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Rudi F Vogel - One of the best experts on this subject based on the ideXlab platform.
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Insights into the pH-dependent, extracellular sucrose utilization and concomitant Levan formation by Gluconobacter albidus TMW 2.1191
Antonie van Leeuwenhoek, 2020Co-Authors: Frank Jakob, Clara Gebrande, Regina M. Bichler, Rudi F VogelAbstract:Many bacteria and archaea produce the polydisperse fructose polymer Levan from sucrose upon biofilm formation via extracellular Levansucrases (EC 2.4.1.10). We have investigated Levansucrase-release and -activities as well as molecular size of the Levan formed by the acetic acid bacterium Gluconobacter albidus TMW 2.1191 at varying environmental pH conditions to obtain insight in the ecological role of its constitutively expressed Levansucrase and the produced Levan. A buffer system was established enabling the recovery of Levansucrase-containing supernatants from preincubated cell suspensions at pH 4.3–pH 5.7. The enzyme solutions were used to produce Levans at different pH values and sucrose concentrations. Finally, the amounts and size distributions of the produced Levans as well as the corresponding Levansucrase activities were determined and correlated with each other. The data revealed that the Levansucrase was released into the environment independently of its substrate sucrose, and that more Levansucrase was released at pH ≥ 5.0. The glucose release and formation of high molecular weight Levans (> 3.5 kDa) from 0.1 M initial sucrose was comparable between pH ~ 4.3–5.7 using equal amounts of released Levansucrase. Hence, this type of Levansucrase appears to be structurally adapted to changes in the extracellular pH and to exhibit a similar total activity over a wide acidic pH range, while it produced higher amounts of larger Levan molecules at higher production pH and sucrose concentrations. These findings indicate the physiological adaptation of G. albidus TMW 2.1191 to efficient colonisation of sucrose-rich habitats via released Levansucrases despite changing extracellular pH conditions in course of acid formation.
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Size-Dependent Rheological Variability of Levan Produced by Gluconobacter Albidus TMW 2.1191
2020Co-Authors: Christoph Simon Hundschell, Rudi F Vogel, Andre Braun, Daniel Wefers, Frank JakobAbstract:Levan is a fructan-type exopolysaccharide, which is produced by many microbes from sucrose via extracellular Levansucrases. The hydrocolloid properties of Levan depend on its molecular weight, while it is unknown why and to which extent Levan is functionally diverse in dependence of its size. The aim of our study was to get deeper insights into the size-dependent, functional variability of Levan. For this purpose, Levans of different sizes were produced using the water kefir isolate Gluconobacter albidus TMW 2.1191 and subsequently rheologically characterized. Three Levan types could be identified, which are similarly branched, but significantly differ in their molecular size and rheological properties among each other. The smallest Levan (< 107 Da) produced without adjustment of the pH exhibited Newton-like flow behavior up to a specific concentration of 25% (w/v). On the contrary, larger Levans (> 108 Da) produced at pH ≥ 4.5 were shear-thinning and showed a gel like behavior at ≥ 5% (w/v). A third (intermediate) Levan variant was obtained via production in buffers at pH 4.0 and exhibited the properties of a viscoelastic fluid at ≥ 5% (w/v). Our study reveals that the variable size and composition of Levan are controllable and more decisive for its functionality than the amount of exerted Levan.
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fermentation ph modulates the size distributions and functional properties of gluconobacter albidus tmw 2 1191 Levan
Frontiers in Microbiology, 2017Co-Authors: Tharalinee Uaarak, Frank Jakob, Rudi F VogelAbstract:Bacterial Levan has gained an increasing interest over the last decades due to its unique characteristics and multiple possible applications. Levan and other exopolysaccharides (EPS) production are usually optimized to obtain the highest concentration or yield while a possible change of the molecular size and mass during the production process is mostly neglected. In this study, the molar mass and radius of Levan samples were monitored during fermentations with the food-grade, Levan-producing acetic acid bacterium (AAB) Gluconobacter (G.) albidus TMW 2.1191 in shake flasks (without pH control) and bioreactors (with pH control at 4.5, 5.5 and 6.5, respectively). In uncontrolled fermentations, the Levan size/molar mass continuously decreased concomitantly with the continuous acidification of the nutrient medium. On the contrary, the amount, molar mass and size of Levan could be directly influenced by controlling the pH during fermentation. Using equal initial substrate amounts, the largest weight average molar mass and geometric radius of Levan were observed at constant pH 6.5, while the highest Levan concentration was obtained at constant pH 4.5. Since there is a special demand to find suitable hydrocolloids from food-grade bacteria to develop novel gluten-free products, these differently produced Levans were used for baking of gluten-free breads, and the best quality improvement was obtained by addition of Levan with the highest mass and radius. This work, therefore, demonstrates for the first time that one bacterial strain can produce specific high molecular weight fractions of one EPS type, which differ in properties and sizes among each other in dependence of the controllable production conditions.
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Influence of Levan-producing acetic acid bacteria on buckwheat-sourdough breads
Food microbiology, 2017Co-Authors: Tharalinee Ua-arak, Frank Jakob, Rudi F VogelAbstract:Buckwheat sourdoughs supplemented with molasses as natural sucrose source were fermented with Levan-producing Gluconobacter (G.) albidus TMW 2.1191 and Kozakia (K.) baliensis NBRC 16680. Cell growth, concomitant Levan and low-molecular-weight metabolite production were monitored. Sourdough breads were prepared with different sourdoughs from both strains (24, 30 and 48 h fermentation, respectively) and analyzed with respect to bread volume, crumb hardness and sensory characteristics. During fermentation, Levan, acetic and gluconic acids were increasingly produced, while spontaneously co-growing lactic acid bacteria additionally formed acetic and lactic acids. Sourdoughs from both strains obtained upon 24 h of fermentation significantly improved the bread sensory and quality, including higher specific volume as well as lower crumb hardness. Buckwheat doughs containing isolated Levan, with similar molecular size and mass compared to in situ produced Levan in the sourdough at 48 h, verified the positive effect of Levan on bread quality. However, the positive effects of Levan were masked to a certain extent by the impact from the natural acidification during fermentations. While Levan-producing acetic acid bacteria are a promising alternative for the development of clean-label gluten-free breads without the need of additives, an appropriate balance between acidification and Levan production (amount and structure) must be reached.
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structural analysis of fructans produced by acetic acid bacteria reveals a relation to hydrocolloid function
Carbohydrate Polymers, 2013Co-Authors: Frank Jakob, Andre Pfaff, Ramon Novoacarballal, Heinrich Rubsam, Thomas Becker, Rudi F VogelAbstract:Abstract Some strains of acetic acid bacteria ( Gluconobacter frateurii TMW 2.767, Gluconobacter cerinus DSM 9533T, Neoasaia chiangmaiensis NBRC 101099, Kozakia baliensis DSM 14400) produce high amounts of fructans, which can be exploited in food applications as previously demonstrated empirically for dough systems. In order to get insight into the structure and functionality of these polymers, we investigated the fructans isolated from these strains with respect to their linkage types and molecular weights/shapes using NMR spectroscopy and AF4-MALS-RI. Each fructan was identified as Levan. The isolated Levan fractions were highly similar according to their basic linearity and linkage types, but differed significantly in terms of their individual molecular weight distributions. In aqueous solutions the size of Levan molecules present in all isolated Levans continuously increased with their molecular weight and they tended to adopt a more compact molecular shape. Our data suggest that the increasing molecular weight of a Levan particle enforces intramolecular interactions to reach the structural compactness of a microgel with hydrocolloid properties.
Frank Jakob - One of the best experts on this subject based on the ideXlab platform.
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Insights into the pH-dependent, extracellular sucrose utilization and concomitant Levan formation by Gluconobacter albidus TMW 2.1191
Antonie van Leeuwenhoek, 2020Co-Authors: Frank Jakob, Clara Gebrande, Regina M. Bichler, Rudi F VogelAbstract:Many bacteria and archaea produce the polydisperse fructose polymer Levan from sucrose upon biofilm formation via extracellular Levansucrases (EC 2.4.1.10). We have investigated Levansucrase-release and -activities as well as molecular size of the Levan formed by the acetic acid bacterium Gluconobacter albidus TMW 2.1191 at varying environmental pH conditions to obtain insight in the ecological role of its constitutively expressed Levansucrase and the produced Levan. A buffer system was established enabling the recovery of Levansucrase-containing supernatants from preincubated cell suspensions at pH 4.3–pH 5.7. The enzyme solutions were used to produce Levans at different pH values and sucrose concentrations. Finally, the amounts and size distributions of the produced Levans as well as the corresponding Levansucrase activities were determined and correlated with each other. The data revealed that the Levansucrase was released into the environment independently of its substrate sucrose, and that more Levansucrase was released at pH ≥ 5.0. The glucose release and formation of high molecular weight Levans (> 3.5 kDa) from 0.1 M initial sucrose was comparable between pH ~ 4.3–5.7 using equal amounts of released Levansucrase. Hence, this type of Levansucrase appears to be structurally adapted to changes in the extracellular pH and to exhibit a similar total activity over a wide acidic pH range, while it produced higher amounts of larger Levan molecules at higher production pH and sucrose concentrations. These findings indicate the physiological adaptation of G. albidus TMW 2.1191 to efficient colonisation of sucrose-rich habitats via released Levansucrases despite changing extracellular pH conditions in course of acid formation.
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Size-Dependent Rheological Variability of Levan Produced by Gluconobacter Albidus TMW 2.1191
2020Co-Authors: Christoph Simon Hundschell, Rudi F Vogel, Andre Braun, Daniel Wefers, Frank JakobAbstract:Levan is a fructan-type exopolysaccharide, which is produced by many microbes from sucrose via extracellular Levansucrases. The hydrocolloid properties of Levan depend on its molecular weight, while it is unknown why and to which extent Levan is functionally diverse in dependence of its size. The aim of our study was to get deeper insights into the size-dependent, functional variability of Levan. For this purpose, Levans of different sizes were produced using the water kefir isolate Gluconobacter albidus TMW 2.1191 and subsequently rheologically characterized. Three Levan types could be identified, which are similarly branched, but significantly differ in their molecular size and rheological properties among each other. The smallest Levan (< 107 Da) produced without adjustment of the pH exhibited Newton-like flow behavior up to a specific concentration of 25% (w/v). On the contrary, larger Levans (> 108 Da) produced at pH ≥ 4.5 were shear-thinning and showed a gel like behavior at ≥ 5% (w/v). A third (intermediate) Levan variant was obtained via production in buffers at pH 4.0 and exhibited the properties of a viscoelastic fluid at ≥ 5% (w/v). Our study reveals that the variable size and composition of Levan are controllable and more decisive for its functionality than the amount of exerted Levan.
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fermentation ph modulates the size distributions and functional properties of gluconobacter albidus tmw 2 1191 Levan
Frontiers in Microbiology, 2017Co-Authors: Tharalinee Uaarak, Frank Jakob, Rudi F VogelAbstract:Bacterial Levan has gained an increasing interest over the last decades due to its unique characteristics and multiple possible applications. Levan and other exopolysaccharides (EPS) production are usually optimized to obtain the highest concentration or yield while a possible change of the molecular size and mass during the production process is mostly neglected. In this study, the molar mass and radius of Levan samples were monitored during fermentations with the food-grade, Levan-producing acetic acid bacterium (AAB) Gluconobacter (G.) albidus TMW 2.1191 in shake flasks (without pH control) and bioreactors (with pH control at 4.5, 5.5 and 6.5, respectively). In uncontrolled fermentations, the Levan size/molar mass continuously decreased concomitantly with the continuous acidification of the nutrient medium. On the contrary, the amount, molar mass and size of Levan could be directly influenced by controlling the pH during fermentation. Using equal initial substrate amounts, the largest weight average molar mass and geometric radius of Levan were observed at constant pH 6.5, while the highest Levan concentration was obtained at constant pH 4.5. Since there is a special demand to find suitable hydrocolloids from food-grade bacteria to develop novel gluten-free products, these differently produced Levans were used for baking of gluten-free breads, and the best quality improvement was obtained by addition of Levan with the highest mass and radius. This work, therefore, demonstrates for the first time that one bacterial strain can produce specific high molecular weight fractions of one EPS type, which differ in properties and sizes among each other in dependence of the controllable production conditions.
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Influence of Levan-producing acetic acid bacteria on buckwheat-sourdough breads
Food microbiology, 2017Co-Authors: Tharalinee Ua-arak, Frank Jakob, Rudi F VogelAbstract:Buckwheat sourdoughs supplemented with molasses as natural sucrose source were fermented with Levan-producing Gluconobacter (G.) albidus TMW 2.1191 and Kozakia (K.) baliensis NBRC 16680. Cell growth, concomitant Levan and low-molecular-weight metabolite production were monitored. Sourdough breads were prepared with different sourdoughs from both strains (24, 30 and 48 h fermentation, respectively) and analyzed with respect to bread volume, crumb hardness and sensory characteristics. During fermentation, Levan, acetic and gluconic acids were increasingly produced, while spontaneously co-growing lactic acid bacteria additionally formed acetic and lactic acids. Sourdoughs from both strains obtained upon 24 h of fermentation significantly improved the bread sensory and quality, including higher specific volume as well as lower crumb hardness. Buckwheat doughs containing isolated Levan, with similar molecular size and mass compared to in situ produced Levan in the sourdough at 48 h, verified the positive effect of Levan on bread quality. However, the positive effects of Levan were masked to a certain extent by the impact from the natural acidification during fermentations. While Levan-producing acetic acid bacteria are a promising alternative for the development of clean-label gluten-free breads without the need of additives, an appropriate balance between acidification and Levan production (amount and structure) must be reached.
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structural analysis of fructans produced by acetic acid bacteria reveals a relation to hydrocolloid function
Carbohydrate Polymers, 2013Co-Authors: Frank Jakob, Andre Pfaff, Ramon Novoacarballal, Heinrich Rubsam, Thomas Becker, Rudi F VogelAbstract:Abstract Some strains of acetic acid bacteria ( Gluconobacter frateurii TMW 2.767, Gluconobacter cerinus DSM 9533T, Neoasaia chiangmaiensis NBRC 101099, Kozakia baliensis DSM 14400) produce high amounts of fructans, which can be exploited in food applications as previously demonstrated empirically for dough systems. In order to get insight into the structure and functionality of these polymers, we investigated the fructans isolated from these strains with respect to their linkage types and molecular weights/shapes using NMR spectroscopy and AF4-MALS-RI. Each fructan was identified as Levan. The isolated Levan fractions were highly similar according to their basic linearity and linkage types, but differed significantly in terms of their individual molecular weight distributions. In aqueous solutions the size of Levan molecules present in all isolated Levans continuously increased with their molecular weight and they tended to adopt a more compact molecular shape. Our data suggest that the increasing molecular weight of a Levan particle enforces intramolecular interactions to reach the structural compactness of a microgel with hydrocolloid properties.
Tiina Alamae - One of the best experts on this subject based on the ideXlab platform.
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a highly active endo Levanase bt1760 of a dominant mammalian gut commensal bacteroides thetaiotaomicron cleaves not only various bacterial Levans but also Levan of timothy grass
PLOS ONE, 2017Co-Authors: Karin Mardo, Heiki Vija, Triinu Visnapuu, Anneli Aasamets, Katrin Viigand, Tiina AlamaeAbstract:Bacteroides thetaiotaomicron, an abundant commensal of the human gut, degrades numerous complex carbohydrates. Recently, it was reported to grow on a β-2,6-linked polyfructan Levan produced by Zymomonas mobilis degrading the polymer into fructooligosaccharides (FOS) with a cell surface bound endo-Levanase BT1760. The FOS are consumed by B. thetaiotaomicron, but also by other gut bacteria, including health-promoting bifidobacteria and lactobacilli. Here we characterize biochemical properties of BT1760, including the activity of BT1760 on six bacterial Levans synthesized by the Levansucrase Lsc3 of Pseudomonas syringae pv. tomato, its mutant Asp300Asn, Levansucrases of Zymomonas mobilis, Erwinia herbicola, Halomonas smyrnensis as well as on Levan isolated from timothy grass. For the first time a plant Levan is shown as a perfect substrate for an endo-fructanase of a human gut bacterium. BT1760 degraded Levans to FOS with degree of polymerization from 2 to 13. At optimal reaction conditions up to 1 g of FOS were produced per 1 mg of BT1760 protein. Low molecular weight (<60 kDa) Levans, including timothy grass Levan and Levan synthesized from sucrose by the Lsc3Asp300Asn, were degraded most rapidly whilst Levan produced by Lsc3 from raffinose least rapidly. BT1760 catalyzed finely at human body temperature (37°C) and in moderately acidic environment (pH 5–6) that is typical for the gut lumen. According to differential scanning fluorimetry, the Tm of the endo-Levanase was 51.5°C. All tested Levans were sufficiently stable in acidic conditions (pH 2.0) simulating the gastric environment. Therefore, Levans of both bacterial and plant origin may serve as a prebiotic fiber for B. thetaiotaomicron and contribute to short-chain fatty acids synthesis by gut microbiota. In the genome of Bacteroides xylanisolvens of human origin a putative Levan degradation locus was disclosed.
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A Highly Active Endo-Levanase BT1760 of a Dominant Mammalian Gut Commensal Bacteroides thetaiotaomicron Cleaves Not Only Various Bacterial Levans, but Also Levan of Timothy Grass
PloS one, 2017Co-Authors: Karin Mardo, Heiki Vija, Triinu Visnapuu, Anneli Aasamets, Katrin Viigand, Tiina AlamaeAbstract:Bacteroides thetaiotaomicron, an abundant commensal of the human gut, degrades numerous complex carbohydrates. Recently, it was reported to grow on a β-2,6-linked polyfructan Levan produced by Zymomonas mobilis degrading the polymer into fructooligosaccharides (FOS) with a cell surface bound endo-Levanase BT1760. The FOS are consumed by B. thetaiotaomicron, but also by other gut bacteria, including health-promoting bifidobacteria and lactobacilli. Here we characterize biochemical properties of BT1760, including the activity of BT1760 on six bacterial Levans synthesized by the Levansucrase Lsc3 of Pseudomonas syringae pv. tomato, its mutant Asp300Asn, Levansucrases of Zymomonas mobilis, Erwinia herbicola, Halomonas smyrnensis as well as on Levan isolated from timothy grass. For the first time a plant Levan is shown as a perfect substrate for an endo-fructanase of a human gut bacterium. BT1760 degraded Levans to FOS with degree of polymerization from 2 to 13. At optimal reaction conditions up to 1 g of FOS were produced per 1 mg of BT1760 protein. Low molecular weight (
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Levan enhances associated growth of bacteroides escherichia streptococcus and faecalibacterium in fecal microbiota
PLOS ONE, 2015Co-Authors: Kaarel Adamberg, Ksenia Pudova, Triinu Visnapuu, Tiina Alamae, Katrin Tomson, Tiina Talve, Marju Puurand, Signe AdambergAbstract:The role of dietary fiber in supporting healthy gut microbiota and overall well-being of the host has been revealed in several studies. Here, we show the effect of a bacterial polyfructan Levan on the growth dynamics and metabolism of fecal microbiota in vitro by using isothermal microcalorimetry. Eleven fecal samples from healthy donors were incubated in phosphate-buffered defined medium with or without Levan supplementation and varying presence of amino acids. The generation of heat, changes in pH and microbiota composition, concentrations of produced and consumed metabolites during the growth were determined. The composition of fecal microbiota and profile of metabolites changed in response to substrate (Levan and amino acids) availability. The main products of Levan metabolism were acetic, lactic, butyric, propionic and succinic acids and carbon dioxide. Associated growth of Levan-degrading (e.g. Bacteroides) and butyric acid-producing (e.g. Faecalibacterium) taxa was observed in Levan-supplemented media. The study shows that the capacity of Levan and possibly also other dietary fibers/prebiotics to modulate the composition and function of colon microbiota can be predicted by using isothermal microcalorimetry of fecal samples linked to metabolite and consortia analyses.
Inglung Shih - One of the best experts on this subject based on the ideXlab platform.
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factors affecting the production and molecular weight of Levan of bacillus subtilis natto in batch and fed batch culture in fermenter
Journal of The Taiwan Institute of Chemical Engineers, 2013Co-Authors: Fangchen Wu, Shouzu Chou, Inglung ShihAbstract:Abstract The production of Levan in batch and fed-batch culture of Bacillus subtilis (natto) Takahashi in fermenter was investigated. Efficient and high yield Levan production (61 g/L at 24 h; 3.4 g/L/h) was obtained when the bacteria were cultured in medium containing sucrose (250 g/L) at pH 7.0, temperature 37 °C and agitation speed 175 rpm; in addition, pulsed feeding of sucrose enhanced the Levan production significantly to 100 g/L (1.7 fold increase). This is the first systematic study of this strain in fermenter and the most efficient Levan production reported to date. The yield and molecular weight of Levan were strictly dependent on the reaction conditions. Sucrose concentration was the most effective factor controlling the molecular weight of the synthesized Levan, this leads to tailor made Levans of different molecular sizes for applications of different purposes.
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selective production and characterization of Levan by bacillus subtilis natto takahashi
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Inglung Shih, Yunti Yu, Chwenjen Shieh, Chienyan HsiehAbstract:To meet the industrial need of an efficient microbial method for increased Levan production, Bacillus subtilis (natto) Takahashi, a commercial natto starter for preparing fermented soybeans (natto), was used to produce Levan. After cultivation for 21 h, 40−50 mg of Levan mL-1 was produced in medium containing 20% (w/w) sucrose, which was ∼50% yield on available fructose. The product consisted of two fractions with different molecular masses (1794 and 11 kDa), which were easily separated by fractionation using an ethanol gradient. The products were well characterized by GPC, 13C NMR, and 1H NMR. The various sugars and concentrations, initial pH, fermentation temperature, and agitation speed affected the Levan production by B. subtilis (natto) Takahashi. Takahashi strain is the most efficient Levan-producing strain among all of the B. subtilis strains tested and, as previously reported, it produced the highest yield of Levan in the least time (21 h) under the common cultivation condition. Keywords: Levan; B...
Ebru Toksoy Oner - One of the best experts on this subject based on the ideXlab platform.
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Effect of temperature on the hydrolysis of Levan treated with compressed hot water fluids.
Food science & nutrition, 2020Co-Authors: Naoto Shimizu, Andres Abea, Tetsuya Ushiyama, Ebru Toksoy OnerAbstract:The hydrolysis of Levan using compressed hot water for the production of functional fructooligosaccharides (FOSs) was investigated. Levans from Erwinia herbicola (EH) and Halomonas smyrnensis (HS) were characterized using scanning electron microscopy and light scattering techniques, and hydrolyzed using compressed hot water at four temperatures (120, 140, 160, and 180°C). The hydrolysates were analyzed using high-performance liquid chromatography and electrospray ionization-mass spectrometry. Levan HS showed a crystalline morphology, whereas Levan EH showed an aggregated structure. Both Levans had molar masses on the order of 106 g/mol, but Levan EH had a smaller radius of gyration, hydrodynamic radius, and intrinsic viscosity. Levan EH hydrolyzed into FOSs at approximately 120°C, whereas Levan HS required a temperature of at least 160°C, possibly because of differences in the degree of branching of the two Levans. Both samples were degraded to fructose when treated at 180°C.
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novel Levan and pnipa temperature sensitive hydrogels for 5 asa controlled release
Carbohydrate Polymers, 2017Co-Authors: Asila Osman, Ebru Toksoy Oner, Mehmet S ErogluAbstract:Abstract Levan based cross-linker was successfully synthesized and used to prepare a series of more biocompatible and temperature responsive Levan/ N -isopropyl acrylamide (Levan/pNIPA) hydrogels by redox polymerization at room temperature. Volume phase transition temperature (VPTT) of the hydrogels were precisely determined by derivative differential scanning calorimetry (DDSC). Incorporation of Levan into the pNIPA hydrogel increased the VPTT from 32.8 °C to 35.09 °C, approaching to body temperature. Swelling behavior and 5-aminosalicylic acid (5-ASA) release of the hydrogels were found to vary significantly with temperature and composition. Moreover, a remarkable increase in thermal stability of Levan within hydrogel with increase of pNIPA content was recorded. The biocompatibility of the hydrogels were tested against mouse fibroblast L929 cell line in phosphate buffer saline (PBS, pH 7.4). The hydrogels showed increasing biocompatibility with increasing Levan ratio, indicating Levan enhanced the hydrogel surface during swelling.
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Review of Levan polysaccharide: From a century of past experiences to future prospects
Biotechnology Advances, 2016Co-Authors: Ebru Toksoy Oner, Lázaro Hernández, Joan CombieAbstract:Levan is a fascinating β-(2,6)-linked fructose polymer with an unusual combination of properties characterized in this review. In nature, Levan is synthesized from sucrose by a wide range of microorganisms and a few plant species. Bacterial Levans often have molecular weights over 500,000 Da, are commonly branched, and form compact nanospheres offering a broad spectrum of applications. The most reLevant genetic, biochemical and structural aspects of the biosynthetic enzyme Levansucrase are detailed. Optimization of parameters for Levan production by intact bacteria and by the isolated enzyme is surveyed. The diversity of current and potential applications of Levan is illustrated by a discussion of uses ranging from personal care and aquaculture to the medical and food industries.
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effective stimulating factors for microbial Levan production by halomonas smyrnensis aad6t
Journal of Bioscience and Bioengineering, 2015Co-Authors: Hande Kazak Sarilmiser, Ozlem Ates, Gonca Ozdemir, Kazim Yalcin Arga, Ebru Toksoy OnerAbstract:Levan is a bioactive fructan polymer that is mainly associated with high-value applications where exceptionally high purity requirements call for well-defined cultivation conditions. In this study, microbial Levan production by the halophilic extremophile Halomonas smyrnensis AAD6 T was investigated systematically. For this, different feeding strategies in fed-batch cultures were employed and fermentation profiles of both shaking and bioreactor cultures were analyzed. Initial carbon and nitrogen source concentrations, production pH, NaCl and nitrogen pulses, nitrogen and phosphorous limitations, trace elements and thiamine contents of the basal production medium were found to affect the Levan yields at different extends. Boric acid was found to be the most effective stimulator of Levan production by increasing the sucrose utilization three-fold and Levan production up to five-fold. This significant improvement implied the important role of quorum sensing phenomenon and its regulatory impact on Levan production mechanism. Levan produced by bioreactor cultures under conditions optimized within this study was found to retain its chemical structure. Moreover, its biocompatibility was assessed for a broad concentration range. Hence H. smyrnensis AAD6 T has been firmly established as an industrially important resource microorganism for high-quality Levan production.
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Levan based nanocarrier system for peptide and protein drug delivery optimization and influence of experimental parameters on the nanoparticle characteristics
Carbohydrate Polymers, 2011Co-Authors: Ali Demir Sezer, Ebru Toksoy Oner, Hande Kazak, Julide AkbugaAbstract:Abstract Microbial Levans are biopolymers produced from sucrose-based substrates by a variety of microorganisms. There is very limited information related to the Levan-based drug delivery systems. In this study, bovine serum albumin (BSA) encapsulated-Levan nanoparticles were prepared using Levan produced by a new Halomonas sp. Effects of polymer and BSA concentrations and rotating speed on in vitro characterization of the nanoparticles were investigated. The size of Levan nanoparticles, with the surface charges +4.3 mV to +7.6 mV, changed between 200 nm and 537 nm. The encapsulation capacity of the particles changed between 49.3% and 71.3% depending on the Levan concentration used in the formulation. The cumulative in vitro release of protein from the particles was shown to be controlled release of BSA. This study affirmed the suitability of Levan by Halomonas sp. to be used as a nanocarrier system for potential delivery of macromolecular drugs such as peptides and proteins.