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PubMed2001

A comparative in vitro evaluation of the fermentation properties of prebiotic oligosaccharides.

AIMS: Comparison of in vitro fermentation properties of commercial prebiotic oligosaccharides. METHODS AND RESULTS: Populations of predominant gut bacterial groups were monitored over 24 h of batch culture through fluorescent in-situ hybridization. Short-chain fatty acid and gas production were also measured. All prebiotics increased the numbers of bifidobacteria and most decreased clostridia. Xylo-oligosaccharides and lactulose produced the highest increases in numbers of bifidobacteria whilst fructo-oligosaccharides produced the highest populations of lactobacilli. Galacto-oligosaccharides (GOS) resulted in the largest decreases in numbers of clostridia. Short-chain fatty acid generation was highest on lactulose and GOS. Gas production was lowest on isomalto-oligosaccharides and highest on inulin. CONCLUSIONS: The oligosaccharides differed in their fermentation characteristics. Isomalto-oligosaccharides and GOS were effective at increasing numbers of bifidobacteria and lactate whilst generating the least gas. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides comparative data on the properties of commercial prebiotics, allowing targeting of dietary intervention for particular applications and blending of oligosaccharides to enhance overall functionality.

Bacteria↗

PubMed1996

Dietary guar gum alters colonic microbial fermentation in azoxymethane-treated rats.

To assess the effects of guar gum on colonic microbial fermentation and cancer development, azoxymethane-treated rats were fed a partially hydrolyzed guar or control diet. Anaerobic fecal incubations were conducted at 8-wk intervals, either without added substrate or with cornstarch or hydrolyzed guar as substrates. Short-chain fatty acids in colonic contents and colonic carcinoma areas were measured at 27 wk. Fecal in vitro fermentation rates were higher for guar-fed rats than for control rats [three-way ANOVA (diet, time, in vitro substrates), P = 0.002]. Fecal in vitro butyrate production was greater for guar-fed rats than for control rats after 3-11 weeks of diet treatment (three-way ANOVA, P = 0.027). Butyrate concentrations of colonic contents at 27 wk were higher in guar-fed than in control rats and higher in the cecum than in the post-cecal colon (two-way ANOVA, P = 0.0001). A regression equation predicting colonic carcinoma area (r2 = 0.279) using propionate and butyrate concentrations of the contents of the post-cecal colon showed propionate as a positive predictor (P < 0.001) and butyrate as a negative predictor (P = 0.033). Our results show that patterns of short-chain fatty acid production may affect the results of fiber-carcinogenesis experiments. Dietary addition of hydrolyzed guar is associated with fecal fermentation low in propionate and high in butyrate; short-chain fatty acid concentrations are greater proximally than distally. These results suggest that butyrate protects against colonic neoplasia, whereas propionate enhances it, and demonstrate that colonic microbiota adapt to produce more butyrate if given time and the proper substrate.

Analysis of Variance↗

PubMedDate not supplied

Dietary fiber and total enteral nutrition: fermentative assessment of five fiber supplements.

Total enteral nutrition (TEN) formulas supplemented with dietary fiber, typically soy polysaccharide, are in widespread clinical use. Five commercially available dietary fiber supplements obtained from fruits (apple, grapefruit, orange, prune, tomato) were examined for potential use in TEN formulas. In vitro fermentations of 0, 4, 8, 12, and 24 hours' duration with human fecal microbiota from three different donors were conducted to assess colonic fermentative effects. Short-chain fatty acid and hydrogen productions differed significantly with fiber source. The most rapid fermentation rate was with tomato followed by orange, grapefruit, apple, and finally prune fiber. Such differences in fermentability should be considered when fiber sources are selected to supplement TEN formulas.

Dietary Fiber↗

PubMed1990

[Extent and effect of fermentation in the large intestine of swine. 1. Ileal flow rate, fermentation ability and colon capacity].

Colonic events (volumina, fermentability, rate of passage) were determined in a complex program with young sows using 8 rations. Ileal cannulated sows were used and 4 slaughtered animals per ration to study volumina contents and to take samples for in vitro fermentation. The results are compared with 81 former experiments using ileal cannulated sows. Ileal nutrient flow was very different in quality and quantity. It varied between 1674 and 520 g OM/d, affecting seriously postileal reactions. Volumina of large intestine varied between 10 and 25 litres or between 83 and 226 ml/kg LW being determined by ileal flow rate (B = 0.90). The flow rate influenced also transit time (B = 0.89). Fermentability of OM in average come to 60% (from 33 to 77%) according to ileal flow composition.

Animal Feed↗

PubMed1992

The influence of contamination with separate mycotoxins (aflatoxins, ochratoxin A, citrinin, patulin, penicillic acid or sterigmatocystin) on the in vitro dry matter and organic matter digestibilities of some roughages (berseem hay and wheat straw).

In vitro study on berseem hay and wheat straw was undertaken to investigate the the effect of mycotoxin contamination on dry matter and organic matter digestibilities. The data revealed a negative effect of most studied mycotoxins on the materials digestibility. Among the investigated mycotoxins, penicillic acid with its two concentrations (5 and 10 nmol) was the most negative, affecting digestibilities of both feed materials. Wheat straw digestibility was more influenced than berseem hay by the ochratoxin A, citrinin and sterigmatocystin (besides the penicillic acid) particularly with their high level (10 nmol). Yet, some mycotoxins act as antibiotics which may affect only the harmful flora but encourage the rumen microflora resulting in slight improvement of digestibility. The rumen conditions were able to metabolize or deform the used levels of all mycotoxins studied. Thus, there were no detectable residues of these mycotoxins in the digestion media after the in vitro fermentation.

Aflatoxins↗

PubMed1991

Degradation of cellulose and forage fiber fractions by ruminal cellulolytic bacteria alone and in coculture with phenolic monomer-degrading bacteria.

We hypothesized that bacterial species capable of metabolizing phenolic monomers may act as catalysts for forage fiber breakdown by increasing microbial access to cell wall polysaccharides. Ruminal cellulolytic bacteria alone and in combination with phenolic-degrading bacteria were examined for differences in their ability to degrade fiber fractions of alfalfa or bromegrass. Electron micrographs of Fibrobacter succinogenes S85 cultured in combination with the ruminal phenolic-degrading organisms Eubacterium oxidoreducens G41 and Syntrophococcus sucromutans S195 indicated that bromegrass was degraded more extensively by the triculture than by the monoculture. The sequential detergent system was used to quantify the digestibility of fiber components from alfalfa and bromegrass. F. succinogenes incubated with the two phenolic-degrading organisms did not degrade more cell wall material than did F. succinogenes alone. However, with two other ruminal cellulolytic organisms, Clostridium longisporum B6405 and Ruminococcus albus B6403, greater (P less than .05, P less than .10, respectively) amounts of hemicellulose were degraded (72 h in vitro fermentation) from whole-plant alfalfa when E. oxidoreducens and S. sucromutants were combined with the cellulolytic species than when their monocultures were tested. Similar increases were not observed using a NDF preparation of alfalfa as the substrate. Based on these in vitro experiments, it does not seem that E. oxidoreducens and S. sucromutans play an important role in improving forage fiber degradation by cellulolytic ruminal bacteria.

Animals↗

PubMed1996

Attempts to induce reductive acetogenesis into a sheep rumen.

A rumen fistulated wether was used for continuous infusion of a 2-bromoethanesulfonic acid (BES) solution (2 g/d in 50 ml of water). The infusion was started after introduction of a pulse dose of BES (2 g) into the rumen. Immediately after introduction of the pulse dose, methane concentration in rumen gases was lowered from about 40 to less than 1%, with concomittant decreases and increases in the molar proportions of acetic and propionic acids respectively in the rumen volatile fatty acids. After 4 days of infusion however, and despite repeated pulse dosage of BES, methanogenesis adapted to BES and methane concentration in rumen gases reached 20%. Addition of BES to incubations of rumen contents with hay resulted in considerable inhibition of methanogenesis. Extra addition of methanol in such incubations increased both acetate and methane production, whereas addition of formate had no effect. In a second experiment using a second rumen fistulated whether, a 4 day control period was followed by 10 days of daily introduction of 11 of cattle cecal contents into the rumen. The cattle cecal contents were collected from slaughterhouse cattle, filtered and kept at -20 degrees C until use. Comparison of in vitro fermentation of thawed with fresh contents showed absence of methanogenesis but not of reductive acetogenesis after freezing and thawing. Evidence for the latter was sought by calculation of metabolic hydrogen recoveries from amounts of end products formed in incubations. In a similar way, evidence for induction of reductive acetogenesis was sought from incubations in vitro, carried out with rumen contents obtained before, during and after introduction of cecal contents into the rumen. No such evidence was obtained.

Acetates↗

PubMed1992

The use of purified condensed tannin as a reference in determining its influence on rumen fermentation.

1. Tannins were purified from the leaves of trees forming part of giraffe's diet in the Kruger National Park. 2. In general, hydrolysable tannin formed less than 10% of the total purified crystal complexes, condensed tannin and possibly some non tannin phenols forming the balance. 3. Each tree species condensed tannin gave a different calibration curve and these were used in the assay. 4. Volatile fatty acid production during in vitro fermentation was greatly reduced when the substrate contained more than 6% condensed tannin.

Animals↗

PubMed1999

In vitro digestibility and fermentability of levan and its hypocholesterolemic effects in rats.

This study describes the in vitro digestibility and fermentability of high molecular weight (ca. 2,000,000) levan and its effect on the metabolism of lipids in growing rats fed cholesterol-free diets. Levan was synthesized from sucrose using bacterial levansucrase immobilized on a honeycomb-shaped ceramic support. Although body weight gain, weight of visceral organs, morphologic changes in the digestive tract, and the serum triacylglycerol and glucose concentrations were not affected by feeding levan diets for 4 weeks, a significant hypocholesterolemic effect was observed. Serum cholesterol level was decreased to 83% or 59% by feeding a 1% or 5% levan diet, respectively. The hypocholesterolemic effect was accompanied by a significant increase in fecal excretion of sterols and lipids. High molecular weight levan, though not hydrolyzed by the salivary amylases, was hydrolyzed by artificial gastric juice and was changed to a low molecular weight (ca. 4,000) levan with a small amount of fructose, but did not produce any fructooligosaccharides. Low molecular weight (ca. 6,000) levan was not hydrolyzed by either pancreatic juice or small intestinal enzymes. This suggests that, in vivo, low molecular weight levan derived from the high molecular weight material is not further digested and reaches the colon intact. The fermentation of low molecular weight levan (ca. 6,000) by several strains of bifidobacteria was not observed. These results showed that the hypocholesterolemic effect of levan may result from the prevention of intestinal sterol absorption, and not from the action of the fermentation products of levan.

Journal Article↗

PubMed2002

Effects of a partially hydrolyzed curdlan on serum and hepatic cholesterol concentration, and cecal fermentation in rats.

A significant reduction was observed for serum and hepatic cholesterol concentrations in the rats fed diet containing a 5% partially hydrolyzed curdlan (PHCD), whereas only the hepatic cholesterol concentration was decreased in the curdlan (CD)-fed rats. The cecal contents in the CD group contained a significantly larger amount of short-chain fatty acids, but not those in the PHCD group. CD, but not PHCD, significantly increased the population of cecal bifidobacteria. From the in vitro fermentation test with cecal contents from cellulose powder (CP) and CD-fed rats, PHCD proved to be easily fermented by both cecal contents; incidentally CD was more susceptible to the cecal contents from CD-fed rats than to those from CP-fed rats. These results suggest that PHCD is involved in the modulation of lipid metabolism and intestinal microflora through a different manner from the native CD in rats.

Animals↗

PubMed1996

Mode of action of the yeast Saccharomyces cerevisiae as a feed additive for ruminants.

Two suggested modes of action of yeast in stimulating rumen fermentation were investigated. The first, that yeast respiratory activity protects anaerobic rumen bacteria from damage by O2, was tested using different strains of yeast that had previously been shown to have differing abilities to increase the viable count of rumen bacteria. Saccharomyces cerevisiae NCYC 240, NCYC 1026, and the commercial product Yea-Sacc, added to rumen fluid in vitro at 1.3 mg/ml, increased the rate of O2 disappearance by between 46 and 89%. The same three preparations also stimulated bacterial numbers in an in vitro fermenter (Rusitec). S. cerevisiae NCYC 694 and NCYC 1088, which had no influence on the viable count in Rusitec, also had no effect on O2 uptake. Respiration-deficient (RD) mutants of S. cerevisiae NCYC 240 and NCYC 1026 were enriched by repeated culturing in the presence of ethidium bromide. S. cerevisiae NCYC 240 and NCYC 1026 stimulated the total and cellulolytic bacterial populations in Rusitec, while the corresponding RD mutants did not. Rigorous precautions to exclude air from Rusitec resulted in S. cerevisiae NCYC 240 no longer stimulating total bacterial numbers, although it still increased numbers of cellulolytic bacteria. The second hypothesis, that yeast provides malic and other dicarboxylic acids which stimulate the growth of some rumen bacteria, was examined by comparing the effects of yeast and malic acid on rumen fermentation in sheep. Three mature sheep were given 0.85 kg barley/d plus 0.55 kg chopped ryegrass hay/d either unsupplemented, or supplemented with 4 g S. cerevisiae NCYC 240/d or 100 mg L-malic acid/d either mixed with the diet or in aqueous solution infused continuously into the rumen. Yeast increased the total viable count of bacteria (P < 0.05) whereas malic acid did not, and no other effect of the treatments reached statistical significance. It was concluded, therefore, that the stimulation of rumen bacteria by S. cerevisiae is at least partly dependent on its respiratory activity, and is not mediated by malic acid.

Animals↗

PubMed1992

Rabadi fermentation of wheat: changes in phytic acid content and in vitro digestibility.

Fermentation of raw as well as autoclaved wheat flour with buttermilk at 30, 35 and 40 degrees C for 6, 12, 18, 24 and 48 h significantly decreased the level of phytic acid; maximum decrease was observed at 40 degrees C for 48 h. Starch as well as protein digestibility (in vitro) improved with an increase in temperature and period of fermentation. Phytic acid had a significant (P less than 0.05) negative correlation with digestibility (in vitro) of both starch and protein of rabadi.

Animals↗

PubMed1993

Fermentation and subsequent disposition of 14C-labelled plant cell wall material in the rat.

A 14C-labelled plant cell wall preparation (14C-PCW) produced from spinach (Spinacia oleracea L.) cell culture exhibits uniform labelling of the major polysaccharide groups (%): pectins 53, hemicellulose 13, cellulose 21, starch 3. This 14C-PCW preparation has been used in rat studies as a marker for plant cell wall metabolism. Metabolism of the 14C-PCW occurred largely over the first 24 h. This was due to fermentation in the caecum. The pectic fraction of the plant cell walls was degraded completely in the rat gastrointestinal tract, but some [14C]cellulose was still detected after 24 h in the colon. Of the 14C, 22% was recovered in the host liver, adipose tissue and skin, 26% excreted as 14CO2 and up to 18% was excreted in the faeces. There was no urinary excretion of 14C. In vitro fermentation using a caecal inoculum showed reduced 14CO2 production, 12% compared with 26% in the intact rat. 14C-PCW is a useful marker to investigate the fate of plant cell wall materials in the gastrointestinal tract. These studies show both bacterial fermentation of the 14C-PCW and host metabolism of the 14C-labelled fermentation products.

Animals↗

PubMed1996

The nutritive value of stackburned yellow maize for livestock: tests in vitro and in broiler chicks.

Difference in the nutritive value of four grades of stackburned yellow maize, obtained from a single storage unit in Mozambique, were examined. Samples were analysed for chemical composition, and subjected to the following in vitro assays for estimating digestibility: total dietary fibre and pancreatin for non-ruminants, and gas production using sheep rumen fluid for ruminant livestock. Samples were also fed to broiler chicks at 600 g/kg diet in a growth trial. There were no significant differences in crude protein contents of the maize samples, but there was evidence for the development of Maillard reaction products. Detectable amino acids were lower in discoloured maize, with decreases of 52% in lysine, 35% in arginine, and 15% in glycine concentration in the most severely discoloured sample compared with control. Total starch, reducing sugar, acid-detergent fibre and amylase-neutral-detergent fibre values increased, while total non-reducing sugar content decreased with increased discolouration. Total dietary fibre and pancreatin assays indicated a lowering in digestibility of maize with increasing discolouration. Weight gain of chicks (P = 0.0228), efficiency of feed utilization (P = 0.0009) and the metabolizable energy value of diets decreased (P < 0.0001) with increasing stackburn discolouration. There were no significant effects on N retention of diets. In vitro fermentation using sheep rumen fluid showed a linear decrease in gas production with increasing maize discolouration, indicating a reduction in rumen degradability with stackburn.

Aflatoxins↗

PubMed1999

Effects of brown midrib 3 mutation in corn silage on dry matter intake and productivity of high yielding dairy cows.

The effects of enhanced in vitro neutral detergent fiber (NDF) digestibility of corn silage on dry matter intake (DMI) and milk yield were evaluated using 32 Holstein cows in a crossover design with 28-d periods. At the beginning of the experiment, cows were 89 d in milk and yielded 45.6 kg/d of milk. Experimental diets contained either brown midrib (bm3) corn silage or isogenic normal corn silage (control) at 44.6% of DM. The NDF digestibility estimated by 30-h in vitro fermentation was higher for bm3 corn silage by 9.7 units. Contents of NDF and lignin were lower for bm3 corn silage by 1.8 and 0.8 units, respectively. Diets were formulated to contain 19% crude protein and 31% NDF and to have a forage to concentrate ratio of 56:44. Daily DMI, milk yield (3.5% fat-corrected milk), and solids-corrected milk were 2.1, 2.6, and 2.7 kg higher, respectively, for cows fed bm3 corn silage. The milk protein and lactose contents were greater for bm3 treatment, but milk fat content was not. Individual milk yield responses of the cows to bm3 treatment were positively related to pretrial milk yield, and DMI response tended to be positively related to pretrial milk yield. Enhanced in vitro NDF digestibility was associated with higher energy intake, which resulted in increased milk yield.

Animals↗

PubMed2006

Influence of glycosidic linkages and molecular weight on the fermentation of maltose-based oligosaccharides by human gut bacteria.

A structure-function study was carried out to increase knowledge of how glycosidic linkages and molecular weights of carbohydrates contribute toward the selectivity of fermentation by gut bacteria. Oligosaccharides with maltose as the common carbohydrate source were used. Potentially prebiotic alternansucrase and dextransucrase maltose acceptor products were synthesized and separated into different molecular weights using a Bio-gel P2 column. These fractions were characterized by matrix-assisted laser desorption/ionization time-of-flight. Nonprebiotic maltooligosaccharides with degrees of polymerization (DP) from three to seven were commercially obtained for comparison. Growth selectivity of fecal bacteria on these oligosaccharides was studied using an anaerobic in vitro fermentation method. In general, carbohydrates of DP3 showed the highest selectivity towards bifidobacteria; however, oligosaccharides with a higher molecular weight (DP6-DP7) also resulted in a selective fermentation. Oligosaccharides with DPs above seven did not promote the growth of "beneficial" bacteria. The knowledge of how specific structures modify the gut microflora could help to find new prebiotic oligosaccharides.

Bacteria↗

PubMed2000

Effects of brown midrib 3 mutation in corn silage on productivity of dairy cows fed two concentrations of dietary neutral detergent fiber: 3. Digestibility and microbial efficiency.

The effects of digestibility of corn silage neutral detergent fiber (NDF) and dietary NDF content on ruminal digestion kinetics, site of nutrient digestion, and microbial N production efficiency were evaluated with eight multiparous high producing dairy cows in a duplicated 4 x 4 Latin square design with 21-d periods. Experimental diets contained corn silage from a brown midrib (bm3) hybrid or its isogenic normal control at two concentrations of dietary NDF (29 and 38%). The NDF digestibility estimated by a 30-h in vitro fermentation was higher for bm3 corn silage by 9.4 units (55.9 vs. 46.5%). Neither ruminal nor total tract NDF digestibility was affected by corn silage treatment. The bm3 corn silage diet decreased starch digestibility in the rumen and in the total tract, but increased postruminal starch digestibility compared with control diet. The bm3 corn silage diets increased microbial N flow to the duodenum and tended to decrease ruminal ammonia concentration. Microbial efficiency was greater for cows fed bm3 corn silage in spite of lower ruminal pH. Higher efficiency of microbial nitrogen production might be attributed to faster passage rate of NDF for cows fed bm3 corn silage compared with those fed control corn silage. Higher in vitro NDF digestibility might predict enhanced NDF fragility and ease of NDF hydrolysis in vivo. Enhanced in vitro NDF digestibility does not necessarily result in increased NDF digestibility either in the rumen or in the total tract, but possibly increases rate of passage and DMI, improving efficiency of microbial N production.

Animal Feed↗

PubMed1991

Mammalian lignan production from various foods.

Mammalian lignans such as enterolactone and enterodiol, which are produced in the colon from precursors in foods, have been suggested as playing a role in the cancer-protective effect of vegetarian diets. Despite this, very little is known regarding the amount that is produced from different food products. Therefore, the objective of this study was to determine the production of mammalian lignans from 68 common plant foods by using the technique of in vitro fermentation with human fecal microbiota, which simulates colonic fermentation. Results showed a wide range (21-67,541 microgram(s)/100 g sample) in the amount of lignans produced. On the average as a group, the oilseeds produced the highest amounts (20,461 +/- 12,685), followed by the dried seaweeds (900 +/- 247), whole legumes (562 +/- 211), cereal brans (486 +/- 90), legume hulls (371 +/- 52), whole grain cereals (359 +/- 81), vegetables (144 +/- 23), and fruits (84 +/- 22). The vegetables produced the second highest concentration of lignans (1,546 +/- 280) when the data were expressed on a moisture-free basis. Flaxseed flour and its defatted meal were the highest producers of lignans (mean 60,110 +/- 7,431). Lignan production with the in vitro method related well to the urinary lignan excretion observed in rats and humans. The data should be useful in the estimation of lignan production from a given diet and in the formulation of high-lignan-producing diet for the purpose of reducing the cancer risk.

4-Butyrolactone↗