE-P, and ACD-P, respectively. Their physicochemical properties, structural characteristics, and antioxidant activities were investigated and compared. Experimental outcomes indicated notable variations in the extraction yields, chemical compositions, monosaccharide constituents and molecular weights of the obtained nine polysaccharides. HRE-P demonstrated the highest activity against ABTS and OH radicals, CWE-P against ABTS, DPPH, and superoxide radicals, and UAE-P against DPPH radicals. In addition, UAE-P, CWE-P, and HAE-P exhibited better protective effects on L929 cells, when compared to the other obtained polysaccharides. Additionally, correlation analysis indicated that monosaccharide composition and total polyphenol content were two prominent variables influencing the bioactivity of H. coralloides polysaccharides.

Characterization of Chilean hot spring-origin Staphylococcus sp. BSP3 produced exopolysaccharide as biological additive

A type of high molecular weight bioactive polymers called exopolysaccharides (EPS) are produced by thermophiles, the extremophilic microbes that thrive in acidic environmental conditions of hot springs with excessively warm temperatures. Over time, EPS became important as natural biotechnological additives because of their noncytotoxic, emulsifying, antioxidant, or immunostimulant activities. In this article, we unravelled a new EPS produced by Staphylococcus sp. BSP3 from an acidic (pH 6.03) San Pedro hot spring (38.1 °C) located in the central Andean mountains in Chile. Several physicochemical techniques were performed to characterize the EPS structure including Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS), Atomic Force Microscopy (AFM), High-Performance Liquid Chromatography (HPLC), Gel permeation chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), 1D Nuclear Magnetic Resonance (NMR), and Thermogravimetric analysis (TGA). It was confirmed that the amorphous surface of the BSP3 EPS, composed of rough pillar-like nanostructures, is evenly distributed. The main EPS monosaccharide constituents were mannose (72%), glucose (24%) and galactose (4%). Also, it is a medium molecular weight (43.7 kDa) heteropolysaccharide. NMR spectroscopy demonstrated the presence of a [→ 6)-⍺-d-Manp-(1 → 6)-⍺-d-Manp-(1 →] backbone 2-O substituted with 1-⍺-d-Manp. A high thermal stability of EPS (287 °C) was confirmed by TGA analysis. Emulsification, antioxidant, flocculation, water-holding (WHC), and oil-holding (OHC) capacities are also studied for biotechnological industry applications. The results demonstrated that BSP3 EPS could be used as a biodegradable material for different purposes, like flocculation and natural additives in product formulation.Graphical

VARIOUS ADHERENT-INVASIVE E. COLI (AIEC) AND NON-AIEC STRAINS ISOLATED FROM CROHN’S DISEASE PATIENTS GROW DIFFERENTLY WITH RUMINOCOCCUS GNAVUS PRE-DIGESTED MUCUS AND R. GNAVUS-RELEASED PRE-DIGESTED ILEAL AND COLONIC MUCUS MONOSACCHARIDES

Abstract BACKGROUND Mucus-digesting Ruminococcus gnavus (R. gnavus), adherent-invasive E. coli (AIEC), and hydrogen sulfide (H2S) are enriched in active Crohn’s disease (CD) patients compared to healthy subjects. Dual colonization of R. gnavus and E. coli LF82 in ex-germ-free mice enhanced distal colitis and H2S production in cecal contents. R. gnavus pre-digestion of mucus enhanced the ileal CD isolate AIEC LF82 growth and H2S production in vitro. H2S enhanced LF82 adhesion and invasion both in vitro and in vivo along with related LF82 adhesion gene expression and Caco-2 cell expression of CEACAM6, a receptor for AIEC ligand FimH. Interactions between other CD-derived AIEC/non-AIEC and R. gnavus are unknown. HYPOTHESIS Different AIEC and non-AIEC may grow and produce H2S differently using mucus digested by R. gnavus, which releases mucus-derived monosaccharides and sulfur substrates. METHODS We studied CD-derived clinical isolates of AIEC 541-15 (phylotype A), 541-1 (B1), LF82 and NRG857c (B2) and non-AIEC T75 (A) and lab strain K12 (A). M9 minimal media was supplemented with porcine gastric mucin (PGM), ileal (MIM) and colonic (MCoM) mucus isolated from germ-free mice. We measured growth kinetics and H2S production by these AIEC and non-AIEC following culture with sterile supernatants of each mucin/mucus media precultured with or without R. gnavus, monosaccharides obtained by R. gnavus digestion of mucus, and several sulfur substrates in the gut added to M9 minimal media. RESULTS AIEC, especially LF82 (B2), grew better with ileal mucus aerobically and, to a lesser extent, anaerobically than non-AIEC strains, with even greater AIEC growth with R. gnavus pre-digested mucus (Fig.1). AIEC produced more H2S with R. gnavus-precultured mucus than with mucus alone. R. gnavus digestion of PGM released mucus monosaccharides (Fig.2A). AIEC strains grew differently with each monosaccharide constituent of R. gnavus pre-digested PGM. AIEC grew better than non-AIEC with each monosaccharide in aerobic conditions, but AIEC (B2) grew better than others in all monosaccharides in anaerobic conditions (Fig.2B). Amongst mucus-relevant sulfur substrates, L-cysteine was the only substrate to enhance E. coli H2S production by all AIEC and non-AIEC strains. All mucus-relevant sulfur substrates supported R. gnavus survival for 24 hrs, while H2S sustained R. gnavus for 48 hrs in minimum media. CONCLUSIONS AIEC grew better and produced more H2S with R. gnavus pre-digested mucus suggesting that co-existence of AIEC with R. gnavus mutually support each other and may explain why they are often observed together in active CD patients. In addition, enhanced AIEC growth with ileal vs. colonic mucus may explain why AIEC are frequently isolated from ileal CD patients. AIEC phylotype growth differences with mucus substrates may explain their persistence in the ileal mucosa. Figure 1 Figure 2

In vitro study on antioxidant and lipid-lowering activities of tobacco polysaccharides

Tobacco polysaccharides were extracted by hot water extraction, and purified and separated using DEAE-52 cellulose chromatography columns, and three purified polysaccharide fractions, YCT-1, YCT-2, and YCT-3, were finally obtained. The physicochemical properties of the three fractions were analyzed by ultraviolet spectroscopy, high-performance liquid chromatography and high-performance gel chromatography. The in vitro antioxidant activity of tobacco polysaccharides was compared among different fractions by using DPPH radical, hydroxyl radical scavenging assay and potassium ferricyanide method. The in vitro hypoglycemic activity was compared using α-amylase and α-glucosidase activity inhibition assay. And the in vitro hypolipidemic activity were investigated by using pancreatic lipase activity inhibition assay and HepG-2 intracellular lipid accumulation assay. All the results showed that the constituent monosaccharides of the three tobacco polysaccharide fractions were similar, but the molar percentages of each monosaccharide were different. The average molecular weights of the three components were 27,727 Da, 27,587 Da, and 66,517 Da, respectively, and the scavenging activities on DPPH radicals and hydroxyl radicals were at a high level with good quantitative-effect relationships. The reducing power were much lower than that of the positive control VC, and the three polysaccharide fractions had a weak inhibitory ability on α-amylase activity, but showed excellent inhibitory ability on α-glucosidase and pancreatic lipase activity. In addition, the results of cellular experiments showed that all three fractions were able to inhibit lipid over-accumulation in HepG-2 cells by increasing the mRNA expression levels of PPAR-α, CPT-1A, and CYP7A1 genes, and the tobacco polysaccharide YCT-3 showed the best effect. The mechanism by which YCT-3 ameliorated the over-accumulation of intracellular lipids in HepG-2 cells was found to be related to its influence on the expression of miR-155-3p and miR-17-3p in the exosomes of HepG-2 cells.Graphical

Ultrasonic extraction of Moringa oleifera seeds polysaccharides: Optimization, purification, and anti-inflammatory activities

Natural polysaccharides exhibit numerous beneficial properties, such as antioxidant, antitumor, hypoglycemic, and hypolipidemic activities. Moringa oleifera seeds are of high dietary and therapeutic value which drew a lot of attention. However, the regulation effect on anti-inflammatory activity of polysaccharides remains to be studied. Herein, novel bioactive polysaccharides (MOSP-1) were extracted from Moringa oleifera seeds, and the anti-inflammatory properties of MOSP-1 were uncovered. Ultrasound-assisted extraction (UAE) was used to prepare the polysaccharides with optimized conditions (70 °C, 43 min, and liquid-solid-ratio 15 mL/g). Then, DEAE-Sepharose Fast Flow columns were applied to isolate and purify MOSP-1. Rhamnose, arabinose, galactose, and glucose were identified as the monosaccharide constituents of MOSP-1, with a molecular weight of 5.697 kDa. Their proportion in molarity was 1:0.183:0.108:0.860 and 8 types of glycosidic linkages were discovered. Bioactive assays showed that MOSP-1 possessed scavenging activities against DPPH and ABTS radicals, confirming its potential antioxidation efficacy. In vitro experiments revealed that MOSP-1 could reduce the expression of inflammation-related cytokines, inhibit the activation of ERK, JNK, and p38 (the MAPK signaling pathway), and enhance phagocytic functions. This study indicates that polysaccharides (MOSP-1) from Moringa oleifera seeds with anti-inflammatory properties may be used for functional food and pharmaceutical product development.

Strong chemotaxis by marine bacteria towards polysaccharides is enhanced by the abundant organosulfur compound DMSP

The ability of marine bacteria to direct their movement in response to chemical gradients influences inter-species interactions, nutrient turnover, and ecosystem productivity. While many bacteria are chemotactic towards small metabolites, marine organic matter is predominantly composed of large molecules and polymers. Yet, the signalling role of these large molecules is largely unknown. Using in situ and laboratory-based chemotaxis assays, we show that marine bacteria are strongly attracted to the abundant algal polysaccharides laminarin and alginate. Unexpectedly, these polysaccharides elicited stronger chemoattraction than their oligo- and monosaccharide constituents. Furthermore, chemotaxis towards laminarin was strongly enhanced by dimethylsulfoniopropionate (DMSP), another ubiquitous algal-derived metabolite. Our results indicate that DMSP acts as a methyl donor for marine bacteria, increasing their gradient detection capacity and facilitating their access to polysaccharide patches. We demonstrate that marine bacteria are capable of strong chemotaxis towards large soluble polysaccharides and uncover a new ecological role for DMSP in enhancing this attraction. These navigation behaviours may contribute to the rapid turnover of polymers in the ocean, with important consequences for marine carbon cycling.

β-(1 → 3)(1 → 6)glucan from Schizophyllum commune 227E.32: High yield production via glucose/xylose co-metabolization

A co-metabolization of xylose and glucose by Schizophyllum commune 227E.32 wild mushroom for exopolysaccharide (EPS) production is presented. Cultivations performed with S. commune 227E.32 at different xylose concentrations demonstrated that the concentration of 50 g·L−1 of xylose achieved the highest EPS production, around 4.46 g·L−1. Scale-up in a stirred tank reactor (STR) was performed. 10 % inoculum showed the highest cost/benefit ratio regarding sugar conversion and EPS production (Y P/S = 0.90 g·g−1), achieving 1.82 g·L−1 of EPS. Isolation, purification, and characterization were conducted with EPS produced in flasks and STR. GC–MS analysis showed glucose as main monosaccharide constituents for both isolates. 13C NMR and HSQC-edited showed that both EPS isolated consisted of a β-D-Glcp (1 → 3) main chain, partially substituted at O-6 with nonreducing β-D-Glcp ends on every third residue, similar to β-D-glucan isolated from S. commune basidiomes known as schizophyllan (SPG). The Mw was determined by GPC to 1.5 × 106 Da (flasks) and 1.1 × 106 Da (STR). AFM topographs revealed a semi-flexible appearance of the β-D-glucan, consistent with the triple helical structures adopted by SPG and overall contour length consistent with a high molar mass.

Sialic acid plays a pivotal role in licensing Citrobacter rodentium’s transition from the intestinal lumen to a mucosal adherent niche

Enteric bacterial pathogens pose significant threats to human health; however, the mechanisms by which they infect the mammalian gut in the face of daunting host defenses and an established microbiota remain poorly defined. For the attaching and effacing (A/E) bacterial family member and murine pathogen Citrobacter rodentium, its virulence strategy likely involves metabolic adaptation to the host's intestinal luminal environment, as a necessary precursor to reach and infect the mucosal surface. Suspecting this adaptation involved the intestinal mucus layer, we found that C. rodentium was able to catabolize sialic acid, a monosaccharide derived from mucins, and utilize it as its sole carbon source for growth. Moreover, C. rodentium also sensed and displayed chemotactic activity toward sialic acid. These activities were abolished when the nanT gene, encoding a sialic acid transporter, was deleted (ΔnanT). Correspondingly, the ΔnanT C. rodentium strain was significantly impaired in its ability to colonize the murine intestine. Intriguingly, sialic acid was also found to induce the secretion of two autotransporter proteins, Pic and EspC, which possess mucinolytic and host-adherent properties. As a result, sialic acid enhanced the ability of C. rodentium to degrade intestinal mucus (through Pic), as well as to adhere to intestinal epithelial cells (through EspC). We thus demonstrate that sialic acid, a monosaccharide constituent of the intestinal mucus layer, functions as an important nutrient and a key signal for an A/E bacterial pathogen to escape the colonic lumen and directly infect its host's intestinal mucosa.

Effects of in vitro digestion and fecal fermentation on physico-chemical properties and metabolic behavior of polysaccharides from Clitocybe squamulosa.

The aim of this study was to establish a human digestion model in vitro to explore the degradation characteristics of a novel high-purity polysaccharide from Clitocybe squamulosa (CSFP2). The results showed that the content of reducing sugars (CR ) of CSFP2 increased from 0.13 to 0.23mg/mL, the molecular weight (Mw) of CSFP2 decreased significantly during the saliva-gastrointestinal digestion. The constituent monosaccharides of CSFP2, including galactose, glucose, and mannose, were stable during in vitro digestion, but their molar ratios were changed from 0.023: 0.737: 0.234 to 0.496: 0.478: 0.027. The surface of CSFP2 changes from a rough flaky structure to a scattered flocculent or rod-shaped structure after the gastrointestinal digestion. However, the apparent viscosity of CSFP2 was overall stable during in vitro digestion. Moreover, CSFP2 still maintains its strong antioxidant capacity after saliva-gastrointestinal digestion. The results showed that CSFP2 can be partially decomposed during digestion. Meanwhile, some physico-chemical properties of the fermentation broth containing CSFP2 changed significantly after gut microbiota fermentation. For example, the pH value (from 8.46 to 4.72) decreased significantly (p<0.05) after 48h of fermentation. the OD 600 value increased first and then decreased (from 2.00 to 2.68 to 1.32) during 48-h fermentation. In addition, CSFP2 could also increase the amounts of short-chain fatty acids (SCFAs) (from 5.5 to 37.15mmol/L) during fermentation (in particular, acetic acid, propionic acid, and butyric acid). Furthermore, the relative abundances of Bacteriodes, Bifidobacterium, Catenibacterium, Lachnospiraceae_NK4A136_group, Megasphaera, Prevotella, Megamonas, and Lactobacillus at genus level were markedly increased with the intervention of CSFP2. These results provided a theoretical basis for the further development of functional foods related to CSFP2.

Extraction of Lycium barbarum polysaccharides using temperature-switchable deep eutectic solvents: A sustainable methodology for recycling and reuse of the extractant

Due to the nonvolatility of deep eutectic solvents (DESs), the recycling and reuse of them is encountering a lot of problems in the extraction and separation field. In this study, temperature-switchable DESs (TS-DESs) were prepared and their temperature-responsive characteristics and phase diagram were studied. TS-DESs were further used as the recyclable extractants for extracting Lycium barbarum polysaccharides (LBP) below their lower critical solution temperature (LCST), and then they can be recovered from the extract above their LCST. The main factors influencing the extraction process were investigated in the single-factor experiments. A maximal extraction yield of 465 mg/g was obtained. The TS-DES was recovered and reused in recycling experiments. The recovery of TS-DES was 80.2 % after the fifth cyclic test. The obtained LBP was studied by determining its molecular weight, assessing its radical scavenging activity, and analyzing its monosaccharide constituents. This study presents a novel method for polysaccharide extraction, which can also provide guidance for bioactive compounds extraction using recyclable extractants.

An insight into microbial sources, classification and industrial applications of xylanases: A rapid review.

Endo 1,4-β-d- xylanases (EC3.2.1.8) are one of the key lignocellulose hydrolyzing enzymes. Xylan, which is present in copious amounts on earth, forms the primary substrate of endo-xylanases which can unchain the constituent monosaccharides linked via β-1,4 glycosidic bonds from the xylan backbone. Researchers have shown keen interest in the xylanases belonging to glycoside hydrolase families 10 and 11 whereas those placed in other GH families are yet to be investigated. Various microbes such as bacteria and fungi harbor these enzymes for the metabolism of their lignocellulose fibers. These microbes can be used as miniature biofactories of xylanase enzymes for a plethora of environmentally benign applications in pulp and paper industry, biofuel production and for improving the quality of food in bread baking and fruit juice industry. This review highlights the potential of microbes in production of xylanase for industrial biotechnology. This article is protected by copyright. All rights reserved.

Effects of thermal treatments on the extraction and in vitro fermentation patterns of pectins from pomelo (Citrus grandis)

Pomelo peel, a by-product of fruit processing, is an excellent source of pectin. We aimed to study the effects of thermal treatments on the extraction and in vitro fermentation patterns of pectins from pomelo peel. We used subcritical water extraction and hot water extraction, with or without chelator (citric acid or EDTA-2Na) assistance to obtain the pectins. The pectin fractions were characterized by their constituent monosaccharide composition and molecular weight (Mw) distribution. The degree of methyl esterification of pomelo pectins was determined using FT-IR spectroscopy. We also compared the fermentation patterns of the pectin using an in vitro simulated human gut fermentation model, monitored Mw changes during fermentation by high performance size exclusion chromatography (HPSEC), and analyzed short-chain fatty acid (SCFA) using gas chromatograph. Our results showed that both chelator assistance and subcritical water treatment increased the pectin yield. Chelator-assisted extraction increased the pectin Mw and decreased the degree of methyl esterification (DM) whereas, subcritical water treatment had the opposite effect. Pectin with low rhamnogalacturonan-I (RG-I) and high homogalacturonan (HG) domain can be obtained from the used pomelo peels by citric acid-assisted extraction. Although gut microbiota intensively utilized uronic acid (UA) of pomelo during early fermentation stages, constituent neutral monosaccharides were consumed even faster than UA. Pomelo pectins enhanced the relative abundance of Bacteroides and Prevotella 9, and stimulated the production of SCFA, particularly acetic acid. Generally, pomelo pectin could be considered a new source for modulating gut microbiota towards a healthy pattern in functional foods.