Fermentation of fructooligosaccharides and inulin by bifidobacteria: a comparative study of pure and fecal cultures

Engineering Human Microbiota: Influencing Cellular and Community Dynamics for Therapeutic Applications

The complex relationship between microbiota, human physiology, and environmental perturbations has become a major research focus, particularly with the arrival of culture-free and high-throughput approaches for studying the microbiome. Early enthusiasm has come from results that are largely correlative, but the correlative phase of microbiome research has assisted in defining the key questions of how these microbiota interact with their host. An emerging repertoire for engineering the microbiome places current research on a more experimentally grounded footing. We present a detailed look at the interplay between microbiota and host and how these interactions can be exploited. A particular emphasis is placed on unstable microbial communities, or dysbiosis, and strategies to reestablish stability in these microbial ecosystems. These include manipulation of intermicrobial communication, development of designer probiotics, fecal microbiota transplantation, and synthetic biology.

Contribution of microbiota to the intestinal physicochemical barrier

The large number of intestinal microorganisms, which exceeds the total number of human cells by ten folds, alludes to a significant contribution to human health. This is vivid in enteric and some systemic diseases emanating from disruption of the microbiota. As life style keeps shifting towards disruption of the microbiota in most societies worldwide, interest in the contribution of the microbiota to gut health has grown enormously. Many studies have been conducted to elucidate the exact contribution of the microbiota to human health. The knowledge gained from these studies indicates that the microbiota interacts with the intestinal milieu to maintain gut health. In this review, the crosstalk of microbiota with the intestinal physicochemical barrier pivotal to the gut innate immunity is highlighted. In particular, the review focuses on the role of the microbiota on competitive exclusion of pathogens, intestinal pH, epithelial mechanical barrier integrity, apical actin cytoskeleton, antimicrobial peptides, and the mucus layer. Understanding this microbe-host relationship will provide useful insight into overcoming some diseases related to the disruption of the host microbiota.

Inulin and Fibersol-2 Combined Have Hypolipidemic Effects on High Cholesterol Diet-Induced Hyperlipidemia in Hamsters

The resistant carbohydrates, inulin, and Fibersol-2, belong to soluble dietary fibers and are considered important prebiotics that maintain biological functions, including glucose homeostasis, lipid regulation, colon disease prevention, and prebiotics characteristics. However, few studies have investigated Fibersol-2 alone or in combination with inulin to assess a pooled effect on modulation of hyperlipidemia. We aimed to investigate the effects of this combined supplement (defined as InF) on hamsters fed a 0.2% cholesterol and 10% lard diet (i.e., high-cholesterol diet, HCD) to induce hyperlipidemia. A total of 40 male hamsters were randomly assigned to five groups (n = 8 per group) for treatment: standard diet, vehicle (control); or vehicle or InF supplementation by oral gavage at 0, 864, 1727, or 2591 mg/kg/day for eight weeks, designated HCD, InF-1X, InF-2X, and InF-3X groups, respectively. The hypolipidemic efficacy and safety of InF supplementation was assessed by serum lipid indexes, hepatic and fecal lipid content, and histology. InF supplementation significantly improved serum levels of triacylglycerol (TG) and low-density lipoprotein cholesterol (LDL-C) and the ratio of LDL-C/HDL-C after two-week treatment, and reduced serum total cholesterol (TC) levels after four-week administration. After eight-week supplementation, InF supplementation dose-dependently improved serum levels of TC, TG, HDL-C, and LDL-C; LDL-C/HDL-C ratio; and hepatic TC and TG levels. It inhibited TC absorption by feces elimination. Our study provides experiment-based evidence to support that this prebiotics remedy may be useful in preventing or treating hyperlipidemia.

Effects of Prebiotic and Synbiotic Supplementation on Inflammatory Markers and Anthropometric Indices After Roux-en-Y Gastric Bypass: A Randomized, Triple-blind, Placebo-controlled Pilot Study

BACKGROUND

Studies have shown that prebiotics and synbiotics modulate the intestinal microbiota and may have beneficial effects on the immune response and anthropometric indices; however, the impact of the use of these supplements after bariatric surgery is not yet known.

GOALS

This study investigated the effects of prebiotic and synbiotic supplementation on inflammatory markers and anthropometric indices in individuals undergoing open Roux-en-Y gastric bypass (RYGB).

STUDY

In this randomized, controlled, and triple-blind trial conducted as a pilot study, individuals undergoing RYGB (n=9) and healthy individuals (n=9) were supplemented with 6 g/d of placebo (maltodextrin), prebiotic (fructo-oligosaccharide, FOS), or synbiotic (FOS+Lactobacillus and Bifidobacteria strains) for 15 days.

RESULTS

Interleukin-1β, interleukin-6, tumor necrosis factor-α, C-reactive protein, albumin, and the C-reactive protein/albumin ratio showed no significant changes on comparison between groups after supplementation. The reduction in the body weight of patients undergoing RYGB was 53.8% higher in the prebiotic group compared with the placebo group (-0.7 kg, P=0.001), whereas the reduction in the BMI and the increase in the percentage of excess weight loss were higher in the placebo and the prebiotic groups compared with the synbiotic group (P<0.05).

CONCLUSIONS

Supplementation of FOS increased weight loss, whereas both prebiotics and synbiotics were not able to promote significant changes in inflammatory markers, although in most analyses, there was a reduction in their absolute values. The use of FOS may represent a potential adjunct in the treatment of obesity.

Characterization of the Gut Microbial Community of Obese Patients Following a Weight-Loss Intervention Using Whole Metagenome Shotgun Sequencing

Background/Objectives

Cross-sectional studies suggested that obesity is promoted by the gut microbiota. However, longitudinal data on taxonomic and functional changes in the gut microbiota of obese patients are scarce. The aim of this work is to study microbiota changes in the course of weight loss therapy and the following year in obese individuals with or without co-morbidities, and to asses a possible predictive value of the gut microbiota with regard to weight loss maintenance.

Subjects/Methods

Sixteen adult patients, who followed a 52-week weight-loss program comprising low calorie diet, exercise and behavioral therapy, were selected according to their weight-loss course. Over two years, anthropometric and metabolic parameters were assessed and microbiota from stool samples was functionally and taxonomically analyzed using DNA shotgun sequencing.

Results

Overall the microbiota responded to the dietetic and lifestyle intervention but tended to return to the initial situation both at the taxonomical and functional level at the end of the intervention after one year, except for an increase in Akkermansia abundance which remained stable over two years (12.7x10³ counts, 95%CI: 322–25100 at month 0; 141x10³ counts, 95%CI: 49-233x10³ at month 24; p = 0.005). The Firmicutes/Bacteroidetes ratio was higher in obese subjects with metabolic syndrome (0.64, 95%CI: 0.34–0.95) than in the “healthy obese” (0.27, 95%CI: 0.08–0.45, p = 0.04). Participants, who succeeded in losing their weight consistently over the two years, had at baseline a microbiota enriched in Alistipes, Pseudoflavonifractor and enzymes of the oxidative phosphorylation pathway compared to patients who were less successful in weight reduction.

Conclusions

Successful weight reduction in the obese is accompanied with increased Akkermansia numbers in feces. Metabolic co-morbidities are associated with a higher Firmicutes/Bacteroidetes ratio. Most interestingly, microbiota differences might allow discrimination between successful and unsuccessful weight loss prior to intervention.

Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health

The colon is inhabited by a dense population of microorganisms, the so-called “gut microbiota,” able to ferment carbohydrates and proteins that escape absorption in the small intestine during digestion. This microbiota produces a wide range of metabolites, including short chain fatty acids (SCFA). These compounds are absorbed in the large bowel and are defined as 1-6 carbon volatile fatty acids which can present straight or branched-chain conformation. Their production is influenced by the pattern of food intake and diet-mediated changes in the gut microbiota. SCFA have distinct physiological effects: they contribute to shaping the gut environment, influence the physiology of the colon, they can be used as energy sources by host cells and the intestinal microbiota and they also participate in different host-signaling mechanisms. We summarize the current knowledge about the production of SCFA, including bacterial cross-feedings interactions, and the biological properties of these metabolites with impact on the human health.

Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health

The colon is inhabited by a dense population of microorganisms, the so-called "gut microbiota," able to ferment carbohydrates and proteins that escape absorption in the small intestine during digestion. This microbiota produces a wide range of metabolites, including short chain fatty acids (SCFA). These compounds are absorbed in the large bowel and are defined as 1-6 carbon volatile fatty acids which can present straight or branched-chain conformation. Their production is influenced by the pattern of food intake and diet-mediated changes in the gut microbiota. SCFA have distinct physiological effects: they contribute to shaping the gut environment, influence the physiology of the colon, they can be used as energy sources by host cells and the intestinal microbiota and they also participate in different host-signaling mechanisms. We summarize the current knowledge about the production of SCFA, including bacterial cross-feedings interactions, and the biological properties of these metabolites with impact on the human health.

In Vitro Fermentation of caprine milk oligosaccharides by bifidobacteria isolated from breast-fed infants

This study was conducted to investigate the catabolism and fermentation of caprine milk oligosaccharides (CMO) by selected bifidobacteria isolated from 4 breast-fed infants. Seventeen bifidobacterial isolates consisting of 3 different species (Bifidobacterium breve, Bifidobacterium longum subsp. longum and Bifidobacterium bifidum) were investigated. A CMO-enriched fraction (CMOF) (50% oligosaccharides, 10% galacto-oligosaccharides (GOS), 20% lactose, 10% glucose and 10% galactose) from caprine cheese whey was added to a growth medium as a sole source of fermentable carbohydrate. The inclusion of the CMOF was associated with increased bifidobacterial growth for all strains compared to glucose, lactose, GOS, inulin, oligofructose, 3'-sialyl-lactose and 6'-sialyl-lactose. Only one B. bifidum strain (AGR2166) was able to utilize the sialyl-CMO, 3'-sialyl-lactose and 6'-sialyl-lactose, as carbohydrate sources. The inclusion of CMOF increased the production of acetic and lactic acid (P < 0.001) after 36 h of anaerobic fermentation at 37 °C, when compared to other fermentable substrates. Two B. bifidum strains (AGR2166 and AGR2168) utilised CMO, contained in the CMOF, to a greater extent than B. breve or B. longum subsp longum isolates, and this increased CMO utilization was associated with enhanced sialidase activity. CMOF stimulated bifidobacterial growth when compared to other tested fermentable carbohydrates and also increased the consumption of mono- and disaccharides, such as galactose and lactose present in the CMOF. These findings indicate that the dietary consumption of CMO may stimulate the growth and metabolism of intestinal Bifidobacteria spp. including B. bifidum typically found in the large intestine of breast-fed infants.

Prebiotic Effects of Agave salmiana Fructans in Lactobacillus acidophilus and Bifidobacterium lactis Cultures

Agave salmiana is a fructan rich species that is widely distributed in Mexico. The aim of this investigation was to extract the fructans of A. salmiana and evaluate their prebiotic effect in 48 hours in vitro cultures of Bifidobacterium lactis and Lactobacillus acidophilus and to compare this effect with other available fructan sources. A significant difference in pH, optical density and biomass was found in the cultures depending on the source of fructans and the type of bacteria. It was possible to determine a dose-response effect of the A. salmiana fructans and the growth of the studied strains.

Dietary Inulin Fibers Prevent Proton-Pump Inhibitor (PPI)-Induced Hypocalcemia in Mice

Background

Proton-pump inhibitor-induced hypomagnesemia (PPIH) is the most recognized side effect of proton-pump inhibitors (PPIs). Additionally, PPIH is associated with hypocalcemia and hypokalemia. It is hypothesized that PPIs reduce epithelial proton secretion and thereby increase the pH in the colon, which may explain the reduced absorption of and Mg²⁺ and Ca²⁺. Fermentation of dietary oligofructose-enriched inulin fibers by the microflora leads to acidification of the intestinal lumen and by this enhances mineral uptake. This study aimed, therefore, to improve mineral absorption by application of dietary inulin to counteract PPIH.

Methods

Here, C57BL/J6 mice were supplemented with omeprazole and/or inulin. Subsequently, Mg²⁺ and Ca²⁺ homeostasis was assessed by means of serum, urine and fecal electrolyte measurements. Moreover, the mRNA levels of magnesiotropic and calciotropic genes were examined in the large intestine and kidney by real-time PCR.

Results

Treatment with omeprazole significantly reduced serum Mg²⁺ and Ca²⁺ levels. However, concomitant addition of dietary inulin fibers normalized serum Ca²⁺ but not serum Mg²⁺ concentrations. Inulin abolished enhanced expression of Trpv6 and S100g in the colon by omeprazole. Additionally, intestinal and renal mRNA levels of the Trpm6 gene were reduced after inulin intake.

Conclusions

This study suggests that dietary inulin counteracts reduced intestinal Ca²⁺ absorption upon PPI treatment. In contrast, inulin did not increase intestinal absorption of Mg²⁺ sufficiently to recover serum Mg²⁺. The clinical potential of dietary inulin treatment should be the subject of future studies.

Agave Inulin Supplementation Affects the Fecal Microbiota of Healthy Adults Participating in a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

BACKGROUND

Prebiotics resist digestion, providing fermentable substrates for select gastrointestinal bacteria associated with health and well-being. Agave inulin differs from other inulin type fibers in chemical structure and botanical origin. Preclinical animal research suggests these differences affect bacterial utilization and physiologic outcomes. Thus, research is needed to determine whether these effects translate to healthy adults.

OBJECTIVE

We evaluated agave inulin utilization by the gastrointestinal microbiota by measuring fecal fermentative end products and bacterial taxa.

METHODS

A randomized, double-blind, placebo-controlled, 3-period, crossover trial was undertaken in healthy adults (n = 29). Participants consumed 0, 5.0, or 7.5 g agave inulin/d for 21 d with 7-d washouts between periods. Participants recorded daily dietary intake; fecal samples were collected during days 16-20 of each period and were subjected to fermentative end product analysis and 16S Illumina sequencing.

RESULTS

Fecal Actinobacteria and Bifidobacterium were enriched (P < 0.001) 3- and 4-fold after 5.0 and 7.5 g agave inulin/d, respectively, compared with control. Desulfovibrio were depleted 40% with agave inulin compared with control. Agave inulin tended (P < 0.07) to reduce fecal 4-methyphenol and pH. Bivariate correlations revealed a positive association between intakes of agave inulin (g/kcal) and Bifidobacterium (r = 0.41, P < 0.001). Total dietary fiber intake (total fiber plus 0, 5.0, or 7.5 g agave inulin/d) per kilocalorie was positively associated with fecal butyrate (r = 0.30, P = 0.005), tended to be positively associated with Bifidobacterium (r = 0.19, P = 0.08), and was negatively correlated with Desulfovibrio abundance (r = -0.31, P = 0.004).

CONCLUSIONS

Agave inulin supplementation shifted the gastrointestinal microbiota composition and activity in healthy adults. Further investigation is warranted to determine whether the observed changes translate into health benefits in human populations. This trial was registered at clinicaltrials.gov as NCT01925560.

Xylooligosaccharide supplementation alters gut bacteria in both healthy and prediabetic adults: a pilot study

BACKGROUND

It has been suggested that gut microbiota is altered in Type 2 Diabetes Mellitus (T2DM) patients.

OBJECTIVE

This study was to evaluate the effect of the prebiotic xylooligosaccharide (XOS) on the gut microbiota in both healthy and prediabetic (Pre-DM) subjects, as well as impaired glucose tolerance (IGT) in Pre-DM.

SUBJECTS/METHODS

Pre-DM (n = 13) or healthy (n = 16) subjects were randomized to receive 2 g/day XOS or placebo for 8-weeks. In Pre-DM subjects, body composition and oral glucose tolerance test (OGTT) was done at baseline and week 8. Stool from Pre-DM and healthy subjects at baseline and week 8 was analyzed for gut microbiota characterization using Illumina MiSeq sequencing.

RESULTS

We identified 40 Pre-DM associated bacterial taxa. Among them, the abundance of the genera Enterorhabdus, Howardella, and Slackia was higher in Pre-DM. XOS significantly decreased or reversed the increase in abundance of Howardella, Enterorhabdus, and Slackia observed in healthy or Pre-DM subjects. Abundance of the species Blautia hydrogenotrophica was lower in pre-DM subjects, while XOS increased its abundance. In Pre-DM, XOS showed a tendency to reduce OGTT 2-h insulin levels (P = 0.13), but had no effect on body composition, HOMA-IR, serum glucose, triglyceride, satiety hormones, and TNFα.

CONCLUSION

This is the first clinical observation of modifications of the gut microbiota by XOS in both healthy and Pre-DM subjects in a pilot study. Prebiotic XOS may be beneficial in reversing changes in the gut microbiota during the development of diabetes.

CLINICAL TRIAL REGISTRATION

NCT01944904 (https://clinicaltrials.gov/ct2/show/NCT01944904).

Comparison of the effects of longer chain inulins with different degrees of polymerization on colonic fermentation in a mixed culture of Swine fecal bacteria

The effects of inulin with three different degrees of polymerization (DP) on microbial dietary fiber fermentation were compared in an in vitro simulator of the porcine large bowel. The three inulin isolates had a DP of 15 (from chicory grown in Hokkaido, Japan), and 10 and 24 (from Orafti, Belgium), while cellulose was used as a control. The Lactobacillus level in the DP 10 group at 48 h and bifidobacteria levels in the DP 15 and DP 24 groups at 24 and 48 h were significantly higher than in the carbohydrate-free and cellulose groups. The SCFA concentrations in all the inulin groups were significantly higher than in the carbohydrate-free and cellulose groups at 24 and 48 h. Ammonia nitrogen concentrations in all the inulin groups were significantly lower than those in the carbohydrate-free and cellulose groups at 24 and 48 h. The three different inulin types were fermentable by gut microbiota as indicated by substantial increases in SCFA. In particular, inulin DP 15 exhibited a clear potential to be used as a prebiotic with significant increases in Lactobacillus and Bifidobacterium populations, and concomitantly propionate and butyrate productions than cellulose at the early incubation time. There was a negative correlation between SCFA and ammonia nitrogen concentrations. These results indicate DP 15 product has similar potential as a prebiotic to DP 10 or DP 24 product and showed substantial equivalence to DP 10 and DP 24 products.

Genome sequencing of Clostridium butyricum DKU-01, isolated from infant feces

Background

Clostridium butyricum is a butyric acid-producing anaerobic bacteriuma, and commonly present as gut microbiota in humans. This species has been used as a probiotic for the prevention of diarrhea in humans. In this study, we report the draft genome of C. butyricum DKU-01, which was isolated from infant feces, to better understand the characteristics of this strain so that it can later be used in the development of probiotic products.

Results

A total of 79 contigs generated by hybrid assembly of sequences obtained from Roche 454 and Illumina Miseq sequencing systems were investigated. The assembled genome of strain DKU-01 consisted of 4,519,722 bp (28.62% G + C content) with a N₅₀ contig length of 108,221 bp and 4,037 predicted CDSs. The extracted 16S rRNA gene from genome sequences of DKU-01 was similar to Clostridium butyricum with 99.63% pairwise similarity. The sequence of strain DKU-01 was compared with previously reported genome sequences of C. butyricum. The value of average nucleotide identity between strains DKU-01 and C. butyricum 60E3 was 98.74%, making it the most similar strain to DKU-01.

Conclusions

We sequenced the DKU-01 strain isolated from infant feces, and compared it with the available genomes of C. butyricum on a public database. Genes related to Fructooligosaccharide utilization were detected in the genome of strain DKU-01 and compared with other genera, such as Bifidobacterium and Streptococcus. We found that strain DKU-01 can metabolize a wide range of carbohydrates in comparative genome result. Further analyses of the comparative genome and fermentation study can provide the information necessary for the development of strain DKU-01 for probiotics.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-015-0055-3) contains supplementary material, which is available to authorized users.

Carbohydrate catabolic diversity of bifidobacteria and lactobacilli of human origin

Because increased proportions of particular commensal bacteria such as bifidobacteria and lactobacilli have been linked to human health through a variety of mechanisms, there is corresponding interest in identifying carbohydrates that promote growth and metabolic activity of these bacteria. We evaluated the ability of 20 carbohydrates, including several commercially available carbohydrates that are sold as prebiotic ingredients, to support growth of 32 human-derived isolates belonging to the genera Bifidobacterium and Lactobacillus, including those isolated from healthy elderly subjects. In general, bifidobacterial strains were shown to display more diverse carbohydrate utilization profiles compared to the tested Lactobacillus species, with several bifidobacterial strains capable of metabolizing xylo-oligosaccharide (XOS), arabinoxylan, maltodextrin, galactan and carbohydrates containing fructo-oligosaccharide (FOS) components. In contrast, maltodextrin, galactan, arabinogalactan and galactomannan did not support robust growth (≥0.8 OD600 nm) of any of the Lactobacillus strains assessed. Carbohydrate fermentation was variable among strains tested of the same species for both genera. This study advances our knowledge of polysaccharide utilization by human gut commensals, and provides information for the rational design of selective prebiotic food ingredients.

Effects of prebiotic supplementation on the expression of proteins regulating iron absorption in anaemic growing rats

Prebiotics may increase intestinal Fe absorption in anaemic growing rats. The present study evaluated the effects of high-performance (HP) inulin and oligofructose on factors that regulate Fe absorption in anaemic rats during the growth phase. Male Wistar rats aged 21 d of age were fed AIN-93G ration without Fe for 2 weeks to induce Fe-deficiency anaemia. The rats were fed on day 35 a control diet, or a diet with 10 % HP inulin, or a diet with 10 % oligofructose, without Fe supplementation. The animals were euthanised after 2 weeks, and segments of the duodenum, caecum, colon and liver were removed. The expression levels of proteins in the intestinal segments were assessed using Western blotting. The levels of serum, urine and liver hepcidin and the concentrations of IL-10, IL-6 and TNF-α in the caecum, colon and liver were measured using the ELISA test. HP inulin increased the expression of the divalent metal transporter 1 protein in the caecum by 162 % (P= 0·04), and the expression of duodenal cytochrome b reductase in the colon by 136 % (P= 0·02). Oligofructose decreased the expression of the protein ferroportin in the duodenum (P= 0·02), the concentrations of IL-10 (P= 0·044), IL-6 (P= 0·036) and TNF-α (P= 0·004) in the caecum, as well as the level of urinary hepcidin (P< 0·001). These results indicate that prebiotics may interfere with the expression of various intestinal proteins and systemic factors involved in the regulation of intestinal Fe absorption in anaemic rats during the growth phase.

Genome of Bifidobacteria and Carbohydrate Metabolism

In recent years, the knowledge about bifidobacteria has considerably evolved thanks to recent progress in molecular biology. The analysis of the whole genome sequences of 48 taxa of bifidobacteria offers new perspectives for their classification, especially to set up limit between two species. Indeed, several species are presenting a high homology and should be reclassified. On the other hand, some subspecies are presenting a low homology and should therefore be reclassified into different species. In addition, a better knowledge of the genome of bifidobacteria allows a better understanding of the mechanisms involved in complex carbohydrate metabolism. The genome of some species of bifidobacteria from human but also from animal origin demonstrates high presence in genes involved in the metabolism of complex oligosaccharides. Those species should be further tested to confirm their potential to metabolize complex oligosaccharides in vitro and in vivo.

Coacervated liposoluble fructan-based host–guest microspheres as unique drug delivery materials

A new approach to drug release with microspheres from acetylated liposoluble fructans is demonstrated. Modification of solubility by acetylation supported their preparation by precipitation–coacervation that was able to encapsulate ∼33% of ibuprofen.

Lean rats gained more body weight from a high-fructooligosaccharide diet

Lean rats gained more body weight from a high-FOS diet and increased more gut Bacteroidetes.

In vitro fermentation of lupin seeds (Lupinus albus) and broad beans (Vicia faba): dynamic modulation of the intestinal microbiota and metabolomic output

Broad beans (Vicia faba) and lupin seeds (Lupinus albus) are legumes rich in a wide range of compounds, which may represent a useful dietary approach for modulating the human gut microbiome.

Galacto-oligosaccharides and Colorectal Cancer: Feeding our Intestinal Probiome

Prebiotics are ingredients selectively fermented by the intestinal microbiota that promote changes in the microbial community structure and/or their metabolism, conferring health benefits to the host. Studies show that β (1-4) galacto-oligosaccharides [β (1-4) GOS], lactulose and fructo-oligosaccharides increase intestinal concentration of lactate and short chain fatty acids, and stool frequency and weight, and they decrease fecal concentration of secondary bile acids, fecal pH, and nitroreductase and β-glucuronidase activities suggesting a clear role in colorectal cancer (CRC) prevention. This review summarizes research on prebiotics bioassimilation, specifically β (1-4) GOS, and their potential role in CRC. We also evaluate research that show that the impact of prebiotics on host physiology can be direct or through modulation of the gut intestinal microbiome, specifically the probiome (autochtonous beneficial bacteria), we present studies on a potential role in CRC progression to finally describe the current state of β (1-4) GOS generation for industrial production.

Diet, gut microbes, and genetics in immune function: can we leverage our current knowledge to achieve better outcomes in inflammatory bowel diseases?

Autoimmune disorders, particularly inflammatory bowel diseases (IBD), are increasing at an alarming frequency. While the exact cause remains elusive, studies have examined how the immune system is shaped in the context of genetic susceptibility, gut microbes, and environmental pressures, including dietary intake. Shifts towards a Westernized high fat, high carbohydrate diet result in changes to gut microbiota structure and function that may aid in triggering and perpetuating autoimmunity by promoting the emergence of pathobionts leading to altered immune activation. This review summarizes our current understanding of dietary-induced changes in gut microbiota on autoimmunity in the context of IBD. We provide a framework for leveraging this knowledge to develop new dietary, microbial and immune-based modulation strategies for individualized risk assessment and improving clinical outcomes.

Prebiotic Oligosaccharides: Comparative Evaluation Using In Vitro Cultures of Infants' Fecal Microbiomes

The objective of this study was to systematically assess the bifidogenic effect of three commonly used prebiotic products using in vitro cultures of infant fecal samples. Fresh stool samples collected from six term infants, each exclusively fed human milk (n = 3) or infant formula (n = 3), at 28 days of age were used as inocula. The following prebiotic products were added at concentrations applicable to infant formula: Vivinal GOS 15 (containing 28.5% galacto-oligosaccharide [GOS]) at 7.2 g/liter, Beneo HP (99.5% long-chain inulin [IN]) at 0.8 g/liter, Beneo Synergy 1 (enriched oligofructose and inulin [OF-IN]) at 4 g/liter, and a combination of Vivinal GOS 15 (7.2 g/liter) and Beneo HP (0.8 g/liter) (GOS-IN). The growth of total bacteria, Bifidobacterium, Bacteroides, Bifidobacterium longum, and Escherichia coli was quantified using specific quantitative PCR (qPCR). Bifidobacterium was also enumerated on selective Beerens agar plates, with representative colonies identified by sequencing of their 16S rRNA genes. Volatile fatty acids (VFA) and pH in the cultures were also determined. Irrespective of the feeding methods, the GOS product, either alone or in combination with Beneo HP, resulted in substantially higher growth of total bifidobacteria, and much of this growth was attributed to growth of B. longum. Beneo Synergy 1 also increased the abundance of total bifidobacteria and B. longum. Corresponding to the increases in these two bacterial groups, acetic acid concentrations were higher, while there was a trend of lower E. coli levels and pH. The lower pH and higher acetic acid concentration might be directly responsible for the lower E. coli population. At the concentrations studied, the GOS product was more bifidogenic and potent in inhibiting E. coli than the other products tested. These results suggest that supplementation of infant formula with GOS may increase intestinal bifidobacteria and benefit infant health.

Monoculture parameters successfully predict coculture growth kinetics of Bacteroides thetaiotaomicron and two Bifidobacterium strains

Microorganisms rarely live in isolation but are most often found in a consortium. This provides the potential for cross-feeding and nutrient competition among the microbial species, which make it challenging to predict the growth kinetics in coculture. In this paper we developed a mathematical model to describe substrate consumption and subsequent microbial growth and metabolite production for bacteria grown in monoculture. The model characterized substrate utilization kinetics of 18 Bifidobacterium strains. Some bifidobacterial strains demonstrated preferential degradation of oligofructose in that sugars with low degree of polymerization (DP) (DP≤3 or 4) were metabolized before sugars of higher DP, or vice versa. Thus, we expanded the model to describe the preferential degradation of oligofructose. In addition, we adapted the model to describe the competition between human colonic bacteria Bacteroides thetaiotaomicron LMG 11262 and Bifidobacterium longum LMG 11047 or Bifidobacterium breve Yakult for inulin as well as cross-feeding of breakdown products from the extracellular hydrolysis of inulin by B. thetaiotaomicron LMG 11262. We found that the coculture growth kinetics could be predicted based on the respective monoculture growth kinetics. Using growth kinetics from monoculture experiments to predict coculture dynamics will reduce the number of in vitro experiments required to parameterize multi-culture models.

Effect of traditional leafy vegetables on the growth of lactobacilli and bifidobacteria

Traditional leafy vegetables, apart from being a staple in the diet of most of sub-Saharan Africa, are an essential part of traditional medicine and are used daily by traditional healers in the region to treat a wide variety of ailments. In this study, a batch culture technique was used to investigate whether 25 infusions from 22 traditional leafy vegetables stimulated the growth of Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus reuteri and Bifidobacterium longum in pure culture. High performance liquid chromatography was used to determine the inulin content of the infusions. Sonchus oleraceus stimulated all four strains and Taraxacum officinale stimulated three strains. In total, 18 plants stimulated at least one of the four probiotic strains. The inulin content of the infusions varied between 2.5% and 3.6%, with Asparagus sprengeri containing the highest percentage. These results indicate that traditional leafy vegetables do stimulate the growth of the selected lactobacilli and bifidobacteria in pure culture and contain inulin. These infusions can now be tested for prebiotic potential using mixed culture systems or human hosts.

A perspective on the complexity of dietary fiber structures and their potential effect on the gut microbiota

Even though there are many factors that determine the human colon microbiota composition, diet is an important one because most microorganisms in the colon obtain energy for their growth by degrading complex dietary compounds, particularly dietary fibers. While fiber carbohydrates that escape digestion in the upper gastrointestinal tract are recognized to have a range of structures, the vastness in number of chemical structures from the perspective of the bacteria is not well appreciated. In this article, we introduce the concept of "discrete structure" that is defined as a unique chemical structure, often within a fiber molecule, which aligns with encoded gene clusters in bacterial genomes. The multitude of discrete structures originates from the array of different fiber types coupled with structural variations within types due to genotype and growing environment, anatomical parts of the grain or plant, discrete regions within polymers, and size of oligosaccharides and small polysaccharides. These thousands of discrete structures conceivably could be used to favor bacteria in the competitive colon environment. A global framework needs to be developed to better understand how dietary fibers can be used to obtain predicted changes in microbiota composition for improved health. This will require a multi-disciplinary effort that includes biological scientists, clinicians, and carbohydrate specialists.

Summer Meeting 2013: growth and physiology of bifidobacteria

Bifidobacteria are a minor fraction of the human colon microbiota with interesting properties for carbohydrate degradation. Monosaccharides such as glucose and fructose are degraded through the bifid shunt, a dedicated pathway involving phosphoketolase activity. Its stoechiometry learns that three moles of acetate and two moles of lactate are produced per two moles of glucose or fructose that are degraded. However, deviations from this 3 : 2 ratio occur, depending on the rate of substrate consumption. Slower growth rates favour the production of acetate and pyruvate catabolites (such as formate) at the cost of lactate. Interestingly, bifidobacteria are capable to degrade inulin-type fructans (ITF) (oligofructose and inulin) and arabinoxylan-oligosaccharides (AXOS). Beta-fructofuranosidase activity enables bifidobacteria to degrade ITF. However, this property is strain-dependent. Some strains consume both fructose and oligofructose, with different preferences and degradation rates. Small oligosaccharides (degree of polymerization or DP of 2-7) are taken up, in a sequential order, indicating intracellular degradation and as such giving these bacteria a competitive advantage towards other inulin-type fructan degraders such as lactobacilli, bacteroides and roseburias. Other strains consume long fractions of oligofructose and inulin. Exceptionally, oligosaccharides with a DP of up to 20 (long-chain inulin) are consumed by specific strains. Also, the degradation of AXOS by α-arabinofuranosidase and β-xylosidase is strain-dependent. Particular strains consume the arabinose substituents, whether or not together with a consumption of the xylose backbones of AXOS, either up to xylotetraose or higher and either extra- or intracellularly. The production of high amounts of acetate that accompanies inulin-type fructan degradation by bifidobacteria cross-feeds other colon bacteria involved in the production of butyrate. However, bifidobacterial strain-dependent differences in prebiotic degradation indicate the existence of niche-specific adaptations and hence mechanisms to avoid competition among each other and to favour coexistence with other colon bacteria.

In vitro fermentation of prebiotic oligosaccharides by Bifidobacterium lactis HN019 and Lactobacillus spp

The utilisation of various prebiotic oligosaccharides by probiotic strains of Bifidobacterium lactis, Lactobacillus rhamnosus and Lactobacillus acidophilus was investigated in order to determine the synbiotic potential of various prebiotic/probiotic combinations. Analysis by HPLC and high-performance anion-exchange chromatography of the cell-free medium taken during growth of the three probiotic bacteria showed differences in the consumption of the various oligosaccharides. Analysis of galactooligosaccharides showed that both L. rhamnosus and B. lactis consumed mostly mono- and di-saccharide, while L. acidophilus consumed oligosaccharides up to trisaccharide. Both B. lactis and L. acidophilus utilised fructooligosaccharides and inulin, but showed different patterns of oligosaccharide consumption. Only L. rhamnosus grew on β-glucan oligosaccharides and preferentially consumed the trisaccharide. The results indicate the synbiotic potential of the various probiotic/prebiotic combinations, particularly L. acidophilus/galactooligosaccharides, L. acidophilus/fructooligosaccharides or inulin and L. rhamnosus/β-glucan oligosaccharides.

Difference in Degradation Patterns on Inulin-type Fructans among Strains of Lactobacillus delbrueckii and Lactobacillus paracasei

Lactobacillus delbrueckii strains were assessed for their degradation patterns of various carbohydrates with specific reference to inulin-type fructans in comparison with those of Lactobacillus paracasei strains. Firstly, growth curves on glucose, fructose, sucrose and inulin-type fructans with increasing degrees of fructose polymerization (i.e., 1-kestose, fructo-oligosaccharides and inulin) of the strains were compared. L. paracasei DSM 20020 grew well on all these sugars, while the growth rates of the 4 L. delbrueckii strains were markedly higher on the fructans with a greater degree of polymerization than on fructose and sucrose. Secondly, sugar compositions of spent cultures of the strains of L. delbrueckii and L. paracasei grown in mMRS containing either the fructans or inulin were determined by thin layer chromatography, in which the spent cultures of L. paracasei DSM 20020 showed spots of short fructose and sucrose fractions, whereas those of the L. delbrueckii strains did not show such spots at all. These results suggest that, unlike the L. paracasei strains, the L. delbrueckii strains do not degrade the inulin-type fructans extracellularly, but transport the fructans capable of greater polymerization preferentially into their cells to be degraded intracellularly for their growth.

Emerging aspects of food and nutrition on gut microbiota

The human gastrointestinal tract contains a highly complex ecosystem that harbors various microorganisms, which together create a unique environment within each individual. There is growing awareness that dietary habits are one of the essential factors contributing to the microbial diversity and community configuration that ultimately affects human health. From an evolutionary perspective, human dietary history can be viewed as a central factor in the selection of the gut microbial community and stabilization of the mutualistic host-microbial interaction, that together drive host phenotype. Herein, current knowledge concerning the influence of major dietary macrostructure and individual food ingredients is presented. This knowledge will provide perspectives for personalized gut microbiota management and, ultimately, movement toward an era of personalized nutrition and medicine.

Functional metagenomics reveals novel pathways of prebiotic breakdown by human gut bacteria

The human intestine hosts a complex bacterial community that plays a major role in nutrition and in maintaining human health. A functional metagenomic approach was used to explore the prebiotic breakdown potential of human gut bacteria, including non-cultivated ones. Two metagenomic libraries, constructed from ileum mucosa and fecal microbiota, were screened for hydrolytic activities on the prebiotic carbohydrates inulin, fructo-oligosaccharides, xylo-oligosaccharides, galacto-oligosaccharides and lactulose. The DNA inserts of 17 clones, selected from the 167 hits that were identified, were pyrosequenced in-depth, yielding in total 407, 420 bp of metagenomic DNA. From these sequences, we discovered novel prebiotic degradation pathways containing carbohydrate transporters and hydrolysing enzymes, for which we provided the first experimental proof of function. Twenty of these proteins are encoded by genes that are also present in the gut metagenome of at least 100 subjects, whatever are their ages or their geographical origin. The sequence taxonomic assignment indicated that still unknown bacteria, for which neither culture conditions nor genome sequence are available, possess the enzymatic machinery to hydrolyse the prebiotic carbohydrates tested. The results expand the vision on how prebiotics are metabolized along the intestine, and open new perspectives for the design of functional foods.

An in vitro evaluation of antioxidant and colonic microbial profile levels following mushroom consumption

The biological activity of mushroom consumption is achieved by the antioxidant effect of constituent biomolecules released during digestion. In the following study, the consumption of mushroom fungi was determined to increase the number of Lactobacillus and Bifidobacterium strains within the colon. The main phenolic antioxidant compounds identified were both gentisic and homogentisic acids. Moreover, the flavonoid catechin as well as a significant amount of δ- and γ-tocopherols was determined. The amount of Lactobacillus and Bifidobacterium strains from different sections of the human colon was significantly correlated with levels of antioxidative biomolecules. The experimental data clearly demonstrate a significant impact of mushroom consumption on the fermentative function of microorganisms in the human colon, resulting in the homeostasis of normal physiological colonic functions.

Effects of high performance inulin supplementation on glycemic status and lipid profile in women with type 2 diabetes: a randomized, placebo-controlled clinical trial

BACKGROUND

Type 2 diabetes mellitus, as a noncommunicable disease, is the main public health challenge in the 21st century. The prevalence of diabetes mellitus adjusted for the world population in Iran was 8% until the year 2010.Lipid levels are considered as important parameters to be evaluated, as high serum lipid levels are often reported as a complication in patients with diabetes mellitus.It is claimed that functional foods may improve complications of diabetes mellitus, so this study was designed to evaluate the effects of high performance inulin on glycemic status and lipid profile of women with type 2 diabetes.

METHODS

The study was a randomized controlled clinical trial. Forty-nine type 2 diabetic females (fiber intake <30g/d, 25<BMI<35 kg/m2) were divided into two groups. Patients in the intervention group (n=24) received 10g/d inulin and patients in the control group (n=25) received 10g/d maltodextrin for 8 weeks.Glycemic status and lipid profile indices were measured pre and post intervention. Data were analyzed using SPSS software (verision11.5). Paired, unpaired t-test and ANCOVA were used to compare quantitative variables.

RESULTS

Supplementation with inulin caused a significant reduction in FBS (8.50%), HbA1c (10.40%), total cholesterol (12.90%), triglyceride (23.60 %), LDL-c (35.30 %), LDL-c/HDL-c ratio (16.25%) and TC/HDL-c ratio (25.20%) and increased HDL-c (19.90%). The changes for the control group parameters were not significant at the end of study.

CONCLUSION

Inulin may help to control diabetes and its complications via improving glycemic and lipid parameters.