Glucose Oligomers Research Articles

Brewers' spent grain liquor as a feedstock for lactate production with Lactobacillusdelbrueckii subsp. lactis.

Brewers’ spent grain (BSG) is a low‐cost by‐product of the brewing process. BSG liquor names the liquid components of BSG, mainly glucose, maltose, and long‐chain α‐1,4‐glycosidic bond glucose oligomers. These substances should be separated in existing BSG biorefineries, as they might lead to an increased formation of microbe‐inhibiting compounds in well‐established hydrothermal/enzymatic saccharification processes. In most cases, this liquid fraction is discarded. The present study presents for the first time an optimized process with BSG liquor for the purpose of producing bulk chemicals (e.g., lactate) in relevant concentrations. The process comprises the application of yeast extract, produced from own brewing processes, as the sole supplemented complex constituent in a simultaneous fermentation and saccharification process. Kinetic parameters for the final optimized process conditions with the organism Lactobacillus delbrueckii subsp. lactis were: maximum specific growth rate µmax = 0.47 h−1, maximum lactate concentration cLac, max = 79.06 g L−1, process yield YPS = 0.89 gLac gSugar −1, lactate production rate qP = 4.18 gLac gCDW −1 h−1, and productivity P 15 h = 4.93 gLac L−1 h−1. BSG liquor, linked with yeast extract from Brewers’ yeast, can be a promising substrate for further bioprocess engineering tasks and contribute to a holistic and sustainable usage of Brewers’ spent grain.

Amorphization and Semi-Dry Conversion of Crystalline Cellulose to Oligosaccharides by Impregnated Phosphoric Acid

Abstract Efficient conversion of crystalline cellulose to useful chemicals is a grand challenge in biorefining. In this work, we report that amorphization and semi-dry conversion of crystalline cellulose to oligosaccharides is achieved by impregnated H3PO4. Specifically, the impregnation of crystalline cellulose with H3PO4 under 5 MPa of He and subsequent drying at room temperature produces amorphous cellulose. The impregnated H3PO4 likely permeates bulk phase cellulose by dissociating the hydrogen bonding network of cellulose during the treatment. The resulting swollen solid is depolymerized to oligosaccharides in 40% yield with 72% selectivity by heat-treatment at 100 °C with no solvent. The analysis of obtained oligosaccharides using nuclear magnetic resonance and mass spectroscopy reveals that the products are oligomers of glucose linked by various kinds of glycosidic bonds that may be useful as prebiotics.

Effect of the elapsed time between sampling and formalin fixation on the N-glycosylation profile of mouse tissue specimens.

Formalin-fixed, paraffin-embedded (FFPE) samples are generally used for histology-study, however, they also possess important molecular diagnostics information. While it has been reported that the N-glycan moieties of glycoproteins is not affected by the FFPE process, no information is available about the effect of the elapsed time between sampling and fixation on the resulting N-glycosylation profile. In this study, lung, brain, heart, spleen, liver, kidney, and intestine mouse tissue specimens were used for N-glycan profiling analysis and the elapsed sampling time effect was investigated with the lung tissue. N-glycan extraction from the tissue samples was performed by glycoprotein retrieval from the FFPE specimens using radioimmunoprecipitation assay (RIPA) buffer followed PNGase F digestion. The released oligosaccharides were fluorophore labeled and analyzed by capillary electrophoresis-laser induced fluorescent detection (CE-LIF). N-glycosylation profiles of freshly collected lung-tissue samples (zero time point), as well as 1 and 2 h after sampling were compared by carbohydrate profiling and exoglycosidase treatment based deep glycomic analysis. It was found that up to two hours of room temperature storage of tissue specimens apparently did not cause changes in the N-glycosylation profiles of complex carbohydrates, but resulted in considerable decrease in the amount of linear glucose oligomers and high mannose type glycans present in the samples.

Integral exploitation from olive cake for energy production in a biorefinery scheme

This research aims to optimize the hydrothermal pretreatment based on previous studies, with the objective of extracting and determining value-added products from olive cake, and improve the energy solid properties. For this purpose, a hydrothermal pretreatment following of an autohydrolysis of the resulting solid were carried out in a biorefinery scheme.To the best of our knowledge this process has not been previously tested with olive cake by other authors. The conditions of the hydrothermal pretreatment were 30°C and 1h to prepare a suitable solid with mild conditions because polyphenols, water soluble extracts and tars precursors were eliminated. Sucrose was the value-added product with the best extraction 2.48% at this conditions. Therefore, resulting solids were subjected to an autohydrolysis to improve the value-added products extractions. The autohydrolysis was based on a design of experiments with temperatures of 120, 140, 160 and 180°C and time of 30, 60 and 90min to study the influence between the independent variables and the dependent variables (yield % and calorific value from each resulting solid and saccharides extractions from liquid extracted). The saccharides extracted were glucose, xylose, fructose, sucrose and glucose and xylose oligomers. Glucose and xylose oligomers contents were highest with 4g and 19.24g per 100g of solid respectively. The solid energy properties were improved because a solid with a calorific value of 5970kcal/kg was obtained. All experimental results were fitted to neural-fuzzy and polynomial model.

Enzymatic hydrolysis and fermentation of corn stover liquor from magnesium oxide pretreatment without detoxification

Corn stover liquor from MgO pretreatment was enzymatically hydrolyzed and fermented without detoxification. It was inferred from the results that glucose and xylose oligomers in corn stover liquor were fully hydrolyzed into glucose and xylose within 8 and 24 h, respectively. Fermentation of hydrolyzed corn stover liquor with E. coli KO11 was completed within 72 h with an ethanol yield and concentration of 96.5% and 7.8 g/L, respectively. Water soluble magnesium acetate formed during MgO pretreatment didn’t reduce enzyme and KO11 activities and functioned as a buffer reagent during hydrolysis and fermentation, thus eliminating the need for additional buffer preparation. Extended fermentation time was caused by aromatic compounds derived from lignin and was eliminated by improving the tolerance of KO11 to corn stover liquor from MgO pretreatment. Direct hydrolysis and fermentation of corn stover liquor from MgO pretreatment eliminated detoxification, simplified bioconversion process, and reduced production cost.

Probiotics and prebiotics in intestinal health and disease: from biology to the clinic.

Probiotics and prebiotics are microbiota-management tools for improving host health. They target gastrointestinal effects via the gut, although direct application to other sites such as the oral cavity, vaginal tract and skin is being explored. Here, we describe gut-derived effects in humans. In the past decade, research on the gut microbiome has rapidly accumulated and has been accompanied by increased interest in probiotics and prebiotics as a means to modulate the gut microbiota. Given the importance of these approaches for public health, it is timely to reiterate factual and supporting information on their clinical application and use. In this Review, we discuss scientific evidence on probiotics and prebiotics, including mechanistic insights into health effects. Strains of Lactobacillus, Bifidobacterium and Saccharomyces have a long history of safe and effective use as probiotics, but Roseburia spp., Akkermansia spp., Propionibacterium spp. and Faecalibacterium spp. show promise for the future. For prebiotics, glucans and fructans are well proven, and evidence is building on the prebiotic effects of other substances (for example, oligomers of mannose, glucose, xylose, pectin, starches, human milk and polyphenols).

Smallest cyclodextrins synthesized

Cyclodextrins are cyclic oligomers of glucose. Their central cavities can hold small molecules, making them attractive for sensor and drug delivery applications. The most common cyclodextrins, CD6, CD7, and CD8, are made commercially via enzymatic processes. The smallest one previously chemically synthesized is CD5. Now Hidetoshi Yamada and coworkers at Kwansei Gakuin University report that they have chemically synthesized the smallest possible cyclodextrins, CD3 and CD4 (Science 2019, DOI: 10.1126/science.aaw3053). To achieve the synthesis, the researchers added a bridge between the O-3 and O-6 oxygen atoms of each glucose ring, which created a bicyclic structure. The bridge adjusts the conformation of the scaffold, shifting the glucose ring to a conformation that favors the α-1,4-glycosidic bond formation needed to make the desired strained cyclodextrins. Although the researchers were able to obtain CD3 and CD4, the synthesis worked better for the trimer than for the tetramer. However, they could make o...

FGB1 and WSC3 are in planta-induced β-glucan-binding fungal lectins with different functions.

In the root endophyte Serendipita indica, several lectin-like members of the expanded multigene family of WSC proteins are transcriptionally induced in planta and are potentially involved in β-glucan remodeling at the fungal cell wall. Using biochemical and cytological approaches we show that one of these lectins, SiWSC3 with three WSC domains, is an integral fungal cell wall component that binds to long-chain β1-3-glucan but has no affinity for shorter β1-3- or β1-6-linked glucose oligomers. Comparative analysis with the previously identified β-glucan-binding lectin SiFGB1 demonstrated that whereas SiWSC3 does not require β1-6-linked glucose for efficient binding to branched β1-3-glucan, SiFGB1 does. In contrast to SiFGB1, the multivalent SiWSC3 lectin can efficiently agglutinate fungal cells and is additionally induced during fungus-fungus confrontation, suggesting different functions for these two β-glucan-binding lectins. Our results highlight the importance of the β-glucan cell wall component in plant-fungus interactions and the potential of β-glucan-binding lectins as specific detection tools for fungi invivo.

Influence of Multiwalled Carbon Nanotubes as Additives in Biomass-Derived Carbons for Supercapacitor Applications.

Glucose-derived carbon/carbon nanotube (CNT) hybrid materials were prepared by hydrothermal carbonization of glucose in the presence of CNTs and subsequent carbonization, physical activation, or chemical activation. The proportion of CNTs added during the hydrothermal polymerization of glucose was varied to ascertain the optimum dose to maximize the performance of the carbon hybrids in supercapacitor applications. Both the thermal treatment applied and the addition of CNTs lead to changes in the textural and chemical properties of the activated carbons. It was observed that samples bearing CNTs exhibit higher number of nucleation centers for glucose oligomers to polymerize, and consequently, the behavior of the hydrothermal carbon toward activation differs according to the activating agent employed. Moreover, the initial chemical speciation dominated by acidic groups shifts to more basic functionalities (quinones and carbonyl groups) with the addition of CNTs. The effect of the different physicochemical properties of the prepared carbons on their electrochemical behavior was evaluated. The addition of 2 wt % of CNTs and subsequent chemical activation leads to electrode materials yielding 206 F g-1 and 78% of capacitance retention up to 0.8 V and 20 A g-1 and high rate cyclability (97% after 5000 cycles). The outstanding performance is ascribed to the high surface area, narrow mesopores, and phenol/carbonyl surface functionalities, which enhance molecular diffusion, the amount of stored energy, and electronic transportation, respectively.

Molecular motions, structure and hydration behaviour of glucose oligomers in aqueous solution.

The degree of polymerization and temperature dependencies of the molecular motions, configuration and hydration behaviour of glucose oligomers (Gn, n = 2 to 7, degree of polymerization) in aqueous solutions were investigated using extremely high-frequency dielectric spectrum measuring techniques up to 50 GHz. The obtained dielectric spectra for the aqueous Gn solutions were well decomposed into four Debye-type relaxation modes. The fastest relaxation mode j = 1 was assigned to the rotational process of free water molecules in the sample solution. The second fastest mode j = 2 was attributed to the exchange process of hydrated water molecules with free water molecules, and the third mode j = 3 was recognized as the rotational process of hydroxy groups attached to each repeating glucopyranoside (Glu) unit after their lifetimes of intramolecular hydrogen bonding. The slowest mode j = 4 at a relaxation time depending on n was assigned to the overall rotation of the Gn molecules possessing configurations similar to that of small fragments of single helical V-type crystalline structures at low temperatures. The presence of the dielectric mode j = 4 revealed that the Glu units possessed electric dipole moments carrying a component parallel to the Gn backbone aligned with the C1 → C4 direction. The number of hydrated water molecules per Glu unit (hydration number, nH) was determined for Gns in aqueous solutions in the temperature range from 10 °C to 70 °C via the relaxation strength of mode j = 1. The Gn oligomers were highly soluble in water within the temperature range examined, possessing nH values slightly dependent on n and demonstrated clear dehydration behaviour at approximately 30 °C with increasing temperature. These temperature dependencies of nH were substantially weaker than those of a model Glu unit compound, methyl α-d-glucopyranoside (G1). Then, the polymerization of glucose oligomers effectively depresses the dehydration behaviour of G1.

Efficient pretreatment of lignocellulosic biomass with high recovery of solid lignin and fermentable sugars using Fenton reaction in a mixed solvent

BackgroundPretreatment of biomass to maximize the recovery of fermentable sugars as well as to minimize the amount of enzyme inhibitors formed during the pretreatment is a challenge in biofuel process. We develop a modified Fenton pretreatment in a mixed solvent (water/DMSO) to combine the advantages of organosolv and Fenton pretreatments. The hemicellulose and cellulose in corncob were effectively degraded into xylose, glucose, and soluble glucose oligomers in a few hours. This saccharide solution, separated from the solid lignin simply by filtration, can be directly applied to the subsequent enzymatic hydrolysis and ethanol fermentation.ResultsAfter the pretreatment, 94% carbohydrates were recovered as soluble monosaccharide (xylose and glucose) and glucose oligomers in the filtrates, and 87% of solid lignin was recovered as the filter residue. The filtrates were directly applied to enzymatic hydrolysis, and 92% of raw corncob glucose was recovered. The hydrolysates containing the glucose and xylose from the enzymatic hydrolysis were directly applied to ethanol fermentation with ethanol yield equals 79% of theoretical yield. The pretreatment conditions (130 °C, 1.5 bar; 30 min to 4 h) are mild, and the pretreatment reagents (H2O2, FeCl3, and solvent) had low impact to environment. Using ferrimagnetic Fe3O4 resulted in similar pretreatment efficiency and Fe3O4 could be removed by filtration.ConclusionsA modified Fenton pretreatment of corncob in DMSO/water was developed. Up to 94% of the carbohydrate content of corncob was recovered as a saccharide solution simply by filtration. Such filtrate was directly applied to the subsequent enzymatic hydrolysis and where 92% of the corncob glucose content was obtained. The hydrolysate so obtained was directly applied to ethanol fermentation with good fermentability. The pretreatment method is simple, and the additives and solvents used have a low impact to the environment. This method provides the opportunity to substantially maximize the carbohydrate and solid lignin recovery of biomass with a comparatively green process, such that the efficiency of biorefinery as well as the bioethanol production process can be improved. The pretreatment is still relatively energy intensive and expensive, and further optimization of the process is required in large-scale operation.

Mixing effects on the kinetics of enzymatic hydrolysis of lignocellulosic Sunn hemp fibres for bioethanol production

This work uses Sunn hemp fibre – a new non-food lignocellulosic energy crop, containing cellulose (75.6%), hemicelluloses (10.05%) and lignin (10.32%) – for enzymatic hydrolysis in second generation bioethanol production. We quantify the effects of reactor mixing on the kinetics of cellulase-mediated depolymerization of Sunn hemp’s cellulose to glucose and other soluble oligomers. The kinetic parameters (Km, Vmax), the nature of product inhibition (non-competitive), and the glucose inhibition constant (Kx) are experimentally determined for cellulose loading of 10–50 mg/ml, at reactor mixing speeds of 0–150 rpm. These kinetic constants are fitted to algebraic expressions that quantify their exponential decrease with increasing mixing speed. After 72 h of hydrolysis performed on 10 mg/ml of cellulose at the optimum enzyme:substrate loading of 1:15, the yields of glucose and reducing sugars decrease from 59% and 65%, respectively, at 0 rpm (i.e., no mixing) to 53.4% and 58.8%, respectively, at 150 rpm. Thus, 90% of the reduction in soluble sugar yield engendered by mixing results from the disappearance of glucose monomers that non-competitively inhibit cellulase. Better macromixing facilitates convective transport of enzymes to solid celluloses while enhancing product inhibition by rapidly homogenizing the inhibitors (glucose, cellobiose) in the reactor. Though faster mixing transforms the hydrolysis system from being mass-transfer limited to being kinetic-limited, the soluble sugar yields decrease as stronger product inhibition overpowers the rate-enhancing effects of mass transfer in well-mixed reactors. We show that batch hydrolysis performed under mass-transfer limitations maximizes sugar yields by reducing product inhibition. However, mixing affects sugar yields from cellulose extracted from recalcitrant lignocelluloses less significantly than that from pure cellulose due to the former’s high crystallinity and degree of polymerization, and low porosity.

Solvent effect of gamma-valerolactone (GVL) on cellulose and biomass hydrolysis in hot-compressed GVL/water mixtures

This study employs a semi-continuous reactor system to investigate the solvent effect of gamma-valerolactone (GVL) on cellulose hydrolysis in hot-compressed GVL/water (HCGW) at 250 °C and 10 MPa. The primary liquid products from cellulose hydrolysis in HCGW at various GVL concentrations are collected and characterised. Both hydrolysis reaction rate and final glucose recovery are found to increase with GVL concentration, with a high glucose recovery of 91% achieved in the primary liquid products of cellulose hydrolysis in 10% GVL/water. Further analyses of the primary liquid products using high performance anion exchange chromatography with pulsed amperometric detection show the reductions in the isomers of glucose oligomers (with reducing end as fructose and mannose) and the increases in the glucose oligomers with low degrees of polymerisation, indicating that GVL addition enhances hydrolysis reactions but suppresses isomerization reactions in the solid phase. Similar effects are also found in the secondary reactions of the primary liquid products during cellulose hydrolysis at reduced flow rates. The experimental results from biomass hydrolysis clearly demonstrate that GVL/water co-solvent is an excellent reaction medium for biomass hydrolysis under acid-free conditions, achieving a near-complete sugar recovery (i.e., 93%) at a low GVL concentration of 5%.

Gastrointestinal Tolerance and Glycemic Response of Isomaltooligosaccharides in Healthy Adults.

Ingredients delivering functional and nutritional benefits are of interest to food manufacturers. Isomaltooligosaccharides (IMOs) which serve as alternate sweeteners fit into this category. IMOs are a mixture of α-(1 → 6) and α-(1 → 4)-linked glucose oligomers, synthesized by an enzymatic reaction from starch (corn, tapioca). The aim of this study was to evaluate the fermentability and glycemic response of IMO in a healthy population. Two randomized, double-blind, placebo-controlled, cross-over human studies were conducted. In the first study (n = 26), participants’ breath hydrogen over 24 h, gastrointestinal tolerance, and glycemic and insulinemic response to BIOLIGOTM IL5040 isomaltooligosaccharide were measured. In another study (n = 10), participants’ two-hour post-prandial glycemic response to BIOLIGOTM IL5040 isomaltooligosaccharide and BIOLIGOTM IL7010 isomaltooligosaccharide was measured compared to dextrose (control). The IMOs differed in the composition of mono and di-saccharide sugars. IMO syrup dose was matched for 50 g of total carbohydrates and was consumed by mixing in water (237 mL/8 oz.). Mean composite gastrointestinal score was not significantly different (p = 0.322) between the control (1.42) and IMO (1.38). Lack of difference in glycemic response (p = 0.662), with no impact on breath hydrogen (24 h; p = 0.319) and intestinal tolerance, demonstrates that IMO is digestible and can be used to replace sugars in product formulations.

Starch digestion in the upper gastrointestinal tract of humans

Starch provides a large proportion of the dietary energy consumed worldwide. The breakdown of dietary starch is driven by α‐amylase produced by the salivary glands and pancreatic acini and is completed by a range of brush‐border bound enzymes. This enzymatic digestion is aided by mechanical and secretory actions of the gastrointestinal tract. The absorption of the resultant glucose in the small intestine is primarily driven by two separate transport proteins − SGLT1 and GLUT2. The control of processes that govern starch digestion is complex and still not fully understood, although it appears that the human gut has the ability to sense both glucose and non‐sweet glucose oligomers. Recent work has also suggested that variations in the genes encoding for α‐amylase also appear to be associated with health outcomes. The authors consider the physiological factors that govern starch digestion and absorption, consider other dietary factors that may impact on this process and attempt to highlight the limitations in current knowledge to help focus future research needs in relation to starch digestion the upper gastrointestinal tract.

β-Glucanase Activity of the Oral Bacterium Tannerella forsythia Contributes to the Growth of a Partner Species, Fusobacterium nucleatum, in Cobiofilms.

Tannerella forsythia and Fusobacterium nucleatum are dental plaque bacteria implicated in the development of periodontitis. These two species have been shown to form synergistic biofilms and have been found to be closely associated in dental plaque biofilms. A number of genetic loci for TonB-dependent membrane receptors (TDR) for glycan acquisition, with many existing in association with genes coding for enzymes involved in the breakdown of complex glycans, have been identified in T. forsythia In this study, we focused on a locus, BFO_0186-BFO_0188, that codes for a predicted TDR-SusD transporter along with a putative β-glucan hydrolyzing enzyme (BFO_0186). This operon is located immediately downstream of a 2-gene operon that codes for a putative stress-responsive extracytoplasmic function (ECF) sigma factor and an anti-sigma factor. Here, we show that BFO_0186 expresses a β-glucanase that cleaves glucans with β-1,6 and β-1,3 linkages. Furthermore, the BFO_0186-BFO_0188 locus is upregulated, with an induction of β-glucanase activity, in cobiofilms of T. forsythia and F. nucleatum The β-glucanase activity in mixed biofilms in turn leads to an enhanced hydrolysis of β-glucans and release of glucose monomers and oligomers as nutrients for F. nucleatum In summary, our study highlights the role of T. forsythia β-glucanase expressed by the asaccharolytic oral bacterium T. forsythia in the development of T. forsythia-F. nucleatum mixed species biofilms, and suggest that dietary β-glucans might contribute in plaque development and periodontal disease pathogenesis.IMPORTANCE The development of dental plaque biofilm is a complex process in which metabolic, chemical and physical interactions between bacteria take a central role. Previous studies have shown that the dental pathogens T. forsythia and F. nucleatum form synergistic biofilms and are closely associated in human dental plaque. In this study, we show that β-glucanase from the periodontal pathogen T. forsythia plays a role in the formation of T. forsythia-F. nucleatum cobiofilms by hydrolyzing β-glucans to glucose as a nutrient. We also unveiled that the expression of T. forsythia β-glucanase is induced in response to F. nucleatum sensing. This study highlights the involvement of β-glucanase activity in the development of T. forsythia-F. nucleatum biofilms and suggests that intake of dietary β-glucans might be a contributing risk factor in plaque development and periodontal disease pathogenesis.

Continuous Carbon Hollow Shell with Zinc Oxide Nanoparticles Embedded as an Anode Material with Excellent Lithium Storage Capability

AbstractContinuous carbon hollow shells with embedded ZnO nanoparticles were synthesized from colloidal polystyrene/ZnO as templates and glucose oligomer as the carbon source followed by calcination. The resulting uniform ZnO/C hollow spheres display a relatively high reversible capacity of 994 mAh g−1 after 100 cycles at 0.1 A g−1 and 812 mAh g−1 after 200 cycles at 1 A g−1, which is superior to most reported ZnO‐based anode materials. The excellent electrochemical performance of the ZnO/C hollow spheres may arise from the following aspects: the shortened pathway of Li ions and electrolyte attributed to the unique hollow shell structures, improved electronic conductivity, firm encapsulation of ZnO nanoparticles, and high specific surface area of the products, which together facilitate the ZnO nanoparticles to undergo the alloying reaction completely.

Human taste detection of glucose oligomers with low degree of polymerization.

Studies have reported that some animals, including humans, can taste mixtures of glucose oligomers (i.e., maltooligosaccharides, MOS) and that their detection is independent of the known T1R2/T1R3 sweet taste receptor. In an effort to understand potential mechanisms underlying the taste perception of glucose oligomers in humans, this study was designed to investigate: 1) the variability of taste sensitivity to MOS with low degree-of-polymerization (DP), and 2) the potential role of hT1R2/T1R3 in the MOS taste detection. To address these objectives, a series of food grade, narrow-DP-range MOS were first prepared (DP 3, 3–4, 5–6, and 6–7) by fractionating disperse saccharide mixtures. Subjects were then asked to discriminate these MOS stimuli as well as glucose (DP 1) and maltose (DP 2) from blanks after the stimuli were swabbed on the tongue. All stimuli were presented at 75 mM with and without a sweet taste inhibitor (lactisole). An α-glucosidase inhibitor (acarbose) was added to all test stimuli to prevent oral digestion of glucose oligomers. Results showed that all six stimuli were detected with similar discriminability in normal tasting conditions. When the sweet receptor was inhibited, DP 1, 2, and 3 were not discriminated from blanks. In contrast, three higher-DP paired MOS stimuli (DP 3–4, 5–6, and 6–7) were discriminated from blanks at a similar degree. Overall, these results support the presence of a sweet-independent taste perception mechanism that is stimulated by MOS greater than three units.

Glycogen synthase from the parabasalian parasite Trichomonas vaginalis: An unusual member of the starch/glycogen synthase family

Trichomonas vaginalis, a parasitic protist, is the causative agent of the common sexually-transmitted infection trichomoniasis. The organism has long been known to synthesize substantial glycogen as a storage polysaccharide, presumably mobilizing this compound during periods of carbohydrate limitation, such as might be encountered during transmission between hosts. However, little is known regarding the enzymes of glycogen metabolism in T. vaginalis. We had previously described the identification and characterization of two forms of glycogen phosphorylase in the organism. Here, we measure UDP-glucose-dependent glycogen synthase activity in cell-free extracts of T. vaginalis. We then demonstrate that the TVAG_258220 open reading frame encodes a glycosyltransferase that is presumably responsible for this synthetic activity. We show that expression of TVAG_258220 in a yeast strain lacking endogenous glycogen synthase activity is sufficient to restore glycogen accumulation. Furthermore, when TVAG_258220 is expressed in bacteria, the resulting recombinant protein has glycogen synthase activity in vitro, transferring glucose from either UDP-glucose or ADP-glucose to glycogen and using both substrates with similar affinity. This protein is also able to transfer glucose from UDP-glucose or ADP-glucose to maltose and longer oligomers of glucose but not to glucose itself. However, with these substrates, there is no evidence of processivity and sugar transfer is limited to between one and three glucose residues. Taken together with our earlier work on glycogen phosphorylase, we are now well positioned to define both how T. vaginalis synthesizes and utilizes glycogen, and how these processes are regulated.

Development of dietary soluble fibres by enzymatic synthesis and assessment of their digestibility in in vitro, animal and randomised clinical trial models

The aim was to develop novel fibres by enzymatic synthesis, to determine their total dietary fibre by AOAC method 2009.01 and to estimate their potential digestibility and assess their digestibility in vivo using glycaemic and insulinaemic responses as markers in mice and randomised clinical trial models. We found that fibre candidates to which α-(1,2) branching was added were resistant to digestion in the mouse model, depending on the amount of branching. These results show that in vivo models are needed to reliably assess the digestibility of α-glycosidic-linked oligomeric dietary fibre candidates, possibly due to absence of brush border α-glucosidase activity in the current in vitro assessment. α-(1,3)-linked and α-(1,6)-linked glucose oligomers were completely digested in humans and mice. In conclusion, it is possible to develop dietary soluble fibres by enzymatic synthesis. Adding α-(1,2) branching increases their resistance to digestion in vivo and can thus improve their suitability as potential fibre candidates.Clinical Trial Registry: ClinicalTrials.gov, NCT02701270