Bacterial, SCFA and gas profiles of a range of food ingredients following in vitro fermentation by human colonic microbiota

Re-evaluation of erythritol (E 968) as a food additive

This opinion addresses the re-evaluation of erythritol (E 968) as food additive and an application for its exemption from the laxative warning label requirement as established under Regulation (EU) No 1169/2011. Erythritol is a polyol obtained by fermentation with Moniliella pollinis BC or Moniliella megachiliensis KW3-6, followed by purifications and drying. Erythritol is readily and dose-dependently absorbed in humans and can be metabolised to erythronate to a small extent. Erythritol is then excreted unchanged in the urine. It does not raise concerns regarding genotoxicity. The dataset evaluated consisted of human interventional studies. The Panel considered that erythritol has the potential to cause diarrhoea in humans, which was considered adverse because its potential association with electrolyte and water imbalance. The lower bound of the range of no observed adverse effect levels (NOAELs) for diarrhoea of 0.5 g/kg body weight (bw) was identified as reference point. The Panel considered appropriate to set a numerical acceptable daily intake (ADI) at the level of the reference point. An ADI of 0.5 g/kg bw per day was considered by the Panel to be protective for the immediate laxative effect as well as potential chronic effects, secondary to diarrhoea. The highest mean and 95th percentile chronic exposure was in children (742 mg/kg bw per day) and adolescents (1532 mg/kg bw per day). Acute exposure was maximally 3531 mg/kg bw per meal for children at the 99th percentile. Overall, the Panel considered both dietary exposure assessments an overestimation. The Panel concluded that the exposure estimates for both acute and chronic dietary exposure to erythritol (E 968) were above the ADI, indicating that individuals with high intake may be at risk of experiencing adverse effects after single and repeated exposure. Concerning the new application, the Panel concluded that the available data do not support the proposal for exemption.

The impact of antimicrobial food additives and sweeteners on the growth and metabolite production of gut bacteria

Metabolic disorders caused by the imbalance of gut microbiota have been associated with the consumption of processed foods. Thus, this study aimed to evaluate the effects of antimicrobial food additives (benzoate, sorbate, nitrite, and bisulfite) and sweeteners (saccharin, stevia, sucralose, aspartame, and cyclamate) on the growth and metabolism of some gut and potentially probiotic bacterial species. The effects on the growth of Bifidobacterium longum, Enterococcus faecium, Lactobacillus acidophilus, and Lactococcus lactis subsp. lactis cultures were investigated using a turbidimetric test and by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). To evaluate the metabolic activity, the cultures were exposed to compounds with the highest antimicrobial activity, subjected to cultivation with inulin (1.5%), and analyzed by liquid chromatography for the production of short-chain fatty acids (acetate, propionate, and butyrate). The results showed that potassium sorbate (25 mg/mL), sodium bisulfite (0.7 mg/mL), sodium benzoate, and saccharin (5 mg/mL) presented greater antimicrobial activity against the studied species. L. lactis and L. acidophilus bacteria had reduced short-chain fatty acid production after exposure to saccharin and sorbate, and B. longum after exposure to sorbate, in comparison to controls (acetic acid reduction 1387 μg/mL and propionic 23 μg/mL p < 0.05).

Optimizing postbiotic production through solid-state fermentation with Bacillus amyloliquefaciens J and Lactiplantibacillus plantarum SN4 enhances antibacterial, antioxidant, and anti-inflammatory activities

Background

Postbiotics are an emerging research interest in recent years and are fairly advanced compared to prebiotics and probiotics. The composition and function of postbiotics are closely related to fermentation conditions.

Methods

In this study, we developed a solid-state fermentation preparation method for postbiotics with antimicrobial, antioxidant, and anti-inflammatory activities. The antibacterial activity was improved 3.62 times compared to initial fermentation conditions by using optimization techniques such as single factor experiments, Plackett-Burman design (PBD), steepest ascent method (SAM), and central composite design (CCD) methods. The optimized conditions were carried out with an initial water content of 50% for 8 days at 37°C and fermentation strains of Bacillus amyloliquefaciens J and Lactiplantibacillus plantarum SN4 at a ratio of 1:1 with a total inoculum size of 8%. The optimized SSF medium content ratios of peptide powder, wheat bran, corn flour, and soybean meal were 4, 37.4, 30, and 28.6%, respectively.

Results

Under these optimized conditions, postbiotics with a concentration of 25 mg/mL showed significant broad-spectrum antibacterial capabilities against Escherichia coli, Salmonella, and Staphylococcus aureus and strong antioxidant activity against ABTS, DPPH, and OH radicals. Moreover, the optimized postbiotics exhibited good anti-inflammatory ability for reducing nitric oxide (NO) secretion in RAW 264.7 macrophage cells in response to LPS-induced inflammation. Furthermore, the postbiotics significantly improved intestinal epithelial wound healing capabilities after mechanical injury, such as cell scratches in IPEC-J2 cells (p < 0.05).

Conclusion

In brief, we developed postbiotics through optimized solid-state fermentation with potential benefits for gut health. Therefore, our findings suggested that the novel postbiotics could be used as potential functional food products for improving body health.

In vitro prebiotic activity of rhLf and galactooligosaccharides on infant intestinal microbiota

Introduction

Objective: human lactoferrin (Lf) and human milk oligosaccharides possess a wide range of functions. So, the present study focusses on the role of Lf and/or galactooligosaccharides (GOS) in the modulation of gut microbiota composition. Methods: recombinant human lactoferrin (rhLf) was added to the first infant formula (0.10, 0.15, 0.20 %) alone or in combination with GOS (1 %) in vessels of a small-scale batch culture fermentation model. Short-chain fatty acids (SCFAs), microbial population groups, and pH were monitored through fermentation for 24 hours. Results: insignificant changes were observed in pH values and acetic acid accumulated during fermentation. Propionic acid content has been insignificantly increased while butyric acid has been insignificantly decreased. Moreover, increments in all bacterial groups except for Bacteroides were observed through the fermentation process. Lactobacillus and Bifidobacterium showed an increase in relation to initial time over the fermentation process, demonstrating the prebiotic effect of lactoferrin and GOS. After 24 hours of fermentation, all tested ingredients showed significant similarities in Enterococcus for controls except for 0.20 % rhLf + 1 % GOS, which provoked a diminution of Enterococci growth. Conclusion: despite the importance of the batch culture fermentation technique in uncovering the prebiotic activity of food ingredients, it is not useful for detecting the prebiotic nature of Lf due to its nature as a protein. Thus, Lf maybe shows its prebiotic activity on the gut microbiota through other mechanisms.

Dietary Supplementation with Mono-Lactate Glyceride Enhances Intestinal Function of Weaned Piglets

Mono-lactate glyceride (LG) is a short-chain fatty acid ester. It has been shown that short-chain fatty acid esters play an important role in maintaining intestinal structure and function. The aim of this study is to investigate the effects of mono-lactate glyceride on growth performance and intestinal morphology and function in weaned piglets. Sixteen 21-day-old weaned piglets of similar weight were distributed arbitrarily to two treatments: The control group (basal diet) and the LG group (basal diet + 0.6% mono-lactate glyceride). The experiment lasted for 21 days. On day 21 of the trial, piglets were weighed, and blood and intestinal samples were collected for further analysis. Results showed that dietary supplementation with 0.6% mono-lactate glyceride decreased (p < 0.05) the diarrhea rate and the contents of malondialdehyde and hydrogen peroxide in the ileum and jejunum and increased (p < 0.05) the expression of intestinal tight junction protein (Occludin) and the activities of superoxide dismutase and catalase in the ileum and colon. In addition, mono-lactate glyceride supplementation could enhance intestinal mucosal growth by increasing (p < 0.05) the mRNA levels of extracellular regulated protein kinases, promote intestinal mucosal water and nutrient transport and lipid metabolism by increasing (p < 0.05) the mRNA levels of b^0,+ amino acid transporter, aquaporin 3, aquaporin 10, gap junction protein alpha 1, intestinal fatty acid-binding protein, and lipoprotein lipase, enhance antiviral and immune function by increasing (p < 0.05) the mRNA levels of nuclear factor kappa-B, interferon-β, mucovirus resistance protein II, 2'-5'-oligoadenylate synthetase-like, interferon-γ, C-C motif chemokine ligand 2, and toll-like receptor 4, and enhance antioxidant capacity by increasing (p < 0.05) the mRNA levels of NF-E2-related factor 2 and glutathione S-transferase omega 2 and decreasing (p < 0.05) the mRNA level of NADPH oxidase 2. These results suggested that dietary supplementation with mono-lactate glyceride could decrease the diarrhea rate by improving intestinal antioxidant capacity, intestinal mucosal barrier, intestinal immune defense function, and intestinal mucosal water and nutrient transport. Collectively, dietary supplementation with 0.6% mono-lactate glyceride improved the intestinal function of weaned piglets.

Systematic Review of Human and Animal Evidence on the Role of Buckwheat Consumption on Gastrointestinal Health

BACKGROUND

Buckwheat is a commonly cultivated crop with growing evidence that it is beneficial to gastrointestinal (GI) health. This systematic review summarizes the role of buckwheat in modifying GI health outcomes and microbiomes.

METHODS

Four medical databases and Google Scholar were systematically searched. Clinical trials, observational studies, animal in vivo, and in vitro studies with human and animal GI-derived samples were included.

RESULTS

There were 32 studies (one randomized controlled trial [RCT], one non-randomized trial, 3 observational, 9 in vitro, and 18 animal in vivo studies) included. In preclinical studies, buckwheat extracts were observed to have cytotoxic potential against human-derived GI cancer cell lines. Animals fed with buckwheat had lower GI mucosal inflammation, higher alpha diversity in the GI microbiome, and higher levels of fecal short-chain fatty acids. Human evidence studies and clinical trials were limited and predominantly of moderate risk of bias. The majority of in vitro studies with GI-derived samples and in vivo studies were reliable without restrictions in study design.

CONCLUSION

In vivo and in vitro studies show that buckwheat may have potential GI benefits due to its anti-oxidant and anti-inflammatory potential; however, human evidence remains limited, and its impact on health in humans remains to be elucidated in future trials.

Current in Vitro and Animal Models for Understanding Foods: Human Gut-Microbiota Interactions

The food-gut microbiota interaction is an important regulator of human health. Numerous in vitro and animal models have thus been developed in order to simulate the specific food-gut microbiota and/or host-gut microbiota interactions in the human colon. This review summarizes the design principles of each model and discusses their advantages and weaknesses in terms of studying food-gut microbiota interactions. In vitro fermentation models appear to be reliable methods to investigate various aspects involved in the food-gut microbiota interactions in humans. However, many physiological perspectives lack appreciation of these models, such as peristaltic movement, biochemical conditions, and gastrointestinal anatomy. Animal models provide more physiological relevance to human trials compared to in vitro models. However, they may have gastrointestinal tract aspects that are distinct from human subjects. This review contains important information that can help the development of more advanced models to study food-gut microbiota interactions in humans.

An Updated Review on Prebiotics: Insights on Potentials of Food Seeds Waste as Source of Potential Prebiotics

Prebiotics are a group of biological nutrients that are capable of being degraded by microflora in the gastrointestinal tract (GIT), primarily Lactobacilli and Bifidobacteria. When prebiotics are ingested, either as a food additive or as a supplement, the colonic microflora degrade them, producing short-chain fatty acids (SCFA), which are simultaneously released in the colon and absorbed into the blood circulatory system. The two major groups of prebiotics that have been extensively studied in relation to human health are fructo-oligosaccharides (FOS) and galactooligosaccharides (GOS). The candidature of a compound to be regarded as a prebiotic is a function of how much of dietary fiber it contains. The seeds of fruits such as date palms have been reported to contain dietary fiber. An increasing awareness of the consumption of fruits and seeds as part of the daily diet, as well as poor storage systems for seeds, have generated an enormous amount of seed waste, which is traditionally discarded in landfills or incinerated. This cultural practice is hazardous to the environment because seed waste is rich in organic compounds that can produce hazardous gases. Therefore, this review discusses the potential use of seed wastes in prebiotic production, consequently reducing the environmental hazards posed by these wastes.

Can Supplemented Skim Milk (SKM) Boost Your Gut Health?

The incorporation of functional ingredients, such as prebiotics and probiotics in food matrices, became a common practice in the human diet to improve the nutritional value of the food product itself. Worldwide, skim milk (SKM) is one of the most consumed food matrices, comprising all the essential nutrients desired for a balanced diet. Thus, the modulation of the human gut microbiota by SKM supplemented with different well-known functional ingredients was evaluated. Four well-studied prebiotics, fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), mannan-oligosaccharides (MOS) and inulin, and one probiotic product, UL-250® (Saccharomyces boulardii) were added at 1% (w/v) to SKM and subjected to a gastrointestinal in vitro model. The impact of each combination on gut microbiota profile and their fermentation metabolites (i.e., short-chain fatty acids–SCFA) was assessed by quantitative polymerase chain reaction (qPCR) and high-performance liquid chromatography (HPLC), respectively. The addition of FOS to SKM had promising results, showing prebiotic potential by promoting the growth of Lactobacillus, Bifidobacterium, and Clostridium cluster IV. Moreover, the increment of SCFA levels and the decrease of total ammonia nitrogen were observed throughout colonic fermentation. Overall, these results demonstrate that the combination SKM + FOS was the most beneficial to the host’s health by positively modulating the gut microbiota.

The Effects of Commonly Consumed Dietary Fibres on the Gut Microbiome and Its Fibre Fermentative Capacity in Adults with Inflammatory Bowel Disease in Remission

Introduction: It has been suggested that the gut microbiome of patients with inflammatory bowel disease (IBD) is unable to ferment dietary fibre. This project explored the in vitro effect of fibre fermentation on production of short-chain fatty acids (SCFA) and on microbiome composition. Methods: Faecal samples were collected from 40 adults (>16 y) with IBD (n = 20 with Crohn’s disease and n = 20 with ulcerative colitis) in clinical remission and 20 healthy controls (HC). In vitro batch culture fermentations were carried out using as substrates maize starch, apple pectin, raftilose, wheat bran, α cellulose and a mixture of these five fibres. SCFA concentration (umol/g) was quantified with gas chromatography and microbiome was profiled with 16S rRNA sequencing. Results: Fibre fermentation did not correct the baseline microbial dysbiosis or lower diversity seen in either patients with CD or UC. For all fibres, up to 51% of baseline ASVs or genera changed in abundance in HC. In patients with IBD, fermentation of fibre substrates had no effect on species or genera abundance. Production of SCFA varied among the different fibre substrates but this was not different between the two IBD groups and compared to HC after either 5 or 24 h fermentation. Conclusions: Despite extensive microbial dysbiosis, patients with IBD have a similar capacity to ferment fibre and release SCFA as HC. Fibre supplementation alone may be unlikely to restore to a healthy status the compositional shifts characteristic of the IBD microbiome.

Microbiome therapeutics for hepatic encephalopathy

Hepatic encephalopathy (HE) is a complication of cirrhosis characterised by neuropsychiatric and motor dysfunction. Microbiota-host interactions play an important role in HE pathogenesis. Therapies targeting microbial community composition and function have been explored for the treatment of HE. Prebiotics, probiotics and faecal microbiota transplant (FMT) have been used with the aim of increasing the abundance of potentially beneficial taxa, while antibiotics have been used to decrease the abundance of potentially harmful taxa. Other microbiome therapeutics, including postbiotics and absorbents, have been used to target microbial products. Microbiome-targeted therapies for HE have had some success, notably lactulose and rifaximin, with probiotics and FMT also showing promise. However, there remain several challenges to the effective application of microbiome therapeutics in HE, including the resilience of the microbiome to sustainable change and unpredictable clinical outcomes from microbiota alterations. Future work in this space should focus on rigorous trial design, microbiome therapy selection, and a personalised approach to HE.

Fecal Microbiota Transplantation in Patients with HBV Infection or Other Chronic Liver Diseases: Update on Current Knowledge and Future Perspectives

Liver disease and gut dysbiosis are strictly associated, and the pathophysiology of this bidirectional relationship has recently been the subject of several investigations. Growing evidence highlights the link between gut microbiota composition, impairment of the gut-liver axis, and the development or progression of liver disease. Therefore, the modulation of gut microbiota to maintain homeostasis of the gut-liver axis could represent a potential instrument to halt liver damage, modify the course of liver disease, and improve clinical outcomes. Among all the methods available to achieve this purpose, fecal microbiota transplantation (FMT) is one of the most promising, being able to directly reshape the recipient’s gut microbial communities. In this review, we report the main characteristics of gut dysbiosis and its pathogenetic consequences in cirrhotic patients, discussing the emerging data on the application of FMT for liver disease in different clinical settings.

Prebiotic Food Intake May Improve Bone Resorption in Japanese Female Athletes: A Pilot Study

The aim of the present study was to clarify the influence of inulin and lactulose-fortified prebiotic food intakes on bone metabolism turnover among Japanese female athletes. The participants included 29 female athletes aged 18–25 years. They were requested to consume their habitual foods or drinks with one pack of prebiotic food every day for 12 weeks. Dietary intake, training time, body composition, blood sample, and fecal microbiota were assessed during this intervention period. Body composition, total energy intake, and training time of the participants revealed no significant changes during the intervention period. The occupation ratio of Bifidobacterium spp. was significantly increased at 3 and 4 weeks (18.0 ± 8.3% and 17.6 ± 8.5%, respectively) compared to that of pre-intervention (11.7 ± 7.3%) (p = 0.019 and p = 0.035, respectively). The serum TRACP-5b level was significantly decreased at 12 weeks (363 ± 112 mU/dL) compared to that at baseline (430 ± 154 mU/dL) (p = 0.018). These results suggest that the prebiotic food used in this study might have beneficial effects on bone health and gut microbial environment among female athletes. Further studies are warranted to identify the mechanism of the prebiotics–gut–bone axis.

Effects of Colonic Fermentation Products of Polydextrose, Lactitol and Xylitol on Intestinal Barrier Repair In Vitro

Many functional food ingredients improve intestinal barrier function through their colonic fermentation products short chain fatty acids (SCFAs). Effects of individual SCFAs have been well studied, but the effects of SCFA mixtures–colonic fermentation products have been rarely investigated. Therefore, this study used an EnteroMix semi-continuous model to simulate the colonic fermentation of three widely used food ingredients, polydextrose, lactitol and xylitol in vitro, and investigated the effects of their fermentation products on impaired colonic epithelial barrier function through a mucus-secreting human HT29-MTX-E12 cell model. Fermentation of polydextrose and lactitol produced mainly acetate, while fermentation of xylitol produced mainly butyrate and resulted in a much higher butyrate proportion. All fermentation products significantly improved intestinal barrier repairing as measured by increased transepithelial electrical resistance and decreased paracellular permeability. Among these, xylitol fermentation products exhibited better repairing effects than that of polydextrose and lactitol. Correlation analysis showed that the repairing effects were attribute to butyrate but not acetate or propionate, implying that in the fermentation products butyrate may play a major role in improving intestinal barrier function. Our results suggest that functional food ingredients that mainly produce butyrate during fermentation may be of more value for improving gut health related to chronic diseases.

Short chain fatty acids and monocarboxylate transporters in irritable bowel syndrome

BACKGROUND/AIMS

Gut microbiota ferments indigestible food that rests in the colon to produce short-chain fatty acids (SCFAs) acetate, propionate, and butyrate. Colonic SCFA stimulate the synthesis of serotonin which is central in irritable bowel syndrome (IBS) pathophysiology. Reduced SCFA have been linked to specific IBS symptoms like colonic hyperalgesia and hypersensitivity. SCFA enter the colonocyte mainly via 2 energy-dependent monocarboxylate transporters, MCT1 (SLC16A1) and SMCT1 (SLC5A8). We investigated specific gut microbiota, SCFA concentrations, and monocarboxylate transporter mRNA expression in patients with IBS.

MATERIAL AND METHODS

A total of 30 IBS patients-15 constipation-predominant (C-IBS) and 15 diarrhoea-predominant (D-IBS)-and 15 healthy controls were recruited. Bacteroidetes and Bifidobacterium species were analyzed using quantitative polymerase chain reaction (qPCR) on stool samples. SCFA concentrations were determined by gas chromatography/mass spectroscopy of stool samples. Monocarboxylate transporter mRNA was quantified by qPCR on colon biopsy specimens.

RESULTS

Bacteroides was significantly increased in the D-IBS group compared with the C-IBS group and healthy controls. Bifidobacterium was significantly reduced in both IBS groups. SCFA ratios were altered in both IBS groups with a reduction of all 3 measured SCFA in C-IBS and acetic acid in D-IBS. MCT1 and SMCT1 were significantly reduced in C-IBS and D-IBS.

CONCLUSION

In agreement with findings of previous studies, the microbiota assessed were significantly altered inferring dysbiosis in IBS. SCFA and their ratios were significantly altered in both IBS groups. SCFA transporters, MCT1 and SMCT1 were significantly reduced in both IBS groups, suggesting reduced colonocyte SCFA transfer. SCFA availability and transfer into the colonocytes may be important in IBS pathogenesis and should be prospectively studied.

Preservation of Human Gut Microbiota Inoculums for In Vitro Fermentations Studies

The use of fecal inoculums for in vitro fermentation models requires a viable gut microbiota, capable of fermenting the unabsorbed nutrients. Fresh samples from human donors are used; however, the availability of fresh fecal inoculum and its inherent variability is often a problem. This study aimed to optimize a method of preserving pooled human fecal samples for in vitro fermentation studies. Different conditions and times of storage at −20 °C were tested. In vitro fermentation experiments were carried out for both fresh and frozen inoculums, and the metabolic profile compared. In comparison with the fresh, the inoculum frozen in a PBS and 30% glycerol solution, had a significantly lower (p < 0.05) bacterial count (<1 log CFU/mL). However, no significant differences (p < 0.05) were found between the metabolic profiles after 48 h. Hence, a PBS and 30% glycerol solution can be used to maintain the gut microbiota viability during storage at −20 °C for at least 3 months, without interfering with the normal course of colonic fermentation.

Re-evaluation of polydextrose (E 1200) as a food additive

This opinion deals with the re-evaluation of polydextrose (E 1200) when used as a food additive. The Panel followed the conceptual framework for the risk assessment of certain additives and considered that: adequate exposure estimates were available; the margin of safety (MOS)/margin of exposure (MOE) for arsenic was between 0.5-14 and 8.5 for lead; the exhaustions of the tolerable weekly intake (TWI) for cadmium would be 165%, 10% for mercury, whereas the exhaustion of the tolerable daily intake (TDI) for nickel would be 9%; the absorption is limited and part of polydextrose is fermented in the large intestine into short-chain fatty acids (SCFA); adequate toxicity data were available; there is no concern with respect to genotoxicity; no adverse effects were reported in subchronic studies in rats, dogs or monkeys nor in chronic or carcinogenicity studies in mice and rats at the highest doses tested of up 12,500 mg/kg body weight (bw) per day and 15,000 mg/kg bw per day, respectively; the nephrocalcinosis in dogs given high doses of polydextrose was considered to be a treatment-related but a secondary effect related to diarrhoea, and hence not relevant for the risk assessment; no adverse effects were reported in reproductive or developmental toxicity studies in rats administered up to 10,000 mg polydextrose/kg bw per day, or in a developmental toxicity study in rabbits up to 1,818 mg/kg bw per day (the highest dose tested). Therefore, the Panel concluded that there is no need for numerical acceptable daily intake (ADI) for polydextrose (E 1200), and that there is no safety concern for the reported uses and use levels of polydextrose as a food additive. The Panel recommended that European Commission considers to lower the maximum limit for lead and to introduce limits for arsenic, cadmium and mercury in the EU specifications for polydextrose (E 1200), and to verify that polydextrose-N as a food additive (E 1200) is no longer marketed in the EU.

Lactobacillus plantarum-Mediated Regulation of Dietary Aluminum Induces Changes in the Human Gut Microbiota: an In Vitro Colonic Fermentation Study

The gut microbiota has been identified as a target of toxic metals and a potentially crucial mediator of the bioavailability and toxicity of these metals. In this study, we show that aluminum (Al) exposure, even at low dose, affected the growth of representative strains from the human intestine via pure culture experiments. In vitro, Lactobacillus plantarum CCFM639 could bind Al on its cell surface as shown by electron microscopy and energy dispersive X-ray analysis. The potential of L. plantarum CCFM639 to reverse changes in human intestine microbiota induced by low-dose dietary Al exposure was investigated using an in vitro colonic fermentation model. Batch fermenters were inoculated with fresh stool samples from healthy adult donors and supplemented with 86 mg/L Al and/or 10⁹ CFU of L. plantarum CCFM639. Al exposure significantly increased the relative abundances of Bacteroidetes (Prevotella), Proteobacteria (Escherichia), Actinobacteria (Collinsella), Euryarchaeota (Methanobrevibacter), and Verrucomicrobiaceae and decreased Firmicutes (Streptococcus, Roseburia, Ruminococcus, Dialister, Coprobacillus). Some changes were reversed by the inclusion of L. plantarum CCFM639. Alterations in gut microbiota induced by Al and L. plantarum CCFM639 inevitably led to changes in metabolite levels. The short-chain fatty acid (SCFAs) contents were reduced after Al exposure, but L. plantarum CCFM639 could elevate their levels. SCFAs had positive correlations with beneficial bacteria, such as Dialister, Streptococcus, Roseburia, and negative correlations with Erwinia, Escherichia, and Serratia. Therefore, dietary Al exposure altered the composition and structure of the human gut microbiota, and this was partially mitigated by L. plantarum CCFM639. This probiotic supplementation is potentially a promising and safe approach to alleviate the harmful effects of dietary Al exposure.

In Vitro Modulation of Gut Microbiota and Metabolism by Cooked Cowpea and Black Bean

Legumes are a rich source of a wide range of compounds that may represent an important tool to overcome gut dysbiosis. In this work, the prebiotic potential of two cooked legumes (cowpea and black bean) was investigated in comparison with potato:beef mixture, as substrates in batch faecal culture fermentation. Prior to the fermentation, all the samples were in vitro digested, passing through three phases, namely mouth, gastric and small intestine simulation, and then in vitro fermented for 6, 24 and 48 h. The shift of pH, production of gas and short-chain fatty acids (SCFAs) and changes in gut microbiota were evaluated along the fermentation time. The pH decreased significantly over time in all media with fermentable sources when compared with the negative control. Gas production was higher in the media containing fermentable source than in the negative control and decreased with fermentation time. The concentration of SCFAs increased over time and it was significantly higher for both legumes than in inulin (positive control) and potato:beef meal. Acetate was the major SCFAs produced during fermentation, particularly in media containing legumes. Both legumes presented a strong prebiotic effect on gut microbiota, showing a significant increase in Bifidobacterium and Lactobacillus. These results suggest that consumption of cooked cowpea and black bean, used alone or as an ingredient of novel functional foods, may contribute to improving intestinal health and therefore human health promotion.

Faster Short-Chain Fatty Acid Absorption from the Cecum Following Polydextrose Ingestion Increases the Salivary Immunoglobulin A Flow Rate in Rats

Salivary immunoglobulin A (IgA) plays a vital role in preventing upper respiratory tract infections (URTI). In our previous study, we showed that the intake of carbohydrates increases the intestinal levels of short-chain fatty acids (SCFAs), which in turn increase salivary IgA levels. However, the mechanism underlying this phenomenon has not been fully elucidated. In this study, we investigated in rats the effect of polydextrose (PDX) ingestion on salivary IgA level and SCFA concentration in cecal digesta and the portal vein. Five-week-old rats were fed with a fiber-free diet (control) or with 40 g/kg of PDX for 28 days. Compared to the control, ingestion of PDX led to a higher salivary IgA flow rate (p = 0.0013) and a higher concentration of SCFAs in the portal vein (p = 0.004). These two data were positively correlated (r_s = 0.88, p = 0.0002, n = 12). In contrast, the concentration of SCFAs in cecal digesta and cecal digesta viscosity were significantly lower following PDX ingestion, compared to the control (p = 0.008 and 0.05, respectively). These findings suggest that the ingestion of PDX increases the absorption rate of SCFAs in the intestine through PDX-induced fermentation, which is accompanied by an increase in SCFA levels in the blood, and ultimately leads to increased salivary IgA levels.

de los Reyes-Gavilán C, Gueimonde M. In Vitro Evaluation of Different Prebiotics on the Modulation of Gut Microbiota Composition and Function in Morbid Obese and Normal-Weight Subjects

The gut microbiota remains relatively stable during adulthood; however, certain intrinsic and environmental factors can lead to microbiota dysbiosis. Its restoration towards a healthy condition using best-suited prebiotics requires previous development of in vitro models for evaluating their functionality. Herein, we carried out fecal cultures with microbiota from healthy normal-weight and morbid obese adults. Cultures were supplemented with different inulin-type fructans (1-kestose, Actilight, P95, Synergy1 and Inulin) and a galactooligosaccharide. Their impact on the gut microbiota was assessed by monitoring gas production and evaluating changes in the microbiota composition (qPCR and 16S rRNA gene profiling) and metabolic activity (gas chromatography). Additionally, the effect on the bifidobacterial species was assessed (ITS-sequencing). Moreover, the functionality of the microbiota before and after prebiotic-modulation was determined in an in vitro model of interaction with an intestinal cell line. In general, 1-kestose was the compound showing the largest effects. The modulation with prebiotics led to significant increases in the Bacteroides group and Faecalibacterium in obese subjects, whereas in normal-weight individuals, substantial rises in Bifidobacterium and Faecalibacterium were appreciated. Notably, the results obtained showed differences in the responses among the tested compounds but also among the studied human populations, indicating the need for developing population-specific products.

Inulin with different degrees of polymerization protects against diet-induced endotoxemia and inflammation in association with gut microbiota regulation in mice

Societal lifestyle changes, especially increased consumption of a high-fat diet lacking dietary fibers, lead to gut microbiota dysbiosis and enhance the incidence of adiposity and chronic inflammatory disease. We aimed to investigate the metabolic effects of inulin with different degrees of polymerization on high-fat diet-fed C57BL/6 J mice and to evaluate whether different health outcomes are related to regulation of the gut microbiota. Short-chain and long-chain inulins exert beneficial effects through alleviating endotoxemia and inflammation. Antiinflammation was associated with a proportional increase in short-chain fatty acid-producing bacteria and an increase in the concentration of short-chain fatty acids. Inulin might decrease endotoxemia by increasing the proportion of Bifidobacterium and Lactobacillus, and their inhibition of endotoxin secretion may also contribute to antiinflammation. Interestingly, the beneficial health effects of long-chain inulin were more pronounced than those of short-chain inulin. Long-chain inulin was more dependent than short-chain inulin on species capable of processing complex polysaccharides, such as Bacteroides. A good understanding of inulin-gut microbiota-host interactions helps to provide a dietary strategy that could target and prevent high-fat diet-induced endotoxemia and inflammation through a prebiotic effect.

Production, Structural Characterization, and In Vitro Assessment of the Prebiotic Potential of Butyl-Fructooligosaccharides

Short-chain fatty acids (SCFAs), especially butyrate, produced in mammalian intestinal tracts via fermentation of dietary fiber, are known biofunctional compounds in humans. However, the variability of fermentable fiber consumed on a daily basis and the diversity of gut microbiota within individuals often limits the production of short-chain fatty acids in the human gut. In this study, we attempted to enhance the butyrate levels in human fecal samples by utilizing butyl-fructooligosaccharides (B-FOS) as a novel prebiotic substance. Two major types of B-FOS (GF3-1B and GF3-2B), composed of short-chain fructooligosaccharides (FOS) bound to one or two butyric groups by ester bonds, were synthesized. Qualitative analysis of these B-FOS using Fourier transform infrared (FT-IR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), nuclear magnetic resonance (NMR) and low-resolution fast-atom bombardment mass spectra (LR-FAB-MS), showed that the chemical structure of GF3-1B and GF3-2B were [O-(1-buty-β-D-fru-(2→1)-O-β-D-fru-(2→1)-O-β-D-fru-O-α-D-glu] and [O-(1-buty)-β-D-fru-(2→1)-O-β-D-fru-(2→1)-O-(4-buty)-β-D-fru-O-α-D-glu], respectively. The ratio of these two compounds was approximately 5:3. To verify their biofunctionality as prebiotic oligosaccharides, proliferation and survival patterns of human fecal microbiota were examined in vitro via 16S rRNA metagenomics analysis compared to a positive FOS control and a negative control without a carbon source. B-FOS treatment showed different enrichment patterns on the fecal microbiota community during fermentation, and especially stimulated the growth of major butyrate producing bacterial consortia and modulated specific butyrate producing pathways with significantly enhanced butyrate levels. Furthermore, the relative abundance of Fusobacterium and ammonia production with related metabolic genes were greatly reduced with B-FOS and FOS treatment compared to the control group. These findings indicate that B-FOS differentially promotes butyrate production through the enhancement of butyrate-producing bacteria and their metabolic genes, and can be applied as a novel prebiotic compound in vivo.

Fermented Soybean Dregs by Neurospora crassa: a Traditional Prebiotic Food

Soybean dregs fermented by Neurospora crassa is a typical traditional food in Gannan district of China. In this study, in vitro imitated gut fermentation was carried out to evaluate whether the oligosaccharides from this fermented soybean dregs had potential prebiotic properties. 11.91% of oligosaccharides were extracted from the fermented soybean dregs at the optimized condition which of 1:25 for ratio of soybean dregs (g) to 50% ethanol (ml), 90 min of extracted duration at 70 °C for twice. The soybean dreg oligosaccharides (SBOS) were progressively purified with Sevag method and on columns filled with AB-8 macroporous resin, and then identified as cellobiose by HPLC-ESI-MS and FT-IR. Oligosaccharides of soybean dregs with 800 mg/L significantly decreased pH value (p < 0.05) and ammonia N concentration (p < 0.05), and increased short chain fatty acid (SCFA) level (p < 0.05) in imitated gut fermentation compared with control group. It was shown that this fermented soybean dregs could be a potential prebiotic food.

Regulatory Function of Buckwheat-Resistant Starch Supplementation on Lipid Profile and Gut Microbiota in Mice Fed with a High-Fat Diet

Buckwheat-resistant starch (BRS) has shown to be a nutrient capable of lowering cholesterol and reducing obesity. In this study, the regulatory effects of tartary buckwheat starch on blood lipid level and gut microbiota (Lactobacillus, Bifidobacterium, Enterococcus, and Escherichia coli) in mice fed with a high-fat diet was investigated. Male C57BL/6 mice were separately fed with a normal diet (CON), a high-fat diet (HFD), and high-fat diet supplemented with buckwheat-resistant starch (HFD+BRS) for 6 weeks. After the feedings, lipid profile, blood glucose, plasma levels of cytokines, short-chain fatty acid content in the colon and intestinal flora of fecal were measured. Furthermore, the antioxidant indices of the liver and duodenum tissues were measured to evaluate the antioxidant capacity of mice. Significantly reduced plasma levels of total cholesterol (TC), triglyceride (TG), glucose, and cytokines were observed in the HFD+BRS group, accompanied by an increased antioxidant capacity in the liver and duodenum. In addition, supplementation with BRS significantly inhibited the increase in plasma lipopolysaccharide, tumor necrosis factor-α, and interleukin-6 levels. Gut microbiota composition was regulated by the supplement of BRS, which promoted the growth of Lactobacillus, Bifidobacterium, and Enterococcus, as well as inhibited the growth of Escherichia coli. In contrast to the HFD group, the content of short-chain fatty acids in mice colon increased in the BRS group. In conclusion, BRS benefited the cholesterol and glucose metabolism, as well as optimized gut microbiota composition in mice fed with a high-fat diet. PRACTICAL APPLICATION: This study identified the beneficial effects of tartary buckwheat-resistant starch on the regulation of blood lipids and intestinal flora in mice fed a high-fat diet. The result of this study will provide a basis for the development of probiotic products supplemented with tartary buckwheat-resistant starch and direction for further research.

Dose-Dependent Alterations to In Vitro Human Microbiota Composition and Butyrate Inhibition by a Supercritical Carbon Dioxide Hops Extract

Hop cones (Humulus lupulus L.) have been used throughout history as an additive in beer brewing and as herbal supplements with medicinal and culinary properties. The objective of this study was to ascertain the effect of a range of concentrations of a supercritical CO2 extract of hops on the composition and metabolism of human gut bacterial communities using in vitro batch culture systems. Fermentations were conducted over 24 h using a mixed human fecal inoculum. Microbial metabolism was assessed by measuring organic acid production and microbial community alterations were determined by 16S rRNA gene sequencing. Butyrate, an important short chain fatty acid in maintaining colonic well-being, decreased at elevated concentrations of hops, which may partly be accounted for by the concomitant reduction of Eubacterium and Coprococcus, known butyrate-producing genera, and also the inhibition of Bifidobacterium, a beneficial organism that has a butyrogenic effect through metabolic cross-feeding with intestinal commensals. The hops compounds also caused dose-dependent increases in the potentially pathogenic Enterobacteriaceae and potentially beneficial Akkermansia. Thus, hops compounds had a significant impact on the structure of the bacterial consortium, which warrants further study including human clinical trials.

The Beneficial Effects of a Polysaccharide from Moringa oleifera Leaf on Gut Microecology in Mice

Moringa oleifera is a natural plant with high nutritional and pharmacological value. Leaves of M. oleifera contain a variety of active substances. In our previous research, we had obtained a polysaccharide separated from M. oleifera leaf, namely MOs-2-a (1.35 × 10⁴ Da). In this study, this polysaccharide was administrated daily to 6 week-old ICR mice for 4 weeks. Then, the body weight, immunity, intestinal digestion, and intestinal microenvironment of Institute of Cancer Research (ICR) mice were investigated. After 4 weeks of feeding intervention with the polysaccharide, the immune and intestinal digestive ability of the ICR mice were significant as shown by the organ index, digestive enzymes, and reduction of serum tumor necrosis factor-alpha and diamine oxidase levels. The polysaccharide could regulate the microbial composition of the intestinal tract in mice by increasing the bacteria that have been reported for antiobesity effects, short chain fatty acid production, and lactic acid production. These findings indicate that the polysaccharide of M. oleifera leaf might be a promising prebiotic that exhibits health promotion effects.

Marine prebiotics: Polysaccharides and oligosaccharides obtained by using microbial enzymes

Utilization of marine algae has increased considerably over the past decades, since biodiversity within brown, red and green marine algae offers possibilities of finding a variety of bioactive compounds. Marine algae are rich sources of dietary fibre. The remarkable positive effects of seaweed dietary fibre on human body are related to their prebiotic activity over the gastrointestinal tract (GIT) microbiota. However, dietary modulation of microorganisms present in GIT can be influenced by different factors such as type and source of the dietary fibre, their molecular weight, type of extraction and purification methods employed, composition and modification of polysaccharide and oligosaccharide. This review will demonstrate evidence that polysaccharides and oligosaccharides from marine algae can be used as prebiotics, emphasizing their use in human health, their application as food and other possible applications. Furthermore, an important approach of microbial enzymes employment during extraction, modification or production of those prebiotics is highlighted.

Dietary Supplementation with Trihexanoin Enhances Intestinal Function of Weaned Piglets

Trihexanoin is a short-chain triglyceride (SCT). Many studies have reported that SCTs play important roles in the maintenance of intestinal epithelial structure and function. The present work was to investigate the effects of trihexanoin on growth performance, carbohydrate and fat metabolism, as well as intestinal morphology and function in weaned piglets. Twenty weaned piglets (21 ± 2 d) were randomly allocated to one of two treatment groups: The control group (basal diet supplemented with 0.5% soya oil); the TH group (basal diet supplemented with 0.5% trihexanoin). Dietary trihexanoin supplementation significantly reduced diarrhea rate; increased the concentrations of LDL, HDL and total protein in plasma; decreased cholesterol concentrations and glutamyl transpeptidase activity in plasma; improved intestinal morphologic structure; altered the mRNA levels and abundances of proteins related to glycogen and fat metabolism, mucosal barrier function, antioxidant capacity and water transport capacity; and altered the community of intestinal microflora. These results indicate that dietary trihexanoin supplementation could reduce diarrhea, regulate carbohydrate and fat metabolism, exert beneficial effects on the intestinal mucosal barrier, protect the intestinal mucosa from injuries, improve intestinal transport and absorption, and enhance antioxidant capacity. In conclusion, dietary supplementation with 0.5% trihexanoin improves the intestinal function and health of weaned piglets.

In vitro Prebiotic Effects of Bamboo Shoots and Potato Peel Extracts on the Proliferation of Lactic Acid Bacteria Under Simulated GIT Conditions

The present study explored the possible prebiotic application of potato peel and bamboo shoot extracts for the proliferation of lactic acid bacteria (LAB) from diverse niches and their tolerance ability to simulated gastrointestinal tract (GIT) conditions was also examined. Initially, the complete 16S rDNA sequencing of selected isolates revealed them as Lactobacillus paracasei (6), Staphylococcus simulans (2), and Streptococcus thermophilus (1). Higher cell densities and rapid pH change were obtained from cultured media supplemented with BS (2%) and PP (2%) as a carbon source. Their higher tolerance and the lowest reducing sugar abilities were obtained for BS at pH 2.5 and 9.0, while at pH 3.5 and 8.0 for PP. The isolates were screened for additional functional and technological properties to harvest the most appropriate starter. The selected isolates harbored promising functional properties such as amylase presence, cell surface hydrophobicity, autoaggregation, proteolytic and lipolytic activity, antifungal action, as well as exopolysaccharide production. On the basis of these attributes, microencapsulated strain K3 was found resistant to gastrointestinal conditions after 2 h, resulting in significantly (p ≤ 0.05) improved survival compared to non-capsulated strain. The current approach presents an interesting economical strategy to modulate LAB through supplementation of plant-derived carbon sources as well as to enhance their survival under GIT.

Continuous combined intake of polydextrose and lactitol stimulates cecal fermentation and salivary IgA secretion in rats

Immunoglobulin A (IgA), which plays an important role in infection defense, is upregulated in the large intestine and oral cavity through dietary fiber intake. However, the mechanism underlying salivary IgA increase through dietary fiber intake remains unknown. This study investigated time-dependent effects of non-absorbable polydextrose (PDX) and lactitol intake on salivary IgA secretion and cecal fermentation. Five-week-old rats were fed a fiber-free diet with or without 25 g/kg PDX and 25 g/kg lactitol for 1, 4, and 8 weeks. Compared to control, those who ingested PDX and lactitol had higher salivary IgA flow rates per weight of submandibular gland tissue at 4 and 8 weeks (P < 0.05), greater cecal weight and digesta at 1, 4, and 8 weeks (P < 0.05), and lower concentrations of short chain fatty acids (SCFAs) in cecal digesta (P = 0.0003). These findings suggest that the consumption of PDX and lactitol may upregulate salivary IgA secretion possibly by stimulating absorption of SCFAs produced by cecal fermentation. Thus, continuous ingestion of PDX and lactitol for up to 4 weeks could increase salivary IgA and promote immune defense against pathogen invasion through the oral route.

The application of in vitro human intestinal models on the screening and development of pre- and probiotics

The importance of the gut microbiota community on host's health and disease has long been recognised and is well documented. The development of pro- and prebiotic interventions offers an opportunity for the modulation of the gut microbiota towards long lasting health. In vitro fermentation models were developed as a powerful tool to study the impact of pro- and prebiotics on the gut microbiota under tightly controlled conditions, which allow dynamic sampling over time in reactors mimicking different colon regions. These models have been further evolved to suit specific experimental purposes, e.g. including immobilised faecal microbiota, peristaltic movement, mucin microcosm and the ability to perform treatments in parallel. In this review we discuss the advantages, disadvantages and technical considerations of the most frequently used models. We further focus on recent advances in the application of these models in prebiotics and probiotics research and outline their predictability for clinical research.

Effects of different thickening agents on infant gut microbiota

Infant microbiota has to progress from an almost sterile to a complex and varied community, so the main objective of this work was to evaluate the effect of three thickening ingredients on infant microbiota, as well as their in vitro gut fermentability. Experiments were performed using fresh faecal samples from healthy donors of 2-3 months of age. Stabilised stool samples were injected into Wheaton serum bottles containing pre-reduced MBM and 1% (w/v) fermentation substrates (locust bean gum, LBG; maize hydroxypropylated distarch phosphate, Mhdp; and pre-gelatinized rice starch, gRS). Samples were taken during fermentation, and pH, gas pressure, SCFA and bacterial population were analysed. The addition of thickeners resulted in a significant negative correlation (p < 0.05) between time and pH, showing significantly lower (p < 0.01) pH values for Mhdp and gRS than for LBG. Modified starches showed significantly higher values (p < 0.05) of total gas production than did LBG. Total SCFA molar concentrations for LBG, as well as propionate production, were significantly higher (p < 0.05) than for Mhdp and gRS. Regarding bacterial population, LBG promoted a more varied microbiota enhancing the growth of Atopobium and Bacteroidetes, whereas Mhdp and gRS induced higher Lactobacillus and Bifidobacteria at the beginning of fermentation. LBG induced moderate gas production and a slow drop of pH, and caused a decreasing acetate : propionate ratio, enhancing the development of a varied faecal microbiota. In contrast, Mhdp and gRS induced high gas production, a sudden drop of pH and a greater production of acetate, which promoted a less varied faecal microbiota.

The effect of prunes on stool output, gut transit time and gastrointestinal microbiota: A randomised controlled trial

BACKGROUND & AIM

Prunes (dried plums) are perceived to maintain healthy bowel function, however their effects on gastrointestinal (GI) function are poorly researched and potential mechanisms of action are not clear. We aimed to investigate the effect of prunes on stool output, whole gut transit time (WGTT), gut microbiota and short-chain fatty acids (SCFA) in healthy adults METHODS: We conducted a parallel group, randomised controlled trial with three treatment arms in 120 healthy adults with low fibre intakes and stool frequency of 3-6 stools/wk. Subjects were randomised to 80 g/d prunes (plus 300 ml/d water); 120 g/d prunes (plus 300 ml/d water) or control (300 ml/d water) for 4 weeks. Stool weight was the primary outcome and determined by 7-day stool collection. Secondary outcomes included stool frequency and consistency (stool diary), WGTT (radio-opaque markers), GI symptoms (diary), microbiota (quantitative PCR) and SCFA (gas liquid chromatography). Group assignment was concealed from the outcome assessors.

RESULTS

There were significantly greater increases in stool weight in both the 80 g/d (mean + 22.2 g/d, 95% CI -1-45.3) and 120 g/d (+32.8 g/d, 95% CI 13.9-51.7) prune groups compared with control (-0.8 g/d, 95% CI -17.2 to 15.6, P = 0.026). Stool frequency was significantly greater following 80 g/d (mean 6.8 bowel movements/wk, SD 3.8) and 120 g/d (5.6, SD 1.9) prune consumption compared with control (5.4, SD 2.1) (P = 0.023), but WGTT was unchanged. The incidence of flatulence was significantly higher after prune consumption. There were no significant differences in any of the bacteria measured, except for a greater increase in Bifidobacteria across the groups (P = 0.046). Prunes had no effect on SCFA or stool pH.

CONCLUSIONS

In healthy individuals with infrequent stool habits and low fibre intake, prunes significantly increased stool weight and frequency and were well tolerated. Prunes may have health benefits in populations with low stool weight.

CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE

ISRCTN42793297 http://www.isrctn.com/ISRCTN42793297.

In vitro modulation of gut microbiota by whey protein to preserve intestinal health

The effect of several types of whey milk - cow, sheep, goat and a mixture of them (60 : 20 : 20, respectively) - was assessed in the human gut microbiota. The prebiotic potential of these substrates was evaluated through in vitro gastrointestinal digestion following faecal batch culture fermentations (mimicking colonic fermentation) for 48 hours, using faeces from normal-weight (NW) and obese (OB) donors. Throughout the fermentation process, pH, gas production, short chain and branched fatty acids (SCFA-BCFA) were measured, as well as the changes of microbiota using qPCR. The pH decreased in all whey samples during the fermentation process. Gas production was higher in all whey samples than in controls, especially at 12 hours (p < 0.05). The diversity of SCFA and BCFA production was significantly different between the donors, in particular cow and mixed whey. Whey milk had a strong prebiotic effect on the gut microbiota of NW and OB donors, showing a significant increase of Bifidobacterium (p < 0.05) with cow, sheep and mixed whey and increase in the Lactobacillus group, particularly in OB donors. Bacteria associated with obesity did not show an increase in any of the groups of donors. Therefore, supplementing a diet with these types of whey can selectively stimulate the growth of probiotic bacteria, enhancing SCFA production, which could improve intestinal disorders. In addition, it may be an interesting approach to the prevention of overweight and obesity and related diseases. Whey milk has a potent prebiotic effect. It can selectively stimulate desirable bacteria and SCFA profile, in both OB and NW donors, contributing to improved intestinal health and reducing obesity.

Review article: the gut microbiome as a therapeutic target in the pathogenesis and treatment of chronic liver disease

BACKGROUND

Mortality from chronic liver disease is rising exponentially. The liver is intimately linked to the gut via the portal vein, and exposure to gut microbiota and their metabolites translocating across the gut lumen may impact upon both the healthy and diseased liver. Modulation of gut microbiota could prove to be a potential therapeutic target.

AIM

To characterise the changes in the gut microbiome that occur in chronic liver disease and to assess the impact of manipulation of the microbiome on the liver.

METHODS

We conducted a PubMed search using search terms including 'microbiome', 'liver' and 'cirrhosis' as well as 'non-alcoholic fatty liver disease', 'steatohepatitis', 'alcohol' and 'primary sclerosing cholangitis'. Relevant articles were also selected from references of articles and review of the ClinicalTrials.gov website.

RESULTS

Reduced bacterial diversity, alcohol sensitivity and the development of gut dysbiosis are seen in several chronic liver diseases, including non-alcoholic fatty liver disease, alcohol-related liver disease and primary sclerosing cholangitis. Perturbations in gut commensals could lead to deficient priming of the immune system predisposing the development of immune-mediated diseases. Furthermore, transfer of stool from an animal with the metabolic syndrome may induce steatosis in a healthy counterpart. Patients with cirrhosis develop dysbiosis, small bowel bacterial overgrowth and increased gut wall permeability, allowing bacterial translocation and uptake of endotoxin inducing hepatic and systemic inflammation.

CONCLUSIONS

Manipulation of the gut microbiota with diet, probiotics or faecal microbiota transplantation to promote the growth of "healthy" bacteria may ameliorate the dysbiosis and alter prognosis.

Prebiotic Galactooligosaccharide Metabolism by Probiotic Lactobacilli and Bifidobacteria

Galactooligosaccharides (GOS) are bifidogenic and lactogenic prebiotics; however, GOS utilization is strain-dependent. In this study, commercially available bifidobacteria and lactobacilli probiotic strains were evaluated for growth in the presence of GOS. Several bifidobacteria and lactobacilli grew on GOS; however, the specific GOS oligomers utilized for growth differed. A subset of probiotic bifidobacteria and lactobacilli revealed three different GOS utilization profiles delineated by the degrees of polymerization (DP) of GOS: (1) utilization of 2 DP GOS, (2) utilization of ≤3 DP GOS, and (3) utilization of all DP GOS. Specifically, Lactobacillus acidophilus NCFM (LA_NCFM) was found to efficiently consume all GOS oligomers. Extracellular β-galactosidase activity in the cell-free supernatant of LA_NCFM correlated with accumulation of galactose. In a LacL-deficient LA_NCFM strain, GOS utilization was abolished. This is the first report of LacL's role in GOS metabolism in LA_NCFM. In vitro GOS utilization should be considered when GOS are delivered with probiotic bifidobacteria and lactobacilli.

Lactobacillus plantarum ZS2058 produces CLA to ameliorate DSS-induced acute colitis in mice

Lactobacillus plantarumZS2058 is an efficient producer of conjugated linoleic acid (CLA)in vitro.

Early Gut Colonization With Lactobacilli and Staphylococcus in Infants: The Hygiene Hypothesis Extended

OBJECTIVES

The aim of the present study was to assess the mode of delivery and type-of-feeding impact on gut microbiota. We demonstrated higher fecal bifidobacteria in infants who were breast-fed (BF) or fed formula with prebiotics polydextrose (PDX) and galactooligosaccharides (GOS) versus formula without prebiotics. Here, we tested feces of that cohort for lactobacilli and Staphylococcus aureus, 2 types of bacteria present in breast milk.

METHODS

In a double-blind, randomized study, 21- to 30-day-old term infants vaginally delivered and exclusively formula-fed received a cow's milk-based formula (control, n = 80) or the same formula with 4 g/L (1:1 ratio) of PDX/GOS (PDX/GOS, n = 77). A reference BF group (n = 71) was included. Stool samples were obtained at baseline and after 30 and 60 days of feeding to assess fecal bacteria by quantitative real-time polymerase chain reaction.

RESULTS

Pairwise comparisons between baseline-adjusted means log10 colony-forming unit per gram feces of total lactobacilli counts (8.37 in control, 8.46 in PDX/GOS, and 8.42 in BF) showed a significant difference only between PDX/GOS and control at 30 and 60 days combined (P = 0.035), utilizing generalized estimating equations method. Baseline-adjusted odds ratio (OR) of colonization with S aureus was lower in control (OR 0.47, 95% confidence interval 0.22-1.00, P = 0.049) and PDX/GOS (OR 0.44, 95% confidence interval 0.21-0.94, P = 0.03) groups versus the BF group.

CONCLUSIONS

Bacteria found in breast milk, such as lactobacilli and S aureus can also be found in infant feces. S aureus, traditionally considered harmful, may aid in educating the coevolving immune system. Modifying formula by adding prebiotics may bring gut microbiota closer to that of BF infants in terms of beneficial microbes.