High Degree Of Polymerization Research Articles

A Long-Chain Dextran Produced by Weissella cibaria Boosts the Diversity of Health-Related Gut Microbes Ex Vivo.

Long-chain dextrans are α-glucans that can be produced by lactic acid bacteria. NextDextTM, a specific long-chain dextran with a high degree of polymerisation, produced using Weissella cibaria, was recently shown to exert prebiotic potential in vitro. In this study, the ex vivo SIFR® technology, recently validated to provide predictive insights into gut microbiome modulation down to the species level, was used to investigate the effects of this long-chain dextran on the gut microbiota of six human adults that altogether covered different enterotypes. A novel community modulation score (CMS) was introduced based on the strength of quantitative 16S rRNA gene sequencing and the highly controlled ex vivo conditions. This CMS overcomes the limitations of traditional α-diversity indices and its application in the current study revealed that dextran is a potent booster of microbial diversity compared to the reference prebiotic inulin (IN). Long-chain dextran not only exerted bifidogenic effects but also consistently promoted Bacteroides spp., Parabacteroides distasonis and butyrate-producing species like Faecalibacterium prausnitzii and Anaerobutyricum hallii. Further, long-chain dextran treatment resulted in lower gas production compared to IN, suggesting that long-chain dextran could be better tolerated. The additional increase in Bacteroides for dextran compared to IN is likely related to the higher propionate:acetate ratio, attributing potential to long-chain dextran for improving metabolic health and weight management. Moreover, the stimulation of butyrate by dextran suggests its potential for improving gut barrier function and inflammation. Overall, this study provides a novel tool for assessing gut microbial diversity ex vivo and positions long-chain dextran as a substrate that has unique microbial diversity enhancing properties.

A rumen-derived bifunctional glucanase/mannanase uncanonically releases oligosaccharides with a high degree of polymerization preferentially from branched substrates

Glycoside hydrolases (GHs) are known to depolymerize polysaccharides into oligo-/mono-saccharides, they are extensively used as additives for both animals feed and our food. Here we reported the characterization of IDSGH5-14(CD), a weakly-acidic mesophilic bifunctional mannanase/glucanase of GH5, originally isolated from sheep rumen microbes. Biochemical characterization studies revealed that IDSGH5-14(CD) exhibited preferential hydrolysis of mannan-like and glucan-like substrates. Interestingly, the enzyme exhibited significantly robust catalytic activity towards branched-substrates compared to linear polysaccharides (P < 0.05). Substrate hydrolysis pattern indicated that IDSGH5-14(CD) predominantly liberated oligosaccharides with a degree of polymerization (DP) of 3–7 as the end products, dramatically distinct from canonical endo-acting enzymes. Comparative modeling revealed that IDSGH5-14(CD) was mainly comprised of a (β/α)8-barrel-like structure with a spacious catalytic cleft on surface, facilitating the enzyme to target high-DP or branched oligosaccharides. Molecular dynamics (MD) simulations further suggested that the branched-ligand, 64-α-D-galactosyl-mannohexose, was steadily accommodated within the catalytic pocket via a two-sided clamp formed by the aromatic residues. This study first reports a bifunctional GH5 enzyme that predominantly generates high-DP oligosaccharides, preferentially from branched-substrates. This provides novel insights into the catalytic mechanism and molecular underpinnings of polysaccharide depolymerization, with potential implications for feed additive development and high-DP oligosaccharides preparation.

Enhanced bacterial cellulose production in Gluconacetobacter xylinus by overexpression of two genes (bscC and bcsD) and a modified static culture

Bacterial cellulose (BC), a nanostructured material, is renowned for its excellent properties. However, its production by bacteria is costly due to low medium utilization and conversion rates. To enhance the yield of BC, this study aimed to increase BC yield through genetic modification, specifically by overexpressing bcsC and bcsD in Gluconacetobacter xylinus, and by developing a modified culture method to reduce medium viscosity by adding water during fermentation. As a result, BC yields of 5.4, 6.2, and 6.8 g/L were achieved from strains overexpressing genes bcsC, bcsD, and bcsCD, significantly surpassing the yield of 2.2 g/L from wild-type (WT) strains. In the modified culture, the BC yields of all four strains increased by >1 g/L with the addition of 20 mL of water during fermentation. Upon comparing the properties of BC, minimal differences were observed between the WT and pbcsC strains, as well as between the static and modified cultures. In contrast, BC produced by strains overexpressing bcsD had a denser microstructural network and exhibited demonstrated higher tensile strength and elongation-to-break. Compared to WT, BC from bcsD overexpressed strains also displayed enhanced crystallinity, higher degree of polymerization and improved thermal stability.

Efficient fractionation of pure hemicellulose with high DP from bleached hardwood pulp using LiBr·3H2O and co-production of dissolving pulp

Hemicellulose was efficiently fractionated from BHKP using LBTH with the coproduction of high-quality dissolving pulp. The obtained hemicellulose was pure glucuronoarabinoxylan with high DP (&gt;200) and unique crystalline and nano structure.

Isolation of cellulose-producing bacteria (Komagataeibacter Saccharivorans) from rotten sapodilla fruit

Bacterial nanocellulose (BNC) is a nanocellulose produced by bacteria with high purity, crystallinity level, water binding ability, a high degree of polymerization, and excellent mechanical characteristics. The selection of BNC-producing bacteria is one of the critical stages in the production of BNC. This study collected samples from fruit sources and was selected to determine isolates that could produce BNC. Based on the 16s rRNA strain analysis, sapodilla isolate has an identity percentage above 98%, so it can be concluded that it has similarities with the bacteria Komagataeibacter saccharivorans. From eleven sources of fruit, two isolates that have the potential to produce cellulose, namely isolate sapodilla, were obtained. The confirmed sapodilla isolate is an acetic acid bacteria, Komagataeibacter saccharivorans. The yield of BNC-made isolate sapodilla Komagataeibacter saccharivorans (0.432 g/L). Confirmed sapodilla isolates that produce cellulose were mainly determined as cellulose I (adsorption at around 3345, 1430, 1160, and 900 cm−1). Few celluloses II (adsorption at about 1335, 1315, and 1280 cm−1 and a blue-shift of the number of waves from 1430 to around 1425 cm−1) and has a crystallinity index of 52.387 % on HS (Hestrin Scrahm) media with diameter nanofibril about 86.46 nm.

STRUCTURAL FEATURES AND PROPERTIES OF MULTICOMPONENT SODIUM-CESIUM/RUBIDIUM ALUMINOBOROSILICATE MODEL MATRIX GLASSES OF BASIS COMPOSITION

Synthesis and study of the structure and various properties of Na-Cs and Na-Rb aluminoborosilicate model glasses with addition of the alkaline-earth cations have been carried out. Vibrational spectroscopy techniques have been used to establish the high degree of polymerization and noticeable structural similarity of all synthesized glasses at fixed ratio of modifying and network-forming cations. It has been shown that increasing fraction of large cations in the total content of modifying cations leads to changes in distribution of modifying cations between the silicate and borate structural units. The observed homogeneity with the similarity of anionic structure, at different content and various combinations of alkali and alkaline-earth cations, points at promising application of these glasses as a basis for synthesis of matrix materials for high-level radioactive waste disposal.

Assessment of Burnout Among Emergency Medicine Residents in Saudi Arabia: A Cross-Sectional Survey

Background: Burnout syndrome is a frequent challenge faced in the emergency department. There exists a dearth of clinical evidence regarding the risk and occurrence of burnout, among emergency residents in Saudi Arabia. Therefore, this study was conducted to assess the parameters of burnout in this cohort. Methods: This prospective, cross-sectional study was conducted via an online survey using Maslach Burnout Inventory for Healthcare Professionals (MBI-HSS) questionnaire. All emergency medicine residents registered under the country&amp;apos;s residency program were invited to participate. The relative importance index (RII) analysis was used to describe the frequency of the MBI-HSS indicators. The t-test of independent groups and the one-way analysis of variance were used to assess the impact of demographic and professional factors. Results: A total of 73 residents completed the questionnaire. Low PA was reported by 53.4% while medium to high DP and EE were reported by 84.9% and 67.1% residents respectively. Female residents had significantly higher EE versus males. Age, marital status and number of children had no correlation with burnout. Emergency residents serving at hospitals of the Ministry of Health reported significantly higher levels of burnout, versus other institutions. The final year of the residency program showed significantly lower levels of burnout than the earlier years. Conclusion: This is the first study from Saudi Arabia, assessing the parameters of burnout, specifically among emergency medicine residents. The study has shown alarmingly high levels of DP, EE and low PA and warrants urgent remedial measures to curb burnout among emergency residents.

Assessment of Burnout Among Emergency Medicine Residents in Saudi Arabia: A Cross-Sectional Survey

Background: Burnout syndrome is a frequent challenge faced in the emergency department. There exists a dearth of clinical evidence regarding the risk and occurrence of burnout, among emergency residents in Saudi Arabia. Therefore, this study was conducted to assess the parameters of burnout in this cohort. Methods: This prospective, cross-sectional study was conducted via an online survey using Maslach Burnout Inventory for Healthcare Professionals (MBI-HSS) questionnaire. All emergency medicine residents registered under the country&amp;apos;s residency program were invited to participate. The relative importance index (RII) analysis was used to describe the frequency of the MBI-HSS indicators. The t-test of independent groups and the one-way analysis of variance were used to assess the impact of demographic and professional factors. Results: A total of 73 residents completed the questionnaire. Low PA was reported by 53.4% while medium to high DP and EE were reported by 84.9% and 67.1% residents respectively. Female residents had significantly higher EE versus males. Age, marital status and number of children had no correlation with burnout. Emergency residents serving at hospitals of the Ministry of Health reported significantly higher levels of burnout, versus other institutions. The final year of the residency program showed significantly lower levels of burnout than the earlier years. Conclusion: This is the first study from Saudi Arabia, assessing the parameters of burnout, specifically among emergency medicine residents. The study has shown alarmingly high levels of DP, EE and low PA and warrants urgent remedial measures to curb burnout among emergency residents.

Геохимия органического вещества природных битумов в разрезе р. Кожвы (Тимано-Печорская провинция)

The objects of study are diaplectic and melt silicate glasses from vein melt impactites of the Kara astrobleme. Microscopic and spectroscopic characteristics of two glasses with fundamentally different formation mechanisms were obtained, which allowed comparing their structural features. We found that silicate diaplectic and melt impact glasses from high-pressure/high-temperature vein bodies of the Kara astrobleme were characterized by similar structural features — a high degree of polymerization, the presence of four-membered and polymembered SiO4 rings, which was characteristic of all glasses were the SiO2 composition. Diaplectic glasses are characterized by the constant presence of three-membered SiO4 rings; melt glasses were characterized by the absence of this feature, which was determined by more extreme conditions for the glass from melt.

Сравнительная характеристика диаплектовых и расплавных силикатных стёкол Карской астроблемы

The objects of study are diaplectic and melt silicate glasses from vein melt impactites of the Kara astrobleme. Microscopic and spectroscopic characteristics of two glasses with fundamentally different formation mechanisms were obtained, which allowed comparing their structural features. We found that silicate diaplectic and melt impact glasses from high-pressure/high-temperature vein bodies of the Kara astrobleme were characterized by similar structural features — a high degree of polymerization, the presence of four-membered and polymembered SiO4 rings, which was characteristic of all glasses were the SiO2 composition. Diaplectic glasses are characterized by the constant presence of three-membered SiO4 rings; melt glasses were characterized by the absence of this feature, which was determined by more extreme conditions for the glass from melt.

Electro-separation of chitooligosaccharides with specific degrees of polymerization using electrodialysis ultrafiltration

Biological activities of chitooligosaccharides (COSs) are related to their purity and intrinsic structure. However, a wide range of size distribution and degree of polymerization (DP) of COS make it challenging for their meticulous biological research and applications. This research investigated the protonation behavior and the separation mechanism of individual COSs molecules at semi-pilot scale using an electrodialysis-ultrafiltration membrane. Results indicated that COSs were protonated to varying degrees in the pH ranges of 3.28 to 7.95 with a pKa value stand nearly at 6.44. A semi pilot scale investigation of operational parameters successfully separated a fraction with degree of polymerization (DP) ≤ 4 (>93% of total COS migrated) at flow velocity 6.79 cm/s and electric potential of 9 V/cm with highest DP 3 (>36% of the fraction) in 60 min. Additionally, few other fractions (DP ≤ 3 and DP ≤ 5) were efficiently separated from the industrial sample at different processing times. Moreover, the selective conditions also prevent the fouling of ultrafiltration membrane. Conclusively, the inadequate or too high applied electric potential and solution flow velocities have significant influence on migration of target molecules.

Exploring separation patterns and mechanisms of proanthocyanidins in grape seeds and pomace with diverse molecular weights, compositions, and structures

The function of proanthocyanidins (PAs) relies on their structure and requires high-purity PAs. Though Sephadex LH-20 gel permeation chromatography (GPC) is expected to separate PAs based on structure, its usage rules and mechanisms remain unclear. This study delves into the PAs separation patterns on Sephadex LH-20, first confirming the purification mechanisms of PAs with various mean degrees of polymerization (DP) using the adsorption kinetic model. The study found that an increase in the molecular weight or mean DP of PAs results in decreased polarity, reduced hydrogen bonding actions, and intensified hydrophobic effect, causing delayed extraction of PAs on Sephadex LH-20, with galloylated PA as an exception, which was extracted first despite its high DP. Additionally, the principles for separating specific composition, such as monomers, dimers, etc., were evaluated. The study sheds light on enhancing the purification efficiency of PAs, thus advancing the precise separation technology of diverse proanthocyanidins.

Effects of thermal program on physicochemical properties and photocatalytic activity of g-C3N4 prepared by dicyandiamide pyrolysis

Graphitic carbon nitride (g-C3N4) can be prepared by the pyrolysis of dicyandiamide, and its properties and performance are greatly affected by the pyrolysis parameters. In this study, the effects of heating rate and pyrolysis time on the physicochemical properties and photocatalytic activity of the obtained g-C3N4 are systematically investigated, and the results are used to guide the controllable production of g-C3N4 in industry. The results show the heating rate has a significant impact on the pore structure, crystallinity, number of amino functional groups, and the stability of structure. The pyrolysis time mainly affects the texture and layer structure of g-C3N4 products. In addition, the polymerization pathways during the dicyandiamide pyrolysis are analyzed through in-situ TG-MS combined with XRD analysis, elucidating the process of dicyandiamide forming complete g-C3N4 products with high polymerization degree by polyaddition, polycondensation and rearrangement. This study provides useful reference strategies for the design of large-scale controllable industrial production of g-C3N4 through pyrolysis of dicyandiamide.

Stepwise transform sugarcane bagasse into xylooligosaccharides and fermentable glucose by hydrothermal-xylanase-acid-cellulase hydrolysis

Hydrothermal pretreatment can effectively degrade the hemicellulosic xylan into xylooligosaccharides; however, the low degree of polymerization (DP) oligomers are dissatisfied. Considering the significance of low DP, one approach to enhance the levels of low DP xylooligosaccharides is to utilize endo-xylanase for degrading the high DP xylooligosaccharides. Therefore, a combination method of hydrothermal and post endo-xylanase hydrolysis was employed in this study to enhance XOS yields. As a result, a maximum XOS of 54.5% with low DP was achieved from sugarcane bagasse, and the ratio of (DP2+DP3)/XOS was remarkably improved. Following the preparation of XOS, an additional acidic hydrolysis using dilute sulfuric acid was performed to enhance the saccharification efficiency of cellulose, resulting in a significant increase in yield of enzymatic hydrolysis to over 90%. Overall, biomass-derived sugar products (XOS and glucose) can be co-produced for adding the value of the sugarcane bagasse by sequential hydrothermal-endo-xylanase-acid-cellulase hydrolysis.

The first established microsatellite markers to distinguish Candida orthopsilosis isolates and detection of a nosocomial outbreak in China.

The infection proportion of Candida orthopsilosis, a member of the C. parapsilosis complex, has increased globally in recent years, and nosocomial outbreaks have been reported in several countries. This study aimed to establish microsatellite loci-based typing method that was able to effectively distinguish among C. orthopsilosis isolates. Three reference C. orthopsilosis genome sequences were analyzed to identify repeat loci. DNA sequences containing over eight bi- or more nucleotide repeats were selected. A total of 51 loci were initially identified, and locus-specific primers were designed and tested with 20 epidemiologically unrelated isolates. Four loci with excellent reproducibility, specificity, and resolution for molecular typing purposes were identified, and the combined discriminatory power (DP, based on 20 epidemiologically unrelated isolates) of these four loci was 1.0. Reproducibility was demonstrated by consistently testing three strains each in triplicate, and stability, demonstrated by testing 10 successive passages. Then, we collected 48 C. orthopsilosis non-duplicate clinical isolates from the China Hospital Invasive Fungal Surveillance Net study to compare the DP of the microsatellite-based typing with internal transcribed spacer (ITS) and amplified fragment length polymorphism (AFLP) typing analyses, using ATCC 96139 as a reference strain. These 49 isolates were subdivided into 12 microsatellite types (COMT1-12), six AFLP types, and three ITS types, while all the isolates with the same COMT belonged to consistent AFLP and ITS type, demonstrating the high DP of our microsatellite-type method. According to our results, COMT12 was found to be the predominant type in China, and COMT5 was the second largest and responsible for causing a nosocomial outbreak. This microsatellite-type method is a valuable tool for the differentiation of C. orthopsilosis and could be vital for epidemiological studies to determine strain relatedness and monitor transmission.

Enhanced production of bacterial cellulose employing banana peel as a cost-effective nutrient resource.

Bacterial cellulose (BC) is an exopolysaccharide produced by bacteria that has unusual structural features and is more refined than plant cellulose. BC has recently gained more attention in a variety of fields including biological and biomedical applications due to its excellent physiochemical properties including easy biodegradability, better water holding capacity, high tensile strength, high thermal stability, and high degree of polymerization. However, application of BC at industrial scale is still limited due to its high production cost and lesser yielding strains. The present study is an attempt to isolate and characterize a novel BC-producing bacterial strain. The bacterial strain S5 has resulted into maximum cellulose production of 4.76 ± 0.49 gL-1 (30°C, pH 7.0). The strain has been further identified as Stenotrophomonas sp. Derivation of nutritional and cultural conditions has resulted into 2.34-fold enhanced BC production (banana peel powder, peptone, tartaric acid, pH 7, 30°C). FTIR spectrum of BC revealed characteristic absorption bands which could be attributed to the O-H band, C-H stretching, C-O-C stretching band, O-H bending, and >CH2 bending, indicative of the β-1,4 glycosidic linkages of cellulose. Thermogravimetric analysis has also revealed stability of polysaccharide backbones and characteristic weight loss points. Employment of banana peel powder has appeared as a proficient low-cost source for large-scale economic production of BC for industrial applications.

Nanocellulose from Cocoa Shell in Pickering Emulsions of Cocoa Butter in Water: Effect of Isolation and Concentration on Its Stability and Rheological Properties.

There is a growing interest in developing new strategies to completely or partially replace cocoa butter in food and cosmetic products due to its cost and health effects. One of these alternatives is to develop stable emulsions of cocoa butter in water. However, incorporating cocoa butter is challenging as it solidifies and forms crystals, destabilizing the emulsion through arrested coalescence. Prevention against this destabilization mechanism is significantly lower than against coalescence. In this research, the rheological properties of nanocellulose from cocoa shell, a by-product of the chocolate industry, were controlled through isolation treatments to produce nanocellulose with a higher degree of polymerization (DP) and a stronger three-dimensional network. This nanocellulose was used at concentrations of 0.7 and 1.0 wt %, to develop cocoa butter in-water Pickering emulsion using a high shear mixing technique. The emulsions remained stable for more than 15 days. Nanocellulose was characterized using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), hot water and organic extractives, atomic force microscopy (AFM), degree of polymerization (DP), and rheological analysis. Subsequently, the emulsions were characterized on days 1 and 15 after their preparation through photographs to assess their physical stability. Fluorescent and electronic microscopy, as well as rheological analysis, were used to understand the physical properties of emulsions.

Biosynthesis and characterization of antibacterial bacterial cellulose composite membrane composed of montmorillonite and exopolysaccharides

Bacterial cellulose (BC), as a natural renewable polymer material, has the advantages of porous nanonetwork structure, high degree of polymerization, high purity, high crystallinity, excellent mechanical properties and biocompatibility. However, BC lacks antibacterial properties, which leads to the limitation of BC material in food packaging and medical materials. In this study, a new antibacterial material using the combination of montmorillonite (MMT), BC and exopolysaccharides (EPS) produced by Weissella confusa H2 was synthesized. Fourier infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis showed that BC-EPS, BC-MMT and BC-EPS-MMT composite membranes conformed to the typical type I cellulose structure. Compared to BC membrane, scanning electron microscopy (SEM) showed that the porosity of BC-EPS, BC-MMT and BC-EPS-MMT composite membranes was low and compact. The physical properties of BC-EPS, BC-MTT and BC-EPS-MTT composite membranes showed lower water vapor transmittance. The BC-MTT and BC-EPS-MTT composite membranes exhibit a lower swelling ratio in 120 min. The thermal properties show that BC-EPS, BC-MTT and BC-EPS-MTT composite membranes have higher thermal stability (352 °C, 310 °C, 314 °C). Additionally, both BC-MMT and BC-EPS-MMT demonstrated strong inhibitory effects against various bacterial strains, including Staphylococcus aureus, Escherichia coli, Salmonella paratyphi A, and Bacillus subtilis. The exceptional properties exhibited by composite membranes establishes them as a highly promising option in the field of food packaging and medical material applications.

The role of CO2 in MSWI fly ash-slag-based binder at the early stage

The current study proposes CO2 can increase the dissociation degree of blast furnace slag (BFS), thus demonstrate the untapped potential to maximize BFS reactivity at the early stage (3d). This low-carbon cementitious materials employs CO2 activation to increase the dissociation of [SiO4]4− and [AlO4]5− species of BFS, with a more significant effect on [AlO4]5−. This has been demonstrated by the 27Si and 29Al NMR spectral fitting statistics, a 20.12 % and 23.86 % increase in the degree of dissociation for [SiO4]4− and [AlO4]5−, respectively. The introduction of CO2 facilitated the dissolution of Ca2+ on the surface of BFS. Additionally, it accelerated the ionization of H2O, leading to the hydroxylation of [AlO4]5−, as well as, the increase in pH of the leachate. Furthermore, low carbon cementitious materials with low clinker (LT3-MSWI fly ash:BFS:PC:FGDG = 20:42:28:10) exhibit excellent compressive strength (40.57 MPa at 3d) and stabilization/solidification (S/S) properties due to a significant number of functional products. C-S-H with a lower C/S ratio, C-A-S-H, hydrocalumite, and AFt phase are the main functional products of LT3, with relative contents of 17.30 wt%, 13.60 wt%, 8.40 wt%, and 6.3 wt%, as determined by the TIMA quantitative analysis system. The role of CO2 induces the formation of longer-chain C-S-H species (MCL = 4.21) with a higher degree of polymerization (Pol = 0.25) for LT3, as contrasted with LH3, where these values stand at MCL = 3.58 and Pol = 0.14, respectively.

Regenerated bacterial cellulose fibres

The global shortage of cotton for textile production, forces the exploitation of forests´ lignocellulosic biomass to produce man-made cellulosic fibres (MMCF). This has a considerable environmental impact, pressing the textile industry to search for new sustainable materials and to the development of sustainable recycling processes. Bacterial cellulose (BC), an exopolysaccharide produced by fermentation, could represent such an alternative. In particular, we tested the possibility of improving the mechanical properties of cellulose filaments with a low degree of polymerization (DP) by combining them with high DP from BC, so far exploited to little extent in the textile field.In this work, BC with different degrees of polymerization (DPcuaxam) (BCneat: 927; BCdep:634 and BCblend: 814) were dissolved in N-methylmorpholine-N-oxide (NMMO) and their spinnability was studied. The rheological behaviour of the dopes was assessed and all were found to be spinnable, at suitable concentrations (BCneat:9.0 %; BCdep:12.2 %; BCblend:10.5 %). A continuous spinning was obtained and the resulting filaments offered similar mechanical performance to those of Lyocell. Further, the blending of BC pulps with different DPs (BCblend, obtained by combining BCneat and BCdep) allowed the production of fibres with higher stiffness (breaking tenacity 56.4 CN.tex−1) and lower elongation (8.29 %), as compared to samples with more homogeneous size distribution (neat BC and depolymerized BC).