Effect of Nitrate on Methane Production and Fermentation by Slurries of Human Faecal Bacteria

Allison, C.; Macfarlane, G.T.

doi:10.1099/00221287-134-6-1397

Cited by 39 publications

(50 citation statements)

References 34 publications

(32 reference statements)

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“…From a microbiological viewpoint, the chemical composition, physical form and amount of substrate available affects bacterial fermentation reactions, which are also dependent on the types and numbers of different bacterial populations in the gut, catabolite regulatory mechanisms, the availability of inorganic electron donors, such as nitrate (Allison & Macfarlane, 1988) and sulfate (Gibson et al 1993), as well as competitive and cooperative interactions between different species in the microbiota .…”

Section: Short-chain Fatty Acids: Intestinal Bacteria: Fermentation: mentioning

confidence: 99%

Regulation of short-chain fatty acid production

2003

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Short-chain fatty acid (SCFA) formation by intestinal bacteria is regulated by many different host, environmental, dietary and microbiological factors. In broad terms, however, substrate availability, bacterial species composition of the microbiota and intestinal transit time largely determine the amounts and types of SCFA that are produced in healthy individuals. The majority of SCFA in the gut are derived from bacterial breakdown of complex carbohydrates, especially in the proximal bowel, but digestion of proteins and peptides makes an increasing contribution to SCFA production as food residues pass through the bowel. Bacterial hydrogen metabolism also affects the way in which SCFA are made. This outcome can be seen through the effects of inorganic electron acceptors (nitrate, sulfate) on fermentation processes, where they facilitate the formation of more oxidised SCFA such as acetate, at the expense of more reduced fatty acids, such as butyrate. Chemostat studies using pure cultures of saccharolytic gut micro-organisms demonstrate that C availability and growth rate strongly affect the outcome of fermentation. For example, acetate and formate are the major bifidobacterial fermentation products formed during growth under C limitation, whereas acetate and lactate are produced when carbohydrate is in excess. Lactate is also used as an electron sink inClostridium perfringensand, to a lesser extent, inBacteroides fragilis. In the latter organism acetate and succinate are the major fermentation products when substrate is abundant, whereas succinate is decarboxylated to produce propionate when C and energy sources are limiting.

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Section: Short-chain Fatty Acids: Intestinal Bacteria: Fermentation: mentioning

confidence: 99%

Regulation of short-chain fatty acid production

2003

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“…Alternate electron acceptors include unsaturated fatty acids (Czerkawski et al 1966), sulfate (Marty and Demeyer 1973) and nitrate (Allison and Macfarlane 1988). The presence of these acceptors can alter the microbial mix within the biofilm and divert electron flow away from methanogenesis.…”

Section: Interspecies H 2 Transfermentioning

confidence: 99%

Interactions between microbial consortia in biofilms: a paradigm shift in rumen microbial ecology and enteric methane mitigation

Leng¹

2014

Anim. Prod. Sci.

132

105

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Abstract. Minimising enteric CH 4 emissions from ruminants is a current research priority because CH 4 contributes to global warming. The most effective mitigation strategy is to adjust the animal's diet to complement locally available feed resources so that optimal production is gained from a minimum of animals. This essay concentrates on a second strategy -the use of feed additives that are toxic to methanogens or that redirect H 2 (and electrons) to inhibit enteric CH 4 emissions from individual animals. Much of the published research in this area is contradictory and may be explained when the microbial ecology of the rumen is considered.Rumen microbes mostly exist in organised consortia within biofilms composed of self-secreted extracellular polymeric substances attached to or within feed particles. In these biofilms, individual colonies are positioned to optimise their use of preferred intermediates from an overall process of organic matter fermentation that generates end-products the animal can utilise. Synthesis of CH 4 within biofilms prevents a rise in the partial pressure of H 2 (pH 2 ) to levels that inhibit bacterial dehydrogenases, and so reduce fermentation rate, feed intake and digestibility. In this context, hypotheses are advanced to explain changes in hydrogen disposal from the biofilms in the rumen resulting from use of anti-methanogenic feed additives as follows.Nitrate acts as an alternative electron sink when it is reduced via NO 2 -to NH 3 and CH 4 synthesis is reduced. However, efficiency of CH 4 mitigation is always lower than that predicted and decreases as NO 3 -ingestion increases. Suggested reasons include (1) variable levels of absorption of NO 3 -or NO 2 -from the rumen and (2) increases in H 2 production. One suggestion is that NO 3 -reduction may lower pH 2 at the surface of biofilms, thereby creating an ecological niche for growth of syntrophic bacteria that oxidise propionate and/or butyrate to acetate with release of H 2 .Chlorinated hydrocarbons also inhibit CH 4 synthesis and increase H 2 and formate production by some rumen methanogens. Formate diffuses from the biofilm and is converted to HCO 3 -and H 2 in rumen fluid and is then excreted via the breath. Short-chain nitro-compounds inhibit both CH 4 and formate synthesis when added to ruminal fluid but have little or no effect in redirecting H 2 to other sinks, so the pH 2 within biofilms may increase to levels that support reductive acetogenesis. Biochar or activated charcoal may also alter biofilm activity and reduce net CH 4 synthesis; direct electron transfer between microbes within biofilms may also be involved. A final suggestion is that, during their sessile life stage, protozoa interact with biofilm communities and help maintain pH 2 in the biofilm, supporting methanogenesis.

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“…According to Macfarlane and Gibson (1994), the formation of SCFA in the gut depends on various factors. From a microbiological viewpoint, the chemical composition, physical form and amount of substrate available affect bacterial fermentation reactions, which are also dependent on the types and numbers of different bacterial populations found in the gut, catabolite regulatory mechanisms, the availability of inorganic electron donors, as well as competitive and cooperative interactions between different species in the microbiota (Allison & Macfarlane, 1988;Macfarlane & Gibson, 1994).…”

Section: Analysis Of Short-chain Fatty Acids (Scfas)mentioning

confidence: 99%

Beneficial effects of fermented vegetal beverages on human gastrointestinal microbial ecosystem in a simulator

Bianchi

Rossi

Sakamoto

et al. 2014

Food Research International

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The aim of this study was to evaluate the effects of four beverage formulations (prebiotic -fructooligosaccharide, probiotic -Lactobacillus casei Lc-01, synbiotic -fructooligosaccharide and L. casei Lc-01 and placebo) based on aqueous extracts of soy and quinoa, towards the human intestinal microbiota using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), a dynamic model of the human gut. To monitor the effects on microbial community composition, plate counts on specific growth media and a PCR-DGGE analysis were performed on samples from all colon compartments -ascending, transverse and descending. To verify the effects on microbial metabolism, we analyzed the ammonium and short chain fatty acids (SCFAs) concentrations. The synbiotic beverage showed the best microbiological results in the ascending colon compartment, stimulating the growth of Lactobacillus spp. and Bifidobacterium spp., and reducing Clostridium spp., Bacteroides spp., enterobacteria and Enterococcus spp. populations in this compartment. A larger reduction (p b 0.05) of ammonia ions in the ascending colon was observed during the synbiotic beverage treatment. No statistical difference was observed in SCFA production among the treatments and the basal period. Plate count and DGGE analysis showed the survival of L. casei Lc-01 in the colon. DGGE analysis also showed higher richness and diversity of the Lactobacillus spp. community during the treatment with synbiotic beverage, with higher accentuation in the ascending colon.

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Effect of Nitrate on Methane Production and Fermentation by Slurries of Human Faecal Bacteria

Cited by 39 publications

References 34 publications

Regulation of short-chain fatty acid production

Regulation of short-chain fatty acid production

Interactions between microbial consortia in biofilms: a paradigm shift in rumen microbial ecology and enteric methane mitigation

Beneficial effects of fermented vegetal beverages on human gastrointestinal microbial ecosystem in a simulator

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