Biomedical subjects

R A Rastall

Publications and source records attributed to R A Rastall.

At least 19 recordsLinked to original sources

PubMed2006

In vitro fermentation of sugar beet arabinan and arabino-oligosaccharides by the human gut microflora.

AIMS: To determine the fermentation profiles by human gut bacteria of arabino-oligosaccharides of varying degree of polymerization. MATERIALS AND METHODS: Sugar beet arabinan was hydrolyzed with a commercial pectinase and eight fractions, of varying molecular weight, were isolated by gel-filtration chromatography. Hydrolysis fractions, arabinose, arabinan and fructo-oligosaccharides were fermented anaerobically by gut bacteria. Total bacteria, bifidobacteria, bacteroides, lactobacilli and the Clostridium perfringens/histolyticum sub. grp. were enumerated using fluorescent in situ hybridization. RESULTS: Bifidobacteria were stimulated to different extents depending on molecular weight, i.e. maximum increase in bifidobacteria after 48 h was seen on the lower molecular weight fractions. Lactobacilli fluctuated depending on the initial inoculum levels. Bacteroides numbers varied according to fraction; arabinan, arabinose and higher oligosaccharides (degree of polymerization, dp > 8) resulted in significant increases at 24 h. Only carbohydrate mixtures with dp of 1-2 resulted in significant increases at 48 h (log 8.77 +/- 0.23). Clostridia decreased on all substrates. CONCLUSIONS: Arabino-oligosaccharides can be considered as potential prebiotics. SIGNIFICANCE AND IMPACT OF THE STUDY: Arabinan is widely available as it is a component of sugar beet pulp, a co-product from the sugar beet industry. Generation of prebiotic functionality from arabinan would represent significant added value to a renewable resource.

Arabinose↗

PubMed2006

In vitro fermentation of mixed linkage glucooligosaccharides produced by Gluconobacter oxydans NCIMB 4943 by the human colonic microflora.

The aim of this study was to develop selectively fermented (prebiotic) carbohydrate molecules which would also result in the generation of butyric acid. Gluco-oligosaccharides produced by Gluconobacter oxydans NCIMB 4943 from various types of maltodextrins were evaluated for their fermentation by mixed cultures of human colonic microflora. The selectivity of growth of desirable bacteria (bifidobacteria, lactobacilli) was studied in stirred pH-controlled (6.8) batch cultures. Bacterial populations were enumerated using fluorescent in situ hybridization (FISH). Gluco-oligosaccharides resulted in significantly (P<0.05) increased numbers of bifidobacteria and lactobacilli within 24 hours. Bacteroides, clostridial and eubacterial populations were slightly decreased at 48 h. There was very little difference in selectivity between the maltodextrin substrates and the products, although maltodextrin displayed a slightly less selective fermentation than the gluco-oligosaccharide products, also stimulating the growth of bacteroides, clostridia and eubacteria. Gluco-oligosaccharides, produced from G19 maltodextrin, resulted in the best prebiotic effect with the highest prebiotic index (PI) of 5.90 at 48 hours. Acetate, propionate and butyrate were all produced from gluco-oligosaccharides, derived from G19 maltodextrin, at 48 hours but no lactate or formate were detected.

Acetic Acid↗

PubMed2006

In vitro three-stage continuous fermentation of gluco-oligosaccharides produced by Gluconobacter oxydans NCIMB 4943 by the human colonic microflora.

Gluco-oligosaccharides produced by Gluconobacter oxydans NCIMB 4943 from maltodextrin as the source, were evaluated for their fermentability by the human colonic microflora. The selectivity of growth of desirable bacteria in the human colon was studied in a three-stage continuous model of the human large intestine. Populations of bacteria, and their fluctuations as a response to the fermentation, were enumerated using fluorescent in situ hybridization (FISH). The gluco-oligosaccharides resulted in increases in numbers of bifidobacteria and the Lactobacillus/Enterococcus group in all 3 vessels of the system, representing the proximal, transverse and distal colonic areas. The prebiotic indices of the gluco-oligosaccharides were 2.29, 4.23 and 2.74 in V1, V2 and V3 respectively.

Bacteria↗

PubMed2005

Prebiotics and resistance to gastrointestinal infections.

Acute gut disorder is a cause for significant medicinal and economic concern. Certain individual pathogens of the gut, often transmitted in food or water, have the ability to cause severe discomfort. There is a need to manage such conditions more effectively. The route of reducing the risk of intestinal infections through diet remains largely unexplored. Antibiotics are effective at inhibiting pathogens; however, these should not be prescribed in the absence of disease and therefore cannot be used prophylactically. Moreover, their indiscriminate use has reduced effectiveness. Evidence has accumulated to suggest that some of the health-promoting bacteria in the gut (probiotics) can elicit a multiplicity of inhibitory effects against pathogens. Hence, an increase in their numbers should prove effective at repressing pathogen colonisation if/when infectious agents enter the gut. As such, fortification of indigenous bifidobacteria/lactobacilli by using prebiotics should improve protection. There are a number of potential mechanisms for lactic acid bacteria to reduce intestinal infections. Firstly, metabolic endproducts such as acids excreted by these micro-organisms may lower the gut pH to levels below those at which pathogens are able to effectively compete. Also, many lactobacilli and bifidobacteria species are able to excrete natural antibiotics, which can have a broad spectrum of activity. Other mechanisms include an improved immune stimulation, competition for nutrients and blocking of pathogen adhesion sites in the gut. Many intestinal pathogens like type 1 fimbriated Escherichia coli, salmonellae and campylobacters utilise oligosaccharide receptor sites in the gut. Once established, they can then cause gastroenteritis through invasive and/or toxin forming properties. One extrapolation of the prebiotic concept is to simulate such receptor sites in the gut lumen. Hence, the pathogen is 'decoyed' into not binding at the host mucosal interface. The combined effects of prebiotics upon the lactic acid flora and anti-adhesive strategies may lead towards new dietary interventions against food safety agents.

Bacterial Infections↗

PubMed2005

In vitro determination of prebiotic properties of oligosaccharides derived from an orange juice manufacturing by-product stream.

Fermentation properties of oligosaccharides derived from orange peel pectin were assessed in mixed fecal bacterial culture. The orange peel oligosaccharide fraction contained glucose in addition to rhamnogalacturonan and xylogalacturonan pectic oligosaccharides. Twenty-four-hour, temperature- and pH-controlled, stirred anaerobic fecal batch cultures were used to determine the effects that oligosaccharides derived from orange products had on the composition of the fecal microbiota. The effects were measured through fluorescent in situ hybridization to determine changes in bacterial populations, fermentation end products were analyzed by high-performance liquid chromatography to assess short-chain fatty acid concentrations, and subsequently, a prebiotic index (PI) was determined. Pectic oligosaccharides (POS) were able to increase the bifidobacterial and Eubacterium rectale numbers, albeit resulting in a lower prebiotic index than that from fructo-oligosaccharide metabolism. Orange albedo maintained the growth of most bacterial populations and gave a PI similar to that of soluble starch. Fermentation of POS resulted in an increase in the Eubacterium rectale numbers and concomitantly increased butyrate production. In conclusion, this study has shown that POS can have a beneficial effect on the fecal microflora; however, a classical prebiotic effect was not found. An increase in the Eubacterium rectale population was found, and butyrate levels increased, which is of potential benefit to the host.

Beverages↗

PubMed2005

Caseinoglycomacropeptide inhibits adhesion of pathogenic Escherichia coli strains to human cells in culture.

Caseinoglycomacropeptide (CGMP) derived from kappa-casein was investigated for its ability to inhibit the adhesion of 3 strains of verotoxigenic Escherichia coli (VTEC) and 3 strains of enteropathogenic Escherichia coli (EPEC) to human HT29 tissue cell cultures. Effects on adhesion of Desulfovibrio desulfuricans, Lactobacillus pentosus, Lactobacillus casei, Lactobacillus acidophilus, and Lactobacillus gasseri were also investigated. Generally, CGMP exerted effective anti-adhesive properties at a dose of 2.5 mg/mL, albeit with a high degree of strain specificity. The CGMP reduced adhesion of VTEC strains to <50% of the control and reduced adhesion of EPEC strains to between 80 and 10% of the control. The CGMP also reduced the adhesion of L. pentosus and L. casei to 44 and 42%, respectively. A slight but significant reduction of L. acidophilus, to 81%, was observed, but no significant effects were detected with either Dsv. desulfuricans or L. gasseri. Further investigation of the dose response relationships with the E. coli strains gave IC50 values ranging between 0.12 and 1.06 mg/mL.

Adenocarcinoma↗

PubMed2004

Bacteria in the gut: friends and foes and how to alter the balance.

The activities of the bacteria resident in the colon of companion animals can have an impact upon the health of the host. Our understanding of this microbial ecosystem is presently increasing due to the development of DNA-based microbiological tools that allow identification and enumeration of nonculturable microorganisms. These techniques are changing our view of the bacteria that live in the gut, and they are facilitating dietary-intervention approaches to modulate the colonic ecosystem. This is generally achieved by the feeding of either live bacteria (probiotics) or nondigestible oligosaccharides (prebiotics) that selectively feed the indigenous probiotics. Feeding studies with a Lactobacillus acidophilus probiotic have shown positive effects on carriage of Clostridium spp. in canines and on recovery from Campylobacter spp. infection in felines. Immune function was improved in both species. Prebiotic feeding studies with lactosucrose and fructo-oligosaccharides in both cats and dogs have shown positive effects on the microflora balance. Recently synbiotic forms (a probiotic together with a prebiotic) targeted at canines have been developed that show promise as dietary-intervention tools.

Animals↗

PubMed2004

Modulation of anti-pathogenic activity in canine-derived Lactobacillus species by carbohydrate growth substrate.

AIMS: To investigate the effect of various carbon sources on the production of extracellular antagonistic compounds against two Escherichia coli strains and Salmonella enterica serotype Typhimurium by three canine-derived lactobacilli strains. METHODS AND MATERIALS: Cell-free preparations, pH neutralized, were used in antibiotic disc experiments as an initial screening. The bacteria/carbohydrate combinations that showed inhibition of the growth of those pathogens, were further investigated in batch co-culture experiments. The cell-free supernatants of the cultures, that decreased the population number of the pathogens in the co-culture experiments to log CFU ml-1 <or= 4, were tested for inhibition of the pathogens in pure cultures at neutral and acidic pH. CONCLUSIONS: The results showed that the substrate seems to affect the production of antimicrobial compounds and this effect could not just be ascribed to the ability of the bacteria to grow in the various carbon sources. L. mucosae, L. acidophilus and L. reuteri, when grown in sugar mixtures consisting of alpha-glucosides (Degree of Polymerization (DP) 1-4) could produce antimicrobial compounds active against all three pathogens in vitro. This effect could not be attributed to a single ingredient of those sugar mixtures and was synergistic. This inhibition had a dose-response characteristic and was more active at acidic pH. SIGNIFICANCE AND IMPACT OF THE STUDY: Knowledge of the effect that the carbon source has on the production of antimicrobial compounds by gut-associated lactobacilli allows the rational design of prebiotic/probiotic combinations to combat gastrointestinal pathogens.

Animals↗

PubMed2003

In vitro evaluation of the fermentation properties of galactooligosaccharides synthesised by alpha-galactosidase from Lactobacillus reuteri.

Stirred, pH-controlled anaerobic batch cultures were used to evaluate the in vitro utilisation by canine gut microflora of novel alpha-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.

Acetic Acid↗

PubMed2003

Synthesis of alpha-galactooligosaccharides with alpha-galactosidase from Lactobacillus reuteri of canine origin.

Crude cell-free extracts from Lactobacillus reuteri grown on cellobiose, maltose, lactose and raffinose were assayed for glycosidic activities. When raffinose was used as the carbon source, alpha-galactosidase was produced, showing the highest yield at the beginning of the stationary growth phase. A 64 kDa enzyme was purified by ultra- and gel filtration, and characterized for its hydrolytic and synthetic activity. Highest hydrolytic activity was found at pH 5.0 at 50 degrees C ( K(M) 0.55 mM, V(max) 0.80 micromol min(-1) mg(-1) of protein). The crude cell-free extract was further used in glycosyl transfer reactions to synthesize oligosaccharides from melibiose and raffinose. At a substrate concentration of 23% (w/v) oligosaccharide mixtures were formed with main products being a trisaccharide at 26% (w/w) yield from melibiose after 8 h and a tetrasaccharide at 18% (w/w) yield from raffinose after 7 h. Methylation analysis revealed the trisaccharide to be 6' alpha-galactosyl melibiose and the tetrasaccharide to be stachyose. In both cases synthesis ceased when hydrolysis of the substrate reached 50%.

Animals↗

PubMed2003

Synthesis of FimH receptor-active manno-oligosaccharides by reverse hydrolysis using alpha-mannosidases from Penicillium citrinum, Aspergillus phoenicis and almond.

Recombinant Penicillium citrinum alpha-1,2-mannosidase, expressed in Aspergillus oryzae, was employed to carry out regioselective synthesis of alpha- d-mannopyranosyl-(1-->2)- d-mannose. Yields (w/w) of 16.68% disaccharide, 3.07% trisaccharide and 0.48% tetrasaccharide were obtained, with alpha1-->2 linkages present at 98.5% of the total linkages formed. Non-specific alpha-mannosidase from almond was highly efficient in reverse hydrolysis and oligosaccharide yields of 45-50% were achieved. The products of the almond mannosidase were a mixture of disaccharides (30.75%, w/w), trisaccharides (12.26%, w/w) and tetrasaccharides (1.89%, w/w) with 1-->2, 1-->3 and 1-->6 isomers. alpha-1,2-linkage specific mannosidase from P. citrinum and alpha-1,6-linkage-specific mannosidase from Aspergillus phoenicis were used in combination to hydrolyse the respective linkages from the mixture of isomers, resulting in alpha- d-mannopyranosyl-(1-->3)- d-mannose in 86.4% purity. The synthesised oligosaccharides can potentially inhibit the adhesion of pathogens by acting as "decoys" of receptors of type-1 fimbriae carried by enterobacteria.

Adhesins, Escherichia coli↗

PubMed2003

Development of a quantitative tool for the comparison of the prebiotic effect of dietary oligosaccharides.

AIMS: To develop a quantitative equation [prebiotic index (PI)] to aid the analysis of prebiotic fermentation of commercially available and novel prebiotic carbohydrates in vitro, using previously published fermentation data. METHODS: The PI equation is based on the changes in key bacterial groups during fermentation. The bacterial groups incorporated into this PI equation were bifidobacteria, lactobacilli, clostridia and bacteroides. The changes in these bacterial groups from previous studies were entered into the PI equation in order to determine a quantitative PI score. PI scores were than compared with the qualitative conclusions made in these publications. In general the PI scores agreed with the qualitative conclusions drawn and provided a quantitative measure. CONCLUSIONS: The PI allows the magnitude of prebiotic effects to be quantified rather than evaluations being solely qualitative. SIGNIFICANCE AND IMPACT OF THE STUDY: The PI equation may be of great use in quantifying prebiotic effects in vitro. It is expected that this will facilitate more rational food product development and the development of more potent prebiotics with activity at lower doses.

Bacteria↗

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↗

PubMed2001

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.

Bacteria↗

PubMed2001

Synthesis and fermentation properties of novel galacto-oligosaccharides by beta-galactosidases from Bifidobacterium species.

beta-Galactosidase enzymes were extracted from pure cultures of Bifidobacterium angulatum, B. bifidum BB-12, B. adolescentis ANB-7, B. infantis DSM-20088, and B. pseudolongum DSM-20099 and used in glycosyl transfer reactions to synthesize oligosaccharides from lactose. At a lactose concentration of 30% (wt/wt) oligosaccharide yields of 24.7 to 47.6% occurred within 7 h. Examination of the products by thin-layer chromatography and methylation analysis revealed distinct product derived spectra from each enzyme. These were found to be different to that of Oligomate 55, a commercial prebiotic galacto-oligosaccharide. Fermentation testing of the oligosaccharides showed an increase in growth rate, compared to Oligomate 55, with products derived from B. angulatum, B. bifidum, B. infantis, and B. pseudolongum. However B. adolescentis had a lower growth rates on its oligosaccharide compared with Oligomate 55. Mixed culture testing of the B. bifidum BS-4 oligosaccharide showed that the overall prebiotic effect was equivalent to that of Oligomate 55.

Bifidobacterium↗

PubMed2000

Evaluation of solid substrates for enzyme production by Coriolus versicolor, for use in bioremediation of chlorophenols in aqueous effluents.

In the development of a system for the removal of chlorophenols from aqueous effluents, a range of solid substrates for the growth of Coriolus versicolor were investigated. Substrates included wood chips, cereal grain, wheat husk and wheat bran. Suitability for transformation of chlorophenols depended on laccase production by the fungus. The greatest amount of laccase (<25 Units g(-1) substrate) was produced on wheat husk and wheat bran over 30 days colonisation. Aqueous extracts of laccase from wheat husk and wheat bran cultures removed 100% of 2,4-dichlorophenol (50 ppm) from solution within 5 h and 75-80% of pentachlorophenol (50 ppm) within 24 h. Wheat bran was formulated into pellets with biscuit flour to provide a compact substrate for fungal immobilisation. Addition of 8-12% yeast extract to the pellets increased laccase production five-fold. Colonised pellets were added to chlorophenol solutions in 200-4000-ml bioreactors, resulting in >90% removal of chlorophenols within 100 min.

Basidiomycota↗

PubMed2000

In vitro fermentability of dextran, oligodextran and maltodextrin by human gut bacteria.

Anaerobic batch culture fermenters were used for a preliminary screening of the in vitro utilization by human gut microflora of dextran and novel oligodextrans (I, II and III) produced in the University of Reading (UK). Glucose and fructooligosaccharides (FOS) were used as reference carbohydrates. As expected, FOS acted as a good prebiotic in that it selectively increased numbers of bifidobacteria in the early stages of the fermentation. Dextran and oligodextrans each resulted in an enrichment of bifidobacteria in the batch cultures, with high levels of persistence up to 48 h. They also produced elevated levels of butyrate ranging from 5 to 14.85 mmol/l. To more effectively simulate conditions that prevail in different regions of the large intestine, a three-stage continuous culture cascade system was used to study further the fermentation of dextran, a low-molecular-mass oligodextran (IV) and maltodextrin. Oligodextran IV was shown to be the best substrate for bifidobacteria and lactobacilli with steady-state populations of bifidobacteria and lactobacilli being higher in all three vessels of the gut model than the respective populations resulting from dextran and maltodextrin. A maximum difference of 1.9 log was observed in vessel 1 for both bifidobacteria and lactobacilli in the case of dextran fermentation, with 1.4 log and 0.8 log in vessel 3 were the maximum differences for bifidobacteria and lactobacilli when maltodextrin was used as the carbohydrate source. Moreover, dextran and oligodextran appeared to stimulate butyrate production, with a maximum production up to 25.39 mmol/l in vessel 3 when fermenting dextran, followed by 21.70 mmol/l in the case of oligodextran IV and only 12.64 mmol/l in the case of maltodextrin.

Bifidobacterium↗

PubMed1999

A study of dextran production from maltodextrin by cell suspensions of Gluconobacter oxydans NCIB 4943.

This study investigated dextran synthesis from a commercial maltodextrin substrate using cell suspensions of G. oxydans NCIB 4943 as catalysts. Experiments were arranged according to a central composite statistical design. The effects of substrate concentration (10-100 g l-1), cell concentration (0.32-32.0 g wet weight l-1), time of reaction (8-48 h) and pH (3.5-5.5), each at three levels, on dextran yield and dextran molecular weight (MW), were investigated. Response surface methodology was used to assess factor interactions, and empirical models describing the two responses were fitted. Most of the variance in dextran yield could be explained by the fitted model (R2 = 0.96). Dextran yield ranged from 1.21 to 41.69%. The presence of significant negative quadratic effects of cell concentration and time indicated that dextran yield reached a plateau and thus, optimum levels of cell concentration and time could be identified to maximize dextran yield. Dextran MW ranged from 6.6 to 38 kDa and was characterized by the significant interactions of reaction time with substrate concentration and cell concentration. The model, however, could account for only 60% of the variance in dextran MW. Possible reasons for this are discussed.

Culture Media↗