Biological properties of fructooligosaccharides with different contents of kestose and nystose in rats

Purification and biochemical characterization of an extracellular fructosyltransferase enzyme from Aspergillus niger sp. XOBP48: implication in fructooligosaccharide production

An extracellular fructosyltransferase (Ftase) enzyme with a molar mass of ≈70 kDa from a newly isolated indigenous coprophilous fungus Aspergillus niger sp. XOBP48 is purified to homogeneity and characterized in this study. The enzyme was purified to 4.66-fold with a total yield of 15.53% and specific activity of 1219.17 U mg^-1 of protein after a three-step procedure involving (NH₄)₂SO₄ fractionation, dialysis and anion exchange chromatography. Ftase showed optimum activity at pH 6.0 and temperature 50 °C. Ftase exhibited over 80% residual activity at pH range of 4.0-10.0 and ≈90% residual activity at temperature range of 40-60 °C for 6 h. Metal ion inhibitors Hg²⁺ and Ag⁺ significantly inhibited Ftase activity at 1 mmol concentration. Ftase showed K _m, v _max and k _cat values of 79.51 mmol, 45.04 µmol min^-1 and 31.5 min^-1, respectively, with a catalytic efficiency (k _cat/K _m) of 396 µmol^-1 min^-1 for the substrate sucrose. HPLC-RI experiments identified the end products of fructosyltransferase activity as monomeric glucose, 1-kestose (GF₂), and 1,1-kestotetraose (GF₃). This study evaluates the feasibility of using this purified extracellular Ftase for the enzymatic synthesis of biofunctional fructooligosaccharides.

Dietary Sugars Analysis: Quantification of Fructooligossacharides during Fermentation by HPLC-RI Method

In this work, a simple chromatographic method is proposed and in-house validated for the quantification of total and individual fructooligossacharides (e.g., 1-kestose, nystose, and 1(F)-fructofuranosylnystose). It was shown that a high-performance liquid chromatography with refractive index detector could be used to monitor the dynamic of fructooligossacharides production via sucrose fermentation using Aspergillus aculeatus. This analytical technique may be easily implemented at laboratorial or industrial scale for fructooligossacharides mass-production monitoring allowing also controlling the main substrate (sucrose) and the secondary by-products (glucose and fructose). The proposed chromatographic method had a satisfactory intra- and inter-day variability (in general, with a relative standard deviation lower than 5%), high sensitivity for each sugar (usually, with a relative error lower than 5%), and low detection (lower than 0.06 ± 0.04 g/L) and quantification (lower than 0.2 ± 0.1 g/L) limits. The correct quantification of fructooligossacharides in fermentative media may allow a more precise nutritional formulation of new functional foods, since it is reported that different fructooligossacharides exhibit different biological activities and effects.

Caffeoylquinic acid-rich extract from chicory seeds improves glycemia, atherogenic index, and antioxidant status in rats

OBJECTIVE

Comparison of the effects of a high-fructose diet supplemented with rutin, a phenolic compound with well-recognized bioavailability and bioactivity, and a chicory (Cichorium intybus L.) seed extract rich in caffeoylquinic acids (CQA) on gut physiology and the development of disorders related to metabolic syndrome.

METHODS

A 28-d experiment was conducted on 32 young male Wistar rats. In comparison with control rats fed a standard corn starch diet (group C), the experimental group (group E) was fed a diet with an increased content of cholesterol and fructose (to 1% and 66% of the diet, respectively), as well as with oxidized soybean oil. Rats from the other two experimental groups were administered the same diet as group E during the first 2 wk of feeding, whereas at the beginning of the last 2 wk, the diet was enriched with rutin (group ER) or the CQA-rich ethanol extract from chicory seeds (9.6% of CQA, group EC), so the amount of added phenolics was equal in both dietary groups (0.15%).

RESULTS

The diet administered in group E caused hyperglycemia and increased blood serum atherogenicity in rats, but did not induce other manifestations of the metabolic syndrome, i.e., dyslipidemia and oxidative stress. Additionally, it affected gut physiology through increasing mucosal sucrase activity and disturbing fermentative processes in the cecum, such as the production of short-chain fatty acids and the activity of microbial enzymes. Similarly to rutin, the dietary addition of the chicory seed extract improved glycemia, which was comparable to that determined in group C. In addition, the extract was found to decrease the atherogenic index to the level observed in group C and to increase blood antioxidant status. Both dietary supplements reduced the content of thiobarbituric acid-reactive substances in kidney and heart tissue when compared with group E.

CONCLUSION

The potential efficacy of the CQA-rich extract from chicory seeds in improving diet-induced metabolic disturbances proved to be better than that of rutin; thus, the extract might be considered as a dietary supplement for carrying out clinical trials.

Consumption of polyphenol concentrate with dietary fructo-oligosaccharides enhances cecal metabolism of quercetin glycosides in rats

OBJECTIVE

We verified the hypothesis that the consumption of polyphenol concentrate (PC), rich in quercetin and its glycosides (36 g/100 g), in association with different dietary fiber matrices, that is, an easily fermentable fructo-oligosaccharides (FOS) or non-fermentable cellulose (CEL), causes a disparate adaptive response of the cecal microbial activity in rats. This in turn facilitates further utilization of biologically active polyphenolic compounds, which are not, as usual, digested in the foregut.

METHODS

Four-week experimental feeding of male Wistar rats consisted of diets containing 5% FOS or CEL, as a source of dietary fiber, with or without 0.3% addition of PC.

RESULTS

Positive changes in rat cecum were observed resulting from the ingestion of an FOS-containing diet, such as decreased pH and increased the production of short-chain fatty acids in the digesta, compared with a CEL-containing diet. The addition of PC to the FOS diet did not eliminate the positive effects of the latter, except for a slight increase in cecal pH and a decrease in microbial glycolytic activity. However, a simultaneous increase in the cecal butyrate pool was also observed. An adaptation process of the microflora enzymatic system to dieting with PC and FOS was proven in further enhanced susceptibility of rutin (quercetin 3-O-glucorhamnoside), hyperoside (quercetin 3-O-galactoside), and quercitrin (quercetin 3-O-rhamnoside) to hydrolysis by the cecal digesta solution.

CONCLUSION

Especially when consumed together, PC and FOS are important dietary factors affecting the susceptibility of quercetin glycosides to microbial metabolism in the cecum. The intensification of the hydrolysis of quercetin glycosides by dietary treatments leads also to the increased metabolism of quercetin itself.

Efforts to emulate human milk oligosaccharides

Research on human milk oligosaccharides (HMO) began with the characterisation of their chemical structures and is now focused on the elucidation of their biological roles. Previously, biological effects could only be investigated with fractions or structures isolated from breast milk; consequently, clinical observations were limited to comparisons between outcomes from breast-fed infants and their formula-fed counterparts. In some cases, it was inferred that the observed differences were caused by the presence of HMO in breast milk. Presently, analytical techniques allow for the fast analysis of milk samples, thus providing insights on the inherent variability of specimens. In addition, methods for the synthesis of HMO have provided single structures in sufficient quantities to perform clinical studies with oligosaccharide-supplemented formulae. Furthermore, studies have been conducted with non-mammalian oligosaccharides with the purpose of assessing the suitability of these structures to functionally emulate HMO. Taken together, these developments justify summarising current knowledge on HMO to further discussions on efforts to emulate human milk in regard to its oligosaccharide content. The present account summarises published data and intends to provide an historical context and to illustrate the state of the field.

Short-chain fructooligosaccharides, in spite of being fermented in the upper part of the large intestine, have anti-inflammatory activity in the TNBS model of colitis

Previous studies have demonstrated the anti-inflammatory effect of fructooligosaccharides (FOS) on intestinal inflammation. The aim of the present study was to elucidate whether the colonic fermentation of these carbohydrates is a pre-requisite for this anti-inflammatory activity.With this aim short chain-FOS (SC-FOS) were used for an in vitro fermentation to elucidate the time of fermentation of these compounds. For the in vivo experiments female Wistar rats were fed several diets with different sources of fibre (5 g/kg): cellulose for control rats (n = 30) or SC-FOS (n = 20) with a high content of kestose (GF(2)) for the SC-FOS group. After one month of feeding the different diets 10 rats from each group were sacrificed to analyze cecal and colonic microflora, SCFA production and pH of intestinal contents. A distal colonic inflammation was induced to other 10 rats from each group by the administration of 10 mg of TNBS dissolved in 0.25 ml of 50% ethanol (v/v). The rest of the rats from the control group (n = 10) were rendered healthy. One week after TNBS treatment rats were sacrificed and several inflammatory parameters as well as intestinal microbiota and SCFA contents were analyzed. In vitro fermentation experiments showed that SC-FOS are fermented during the first 12 h after incorporating the oligosaccharides to intestinal contents, thus suggesting a preferential fermentation of these carbohydrates in the ileum and cecum. In fact, SC-FOS increased cecal lactobacilli and bifidobacteria counts as well as SCFA production in healthy rats. In colitic rats, SC-FOS feeding caused a decrease of MPO activity, leukotriene B4 (LTB4) production and iNOS expression. This anti-inflammatory effect was evidenced macroscopically by a significant reduction in the extent of colonic damage. SC-FOS also promoted a more favorable intestinal microbiota, increasing lactobacilli and bifidobacteria counts. In conclusion, although oligosaccharides are preferentially fermented in the upper parts of the large intestine, its prebiotic effect is extended to the distal colonic segments, thus exerting a positive effect on colonic inflammation.