Search

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., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The effects of the partial replacement of maltodextrin by native agave fructans on the characteristics of spray-dried pineapple and mango powder were evaluated in this study. An experimental 3 3 design, three concentrations of maltodextrin (5, 7, and 10%), three concentrations of native agave fructans (0, 2, and 4%), and three feed temperatures (110, 115, and 120  ℃) were used. The results using the treatment in which only maltodextrin was used as a reference indicated that an increment in the inlet temperature decreases the moisture content, a w , and solubility. Likewise, an increase (more than 2%) in fructans concentration generates products with increased a w , moisture, hygroscopicity, wettability, and greater solubility. Additionally, no modification of storage stability was observed. Mango and pineapple powder color were affected mainly by the inlet temperature, causing an increase in luminosity (L*) and a decrease in parameter ( a*). A scanning electron microscopy showed spherical powder particles with certain contractions; powder stability in treatments with native agave fructans was not modified in the treatment at 2%. Finally, the addition of 2% agave fructans as carrier material was able to reduce the maltodextrin concentration of the spray drying process.

Fructans are naturally occurring plant oligosaccharides with sweetening properties. Fructans (FAs) isolated from Jerusalem artichokes (Helianthus tuberosus) were studied with respect to intestinal handling and influence on blood glucose (BG), insulin, and C-peptide responses in eight healthy subjects. The responses were compared with those for fructose ingestion. The effect of FAs added to a wheat-starch meal was also studied. Standardized breath-hydrogen excretion indicated that FAs were completely malabsorbed and, after a 20-g dose, traces of FA were detected in 24-h urine collections in one subject only. Orocecal transit times were longer for FAs than for lactulose and fructose. The BG and insulin increments were very low after FA ingestion, lower than after fructose ingestion, whereas hydrogen production was much higher. Areas under BG curves tended to be smaller when 10 g FA was added to a 50-g wheat-starch meal, but there was no apparent interference with starch absorption.

Levans are natural polymers of the sugar fructose found in many plants and microbial products. Like dextrans, they are formed as an undesirable by-product of sugar juice processing. On the other hand, levans, which can only be produced from sucrose, have potential industrial applications as thickeners and encapsulating agents and could provide additional, valuable products from sugarcane juice. A strain of B. polymyxa (NRRL B-18475) produced a high yield of polysaccharide when grown on sucrose solution. Hydrolysis and subsequent analyses showed the product to consist entirely of D-fructose. 13C-NMR and methylation analyses indicated the products to be a beta(2----6)-linked polymer of fructose, with 12% branching. The polysaccharide has a Mr of approximately 2 million and is readily soluble in water. Levan has not been utilized, but if developed, could be useful in food and other industrial applications.

High molecular-weight levans elaborated by 8 separate strains of Actinomyces viscosus were purified: the inteactions of these levans with concanavalin A and anti-fructan myeloma immunoglobulins UPC-10 and J606 were examined by the quantitative precipitin method. Oligosaccharides released from the levans by partial acid hydrolysis were separated by partition chromatography on paper and characterized in situ by selective spray reagents. The liberated oligomers were compared with oligomers of known structure released from levans of Aerobacter levanicum and Leuconostoc mesenteriodes B512 as well as with plant inulin. The fragmentation analysis indicated a structure for Actinomyces levans comprising chains of beta (2----6)-linked fructofuranosyl units joined through multiple (1,2,6)-linked fructosyl branch units.

The fructan of Streptococcus mutans OMZ 176 was shown to have a levan structure by comparing the chromatographic mobilities of the saccharides produced by partial acid hydrolysis of ghe fructan and known levan and inulin. This was confirmed by using concanavalin A as a lectin in a double-diffusion gel technique.

D-Fructans synthesized from sucrose by cell-free systems of strains of Streptococcus mutans and Strep. salivarius have been shown by methylation and enzymatic studies to have different glycosidic linkages. The cold water-insoluble D-fructans from Strep. mutans strain BHT and JC-1 have inulin-type structures consisting beta-(2 leads to 1)-D-fructofuranosidic linkages, with average repeating units of 8 and 27 sugar residues, respectively, whereas the water-soluble fructan from Strep. salivarius strain HHT has a levan-type branched structure consisting beta-(2 leads to 6)-D-fructofuranosidic linkages with an average repeating unit of 9 sugar residues. The solubility properties of these fructants are discussed on the basis of the structural differences.

Levan production by strains of Erwinia herbicola is common, and this property has some taxonomic significance for species differentiation within the "herbicola" group. The extracellular polysaccharide elaborated by strain 403 was characterized by nuclear magnetic resonance spectroscopy and methylation analysis. Results showed it to be a typical bacterial levan.

Exopolysaccharides (EPS) of the soybean pathogen Pseudomonas syringae pv. glycinea were isolated from culture filtrates and infected soybean leaves. Levan (a polyfructan with a C-2----C-6 backbone and C-2----C-1 branching) or acetylated alginate (a linear polyuronide of C-1----C-4-linked mannuronic and guluronic acids) was isolated from culture filtrates when bacterial strains were grown in a semisynthetic medium containing sucrose or glucose, respectively, as the primary carbon source. Acetylated alginate was the only EPS isolated from soybean [Glycine max (L.) Merr.] leaves inoculated with compatible (disease-inducing) strains of P. syringae pv. glycinea. The acetyl content of the P. syringae pv. glycinea alginates varied from 3 to 14%, and the amount of guluronic acid varied from less than 1 to 20%. The P. syringae pv. glycinea alginates from in vitro batch cultures were of lower molecular weight and polydispersity than those from in planta cultures, and both were of lower molecular weights than alginates produced by Pseudomonas aeruginosa.

A strain of Bacillus sp. was isolated which is an active producer of levan. The dynamics of the polysaccharide biosynthesis was studied depending on concentrations of sucrose in the medium. The amount of the synthesized levan was proportional to the concentration of sucrose ranging from 0.2 to 6%, being a maximum of 28.2 mg/ml in the medium containing 12% of sucrose. The presence of urea or ammonium sulfate in the medium stimulates the levan biosynthesis. A medium with pH 6.0--6.8 is optimal for the polysaccharide formation. Levan, synthesized by Bacillus sp., is a polysaccharide with the molecular weight more than 2 mln. Levansucrase is an induced enzyme, whose inductors are sucrose and raffinose.

The fate of cereal fructans and inulin in the gastrointestinal tract was investigated by using a rat model. Male Wistar rats received diets containing 5.0% of a preparation of cereal fructans or 4.7 or 9.4% inulin. Each diet was tested with or without Nebacitin, an antibiotic drug given to suppress the intestinal microflora. The availability of fructans in the upper gastrointestinal tract was calculated from the recovery in feces in Nebacitin-treated rats. Animals receiving cereal fructans developed diarrhea, which made it impossible to measure the bioavailability of this substrate. With inulin, the extent of digestion and absorption appeared to be 18-26%. This might, at least to some degree, be explained by hydrolysis by gastric juice in the stomach. Thus, in an in vitro assay, mild acid hydrolysis (0.05 M HCl, 37 degrees C, 120 min) converted about 8% of inulin to free fructose. The apparent digestibility of the fructans was calculated from its recovery in feces from untreated rats. Only minute amounts of fructans could be detected, hence, cereal fructans as well as inulin reaching the hindgut appeared to be almost completely fermentable.