In vitro effects of selected synbiotics on the human faecal microbiota composition

Synbiotics are recognized means of modulating gut microbiota composition and activities. However, whether synbiotics are superior to prebiotics and probiotics alone in moderating the gut microbiota towards a purportedly healthy composition has not been determined. Eight selected synbiotics (short-chain fructooligosaccharides or fructooligosaccharides, each combined with one of four probiotics, Lactobacillus fermentum ME-3, Lactobacillus plantarum WCFS1, Lactobacillus paracasei 8700:2 or Bifidobacterium longum 46) were added to 24-h pH-controlled anaerobic faecal batch cultures. The prebiotic and probiotic components were also tested alone to determine their respective role within the synbiotic for modulation of the faecal microbiota. Effects upon major groups of the microbiota were evaluated using FISH. Rifampicin variant probiotic strains were used to assess probiotic levels. Synbiotic and prebiotics increased bifidobacteria and the Eubacterium rectale-Clostridium coccoides group. Lower levels of Escherichia coli were retrieved with these combinations after 5 and 10 h of fermentation. Probiotics alone had little effect upon the groups, however. Multivariate analysis revealed that the effect of synbiotics differed from the prebiotics as higher levels of Lactobacillus-Enterococcus were observed when the probiotic was stimulated by the prebiotic component. Here, the synbiotic approach was more effective than prebiotic or probiotic alone to modulate the gut microbiota.     

Fermentation properties of gentio-oligosaccharides

AIMS: To investigate the fermentation properties of gentio-oligosaccharides (GOS), as compared to fructo-oligosaccharides (FOS) and maltodextrin in mixed faecal culture. METHODS AND RESULTS: The substrates were incubated in 24 h batch culture fermentations of human faecal bacteria. Fluorescent in situ hybridization was used to determine changes in populations of bifidobacteria, lactobacilli, clostridia, bacteroides, streptococci and Escherichia coli. Gas and short-chain fatty acid (SCFA) production was also measured. GOS gave the largest significant increases in bifidobacteria, lactobacilli and total bacterial numbers during the incubations. However, FOS appeared to be a more selective prebiotic as it did not significantly stimulate growth of bacterial groups which were not probiotic in nature. GOS and maltodextrin produced the highest levels of SCFA. Lowest gas production was seen with GOS and highest with FOS. CONCLUSIONS: GOS possessed bifidogenic activity in vitro. Although fermentation of GOS was not as selective as FOS, gas production was lower. Gas production is often seen as an undesirable side effect of prebiotic consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: The study has provided the first data on fermentation of GOS in mixed faecal culture. The study has also used molecular microbiology methods (FISH) to quantify bacterial groups. The data extend our knowledge of the selectivity of fermentation of oligosaccharides by the gut microflora.     

In vitro evaluation of the microbiota modulation abilities of different sized whole oat grain flakes

Epidemiological studies and healthy eating guidelines suggest a positive correlation between ingestion of whole grain cereal and food rich in fibre with protection from chronic diseases. The prebiotic potential of whole grains may be related, however, little is known about the microbiota modulatory capability of oat grain or the impact processing has on this ability. In this study the fermentation profile of whole grain oat flakes, processed to produce two different sized flakes (small and large), by human faecal microbiota was investigated in vitro. Simulated digestion and subsequent fermentation by gut bacteria was investigated using pH controlled faecal batch cultures inoculated with human faecal slurry. The different sized oat flakes, Oat 23’s (0.53–0.63 mm) and Oat 25’s/26’s (0.85–1.0 mm) were compared to oligofructose, a confirmed prebiotic, and cellulose, a poorly fermented carbohydrate. Bacterial enumeration was carried out using the culture independent technique, fluorescent in situ hybridisation, and short chain fatty acid (SCFA) production monitored by gas chromatography. Significant changes in total bacterial populations were observed after 24 h incubation for all substrates except Oat 23’s and cellulose. Oats 23’s fermentation resulted in a significant increase in the Bacteroides–Prevotella group. Oligofructose and Oats 25’s/26’s produced significant increases in Bifidobacterium in the latter stages of fermentation while numbers declined for Oats 23’s between 5 h and 24 h. This is possibly due to the smaller surface area of the larger flakes inhibiting the simulated digestion, which may have resulted in increased levels of resistant starch (Bifidobacterium are known to ferment this dietary fibre). Fermentation of Oat 25’s/26’s resulted in a propionate rich SCFA profile and a significant increase in butyrate, which have both been linked to benefiting host health. The smaller sized oats did not produce a significant increase in butyrate concentration. This study shows for the first time the impact of oat grain on the microbial ecology of the human gut and its potential to beneficially modulate the gut microbiota through increasing Bifidobacterium population.     

Investigation of the faecal microbiota associated with canine chronic diarrhoea

Diarrhoea is a common problem in dogs and can result in disturbance of the normal intestinal microbiota. However, little is known about the gastrointestinal microbiota of dogs with chronic diarrhoea and controlled canine studies of dietary management are scarce. The aims of this study were to investigate the predominant faecal microbiota of chronic diarrhoea dogs and to examine the effect(s) of a fibre blend on the canine faecal microbiota. A 3-week fibre supplementation feeding study was performed in nine chronic diarrhoea and eight control dogs. Atopobium cluster, Lactobacillus–Enterococcus group and Clostridium cluster XIV were the predominant bacterial groups in all dogs. Chronic diarrhoea dogs had significantly higher Bacteroides counts at baseline and significantly lower Atopobium cluster counts following fibre supplementation compared with control dogs. Atopobium cluster levels increased significantly in control dogs, while counts of sulphate-reducing bacteria decreased significantly and Clostridium clusters I and II counts increased significantly in chronic diarrhoea dogs during fibre supplementation. Microbial profiles (detected by denaturing gradient gel electrophoresis) demonstrated interindividual variation, with greater similarity seen between the chronic diarrhoea and control dogs' profiles after fibre supplementation compared with baseline. In conclusion, fibre supplementation induced changes in the canine faecal microbiota, with greater resemblance between the microbiota of chronic diarrhoea and control dogs after this dietary modulation.     

Propionibacterium acidipropionici CRL1198 influences the production of acids and the growth of bacterial genera stimulated by inulin in a murine model of cecal slurries

Different attempts have been made to improve the health status of humans and animals by increasing the intestinal production of short-chain fatty acids (SCFA) derived from non-digestible carbohydrates fermentation. In this paper we investigate the in vitro production of short-chain fatty acids (SCFA) after addition of inulin, propionibacteria or a combination of both in an experimental model of mice cecal slurries. The development of bacterial genera which are usually stimulated by inulin addition was also investigated. According to our experimental data, acetic acid and butyric acids concentrations increased after incubation in slurries that had no supplements. By contrast, butyric acid concentrations remained in the basal value when supplements were used. Fermentation of only inulin did not increase the concentration of total SCFA. Propionibacterium acidipropionici CRL1198 improved the production of propionic acid in cecal slurries when it was added alone, but the effect was more noticeable in the combination with inulin. A modulation of the global fermentative activity of the cecal microbiota was evidenced by the increase on the ratio propionic acid/SCFA in supplementations with propionibacteria. Statistical analysis of data demonstrated that samples from homogenates with propionibacteria alone or combined with inulin belong to the same cluster. The presence of propionibacteria limited the growth of Bacteroides fragilis and Clostridium hystoliticum groups in slurries with and without inulin. The growth of Bifidobacterium was not modified and the stimulating effect of inulin on lactobacilli disappeared in the presence of propionibacteria. In conclusion, dairy propionibacteria are potential candidates to develop new functional foods helpful to ensure the intestinal production of SCFA during inulin supplementation and to control the overgrowth of bacteria belonging to Bacteroides and Clostridium genera.     

Lactic acid bacteria isolated from canine faeces

AIMS: Lactic acid bacteria (LAB) were isolated and sequenced from the faeces of healthy dogs. Five of these strains were selected and further characterized to clarify the potential of these strains as probiotics for canine. METHODS AND RESULTS: LAB were found in 67% (14/21) of the canine faeces samples when plated on Lactobacilli Selective Media without acetic acid. Out of 13 species identified with partial 16S rRNA gene sequencing, Lactobacillus fermentum LAB8, L. mucosae LAB12, L. rhamnosus LAB11, L. salivarius LAB9 and Weissella confusa LAB10 were selected as candidate probiotic strains based on their frequency, quantity in faeces, growth density, acid tolerance and antimicrobial activity. The minimal inhibitory concentration values of these isolates were determined for 14 antibiotics. L. salivarius LAB9, W. confusa LAB10 and L. mucosae LAB12 were viable in pH 2 for 4 h (mLBS), indicating tolerance to acidity and thus the potential to survive in gastrointestinal tract of the canine. The LAB8-LAB12 strains showed antimicrobial activity against Micrococcus luteus A1 NCIMB86166. CONCLUSIONS: Thirteen different LAB species were found from the faecal microbiota of the healthy canines. Five acid tolerant and antimicrobially active LAB strains with the capacity to grow to high densities both aerobically and anaerobically were chosen to serve as candidate probiotics. SIGNIFICANCE AND IMPACT OF THE STUDY: The selected LAB strains are among the first host-specific LAB with antimicrobial activity isolated from canines that could serve as potential probiotics for canine use.     

In vitro fermentation characteristics of selected glucose-based polymers by canine and human fecal bacteria

This research evaluated fermentation characteristics (short-chain fatty acid [SCFA] production, pH, and gas production) resulting from fermentation of glucose-based carbohydrates using canine (n = 3) and human (n = 3) fecal inoculum. Substrates included lyophilized canine ileal digesta containing maltodextrin, gamma-cyclodextrin, high molecular weight (MW) pullulan (MW 100000), or low MW pullulan (MW 6300) obtained from an in vivo experiment. Fermentation for 6 and 10 h with human fecal microflora resulted in higher gas and SCFA production than did canine fecal microflora. High MW pullulan fermentation resulted in the highest (p < 0.05) gas production and lowest (p < 0.05) pH for both dogs and humans. Total SCFA production was highest (p < 0.05) for low MW pullulan fermented by canine microflora, and for gamma-cyclodextrin, high MW pullulan, and low MW pullulan fermented by human microflora. Differences were noted in fermentation characteristics of substrates present in ileal digesta.     

运动、肠道菌群代谢物——短链脂肪酸与骨骼肌代谢调控

寄生于人体的肠道菌群是一个高度动态化和个体化的复杂生态系统,受遗传、环境、饮食、年龄和运动等因素的影响,并通过其产生的代谢物与机体众多组织器官产生广泛的应答效应。短链脂肪酸(short chain fatty acid, SCFA)主要是由位于盲肠和结肠内的菌群以膳食纤维为底物发酵产生,其被吸收进入肠系膜上下静脉,随后汇入门静脉至肝。部分短链脂肪酸被肝作为糖异生和脂质合成的底物,剩余的短链脂肪酸以游离脂肪酸的形式经肝静脉进入外周循环。研究发现,运动可使产生SCFA的肠道菌群组分的丰度提高和参与调控SCFA生成的相关基因表达增加,使肠道中短链脂肪酸含量增加。由短链脂肪酸刺激结肠内分泌细胞合成分泌的胰高血糖素样肽1(glucagon like peptide-1, GLP-1)可促使胰岛B细胞合成分泌胰岛素,进而调节骨骼肌的葡萄糖摄取与糖原合成。此外,短链脂肪酸通过提高骨骼肌胰岛素受体底物1(insulin receptor substrate 1,IRS1)基因转录起始位点附近的组蛋白乙酰化水平,增强骨骼肌的胰岛素敏感性。同时,短链脂肪酸通过激活腺苷酸活化蛋白质激酶(AMP-activated protein kinase, AMPK)促进骨骼肌的脂肪酸摄取、脂肪分解和线粒体生物发生,抑制脂肪合成。本文就肠道菌群代谢物——短链脂肪酸概述、运动对产生短链脂肪酸的肠道菌群的影响和运动介导肠道菌群代谢物——短链脂肪酸对骨骼肌代谢调控机制的最新研究进展进行综述,为骨骼肌运动适应的新机制研究提供理论依据。     

Oral Administration of Compound Probiotics Ameliorates HFD-Induced Gut Microbe Dysbiosis and Chronic Metabolic Inflammation via the G Protein-Coupled Receptor 43 in Non-alcoholic Fatty Liver Disease Rats

Probiotics and Antimicrobial Proteins - The aim of this study was to investigate how the effects of compound probiotics modulate the gut microbiota, short-chain fatty acid (SCFA), body composition,...     

Beyond purified dietary fibre supplements: Compositional variation between cell wall fibre from different plants influences human faecal microbiota activity and growth in vitro

Dietary fibre is a major energy source for the human gut microbiota, but it is unclear to what extent the fibre source and complexity affect microbial growth and metabolite production. Cell wall material and pectin were extracted from five different dicotyledon plant sources, apples, beet leaves, beetroots, carrots and kale, and compositional analysis revealed differences in the monosaccharide composition. Human faecal batch incubations were conducted with 14 different substrates, including the plant extracts, wheat bran and commercially available carbohydrates. Microbial activity was determined for up to 72 h by measuring gas and fermentation acid production, total bacteria (by qPCR) and microbial community composition by 16S rRNA amplicon sequencing. The more complex substrates gave rise to more microbiota variation compared with the pectins. The comparison of different plant organs showed that the leaves (beet leaf and kale) and roots (carrot and beetroot) did not give rise to similar bacterial communities. Rather, the compositional features of the plants, such as high arabinan levels in beet and high galactan levels in carrot, appear to be major predictors of bacterial enrichment on the substrates. Thus, in-depth knowledge on dietary fibre composition should aid the design of diets focused on optimizing the microbiota.     

The influence of Staphylococcus aureus on gut microbial ecology in an in vitro continuous culture human colonic model system

An anaerobic three-stage continuous culture model of the human colon (gut model), which represent different anatomical areas of the large intestine, was used to study the effect of S. aureus infection of the gut on the resident faecal microbiota. Studies on the development of the microbiota in the three vessels were performed and bacteria identified by culture independent fluorescence in situ hybridization (FISH). Furthermore, short chain fatty acids (SCFA), as principal end products of gut bacterial metabolism, were measured along with a quantitative assessment of the predominant microbiota. During steady state conditions, numbers of S. aureus cells stabilised until they were washed out, but populations of indigenous bacteria were transiently altered; thus S. aureus was able to compromise colonisation resistance by the colonic microbiota. Furthermore, the concentration of butyric acid in the vessel representing the proximal colon was significantly decreased by infection. Thus infection by S. aureus appears to be able to alter the overall structure of the human colonic microbiota and the microbial metabolic profiles. This work provides an initial in vitro model to analyse interactions with pathogens.     

Effects of lactose on colon microbial community structure and function in a four-stage semi-continuous culture system

A semi-continuous four-channel colon simulator was used to study the effects of lactose for the first time on the growth and fermentation dynamics of colonic microbiota. In six separate simulations, lactose supplementation increased the total SCFA concentration by 3-5 fold as compared with the baseline in the respective vessels. The total bacterial density was inversely correlated with lactic acid production (P = 0.003), while production of butyrate (P = 0.007) and propionate (P = 0.02) correlated with higher numbers of bacteria. A major shift in the microbial community structure in the lactose supplemented vessels was demonstrated by bacterial genomic %G+C-profiling of the total population, where lactose supplementation induced a clearly dominant peak in the bifidobacteria prominent area, %G+C 60-65. The transient shift to increased numbers of bifidobacteria (23-27%) of all bacteria in the first two vessels was also confirmed by the bifidobacteria-specific QPCR-method. In conclusion, lactose produced dramatic changes in microbiota composition and activity as compared with the baseline fermentation.     

In vitro evaluation of the fermentation properties of galactooligosaccharides synthesised by α-galactosidase from<Emphasis Type="Italic"> Lactobacillus reuteri</Emphasis>

Stirred, pH-controlled anaerobic batch cultures were used to evaluate the in vitro utilisation by canine gut microflora of novel -galactooligosaccharides synthesised with an enzyme extract from a canine Lactobacillus reuteri strain. Fructooligosaccharides (FOS), melibiose and raffinose were used as reference carbohydrates for the prebiotic properties of the synthesised oligosaccharide (galactosyl melibiose mixture—GMM). Addition of Lactobacillus acidophilus was used as control for the evaluation of the synbiotic properties of the oligosaccharide with L. reuteri. Populations of predominant gut bacterial groups were monitored over 48 h of batch culture by fluorescent in situ hybridisation, and short-chain fatty acid (SCFA) production was measured. GMM showed a higher increase in bifidobacteria and lactobacilli population number and size as well as a higher decrease in clostridia population number and size compared to the commercial prebiotics (FOS, melibiose, raffinose). This prebiotic effect was further increased by the addition of L. reuteri followed by a change in the SCFA production pattern compared to GMM alone or GMM with L. acidophilus. The observed change in SCFA production was in accordance with the fermentation properties of L. reuteri, suggesting that the novel synbiotic had a significant effect on the canine gut microflora fermentation.     

Comparative effects of exopolysaccharides from lactic acid bacteria and fructo-oligosaccharides on infant gut microbiota tested in an in vitro colonic model with immobilized cells

The aim of this study was to compare the effects of purified exopolysaccharides from Lactobacillus rhamnosus RW-9595M with those of a well-known prebiotic (short-chain fructo-oligosaccharides) on infant colonic microbiota using a new three-stage chemostat model with immobilized infant faecal microbiota. Two continuous cultures with different faecal inocula were tested with different compositions of carbohydrate media. During the first fermentation (F1), fructo-oligosaccharides tested at a concentration of 9.8 g L(-1) increased the number of lactobacilli and decreased coliforms both in gel beads and in effluent from all three reactors, in agreement with data from the literature. During the second fermentation (F2), the effect of fructo-oligosaccharides tested at a lower concentration (7.5 g L(-1)) was reduced compared with F1. Fructo-oligosaccharides also increased total organic acid concentration and decreased ammonia production. Results obtained for exopolysaccharide tested at 1.5 g L(-1) indicate that exopolysaccharides from L. rhamnosus RW-9595M was not metabolized by infant microbiota and lacked any prebiotic effect.     

Probiotics – do they have a role in the pig industry?

The delivery of certain living microorganisms in food has long been suggested as having positive health effects in humans. This practice has extended into food animal production, with a variety of microorganisms being used; lactic acid bacteria, various Bacillus species and the yeast Saccharomyces cerevisiae have been particularly used in the pig industry. The increased interest in probiotics is essentially due to the problem of microbial resistance to antibiotics and following the ban of the use of antibiotics in animal production, probiotics being considered an alternative means to reduce pathogen infection and improve animal health especially around the time of weaning. However, there is still a need to clarify the probiotic effectiveness in pigs, and the underlying mechanisms. When assessing the efficacy of probiotics one must consider the particular strain of organism being used and the production stage of the pigs being treated. The reproducible delivery of probiotics in industrial pig production is problematic as maintenance of viability is key to their beneficial activity, but difficult to achieve with commonly used feed processing technologies. One specific context where probiotics organisms may be reliably delivered is in systems utilising fermented liquid feeds. Liquid feed may be fermented by the activity of wild lactic acid bacteria or may be stimulated using specific isolates as 'starters'; the latter system has advantages in terms of reproducibility and speed of fermentation. The farm context in which the organism is used is likely to be critical; the use of probiotics is more likely to result in measurable economic gains in animals living in sub-optimal conditions rather than in those reared in the highest welfare and husbandry conditions. The establishment of a beneficial lactic acid bacteria population at birth may lead to healthier animals, this may be most effectively achieved by treating sows, which provide an amplification step and flood the neonatal pigs' environment with desirable bacterial strains. In contrast, it may be sufficient to provide a supportive, protective microbiota around the time of weaning as this is a time of major crisis with instability and loss of certain bacterial populations.     

In vitro Effects of Prebiotics and Synbiotics on Apis cerana Gut Microbiota

This study aimed to investigate in vitro effects of the selected prebiotics alone, and in combination with two potential probiotic Lactobacillus strains on the microbial composition of Apis cerana gut microbiota and acid production. Four prebiotics, inulin, fructo-oligosaccharides, xylo-oligosaccharides, and isomalto-oligosaccharides were chosen, and glucose served as the carbon source. Supplementation of this four prebiotics increased numbers of Bifidobacterium and lactic acid bacteria while decreasing the pH value of in vitro fermentation broth inoculated with A. cerana gut microbiota compared to glucose. Then, two potential probiotics derived from A. cerana gut at different dosages, Lactobacillus helveticus KM7 and Limosilactobacillus reuteri LP4 were added with isomalto-oligosaccharides in fermentation broth inoculated with A. cerana gut microbiota, respectively. The most pronounced impact was observed with isomalto-oligosaccharides. Compared to isomalto-oligosaccharides alone, the combination of isomalto-oligosaccharides with both lactobacilli strains induced the growth of Bifidobacterium, LAB, and total bacteria and reduced the proliferation of Enterococcus and fungi. Consistent with these results, the altered metabolic activity was observed as lowered pH in in vitro culture of gut microbiota supplemented with isomalto-oligosaccharides and lactobacilli strains. The symbiotic impact varied with the types and concentration of Lactobacillus strains and fermentation time. The more effective ability was observed with IMO combined with L. helveticus KM7. These results suggested that isomalto-oligosaccharides could be a potential prebiotic and symbiotic with certain lactobacilli strains on A. cerana gut microbiota.     

Effects of Lactose on Colon Microbial Community Structure and Function in a Four-Stage Semi-Continuous Culture System

A semi-continuous four-channel colon simulator was used to study the effects of lactose for the first time on the growth and fermentation dynamics of colonic microbiota. In six separate simulations, lactose supplementation increased the total SCFA concentration by 3–5 fold as compared with the baseline in the respective vessels. The total bacterial density was inversely correlated with lactic acid production (P=0.003), while production of butyrate (P=0.007) and propionate (P=0.02) correlated with higher numbers of bacteria. A major shift in the microbial community structure in the lactose supplemented vessels was demonstrated by bacterial genomic %G+C-profiling of the total population, where lactose supplementation induced a clearly dominant peak in the bifidobacteria prominent area, %G+C 60–65. The transient shift to increased numbers of bifidobacteria (23–27%) of all bacteria in the first two vessels was also confirmed by the bifidobacteria-specific QPCR-method. In conclusion, lactose produced dramatic changes in microbiota composition and activity as compared with the baseline fermentation.     

Commensal microbe-derived SCFA alleviates atrial fibrillation via GPR43/NLRP3 signaling

Rationale: Dysbiotic gut microbiota (GM) and NLRP3 inflammasome are proarrhythmic factors in atrial fibrillation (AF). Herein, whether short-chain fatty acid (SCFA) produced from GM fermentation of dietary fiber serving as invisible mediators is yet unclear. Thus, the current study aimed to determine whether SCFA alleviated from NLRP3 signaling-mediated atrial remodeling protects AF development.Methods: First, a cross-sectional study based on the GC-MS metabolomics was performed to explore the association between fecal SCFA levels and AF traits in a cohort consisted of 48 individuals. Then, a well-established mice model fed diet deficient or enriched in dietary fiber was established to elucidate the pathophysiological role of SCFA involved in AF susceptibility, atrial remodeling, and G-protein-coupled receptor 43 (GPR43)/NLRP3 signaling. Finally, the effects of SCFA were verified on HL-1 cells.Results: Fecal SCFA levels were remarkably reduced in AF patients with a declining trend from paroxysmal to persistent AF. Prolonged P wave duration based on surface ECG and increased left atrial diameter gained from echocardiography was identified in low-fiber diet mice but lost in SCFA-supplemented group. Lack of dietary fiber enhanced susceptibility to AF under burst pacing, whereas SCFA might exert a protective effect. The supplementation of SCFA prevented dietary fiber deficiency-upregulated phosphorylation of calmodulin-dependent protein kinase II and ryanodine receptor 2, the disarray fibrosis, collagen expression, and NLRP3 inflammasome activation in atrial tissue. Finally, the AF protective roles of SCFA were identified through GPR43 mediated deactivation of NLRP3 by GPR43 knockdown in HL-1 cells.Conclusions: SCFA derived from dietary fiber fermentation by gut commensals alleviates AF development via GPR43/NLRP3 signaling.     

Influence of isomalto-oligosaccharides on intestinal microbiota in rats

Aims: Isomalto‐oligosaccharides (IMO) with α(1→6) and α(1→4) glucosidic linkages are produced by enzymatic conversion of starch. IMO are only partially digestible but data on their influence on intestinal microbiota are limited. It was the aim of this study to investigate the effect of IMO diet on intestinal microbiota and short‐chain fatty acids production (SCFA) in rats. Methods and results: Three groups of F344 rats, each consisting of six animals, were fed IMO, inulin or a control diets for six weeks. A qualitative assessment of the intestinal microbiota was achieved by PCR‐denaturing gradient gel electrophoresis (DGGE). Major bacterial taxa were quantified by quantitative PCR (qPCR), and SCFA were measured using gas chromatography. Quantitative PCR demonstrated that lactobacilli were one of the dominant bacterial taxa in faecal samples from rats. IMO increased the number of lactobacilli and the total number of intestinal bacteria in rats fed IMO compared with animals receiving control and inulin diets. Furthermore, PCR‐DGGE with lactobacilli‐specific primers showed an altered biodiversity of lactobacilli in rats fed IMO compared with control diet. Conclusions: IMO selectively stimulates lactobacilli and increases their diversity in rats. Significance and impact of study: Isomalto‐oligosaccharides specifically stimulate growth of intestinal lactobacilli in a rat model system.     

Potato powders prepared by successive cooking-process depending on resistant starch content affect the intestinal fermentation in rats

The effects of resistant starch (RS) in dry potato powders prepared by various processes on intestinal fermentation in rats were assessed. Rats were fed raw potato powder (RP), blanched potato powder (BP), steamed potato powder (SP), or drum-dried potato powder (DP) for 4 weeks. The cecal RS content was significantly higher in the RP group than in the control diet (CN) group and other dry potato powder groups. Cecum pH was significantly lower in the RP group compared to the CN group, and was also significantly lower than that in the SP, BP, and DP groups. Lactic acid bacteria levels in the RP group were significantly higher than those in the CN group, and levels in the SP group also increased relative to the control group. Lactobacillus levels in the RP group were higher than in the CN and other dry potato powder groups. Cecal short-chain fatty acid (SCFA) concentrations in the RP group followed by the SP group exhibited significantly higher levels relative to the control levels. Dry potato powders containing RS produced during the cooking process may represent a useful food material that increases intestinal concentrations of SCFA and enhances the growth of certain lactic acid bacteria.