The prebiotic effects of biscuits containing partially hydrolysed guar gum and fructo-oligosaccharides - a human volunteer study

Prebiotics are non-digestible food ingredients that target selected groups of the human colonic microflora, thus having the ability to alter the composition towards a more ‘beneficial' community, i.e. selectively increasing populations of bifidobacteria and/or lactobacilli. In the present study the prebiotic potential of partially hydrolysed guar gum (PHGG) and fructo-oligosaccharides (FOS) in a biscuit was assessed in human volunteers. Fluorescent in situ hybridization using oligonucleotide probes targeting Bacteroides spp., Bifidobacterium spp., Clostridium spp. and Lactobacillus-Enterococcus spp. were used for the bacteriology and total bacteria were enumerated using the fluorescent stain 4′,6-diamidino-2-phenylindole. Thirty-one volunteers consumed daily either three experimental biscuits (providing a total (g/d) of 6·6 FOS and 3·4 PHGG) or three placebo biscuits for two 21-d crossover periods. Bifidobacteria significantly increased in number on ingestion of the experimental biscuits compared with pre-treatment and placebo population levels. Bifidobacterial numbers returned to pretreatment levels within 7 d of the cessation of intake of experimental biscuits. A correlation was observed between the initial faecal bifidobacterial numbers and the magnitude of bifidogenesis, with volunteers who possessed low initial population levels of bifidobacteria experiencing the greatest increase in bifidogenesis. No changes were observed in the other bacterial groups monitored during the trial. Thus, the prebiotic nature of FOS and PHGG was maintained in a final food product as evidenced from the selective increase in bifidobacterial number

A randomised, double- blind, cross-over study investigating the prebiotic effect of agave fructans in healthy human subjects

This placebo-controlled, randomised, double-blind, cross-over human feeding study aimed to determine the prebiotic effect of agave fructans. A total of thirty-eight volunteers completed this trial. The treatment consisted of 3 weeks' supplementation with 5 g/d of prebiotic agave fructan (Predilife) or equivalent placebo (maltodextrin), followed by a 2-week washout period following which subjects were crossed over to alternate the treatment arm for 3 weeks followed by a 2-week washout. Faecal samples were collected at baseline, on the last day of treatment (days 22 and 58) and washout (days 36 and 72), respectively. Changes in faecal bacterial populations, SCFA and secretory IgA were assessed using fluorescent in situ hybridisation, GC and ELISA, respectively. Bowel movements, stool consistencies, abdominal comfort and mood changes were evaluated by a recorded daily questionnaire. In parallel, the effect of agave fructans on different regions of the colon using a three-stage continuous culture simulator was studied. Predilife significantly increased faecal bifidobacteria (log10 9·6 (sd 0·4)) and lactobacilli (log10 7·7 (sd 0·8)) compared with placebo (log10 9·2 (sd 0·4); P = 0·00) (log10 7·4 (sd 0·7); P = 0·000), respectively. No change was observed for other bacterial groups tested, SCFA, secretory IgA, and PGE2 concentrations between the treatment and placebo. Denaturing gradient gel electrophoresis analysis indicated that bacterial communities were randomly dispersed and no significant differences were observed between Predilife and placebo treatments. The in vitro models showed similar increases in bifidobacterial and lactobacilli populations to that observed with the in vivo trial. To conclude, agave fructans are well tolerated in healthy human subjects and increased bifidobacteria and lactobacilli numbers in vitro and in vivo but did not influence other products of fermentatio

Potential of novel dextran oligosaccharides as prebiotics for obesity management through in vitro experimentation

The energy-salvaging capacity of the gut microbiota from dietary ingredients has been proposed as a contributing factor for the development of obesity. This knowledge generated interest in the use of non-digestible dietary ingredients such as prebiotics to manipulate host energy homeostasis. In the present study, the in vitro response of obese human faecal microbiota to novel oligosaccharides was investigated. Dextrans of various molecular weights and degrees of branching were fermented with the faecal microbiota of healthy obese adults in pH-controlled batch cultures. Changes in bacterial populations were monitored using fluorescent in situ hybridisation and SCFA concentrations were analysed by HPLC. The rate of gas production and total volume of gas produced were also determined. In general, the novel dextrans and inulin increased the counts of bifidobacteria. Some of the dextrans were able to alter the composition of the obese human microbiota by increasing the counts of Bacteroides–Prevotella and decreasing those of Faecalibacterium prausnitzii and Ruminococcus bromii/R. flavefaciens. Considerable increases in SCFA concentrations were observed in response to all substrates. Gas production rates were similar during the fermentation of all dextrans, but significantly lower than those during the fermentation of inulin. Lower total gas production and shorter time to attain maximal gas production were observed during the fermentation of the linear 1 kDa dextran than during the fermentation of the other dextrans. The efficacy of bifidobacteria to ferment dextrans relied on the molecular weight and not on the degree of branching. In conclusion, there are no differences in the profiles between the obese and lean human faecal fermentations of dextrans

The prebiotic effect of α-1,2 branched, low molecular weight dextran in the batch and continuous faecal fermentation system

The aim of this study was to establish the effect of smaller molecular weight (0.5 and 1.0 kDa) on prebiotic efficacy and its putative sustainability in the human gut. The prebiotic effect of α-1,2 branched, 0.5 and 1 kDa dextrans were evaluated in faecal batch fermentations as compared with inulin. Both dextrans induce similar selectivity towards Bifidobacterium sp., Lactobacillus/Enterococcus and Bacteroides/Prevotella, and producing similar concentrations of short chain fatty acids. However, the 0.5 kDa dextran was fermented faster than the 1 kDa dextran, where both produced lower amount of gas than inulin. The fermentation of 1 kDa dextran was further investigated in continuous gut models. The dextran increased Bifidobacterium and Roseburia sp. populations in the final vessel, while decreasing Clostridium histolyticum and Faecalibacterium prausnitzii. Overall, the α-1,2 branched, 1 kDa dextran induced selective effect on the gut microbiota and stimulated short chain fatty acids, indicating prebiotic sustainability in distal regions of the gut

In vitro modeling of bile acid processing by the human fecal microbiota

Bile acids, the products of concerted host and gut bacterial metabolism, have important signaling functions within the mammalian metabolic system and a key role in digestion. Given the complexity of the mega-variate bacterial community residing in the gastrointestinal tract, studying associations between individual bacterial genera and bile acid processing remains a challenge. Here, we present a novel in vitro approach to determine the bacterial genera associated with the metabolism of different primary bile acids and their potential to contribute to inter-individual variation in this processing. Anaerobic, pH-controlled batch cultures were inoculated with human fecal microbiota and treated with individual conjugated primary bile acids (500 μg/ml) to serve as the sole substrate for 24 h. Samples were collected throughout the experiment (0, 5, 10, and 24 h) and the bacterial composition was determined by 16S rRNA gene sequencing and the bile acid signatures were characterized using a targeted ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) approach. Data fusion techniques were used to identify statistical bacterial-metabolic linkages. An increase in gut bacteria associated bile acids was observed over 24 h with variation in the rate of bile acid metabolism across the volunteers (n = 7). Correlation analysis identified a significant association between the Gemmiger genus and the deconjugation of glycine conjugated bile acids while the deconjugation of taurocholic acid was associated with bacteria from the Eubacterium and Ruminococcus genera. A positive correlation between Dorea and deoxycholic acid production suggest a potential role for this genus in cholic acid dehydroxylation. A slower deconjugation of taurocholic acid was observed in individuals with a greater abundance of Parasutterella and Akkermansia. This work demonstrates the utility of integrating compositional (metataxonomics) and functional (metabonomics) systems biology approaches, coupled to in vitro model systems, to study the biochemical capabilities of bacteria within complex ecosystems. Characterizing the dynamic interactions between the gut microbiota and the bile acid pool enables a greater understanding of how variation in the gut microbiota influences host bile acid signatures, their associated functions and their implications for health

An evaluation of the prebiotic potential of microbial levans from Erwinia sp. 10119

Levan, a bacterial exopolysaccharide (EPS), has been suggested to have several biological activities, such as antitumour activity and lowering blood pressure. There has also been interest in its potential prebiotic activity. This study investigated the fermentation profile of a levan fraction from Erwinia sp. 10119 (average DP=137) throughout a three-stage continuous gut model system, in which inulin HP (average DP=40) was included as a comparison. Levan-type fructan was found to selectively stimulate the growth of Bifidobacterium and Eubacterium rectale - Clostridium coccoides group in all fermenter vessels, with significant (p < 0.05) increases in the concentration of both acetate and butyrate. The increases in Bifidobacterium population were significantly (p < 0.05) higher in the models treated with levan-type fructan (0.8–1.24 log cell/mL) compared to the models treated with inulin HP (0.62–0.7 log cell/mL), indicating a stronger bifidogenic effect of levan-type fructan and a prolonged persistence in the colon due to its higher DP

Hazelnut milk fermentation using probiotic Lactobacillus rhamnosus GG and inulin

Following the consumer demand of healthy vegetable products due to their interesting nutritional profiles and potential functionalities, the fermentation process of hazelnut milk with Lactobacillus rhamnosus GG and S.thermophilus was studied. The effect of different factors (glucose, inulin and inoculum contents) was analysed to ensure sufficient probiotic survivals in a minimum time. The shelf life of the optimised product was characterised in terms of its main physicochemical and quality parameters (probiotic survivals and sensory analysis). Results showed that the defined formulation allowed high probiotic survivals (approximate to 10(8)cfumL(-1)) throughout cold storage and >60% survived to the in vitro digestion process (approximate to 10(5)cfumL(-1)). Lactobacillus rhamnosus GG was no able to degrade inulin, which remained to exert health benefits in the host. 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Prebiotic potential of a maize-based soluble fibre and impact of dose on the human gut microbiota

Dietary management of the human gut microbiota towards a more beneficial composition is one approach that may improve host health. To date, a large number of human intervention studies have demonstrated that dietary consumption of certain food products can result in significant changes in the composition of the gut microbiota i.e. the prebiotic concept. Thus the prebiotic effect is now established as a dietary approach to increase beneficial gut bacteria and it has been associated with modulation of health biomarkers and modulation of the immune system. Promitor™ Soluble Corn Fibre (SCF) is a well-known maize-derived source of dietary fibre with potential selective fermentation properties. Our aim was to determine the optimum prebiotic dose of tolerance, desired changes to microbiota and fermentation of SCF in healthy adult subjects. A double-blind, randomised, parallel study was completed where volunteers (n = 8/treatment group) consumed 8, 14 or 21 g from SCF (6, 12 and 18 g/fibre delivered respectively) over 14-d. Over the range of doses studied, SCF was well tolerated Numbers of bifidobacteria were significantly higher for the 6 g/fibre/day compared to 12g and 18g/fibre delivered/day (mean 9.25 and 9.73 Log10 cells/g fresh faeces in the pre-treatment and treatment periods respectively). Such a numerical change of 0.5 Log10 bifidobacteria/g fresh faeces is consistent with those changes observed for inulin-type fructans, which are recognised prebiotics. A possible prebiotic effect of SCF was therefore demonstrated by its stimulation of bifidobacteria numbers in the overall gut microbiota during a short-term intervention

Insight into the prebiotic concept: lessons from an exploratory, double blind intervention study with inulin-type fructans in obese women

Objective To highlight the contribution of the gut microbiota to the modulation of host metabolism by dietary inulin-type fructans (ITF prebiotics) in obese women. Methods A double blind, placebo controlled, intervention study was performed with 30 obese women treated with ITF prebiotics (inulin/oligofructose 50/50 mix; n=15) or placebo (maltodextrin; n=15) for 3 months (16 g/day). Blood, faeces and urine sampling, oral glucose tolerance test, homeostasis model assessment and impedancemetry were performed before and after treatment. The gut microbial composition in faeces was analysed by phylogenetic microarray and qPCR analysis of 16S rDNA. Plasma and urine metabolic profiles were analysed by 1H-NMR spectroscopy. Results Treatment with ITF prebiotics, but not the placebo, led to an increase in Bifidobacterium and Faecalibacterium prausnitzii; both bacteria negatively correlated with serum lipopolysaccharide levels. ITF prebiotics also decreased Bacteroides intestinalis, Bacteroides vulgatus and Propionibacterium, an effect associated with a slight decrease in fat mass and with plasma lactate and phosphatidylcholine levels. No clear treatment clustering could be detected for gut microbial analysis or plasma and urine metabolomic profile analyses. However, ITF prebiotics led to subtle changes in the gut microbiota that may importantly impact on several key metabolites implicated in obesity and/or diabetes. Conclusions ITF prebiotics selectively changed the gut microbiota composition in obese women, leading to modest changes in host metabolism, as suggested by the correlation between some bacterial species and metabolic endotoxaemia or metabolomic signatures

Prebiotic potential of a new sweetener based on galactooligosaccharides and modified mogrosides

This study was conducted to investigate the sweetness intensity and the potential fecal microbiome modulation of galactooligosaccharides in combination with enzymatically modified mogrosides (mMV-GOS), both generated through a patented single-pot synthesis. Sweetness intensity was performed in vivo by trained sensory panelists. The impact on the human fecal microbiome was evaluated by in vitro pH-controlled batch fermentation, and bacterial populations and organic acid concentrations were measured by qPCR and GC-FID, respectively. Significant growth (p ≤ 0.05) during the fermentation at 10 h of bacterial populations includes Bifidobacterium (8.49 ± 0.44 CFU/mL), Bacteroides (9.73 ± 0.32 CFU/mL), Enterococcus (8.17 ± 0.42 CFU/mL), and Clostridium coccoides (6.15 ± 0.11 CFU/mL) as compared to the negative control counts for each bacterial group (7.94 ± 0.27, 7.84 ± 1.11, 7.52 ± 0.37, and 5.81 ± 0.08 CFU/mL, respectively) at the same time of fermentation. Likewise, the corresponding significant increase in production of SCFA in mMV-GOS at 10 h of fermentation, mainly seen in acetate (20.32 ± 2.56 mM) and propionate (9.49 ± 1.44 mM) production compared to a negative control at the same time (8.15 ± 1.97 and 1.86 ± 0.24 mM), is in line with a positive control (short-chain fructooligosaccharides; 46.74 ± 12.13 and 6.51 ± 1.91 mM, respectively) revealing a selective fermentation. In conclusion, these substrates could be considered as novel candidate prebiotic sweeteners, foreseeing a feasible and innovative approach targeting the sucrose content reduction in food. This new ingredient could provide health benefits when evaluated in human studies by combining sweetness and prebiotic fiber functionality