Prebiotic levan type fructan from Bacillus subtilis PR-C18 as a potent antibiofilm agent: Structural elucidation and in silico analysis

The global demand for therapeutic prebiotics persuades the quest for novel exopolysaccharides that can retard the growth of pathobionts and healthcare-associated pathogens. In this regard, an exopolysaccharide (3.69 mg/mL) producing strain showing prebiotic and antibiofilm activity was isolated from indigenous pineapple pomace of Tripura and identified as Bacillus subtilis PR-C18. Zymogram analysis revealed EPS PR-C18 was synthesized by levansucrase (∼57 kDa) with a maximal activity of 4.62 U/mg. Chromatography techniques, FTIR, and NMR spectral data revealed the homopolymeric nature of purified EPS with a molecular weight of 3.40 × 104 Da. SEM and rheological study unveiled its microporous structure and shear-thinning effect. Furthermore, EPS PR-C18 showed remarkable emulsification, flocculation, water retention, water solubilization, and antioxidant activity. DSC-TGA data demonstrated its high thermostability and cytotoxicity analysis verified its nontoxic biocompatible nature. In addition, the antibiofilm activity of EPS PR-C18 was validated using molecular docking, molecular simulation, MM-GBSA and PCA studies, which exhibited its strong binding affinity (-20.79 kcal/moL) with PelD, a virulence factor from Pseudomonas aeruginosa. Together, these findings support the future exploitation of EPS PR-C18 as an additive or adjuvant in food and pharmaceutical sectors.

Production, effects, and applications of fructans with various molecular weights

Fructan, a widespread functional polysaccharide, has been used in the food, pharmaceutical, cosmetic, and material production fields because of its versatile physicochemical properties and biological activities. Inulin from plants and levan from microorganisms are two of the most extensively studied fructans. Fructans from different plants or microorganisms have inconsistent molecular weights, and the molecular weight of fructan affects its properties, functions, and applications. Recently, increasing attention has been paid to the production and application of fructans having various molecular weights, and biotechnological processes have been explored to produce tailor-made fructans from sucrose. This review encompasses the introduction of extraction, enzymatic transformation, and fermentation production processes for fructans with diverse molecular weights. Notably, it highlights the enzymes involved in fructan biosynthesis and underscores their physiological effects, with a special emphasis on their prebiotic properties. Moreover, the applications of fructans with varying molecular weights are also emphasized.

Investigating the cryoprotective efficacy of fructans in mammalian cell systems via a structure-functional perspective

Fructans have long been known with their role in protecting organisms against various stress factors due to their ability to induce controlled dehydration and support membrane stability. Considering the vital importance of such features in cryo-technologies, this study aimed to explore the cryoprotective efficacy of fructans in mammalian cell systems where structurally different fructan polymers were examined on in vitro cell models derived from organs such as the liver, frequently used in transplantation, osteoblast, and cord cells, commonly employed in cell banking, as well as human seminal fluids that are of vital importance in assisted reproductive technology. To gain insights into the fructan/membrane interplay, structural differences were linked to rheological properties as well as to lipid membrane interactions where both fluorescein leakage from unilamellar liposomes and membrane integrity of osteoblast cells were monitored. High survival rates obtained with human endothelial, osteoblast and liver cells for up to two months clearly showed that fructans could be considered as effective non-permeating cryoprotectants, especially for extended periods of cryopreservation. In trials with human seminal fluid, short chained levan in combination with human serum albumin and glycerol proved very effective in preserving semen samples across multiple patients without any morphological abnormalities.

Structural characterization of an inulin neoseries-type fructan from Ophiopogonis Radix and the therapeutic effect on liver fibrosis in vivo

Ophiopogonis Radix is a well-known Traditional Chinese Medicine and functional food that is rich in polysaccharides and has fructan as a characteristic component. In this study, an inulin neoseries-type fructan designated as OJP-W2 was obtained and characterized from Ophiopogonis Radix, and its potential therapeutic effect on liver fibrosis in vivo were investigated. Structural studies revealed that OJP-W2 had a molecular weight of 5.76 kDa and was composed of glucose and fructose with a molar ratio of 1.00:30.87. Further analysis revealed OJP-W2 has a predominantly lineal (1-2)-linked β-D-fructosyl units linked to the glucose moiety of the sucrose molecule with (2-6)-linked β-D-fructosyl side chains. Pharmacological studies revealed that OJP-W2 exerted a marked hepatoprotective effect against liver fibrosis, the mechanism of action was involved in regulating collagen deposition (α-SMA, COL1A1 and liver Hyp contents) and TGF-β/Smads signaling pathway, alleviating liver inflammation (IL-1β, IL-6, CCL5 and F4/80) and MAPK signaling pathway, and inhibiting hepatic apoptosis (Bax, Bcl-2, ATF4 and Caspase 3). These data provide evidence for expanding Ophiopogonis Radix-acquired fructan types and advancing our understanding of the specific role of inulin neoseries-type fructan in liver fibrosis therapy.

Identification of carbohydrate in Polygonatum kingianum Coll. et Hemsl and inhibiting oxidative stress

The specific structure of Polygonatum kingianum Coll. et Hemsl polysaccharide (PKP) has been rarely reported. In this study, an inulin-type fructan PKP-1, was extracted and purified from Polygonatum kingianum Coll. et Hemsl, and its structural characteristics and antioxidants activity were evaluated. The molecular weights of PKP-1 was determined to be 4.802 kDa. Monosaccharide composition analysis evidenced that PKP-1 was composed of galactose, glucose and fructose in a molar ratio of 0.8 %:7.2 %:92.0 %. Glycosidic linkage and Nuclear Magnetic Resonance (NMR) analysis revealed that PKP-1 exhibited a primary sugar residue linkage of →1-β-d-Fruf-2→2,6-β-d-Fruf-1→, where β-d-Fruf-2→ acts as the side chain and links to the C-6 position of →2,6-β-d-Fruf-1→. In vitro antioxidant activity assays demonstrated that PKP-1 enhanced the mitigation of hepatic oxidative stress in HepG2 cells induced by free fatty acids. This effect was marked by increased enzymatic activities of superoxidase dismutase (SOD) and catalase (CAT), along with elevated glutathione (GSH) levels. These findings indicate that PKP-1 could be used as a potential natural antioxidant.

An inulin-type fructan CP-A from Codonopsis pilosula alleviates TNBS-induced ulcerative colitis based on serum-untargeted metabolomics

Ulcerative colitis (UC) is an inflammatory disease with abdominal pain, diarrhea, and bloody stool as the main symptoms. Several studies have confirmed that polysaccharides are effective against UC. It is commonly accepted that the traditional benefits of Radix Codonopsis can be attributed to its polysaccharide contents, and inulin-type fructan CP-A is the main active monomer in the polysaccharide components. Herein, we established a 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced UC rat model and lipopolysaccharide (LPS)-induced colonic epithelial cell model (NCM460) to investigate the effect of CP-A on UC. Untargeted metabolomics studies were conducted to identify differential metabolites using ultra-high performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS) and enrich metabolic pathways in rat serum. The in vivo assays demonstrated that CP-A reduces colonic macroscopic injury, disease activity index (DAI), histopathological score, interleukin (IL)-8, and tumor necrosis factor-α (TNF-α) levels, as well as the expression of intercellular adhesion molecules. On the other hand, CP-A increases IL-10 and transforming growth factor-β (TGF-β) levels. The in vitro experiments indicated that CP-A treatment could reduce nitric oxide (NO) and IL-1β after LPS stimulation. The metabolomics results suggested that CP-A therapy for UC may be related to the mammalian target of rapamycin (mTOR) signaling pathway. The in vitro and in vivo validation of the pathway showed similar results, indicating that CP-A alleviates UC by preventing the activation of mTOR/p70S6K signaling pathway. These findings offer a fresh approach to treating UC and a theoretical foundation for the future advancement of CP-A.NEW & NOTEWORTHY We report that an inulin-type fructan from Codonopsis pilosula CP-A exhibits a therapeutic effect on experimental colitis. Its mechanism may be to alleviate intestinal inflammation by preventing the activation of mammalian target of rapamycin (mTOR)/p70S6K signaling pathway. These findings offer a fresh approach to treating ulcerative colitis (UC) and a theoretical foundation for the future advancement of CP-A.

The agavins (Agave carbohydrates) story

Fructans, are carbohydrates defined as fructose-based polymers with countable degree of polymerization (DP) ranging so far from DP3 to DP60. There are different types of fructans depending on their molecular arrangement. They are categorized as linear inulins and levans, neoseries of inulin and levan, branched graminans, and highly branched neofructans, so called agavins (Agave carbohydrates). It is worth to note that agavins are the most recently described type of fructans and they are also the most complex ones. The complexity of these carbohydrates is correlated to their various isomers and degree of polymerization range, which is correlated to their multifunctional application in industry and human health. Here, we narrate the story of the agavins' discovery. This included their chemical characterization, their benefits, biotechnological applications, and drawbacks over human health. Finally, a perspective of the study of agavins and their interactions with other metabolites through metabolomics is proposed.

Unraveling the role of flexible coil near calcium binding site of levansucrase on thermostability and product profile via proline substitution and molecular dynamics simulations

Due to its bioactivity and versatile applications, levan has appeared as a promising biomaterial. Levansucrase is responsible for the conversion of sucrose into levan. With the goal of enhancing levan production, the strategy for enhancing the stability of levansucrase is being intensively studied. To make proteins more stable under high temperatures, proline, the most rigid residue, can be introduced into previously flexible regions. Herein, G249, D250, N251, and H252 on the flexible coil close to the calcium binding site of Bacillus licheniformis levansucrase were replaced with proline. Mutations at G249P greatly enhance both the enzyme's thermodynamic and kinetic stability, while those at H252P improve solely the enzyme's kinetic stability. GPC analysis revealed that G249P synthesize more levan, but H252P generate primarily oligosaccharides. Molecular dynamics simulations (MD) and MM/GBSA analysis revealed that G249P mutation increased not only the stability of levansucrase, but also affinity toward fructan.

Effect of extraction methods on the chemical, structural, and rheological attributes of fructan derived from Arctium lappa L. roots

The focus of this study was the evaluation of how extraction techniques impact the chemical, structural, and rheological attributes of fructans extracted from Arctium lappa L. roots. Three distinct extraction procedures were used, utilizing water as solvent, infusion extraction conducted at ambient temperature (25 °C for 5 min), thermal extraction employing reflux (100 °C for 2 h), and ultrasound-assisted extraction (50 °C for 1.38 h with a 158 W output). Chemical characterization by Nuclear Magnetic Resonance (NMR) and colorimetric analyses revealed the obtaining of inulin-type fructans (yield 83 %). The degree of polymerization (DP) was found to be the lowest for ultrasound-assisted extraction (14.38), followed by the room-temperature (20.41) and thermal (21.14) extraction techniques. None of the extraction techniques appeared to modify the molecular structure of the isolated compounds. In X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses, distinct crystallization patterns were observed for the room-temperature and thermal extraction techniques, though all fractions consistently exhibited characteristic bands of inulin-type fructan. Rheological assessments indicated a viscoelastic nature of the fractions, with those extracted thermally demonstrating a greater viscosity. This study shows that the choice of extraction method can influence the structural characteristics of inulin-type fructans derived from the burdock root.

Optimized acid hydrolysis conditions for better characterization the structure of inulin-type fructan from Polygonatum sibiricum

Polygonatum sibiricum is an edible plant species in China known for its abundant polysaccharides. However, correlations between its analytical methods and fine structure have not been established. This is usually due to incomplete cleavage of the glycosidic linkages and instability of hydrolysis. In this study, a new optimal acid hydrolysis method for monosaccharide composition (2 M H2SO4 for 1 h) and methylation analysis (2 mol TFA hydrolysis at 100 °C for 1 h) was developed for characterization of inulin-type fructans, resulting in significantly improved monosaccharide recovery and providing more reliable methylation data. The effectiveness of this method was demonstrated through its application to the study of polysaccharide from P. sibiricum (IPS-70S). The results showed that IPS-70S with a molecular weight of 3.6 kDa is an inulin-type fructans consisting of fructose and glucose in a molar ratio of 27:1. Methylation and NMR analysis indicated that IPS-70S contains →2)-Fruf-(6 → or →2)-Fruf-(1 → with branching →1,6)-Fruf-(2 → and terminates in Glcp-(1 → or Fruf-(2→. In conclusion, optimal acid hydrolysis applicable to the specific polysaccharides contribute to its structurally characterized. The newly optimized acid hydrolysis method for monosaccharide composition and methylation analysis offers a reliable and effective approach to the structural characterization of inulin-type fructans from P. sibiricum. Providing reliable basis for the overall work of NMR analysis and structural analysis, which have potential significance in the field of polysaccharides structural characterization.

Determination of Molecular Dimensions of Carbohydrate Polymers (Polysaccharides) by Size Exclusion Chromatography (SEC)

Calibrated size exclusion chromatography (SEC) is a useful tool for the analysis of molecular dimensions of polysaccharides. The calibration takes place with a set of narrow distributed dextran standards and peak position technique. Adapted columns systems and dissolving processes enable for the adequate separation of carbohydrate polymers. Plant-extracted fructan (a homopolymer with low molar mass and excellent water solubility) and mucilage (differently structured, high molar mass heteropolysaccarides that include existing supramolecular structures, and require a long dissolving time) are presented as examples of the versatility of this technique. Since narrow standards similar to the samples (chemically and structurally) are often unavailable, it must be noted that the obtained molar mass values and distributions by this method are only apparent (relative) values, expressed as dextran equivalents.

Fructan-type prebiotic dietary fibers: Clinical studies reporting health impacts and recent advances in their technological application in bakery, dairy, meat products and beverages

Fructooligosaccharides (FOS) and inulin are the most used fructans in food manufacturing, including bakery, dairy, meat products and beverages. In this context, this review investigated the recent findings concerning health claims associated with a diet supplemented with fructans according to human trial results. Fructans have been applied in different food classes due to their proven benefits to human health. Human clinical trials have revealed several effects of fructans supplementation on health such as improved glycemic control, growth of beneficial gut bacteria, weight management, positive influence on immune function, and others. These dietary fibers have a wide range of compounds with different molecular sizes, implying a great variety of technological properties depending on the food application of interest. Inulin has been mainly applied as a fat substitute and prebiotic ingredient. In general, inulin reduces the energy content and improves the structure, viscosity, emulsion, and water retention parameters of food products. Meanwhile, FOS have been more successful when used as a sucrose substitute and prebiotic ingredient. However, overall, FOS and inulin are promising alternatives for the development of structured systems dedicated to increase the functionality of foods and beverages besides reducing fat in bakery, dairy, and meat products.

Characterization of levans produced by levansucrases from Bacillus amyloliquefaciens and Gluconobacter oxydans: Structural, techno-functional, and anti-inflammatory properties

Levans of different structures and molecular weights (MW) can display various techno-functional and health-promoting properties. In the present study, selected levans were produced by the transfructosylation of sucrose catalyzed by levansucrases from Bacillus amyloliquefaciens and Gluconobacter oxydans, and their structural, techno-functional and anti-inflammatory properties were investigated. NMR and methylation/GC analysis confirmed the structure of β-(2, 6) levans. The structural characterization led to the classification of levans as high MW (HMW, ≥100 kDa), low MW (LMW, ≤20 kDa) and mix L/HMW ones. Levan with higher MW had more linear fructosyl units with fewer reducing ends and branching residues. LMW levan showed the highest foaming capacity and stability while HMW levan had the highest emulsion stability. HMW and mix L/HMW levans showed comparable water and oil-holding capacities, which were higher than LMW. HMW and mix L/HMW levans were found to have gelling properties at low concentrations. The rheological behaviour of HMW levan-based gel was a more viscous-like gel, while that of mix L/HMW levan-based one showed more elastic solid like-gel. The temperature also influenced the rheology of levan, showing that the mix L/HMW levan gel network was the most thermal stable as its viscoelasticity remained constant at the highest temperature (75 °C). Studies on the biological activity of levans of HMW and LMW revealed in-vitro anti-inflammatory properties as they significantly reduced the production of LPS-triggered pro-inflammatory cytokines in differentiated Caco-2 cells.

Insights into the heterogeneity of levan polymers synthesized by levansucrase Bs-SacB from Bacillus subtilis 168

Levan is an enzymatically synthesized fructose polymer with widely reported structural heterogeneity depending on the producing levansucrase, the reaction conditions employed for its synthesis and the characterization techniques. We studied here the specific properties of levan produced by recombinant levansucrase from B. subtilis 168 (Bs-SacB), often characterized as a bimodal distribution, that is, a mixture of low and high molecular weight levan. We found significant differences between both levans in terms of the already reported molecular weight, size and morphology using different analytical methods. The low molecular weight levan consists of a non-uniform polymer ranging from 50 to 230 kDa, synthesized through a non-processive mechanism that can spontaneously form spherical nanoparticles in the reaction medium. In contrast, high molecular weight levan is a uniform polymer, most probably synthesized through a processive mechanism, with an average molecular weight of 30,750 kDa and a poorly defined nano-structure. This is the first report exploring differences in morphology between low and high molecular weight levans. Our findings demonstrate that only the low molecular weight levan forms spherical nanoparticles in the reaction medium and that high molecular weight levan is mainly composed of a 33,000 kDa fraction with a microgel behavior.

Similarities and differences of nano-sized levan synthesized by Bacillus haynesii at low and high temperatures: Characterization and bioactivity

Levan is a biopolymer with many different uses. Temperature is an important parameter in biopolymer synthesis. Herein, levan production was carried out from Bacillus haynesii, a thermophilic microorganism, in the temperature range of 4 °C-95 °C. The highest levan production was measured as 10.9 g/L at 37 °C. The synthesized samples were characterized by FTIR and NMR analysis. The particle size of the levan samples varied between 153 and 824.4 nm at different temperatures. In levan samples produced at high temperatures, the water absorption capacity is higher in accordance with the particle size. Irregularities were observed in the surface pores at temperatures of 60 °C and above. The highest emulsion capacity of 83.4 % was measured in the sample synthesized at 4 °C. The antioxidant activity of all levan samples synthesized at different temperatures was measured as 84 % on average. All synthesized levan samples showed antibacterial effect on pathogenic bacteria. In addition, levan synthesized at 45 °C showed the highest antimicrobial effect on E. coli ATCC 35218 with an inhibition zone of 21.3 ± 1.82 mm. Antimicrobial activity against yeast sample C. albicans, was measured only in levan samples synthesized at 80 °C, 90 °C, 95 °C temperatures. Levan synthesized from Bacillus haynesii at low and high temperatures showed differences in characterization and bioactivity.

Glycoside hydrolase family 32 enzymes from Bombella spp. catalyze the formation of high-molecular weight fructans from sucrose

AIMS

Acetic acid bacteria of the genus Bombella have not been reported to produce exopolysaccharides (EPS). In this study, the formation of fructans by B. apis TMW 2.1884 and B. mellum TMW 2.1889 was investigated.

METHODS AND RESULTS

Out of eight strains from four different Bombella species, only B. apis TMW 2.1884 and B. mellum TMW 2.1889 showed EPS formation with 50 g l-1 sucrose as substrate. Both EPS were identified as high-molecular weight (HMW) polymers (106-107 Da) by asymmetric flow field-flow fractionation coupled to multi angle laser light scattering and UV detecors (AF4-MALLS/UV) and high performance size exclusion chromatography coupled to MALLS and refractive index detectors (HPSEC-MALLS/RI) analyses. Monosaccharide analysis via trifluoroacetic acid hydrolysis showed that both EPS are fructans. Determination of glycosidic linkages by methylation analysis revealed mainly 2,6-linked fructofuranose (Fruf) units with additional 2,1-linked Fruf units (10%) and 2,1,6-Fruf branched units (7%). No glycoside hydrolase (GH) 68 family genes that are typically associated with the formation of HMW fructans in bacteria could be identified in the genomes. Through heterologous expression in Escherichia coli Top10, an enzyme of the GH32 family could be assigned to the catalysis of fructan formation. The identified fructosyltransferases could be clearly differentiated phylogenetically and structurally from other previously described bacterial fructosyltransferases.

CONCLUSIONS

The formation of HMW fructans by individual strains of the genus Bombella is catalyzed by enzymes of the GH32 family. Analysis of the fructans revealed an atypical structure consisting of 2,6-linked Fruf units as well as 2,1-linked Fruf units and 2,1,6-Fruf units.

Fructose-Containing Plant Carbohydrates: Biological Activities and Medical Applications

The review considers the chemical structure specifics and distribution in plants for fructose-containing carbohydrates (fructans). Various biological activities were observed in fructans and associated with their physicochemical features. Fructans affect many physiological and biochemical processes in the human body, improving health and reducing the risk of various disorders. Prebiotic activity is the most important physiological function of fructans. Fructans improve the microflora composition in the colon and intestinal mucosa by increasing the content of useful bacteria and decreasing the content of potentially harmful microorganisms, stimulate the physiological functions of the microflora, and provide for a better state of the intestine and a better health status. By modifying the intestinal microbiota and utilizing certain additional mechanisms, fructans can favorably affect the immune function, decrease the risk of various inflammatory processes, and to reduce the likelihood of tumorigenesis due to exposure to carcinogens. Fructans improve carbohydrate and lipid metabolism by reducing the blood levels of glucose, total cholesterol, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL) and increasing the blood content of high-density lipoprotein (HLD). Fructans are low in calories, and their use in foods reduces the risk of obesity. Fructans facilitate higher calcium absorption and increase the bone density, thus reducing the risk of osteoporosis. Fructants protect the body from oxidative stress, intestinal infections, and parasitic invasions.

Hydrolysis-transglycosylation of sucrose and production of β-(2→1)-fructan by inulosucrase from Neobacillus drentensis 57N

Inulin, β-(2→1)-fructan, is a beneficial polysaccharide used as a functional food ingredient. Microbial inulosucrases (ISs), catalyzing β-(2→1)-transfructosylation, produce β-(2→1)-fructan from sucrose. In this study, we identified a new IS (NdIS) from the soil isolate, Neobacillus drentensis 57N. Sequence analysis revealed that, like other Bacillaceae ISs, NdIS consists of a glycoside hydrolase family 68 domain and shares most of the 1-kestose-binding residues of the archaeal IS, InuHj. Native and recombinant NdIS were characterized. NdIS is a homotetramer. It does not require calcium for activity. High performance liquid chromatography and 13C-nuclear magnetic resonance indicated that NdIS catalyzed the hydrolysis and β-(2→1)-transfructosylation of sucrose to synthesize β-(2→1)-fructan with chain lengths of 42 or more residues. The rate dependence on sucrose concentration followed hydrolysis-transglycosylation kinetics, and a 50% transglycosylation ratio was obtained at 344 m m sucrose. These results suggest that transfructosylation from sucrose to β-(2→1)-fructan occurs predominantly to elongate the fructan chain because sucrose is an unfavorable acceptor.

Synthesis and molecular characterization of levan produced by immobilized Microbacterium paraoxydans

In this study, we report high molecular weight (HMW) levan production by whole cells of Microbacterium paraoxydans, previously reported to be a good producer of fructooligosaccharides. Structural analysis of the extracellularly produced fructan indicated the glycosidic bonds between the adjacent fructose to be of β-(2, 6) linkage with over 90% of the fructan to have molecular weight around 2 × 108 Da and 10% with a molecular weight of ∼20 kDa. Immobilization of the cells in Ca-alginate led to the production of 44.6 g/L levan with a yield of 0.29 g/g sucrose consumed. Factors affecting the conversion rate were identified by One-Factor-At-a-Time (OFAT) analysis and the combination of these (initial sucrose concentration of 400 g/L, 100 mM buffer pH 7, the temperature of 37 °C and 20 mM CaCl2) led to the production of ∼129 g/L of levan with a yield of ∼0.41 g/g sucrose consumed and volumetric productivity of 1.8 g/L/h.

Inulin-type fructans obtained from Atractylodis Macrocephalae by water/alkali extraction and immunoregulatory evaluation

Two homogenous polysaccharides extracted from Atractylodes macrocephala Koidz. were investigated by water extraction (AMP-F_W) and alkali solution extraction (AMP-F_A) after purification by anion exchange column and size exclusion chromatography. The molecular weight of AMP-F_W and AMP-F_A were 2874 Da and 3438 Da, respectively, estimated by high performance gel permeation chromatography (HPGPC). The monosaccharide compositions of AMP-F_W and AMP-F_A were glucose and fructose at a molar ratio of 0.11:0.89 determined by high performance anion exchange chromatography (HPAEC). The functional groups, glycosidic linkages and the chemical structure were characterized by FT-IR, GC-MS and NMR, which comprehensively indicated a similar inulin-type fructan structure of the two polysaccharides from A. macrocephala. However, the scanning electron microscopy (SEM) results showed different microstructures that irregular lamellar shape for the AMP-F_W and spheroid shape for the AMP-F_A. The further studies on immunomodulation showed that AMP-F_W at 50 μg/mL could significantly (P < 0.05) stimulate RAW 264.7 cells by enhancing the mRNA expression of TNF-α and IL-1β, which had a relative high immunomodulatory potential when compared to AMP-F_A. Their activation on different toll-like receptors (TLR) also indicated their different roles in the immunoregulation. Overall, these findings reported here will serve as the basis for further structure-activity relationship studies.

Preparation, Structural Characterisation, and Bioactivities of Fructans: A Review

Polysaccharides are important components of higher plants and have attracted increasing attention due to their many nutraceutical benefits in humans. Fructans, heterogeneous fructose polymers that serve as storage carbohydrates in various plants, represent one of the most important types of natural polysaccharides. Fructans have various physiological and therapeutic effects, which are beneficial to health, and have the ability to prevent or treat various diseases, allowing their wide use in the food, nutraceutical, and pharmaceutical industries. This article reviews the occurrence, metabolism, preparation, characterisation, analysis, and bioactivity of fructans. Further, their molecular weight, monosaccharide composition, linkages, and structural determination are described. Taken together, this review provides a theoretical foundation for further research into the structure-function relationships of fructans, as well as valuable new information and directions for further research and application of fructans in functional foods.

Complete secretion of recombinant Bacillus subtilis levansucrase in Pichia pastoris for production of high molecular weight levan

Three signal peptides from α-mating factor (α-MF), inulinase (INU) and native levansucrase (LS) were compared for secretion efficiency of Bacillus subtilis levansucrase SacB-T305A in Pichia pastoris GS115. The first complete secretion of bacterial levansucrase in yeasts under methanol induction was achieved while using α-MF signal. The secreted recombinant Lev(α-MF) proved to be glycosylated by combination of NanoLC-MS/MS and Endo H digestion. Interestingly, glycosylation not only improved significantly the polymerase thermostability, but also reversed the products profiles to favor synthesis of high molecular weight (HMW) levan which accounted for approximately 73 % to total levan-type polysaccharides. It indicated for the first time that the glycosylation of recombinant B. subtilis levansucrase affected significantly the products molecular weight distribution. It also provided a promising enzymatic way to effectively product HMW levan from sucrose resources.

Lipopolysaccharide associated with β-2,6 fructan mediates TLR4-dependent immunomodulatory activity in vitro

Levan, a β-2,6 fructofuranose polymer produced by microbial species, has been reported for its immunomodulatory properties via interaction with toll-like receptor 4 (TLR4) which recognises lipopolysaccharide (LPS). However, the molecular mechanisms underlying these interactions remain elusive. Here, we investigated the immunomodulatory properties of levan using thoroughly-purified and characterised samples from Erwinia herbicola and other sources. E. herbicola levan was purified by gel-permeation chromatography and LPS was removed from the levan following a novel alkali treatment developed in this study. E. herbicola levan was then characterised by gas chromatography-mass spectrometry and NMR. We found that levan containing LPS, but not LPS-depleted levan, induced TLR4-mediated cytokine production by bone marrow-derived dendritic cells and/or activated TLR4 reporter cells. These data indicated that the immunomodulatory properties of the levan toward TLR4-expressing immune cells were mediated by the LPS. This work also demonstrates the importance of LPS removal when assessing the immunomodulatory activity of polysaccharides.

A dandelion polysaccharide and its selenium nanoparticles: Structure features and evaluation of anti-tumor activity in zebrafish models

In this study, an inulin fructan (TMP50-2) with moderate anti-tumor activity was obtained from dandelion. To further improve the anti-tumor activity of TMP50-2, a monodisperse and stable spherical nanoparticle (Tw-TMP-SeNP, 50 nm) was fabricated. Physico-chemical analysis revealed that TMP50-2 and Tween 80 were tightly wrapped on the surface of SeNPs by forming CO⋯Se bonds or through hydrogen bonding interaction (OH⋯Se). In vitro anti-tumor assay showed that Tw-TMP-SeNP treatment could significantly inhibit the proliferation of cancer cells (HepG2, A549, and HeLa) in a dose-dependent manner, while HepG2 cells were more susceptible to Tw-TMP-SeNP with an IC₅₀ value of 46.8 μg/mL. The apoptosis induction of HepG2 cells by Tw-TMP-SeNP was evidenced by increasing the proportion of apoptotic cells ranging from 12.5% to 27.4%. Furthermore, in vivo zebrafish model confirmed the anti-tumor activity of Tw-TMP-SeNP by inhibiting the proliferation and migration of tumor cells as well as the angiogenesis of zebrafish embryos.

Box-Wilson Design for Optimization of in vitro Levan Production and Levan Application as Antioxidant and Antibacterial Agents

Background

Levan or fructan, a polysaccharide of fructose, is widely used in various commercial industries. Levan could be produced by many organisms, including plants and bacteria. The cloning of the gene from Bacillus licheniformis, which expressed levansucrase in Escherichia coli host, was carried out successfully. In the present study, we performed the in vitro production of levan and analyzed its potential application as antibacterial and antioxidant agents.

Methods

In vitro levan production catalyzed by heterologous-expressed levansucrase Lsbl-bk1 and Lsbl-bk2 was optimized with Box-Wilson design. The antibacterial activity of the produced levan was carried out using agar well diffusion method, while its antioxidant activity was tested by free radical scavenging assays.

Results

The optimum conditions for levan production were observed at 36 °C and pH 7 in 12% (w/v) sucrose for levansucrase Lsbl-bk1, while the optimum catalysis of levansucrase Lsbl-bk2 was obtained at 32 oC and pH 8 in the same sucrose concentration. The in vitro synthesized levan showed an antibacterial activity within a concentration range of 10-20% (w/v) against Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa. The same levan was also able to inhibit the 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity with the antioxidant strength of 75% compared to ascorbic acid inhibition.

Conclusion

Our study, therefore, shows that the optimized heterologous expression of levansucrases encoded by Lsbl-bk1 and Lsbl-bk2 could open the way for industrial levan production as an antibacterial and antioxidant agent.

Characterization of inulin-type fructans from two species of Radix Codonopsis and their oxidative defense activation and prebiotic activities

BACKGROUND

Codonopsis pilosula and C. tangshen are both plants widely used in traditional Chinese medicine. Polysaccharides, which are their primary active components, are thought to be important in their extensive use. In this study, two neutral polysaccharide fractions of C. pilosula (CPPN) and C. tangshen (CTPN) were obtained by fractionation on a DEAE-Sepharose column and characterized.

RESULTS

It was confirmed that the neutral polymers CPPN and CTPN were β-(2,1)-linked inulin-type fructans with non-reducing terminal glucose, and degree of polymerization (DP) of 19.6 and 25.2, respectively. The antioxidant and prebiotic activities in vitro were assayed based on IPEC-J2 cell lines and five strains of Lactobacillus. Results indicated that the effects of CPPN and CTPN were increased antioxidant defense in intestinal epithelial cells through enhanced cell viability, improved expression of total antioxidant capacity, glutathione peroxidase, superoxide dismutase and catalase, and reduced levels of malondialdehyde and lactic dehydrogenase. The prebiotic activity of CPPN and CTPN was demonstrated by the promoting effect on Lactobacillus proliferation in vitro. The different biological activities obtained between the two fractions are probably due to the different DP and thus molecular weights of CPPN and CTPN.

CONCLUSION

The inulin fractions from C. pilosula and C. tangshen were natural sources of potential intestinal antioxidants as well as prebiotics, which will be valuable in further studies and new applications of inulin-containing health products. © 2020 Society of Chemical Industry.

Targeted Hybrid Nanocarriers as a System Enhancing the Skin Structure

The skin is constantly exposed to external and internal factors that disturb its function. In this work, two nanosystems-levan nanoparticles and a surfactin-stabilized nanoemulsion were preserved (tested for microbial growth) and characterized (size, polydispersity, Zeta potential, and stability). The nanosystems were introduced in the model formulations-cream, tonic, and gel, and confirmed by TEM. The analysis showed that nanoemulsion has a spherical morphology and size 220–300 nm, while levan nanoparticles had irregular shapes independently of the use of matrix and with particle size (130–260 nm). Additionally, we examined the antiradical effect of levan nanoparticles and nanoemulsion in the prototype of formulations by scavenging DPPH (2,2-diphenyl-1-picrylhydrazyl; EPR spectroscopy). The model cream with both nanosystems and the whole range of products with nanosystems were evaluated in vivo for hydration, elasticity, smoothness, wrinkles and vascular lesions, discoloration, respectively. The cream improved skin condition in all tested parameters in at least 50% of volunteers. The use of more comprehensive care, additionally consisting of a tonic and gel, reduced the previously existing skin discoloration to 10.42 ± 0.58%. The presented prototype formulations are promising in improving skin conditions.

Structure-Based Identification of Natural Products as SARS-CoV-2 Mpro Antagonist from Echinacea angustifolia Using Computational Approaches

Coronavirus disease-19 (COVID-19) pandemic, caused by the novel SARS-CoV-2 virus, continues to be a global threat. The number of cases and deaths will remain escalating due to the lack of effective therapeutic agents. Several studies have established the importance of the viral main protease (Mpro) in the replication of SARS-CoV-2 which makes it an attractive target for antiviral drug development, including pharmaceutical repurposing and other medicinal chemistry approaches. Identification of natural products with considerable inhibitory potential against SARS-CoV-2 could be beneficial as a rapid and potent alternative with drug-likeness by comparison to de novo antiviral drug discovery approaches. Thereof, we carried out the structure-based screening of natural products from Echinacea-angustifolia, commonly used to prevent cold and other microbial respiratory infections, targeting SARS-CoV-2 Mpro. Four natural products namely, Echinacoside, Quercetagetin 7-glucoside, Levan N, Inulin from chicory, and 1,3-Dicaffeoylquinic acid, revealed significant docking energy (>-10 kcal/mol) in the SARS-CoV-2 Mpro catalytic pocket via substantial intermolecular contacts formation against co-crystallized ligand (<-4 kcal/mol). Furthermore, the docked poses of SARS-CoV-2 Mpro with selected natural products showed conformational stability through molecular dynamics. Exploring the end-point net binding energy exhibited substantial contribution of Coulomb and van der Waals interactions to the stability of respective docked conformations. These results advocated the natural products from Echinacea angustifolia for further experimental studies with an elevated probability to discover the potent SARS-CoV-2 Mpro antagonist with higher affinity and drug-likeness.

Fructans Are Differentially Distributed in Root Tissues of Asparagus

Inulin- and neoseries-type fructans [fructooligosaccharides (FOS) and fructopolysaccharides] accumulate in storage roots of asparagus (Asparagus officinalis L.), which continue to grow throughout the lifespan of this perennial plant. However, little is known about the storage of fructans at the spatial level in planta, and the degree of control by the plant is largely uncertain. We have utilized mass spectrometry imaging (MSI) to resolve FOS distribution patterns in asparagus roots (inner, middle, and outer tissues). Fructan and proteome profiling were further applied to validate the differential abundance of various fructan structures and to correlate observed tissue-specific metabolite patterns with the abundance of related fructan biosynthesis enzymes. Our data revealed an increased abundance of FOS with higher degree of polymerization (DP > 5) and of fructopolysaccharides (DP11 to DP17) towards the inner root tissues. Three isoforms of fructan:fructan 6G-fructosyltransferase (6G-FFT), forming 6G-kestose with a β (2-6) linkage using sucrose as receptor and 1-kestose as donor, were similarly detected in all three root tissues. In contrast, one ß-fructofuranosidase, which likely exhibits fructan:fructan 1-fructosyltransferase (1-FFT) activity, showed very high abundance in the inner tissues and lower levels in the outer tissues. We concluded a tight induction of the biosynthesis of fructans with DP > 5, following a gradient from the outer root cortex to the inner vascular tissues, which also correlates with high levels of sucrose metabolism in inner tissues, observed in our study.

Raman spectroscopy for the analysis of different exo-polysaccharides produced by bacteria

In this study, Raman spectroscopy is employed for the characterization and comparison of two different classes of exo-polysaccharides including glucans and fructans which are produced by different bacteria. For this purpose, nine samples are used including five samples of glucans and four of fructans. Raman spectral results of all these polysaccharides show clear differences among various glucans as well as fructans showing the potential of this technique to identify the differences within the same class of the compounds. Moreover, these two classes are also compared on the basis of their Raman spectral data and can be differentiated on the basis of their unique Raman features. Multivariate data analysis techniques, Principle Component Analysis (PCA) is found very helpful for the comparison of the Raman spectral data of these classes of the carbohydrates.

Apoplastic maize fructan exohydrolase Zm-6-FEH displays substrate specificity for levan and is induced by exposure to levan-producing bacteria

Fructan exohydrolases (FEHs) are structurally related to cell wall invertases. While the latter are ubiquitous in higher plants, the role of FEHs in non-fructan species has remained enigmatic. To explore possible roles of FEHs in maize, a full length putative Zm-6-FEH-encoding cDNA was cloned displaying high sequence similarity with cell wall invertases. For functional characterization, Zm-6-FEH protein was expressed in Picha pastoris and in Nicotiana benthamiana leaves. Enzyme activity of recombinant Zm-6-FEH protein showed a strong preference for levan as substrate. Expression profiling in maize seedlings revealed higher transcript amounts in the more mature leaf parts as compared to the growth zone at the base of the leaf, in good correlation with FEH enzyme activities. Subcellular localization analysis indicated Zm-6-FEH location in the apoplast. Noteworthy, incubation of leaf discs with levan and co-incubation with high levan-producing bacteria selectively up-regulated transcript levels of Zm-6-FEH, accompanied by an increase of 6-FEH enzyme activity. In summary, the results indicate that Zm-6-FEH, a novel fructan exohydrolase of a non-fructan species, may have a role in plant defense against levan-producing bacteria.

Fabrication and Application of Levan-PVA Hydrogel for Effective Influenza Virus Capture

To prevent the transmission of pathogenic microorganisms such as the influenza virus, efficient pathogen-capturing materials are required. Here, we report a new pathogen-capturing and recovery material using levan polysaccharide. We fabricated hydrogels by blending levan and poly(vinyl alcohol) (PVA) and by using glutaraldehyde as a cross-linking agent. Fabricated levan-PVA hydrogels have a high water solubility and water adsorption ability. SEM observations showed that levan-PVA hydrogels have a 3D porous structure. We confirmed by RT-PCR analysis that the influenza virus capture efficiency of levan-PVA hydrogels is higher than that of commercial cotton swabs. Moreover, we confirmed that levan-PVA hydrogels on gauze as a filter material effectively captured bioaerosol samples. Therefore, levan-PVA hydrogels are expected to serve as simple and efficient pathogen capture and recovery materials.

Fermentation of Chicory Fructo-Oligosaccharides and Native Inulin by Infant Fecal Microbiota Attenuates Pro-Inflammatory Responses in Immature Dendritic Cells in an Infant-Age-Dependent and Fructan-Specific Way

SCOPE

Inulin-type fructans are commonly applied in infant formula to support development of gut microbiota and immunity. These inulin-type fructans are considered to be fermented by gut microbiota, but it is unknown how fermentation impacts immune modulating capacity and whether the process of fermentation is dependent on the infant's age.

METHODS AND RESULTS

The in vitro fermentation of chicory fructo-oligosaccharides (FOS) and native inulin are investigated using pooled fecal inocula of two- and eight-week-old infants. Both inocula primarily utilize the trisaccharides in FOS, while they almost completely utilize native inulin with degree of polymerization (DP) 3-8. Fecal microbiota of eight-week-old infants degrades longer chains of native inulin up to DP 16. This correlates with a higher abundance of Bifidobacterium and higher production of acetate and lactate after 26 h of fermentation. Fermented FOS and native inulin attenuate pro-inflammatory cytokines produced by immature dendritic cells (DCs), but profiles and magnitude of attenuation are stronger with native inulin than with FOS.

CONCLUSION

The findings demonstrate that fermentation of FOS and native inulin is dependent on the infant's age and fructan structure. Fermentation enhances attenuating effects of pro-inflammatory responses in DCs, which depend mainly on microbial metabolites formed during fermentation.

Bacillus licheniformis levan as a functional biopolymer in topical drug dosage forms: From basic colloidal considerations to actual pharmaceutical application

Ongoing demand in sustainable and biocompatible drug dosage forms is reflected in the search for novel pharmaceutical excipients with equal properties. A group of microbial exopolysaccharides offers a variety of biopolymers with many alleged uses and effects. This study aims to assess applicative properties of levan obtained from Bacillus licheniformis NS032, focusing on its potential co-stabilizing and drug release-controlling functions in pertaining emulsion systems. Despite its high molecular weight and partial existence in globular nanometric structures (180-190 nm), levan was successfully incorporated into both tested colloidal systems: those stabilized with synthetic/anionic or natural-origin/non-ionic emulsifiers. In the tested levan concentrations range (0.2-3.0% w/w) the monitored flow and thermal parameters failed to show linear concentration dependence, which prompted us to revisit certain colloidal fundamentals of this biopolymer. Being a part of the external phase of the investigated emulsion systems, levan contributed to formation of a matrix-like environment, offering additional stabilization of the microstructure and rheology modifying properties (hysteresis loop elevation as high as 4167±98 to 20792±3166 Pa•s^-1), especially in case of the samples where lamellar liquid crystalline formation occurred. Apart from its good water solubility and considerable conformational flexibility, the investigated homofructan easily saturated the external phase of the samples stabilized with a conventional anionic emulsifier, leading to similar properties of 0.2% and 3.0% levan-containing samples. After closer consideration of thermal and release behavior, this was considered as a favorable property for a novel excipient, offering tailored formulation characteristics even with lower levan concentrations, consequently not compromising the potential cost of the final drug dosage form.

Fructans as Immunomodulatory and Antiviral Agents: The Case of Echinacea

Throughout history, medicinal purposes of plants have been studied, documented, and acknowledged as an integral part of human healthcare systems. The development of modern medicine still relies largely on this historical knowledge of the use and preparation of plants and their extracts. Further research into the human microbiome highlights the interaction between immunomodulatory responses and plant-derived, prebiotic compounds. One such group of compounds includes the inulin-type fructans (ITFs), which may also act as signaling molecules and antioxidants. These multifunctional compounds occur in a small proportion of plants, many of which have recognized medicinal properties. Echinacea is a well-known medicinal plant and products derived from it are sold globally for its cold- and flu-preventative and general health-promoting properties. Despite the well-documented phytochemical profile of Echinacea plants and products, little research has looked into the possible role of ITFs in these products. This review aims to highlight the occurrence of ITFs in Echinacea derived formulations and the potential role they play in immunomodulation.

Fast super/subcritical fluid chromatographic enantioseparations on superficially porous particles bonded with broad selectivity chiral selectors relative to fully porous particles

Superficially porous particles (SPPs) have shown advantages in enantiomeric separations in HPLC by conserving selectivity while providing higher efficiency separations with significantly reduced analysis times. The question arises as to whether the same advantages can be found to the same extent in super/subcritical fluid chromatography. In this work, the low viscosity advantage of carbon dioxide/MeOH mixtures is coupled with high-efficiency 2.7 μm superficially porous particles for enantiomeric separations. Given the fact that the viscosity of the mobile phase is typically ten times lower than liquid mobile phases it is possible to use flow rates as high as 14 mL/min on 5 cm packed columns. Superficially porous particles (SPPs) were grafted with teicoplanin (TeicoShell), a chemically modified macrocyclic glycopeptide (NicoShell), vancomycin (VancoShell), and isopropyl derivatized cyclofructan-6 (LarihcShell-P). One hundred chiral analytes were separated in a very short time frame, as little as 0.2 min (13 s). Even shorter separations can be obtained with advances in SFC instrumentation. The LarihcShell-P is the only chiral crown ether-based selector which showed high selectivity for primary amines. The Teicoshell column offered unique separations for acidic and neutral analytes. The NicoShell and the VancoShell were useful in separating amine (secondary and tertiary) containing pharmaceutical drugs and controlled substances. By chemically modifying a macrocyclic glycopeptide (NicoShell) we report the first enantiomeric separation of nicotine under SFC conditions within 3 min with a resolution of >3. Additionally, van Deemter plots are constructed comparing the fully porous particles and superficially porous particles bonded with the same chiral selectors. In toto the SPP advantages also were found for SFC. However instrumental shortcomings involving extra column effects and pressure limitations need to be addressed by instrument manufacturers to realize the full advantages of SPPs and other smaller particle supports.

New Levan-Type Exopolysaccharide from Bacillus amyloliquefaciens as an Antiadhesive Agent against Enterotoxigenic Escherichia coli

A special levan-type exopolysaccharide (EPS) from Bacillus amyloliquefaciens JN4 with antiadhesive activity against enterotoxigenic Escherichia coli (ETEC) was purified and identified. Chemical analysis indicated that EPS-JN4 with a low molecular weight of 8 kDa is composed of fructose and glucose with a molar ratio of 46.1:1. Structural analysis clarified that EPS-JN4 contains a main chain of β-(2,6)-linked Fruf residues and intensive branches of a single 2-linked Fruf at every six residues. Furthermore, the superior antiadhesive activity of EPS-JN4 against ETEC showed its potential usage as an antiadhesive agent for diarrhea prevention. EPS-JN4 is a specific type of levan family, for its small molecular size and intensive branches. The results expand the knowledge on structural types of levan and illustrate its potential as an antiadhesive agent for diarrhea prevention, which will be conducive to elucidate the relation between structure and function.

Adsorptive removal of bisphenol A from aqueous solutions using phosphonated levan

In this study, the potential use of phosphonated Halomonas Levan (PhHL) as a natural and cost effective adsorbent for Bisphenol A (BPA), was systematically investigated via the study of the adsorption equilibrium, kinetics, and reuse potential as well as the interpretation of adsorption mechanism. The effects of pH and temperature on the adsorption were also evaluated. The maximum amount of BPA adsorbed on the unit weight of PhHL was determined as 104.8 (∓5.02) mg/g (at 298 K) and the maximum adsorption capacity was calculated as 126.6 mg/g by Sips model. FTIR and XPS studies were conducted to elucidate the adsorption mechanism. Based on the obtained results OH-pi and CH-pi interactions were found to be effective in the adsorption mechanism. The reuse ability was studied with three cycles of adsorption-desorption, and the results showed that the BPA adsorbed per gram of the PhHL decreased 28.6% after the third cycle. This study has shown that PhHL can be used as an effective adsorbent for the removal of BPA from aqueous solutions. The obtained results may be useful in the development of PhHL based adsorption systems for the removal of EDCs with similar chemical properties to BPA.

Effect of the Degree of Polymerization of Fructans on Ex Vivo Fermented Human Gut Microbiome

Prebiotic supplements are used to promote gastrointestinal health by stimulating beneficial bacteria. The aim of this study was to compare the potential prebiotic effects of fructans with increasing degrees of polymerization, namely fructooligosaccharides (FOS) and inulins with a low and high polymerization degree (LPDI and HPDI, respectively), using an ex vivo fermentation system to simulate the colonic environment. The system was inoculated with pooled feces from three healthy donors with the same baseline enterotype. Changes in microbiota composition were measured by 16S metagenomic sequencing after 2, 7, and 14 days of fermentation, and acid production was measured throughout the experiment. Alpha-diversity decreased upon inoculation of the ex vivo fermentation under all treatments. Composition changed significantly across both treatments and time (ANOSIM p < 0.005 for both factors). HPDI and LPDI seemed to be similar to each other regarding composition and acidification activity, but different from the control and FOS. FOS differed from the control in terms of composition but not acidification. HDPI restored alpha-diversity on day 14 as compared to the control (Bonferroni p < 0.05). In conclusion, the prebiotic activity of fructans appears to depend on the degree of polymerization, with LPDI and especially HPDI having a greater effect than FOS.

Characterization of Inulin-Type Fructan from Platycodon grandiflorus and Study on Its Prebiotic and Immunomodulating Activity

Platycodon grandiflorus is a plant widely used in traditional Chinese medicine, of which polysaccharides are reported to be the main components responsible for its bio-functions. In this work, the inulin-type fructan (PGF) was obtained by DEAE anion exchange chromatography from the water extracted from P. grandifloras. Characterization was performed with methanolysis, methylation, and NMR and the results showed that PGF is a β-(2-1) linked fructan, with terminal glucose and with a degree of polymerization of 2–10. In order to study its biofunctions, the prebiotic and immunomodulation properties were assayed. We found that PGF exhibited good prebiotic activity, as shown by a promotion on six strains of lactobacillus proliferation. Additionally, the PGF also displayed direct immunomodulation on intestinal epithelial cells and stimulated the expressions of anti-inflammatory factors. These results indicated that the inulin from P. grandiflorus is a potential natural source of prebiotics as well as a potential intestinal immunomodulator, which will be valuable for further studies and new applications.

Levan-Capped Silver Nanoparticles for Bactericidal Formulations: Release and Activity Modelling

An environmentally friendly technique was used to produce levan-capped silver nanoparticles of about 30 nm (with a loading of 30%) that showed bactericide effect, for E. coli and B. subtilis. That effect was mathematically studied with a dose-response model (lethal dose of 12.4 ppm and 6.8 ppm respectively). These silver nanoparticles were subsequently introduced in a gel to create a silver release system with bacteria inhibition activity. Silver release from the gel and its bactericidal activity was theoretically studied to develop a unique model that is able to predict accurately both silver release and lethal dose for any type of bacteria. This model will be useful for performing predictions for future silver in gel applications.

Quantification of free sugars, fructan, pungency and sweetness indices in onion populations by FT-MIR spectroscopy

BACKGROUND

To facilitate faster phenotyping of onions (Allium cepa L.), Fourier-transform mid infrared (FT-MIR) spectroscopy with partial least squares (PLS) regression modelling was evaluated for the determination of pungency (pyruvate), sweetness (free sugars) and fructan in juice samples (n = 605) expressed from bulbs from breeding populations.

RESULTS

Fourier-transform infrared (FTIR) spectra (range 1700-900 cm^-1 ) were obtained from droplets (30 μL) of unprocessed juice. Goodness-of-fit (r² ) and prediction errors (standard error of cross validation) for optimal PLS models were: soluble solids (0.997, 0.1 °Brix), pyruvate [0.825, 0.8 μmol g^-1 fresh weight (FW)], fructan (0.98, 1.9 mg g^-1 FW), glucose (0.941, 1.1 mg g^-1 FW), fructose (0.967, 1.0 mg g^-1 FW) and sucrose (0.919, 1.7 mg g^-1 FW). FTIR models for industry sweetness indices based on glucose or sucrose equivalents were also developed. Because of its very low concentration (0.8-12 μmol g^-1 FW) relative to other compounds, pyruvate was the weakest model developed. Fructan could be determined spectroscopically without the need for enzymatic digestion.

CONCLUSIONS

All of the chemometric models developed are acceptable for screening purposes. Those for soluble solids, fructan and fructose are also suitable for routine analysis. FT-MIR can therefore be utilised for the simultaneous determination of pungency, sweetness and fructan in this crop. © 2018 Society of Chemical Industry.

Preparation of a novel water-soluble gel from Erwinia amylovora levan

Less attention has been focused on the industrial applications of levan-type fructan than that of inulin. Levan-type fructan is a unique homopolysaccharide consisting of fructose residues with a β-(2, 6) linkage that possesses unique physiochemical properties such as low intrinsic viscosity. In this study, the recombinant levansucrase from Erwinia amylovora was used to efficiently produce levan from sucrose, and under optimised conditions, 195 g/L levan was produced from 500 g/L sucrose, with the highest conversion rate of 59%. The physicochemical properties of E. amylovora levan, such as surface morphology, thermal behaviour, rheology behaviour and texture analysis, were evaluated and compared with those of commercial gels, including xanthan, guar, carrageenan and Arabic gums. The produced E. amylovora levan showed a series of acceptable physicochemical properties, indicating a potential application for levan as a novel water-soluble micro gel. The conclusions of this study support the exploration of the use of more hydrogels in the food, medicinal and cosmetic industries.

Fructooligosaccharides and appetite

PURPOSE OF REVIEW

Dietary fiber may play a role in obesity prevention through reduction of body weight and control of appetite, however, not all fibers are created equally, and characteristics of fiber such as viscosity, fermentability and solubility may affect appetite differently.

RECENT FINDINGS

Although early studies supported that fructan fibers, including inulin, fructooligosaccharides, and oligofructose affected satiety, more recent studies are less supportive. We found that a higher dose of fiber such as oligofructose (16 g/day) is needed and for a longer duration (12-16 weeks) to detect differences in appetite and subsequent energy intake, whereas, practical amounts of fructooligosaccharides, less than 10 g/day, generally do not affect satiety or food intake. It should be noted that there are many sources of fructan fibers, both in native foods, chicory roots, agave, and Jerusalem artichokes and isolated forms that vary in chain length.

SUMMARY

Fructan fibers, which include fructooligosaccharides, oligofructose, and inulin, provided in low doses (<10 g/day), generally do not affect measures of human appetite including satiety or food intake and should not be recommended as a fiber with sole satiating power.

Biosafe, Eco-Friendly Levan Polysaccharide toward Transient Electronics

New options in the material context of transient electronics are essential to create or expand potential applications and to progress in the face of technological challenges. A soft, transparent, and cost-effective polymer of levan polysaccharide that is capable of complete, programmable dissolution is described when immersed in water and implanted in an animal model. The results include chemical analysis, the kinetics of hydrolysis, and adjustable dissolution rates of levan, and a simple theoretical model of reactive diffusion governed by temperature. In vivo experiments of the levan represent nontoxicity and biocompatibility without any adverse reactions. On-demand, selective control of dissolution behaviors with an animal model demonstrates an effective triggering strategy to program the system's lifetime, providing the possibility of potential applications in envisioned areas such as bioresorbable electronic implants and drug release systems.

The fructan syndrome: Evolutionary aspects and common themes among plants and microbes

Fructans are multifunctional fructose-based water soluble carbohydrates found in all biological kingdoms but not in animals. Most research has focused on plant and microbial fructans and has received a growing interest because of their practical applications. Nevertheless, the origin of fructan production, the so-called "fructan syndrome," is still unknown. Why fructans only occur in a limited number of plant and microbial species remains unclear. In this review, we provide an overview of plant and microbial fructan research with a focus on fructans as an adaptation to the environment and their role in (a)biotic stress tolerance. The taxonomical and biogeographical distribution of fructans in both kingdoms is discussed and linked (where possible) to environmental factors. Overall, the fructan syndrome may be related to water scarcity and differences in physicochemical properties, for instance, water retaining characteristics, at least partially explain why different fructan types with different branching levels are found in different species. Although a close correlation between environmental stresses and fructan production is quite clear in plants, this link seems to be missing in microbes. We hypothesize that this can be at least partially explained by differential evolutionary timeframes for plants and microbes, combined with potential redundancy effects.

Structure Features and Anti-Gastric Ulcer Effects of Inulin-Type Fructan CP-A from the Roots of Codonopsis pilosula (Franch.) Nannf

Radix Codonopsis has been used in traditional Chinese medicine for strengthening the immune system, improving poor gastrointestinal function, treating gastric ulcers and chronic gastritis and so on. In the present study, an inulin-type fructan CP-A was obtained from the roots of Codonopsis pilosula (Franch.) Nannf. and its structure was confirmed by MS and NMR as (2 → 1) linked-β-d-fructofuranose. The protective effects of CP-A against ethanol-induced acute gastric ulcer in rats were intensively investigated. A Lacy assay demonstrated that CP-A-treated group (50 mg/kg) showed the gastric damage level 1, which was similar to the positive control group, while the model group exhibited the gastric damage level 3. The Guth assay demonstrated that the mucosa ulcer index for CP-A groups at the doses of 50 mg/kg and 25 mg/kg significantly decreased compared with that in the model group (p < 0.05). Meanwhile, CP-A significantly increased the activities of SOD and GSH-Px, and decreased the contents of MDA and NO, and the activity of MPO in gastric tissue in a dose-dependent manner (p < 0.05). The present research reported for the first time that inulin-type fructan CP-A were likely the potential component in Radix Codonopsis for treatment of acute gastric ulcers.

Enzymatic Synthesis and Structural Characterization of Theanderose through Transfructosylation Reaction Catalyzed by Levansucrase from Bacillus subtilis CECT 39

This work addresses the high-yield and fast enzymatic production of theanderose, a naturally occurring carbohydrate, also known as isomaltosucrose, whose chemical structure determined by NMR is α-d-glucopyranosyl-(1 → 6)-α-d-glucopyranosyl-(1 → 2)-β-d-fructofuranose. The ability of isomaltose to act as an acceptor in the Bacillus subtilis CECT 39 levansucrase-catalyzed transfructosylation reaction to efficiently produce theanderose in the presence of sucrose as a donor is described by using four different sucrose:isomaltose concentration ratios. The maximum theanderose concentration ranged from 122.4 to 130.4 g L^-1, was obtained after only 1 h and at a moderate temperature (37 °C), leading to high productivity (109.7-130.4 g L^-1h^-1) and yield (up to 37.3%) values. The enzymatic synthesis was highly regiospecific, since no other detectable acceptor reaction products were formed. The development of efficient and cost-effective procedures for the biosynthesis of unexplored but appealing oligosaccharides as potential sweeteners, such as theanderose, could help to expand its potential applications which are currently limited by their low availability.

Architecture and physicochemical characterization of Bacillus biofilm as a potential enzyme immobilization factory

Biocatalysis for industrial application is based on the use of enzymes to perform complex transformations. However, these systems have some disadvantage related to the costs of the biocatalyst. In this work, an alternative strategy for producing green immobilized biocatalysts based on biofilm was developed.A study of the rheological behavior of the biofilm from Bacillus sp. Mcn4, as well as the determination of its composition, was carried out. The dynamic rheological measurements, viscosity (G") and elasticity (G') module, showed that the biofilm presents appreciable elastic components, which is a recognized property for enzymes immobilization. After the partial purification, the exopolysaccharidewas identified as a levan with a non-Newtonian behavior. Extracellular DNA with fragments between 10,000 and 1000bp was detected also in the biofilm, and amyloid protein in the extracellular matrix using a fluorescence technique was identified. Bacillus sp. Mcn4 biofilms were developed on different surfaces, being the most stable those developed on hydrophilic supports. The biofilm showed lipase activity suggesting the presence of constitutive lipases entrapped into the biofilm. Indeed, two enzymes with lipase activity were identified in native PAGE. These were used as biocatalysts, whose reuse showed a residual lipase activity after more than one cycle of catalysis. The components identified in the biofilm could be the main contributors of the rheological characteristic of this material, giving an exceptional environment to the lipase enzyme. Based on these findings, the current study proposes green and natural biopolymers matrix as support for the enzyme immobilization for industrial applications.

Microencapsulation of Eugenia uniflora L. juice by spray drying using fructans with different degrees of polymerisation

The objective of this work was to microencapsulate pitanga (Eugenia uniflora L.) juice by spray drying, using High Performance Agave Fructans (HPAF) and High Degree of Polymerisation Agave Fructans (HDPAF) and maltodextrin (MD), respectively, as the wall materials. The physicochemical and antioxidant properties of the capsules during storage at various temperatures were evaluated. The microparticles developed using fructans HPAF and HDPAF, exhibited similar physicochemical and flow properties to those presented by the microparticles prepared with MD. The highest yield and concentration of anthocyanins after drying and during storage were found for a 1:6 core:wall material ratio. The total color change was a good indicator of the microcapsule stability. This study showed that both fructans fraction possess similar encapsulating properties to MD and that the HDPAF were more efficacious than MD at protecting the antioxidants during drying and storage.