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PubMed2002

Development of a static headspace gas chromatographic procedure for the routine analysis of volatile fatty acids in wastewaters.

An optimised procedure has been developed for the routine analysis of volatile fatty acids in wastewater matrices, using static headspace gas chromatography with flame ionisation detection. Factors such as sample volume, sample pre-treatment and the time and temperature of sample equilibration have been included in an optimisation model designed to provide maximum detector response for acetic, propionic, iso- and n-butyric and iso- and n-valeric acids in the concentration range 0-1000 mg/l. Optimal headspace conditions were observed when equilibrating at 85 degrees C for 30 min, using a 2.0 ml sample volume with the addition of 1.0 ml of NaHSO4 (62%, w/v) into standard 22.3 ml vials. 2-Ethylbutyric acid was used as an internal standard. The suitability of ordinary least squares regression and weighted least squares regression models for the purposes of calibration and quantification were investigated. A weighted least squares linear regression model applied to the heteroscedastic data provided lower detection limits, e.g. 3.7 and 3.3 mg/l for acetic and propionic acids.

Calibration↗

PubMed2002

Manipulation of colonic bacteria and volatile fatty acid production by dietary high amylose maize (amylomaize) starch granules.

AIMS: To study the effects of amylomaize starch and modified (carboxymethylated and acetylated) amylomaize starches on the composition of colonic bacteria and the production of volatile fatty acids, in mice. METHODS AND RESULTS: Balb/c mice were fed with experimental diets containing various amount of amylomaize and modified amylomaize starches. Colonic bacterial populations and short-chain fatty acids were monitored. Results showed that the increases in indigenous bifidobacteria were detected in mice fed all starches tested; however, the highest numbers were observed in the group fed with 40% unmodified amylomaize starch. The starch type influenced the populations of indigenous Lactobacillus, Bacteroides and coliforms. High Lactobacillus numbers were achieved in the colon of mice fed with high concentration of amylomaize starch. Acetylated amylomaize starch significantly reduced the population of coliforms. In addition, orally dosed amylomaize utilizing bifidobacteria reached their highest levels when fed together with amylomaize or carboxymethylated amylomaize starch and in both cases butyrate levels were markedly increased. CONCLUSIONS: These results indicate that different amylomaize starches could generate desirable variation in gut microflora and that particular starches may be used to selectively modify gut function. SIGNIFICANCE AND IMPACT OF STUDY: Amylomaize starch appeared to enhance the desirable composition of colonic bacteria in mice, and suggested it possessed the potential prebiotic properties. Therefore, resistant starch and its chemical derivatives may exert beneficial impacts to the human colon.

Amylose↗

PubMed1988

[The use of a partly-hydrolysed straw meal in the feeding of weaned piglets. 2. Concentration and production of volatile fatty acids in the large intestine by the use of test rations with various portions of straw].

The ad libitum influence of various quotas of partly hydrolysed straw meal (PHSM) on the fermentation and production of volatile fatty acids (VFA) in the colon in the measuring periods 2nd and 8th weeks of keeping was checked within a feeding experiment with weaned piglets of the country species (42nd-98th day of life; 1st-8th week of keeping). The straw hydrolysis product was fed in a parallel experiment without or after neutralization with CaCO3 in quotas of, 5, 10 and 15% related to dry matter in comparison to the feeding of sole concentrate feed. The measuring in the 2nd week of keeping (adaptation phase) was blurred by the diarrhea in the groups with regard to the concentration, production and molar proportion of VFA. The concentration and production quota of VFA was diminished and the C2:C3 relation as well as the molar quota of branched-chain fatty acids increased in the comparison of the groups above all under the feeding conditions of the sole use of concentrate and--less distinctly--of quotas of 5% PHSM (insufficient dietetic effect) in the feed mixture. Measuring in the 8th week, in which diarrhea did not play a role in any of the groups, showed a significant, ration specific influence on the fermentation pattern of VFA. With the increasing quota of PHSM in the feed mixture (x) a significantly positive relation with the molar acetate quota (y) could be calculated (y = 52.6 + 0.36x;r = 0.50). The C2:C3 relation after sole concentrate feeding rose to 2.6:1 at a 15% PHSM integration. In this, the molar increase of acetate was predominantly linked with a decrease of the butyrate and valerate quotas. A falling tendency of the molar iso-acid quota in the colon digesta was registered with the growing straw quota in the feed mixture. The daily production quota of VFA varied in the measuring period in the 8th week of keeping between 400 and 800 mmol/animal.d without an ascertainable influence of the crude fibre quota of the straw. In comparative calculations with other test results, however, a significant positive correlation between the daily intake of digestible organic matter and the production of VFA in the large intestine could be proved.

Animal Feed↗

PubMed1986

Net absorption of glucose, L-lactate, volatile fatty acids, and nitrogenous compounds by bovine given abomasal infusions of starch or glucose.

Three experiments were conducted to evaluate effects of abomasal infusion of glucose or starch on absorption of metabolites (glucose, L-lactate, volatile fatty acids, and nitrogenous compounds) from portal-drained viscera of a nonlactating Holstein cow and two Hereford X Angus heifers. Portal blood and plasma flow were determined by dilution of para-aminohippuric acid. Net absorption was portal-arterial concentration difference times portal plasma flow. Plasma concentration and portal-arterial difference of glucose increased rapidly and directly in response to increased rates of abomasal glucose infusion in the cow (Experiment 1). In the cow (Experiment 2), net absorption of L-lactate was greater with carbohydrate than with water infusion; net absorption of L-lactate was greater and of n-butyrate was less with starch than with glucose infusion. These responses were not evident in the heifers (Experiment 3). Net absorption of alpha-amino-N in the heifers was greater with starch than with glucose infusion. Increased concentrate intake by the heifers did not interact with responses to abomasal infusions. Recovery of infused glucose as absorbed glucose was similar for the cow and the heifers (65%). However, heifers absorbed (as glucose) 35% of infused starch and the cow only 8%.

Abomasum↗

PubMed2002

On-line titration of volatile fatty acids for the process control of anaerobic digestion plants.

The on-line titration of volatile fatty acids (VFA) was found to be a reliable method to measure the substrate (metabolite) concentration without the use of expensive analytical devices. A measurement cell was designed that ensures stable long-term operation, high throughputs and copes with both very low and very high VFA concentrations. Using synthetic textile wastewater, a recalibration of the pH probe was necessary only twice a week. A good reproducibility of the VFA concentrations was determined and standard deviations were below +/- 1% of the measured concentration. Changing salt concentrations of the wastewater in the range of 2.5-150 gl(-1) NaCl did not influence the determined VFA concentration significantly. The method was suitable to control the hydraulic retention time in an acidic phase reactor and to determine the acidification rates of wastewater compounds in batch experiments.

Bacteria, Anaerobic↗

PubMed1985

The digestion of fibre by pigs. 2. Volatile fatty acid concentrations in large intestine digesta.

The effect of including lupin (Lupinus sp.) hulls, maize cobs, wheat bran and lucerne (Medicago sativa) stems in a basal fibre-free diet on the concentrations and the relative proportions of volatile fatty acids (VFA) in the proximal colon of pigs, 17-18 h after feeding, was studied. Concentrations of total VFA in the proximal colon increased with increasing levels of neutral-detergent fibre (NDF) intake, and this increase was highly dependent on the source of NDF in the diet. Molar proportions of the VFA were significantly affected by the level of NDF intake only in the cases of acetic and butyric acids, whereas the source of dietary NDF had a marked influence on the molar proportions of all acids. The results indicate that the extent of fermentative breakdown of fibre in the pig intestine can be influenced substantially by the type and the level of fibre in the diet.

Animals↗

PubMed1996

Effect of ileal infusion of volatile fatty acids on feed intake and urinary magnesium excretion in sheep.

Five 2-year-old female sheep fitted with cannulae in the terminal ileum and proximal colon were infused, intra-ilealy during a 24 h period, with volatile fatty acids (VFA) (ratio of acetic:propionic:butyric acid, 0.80:0.15:0.05) at rate of 0, 220, 440, 660 or 880 mmol/day in 21 deionized water. Daily feed intake was progressively depressed by VFA and reached 87 +/- 4.7% (S.E.M.) at the highest rate of infusion. Colonic digesta pH decreased by 2.1 +/- 0.48 units and Mg solubility increased from 21 +/- 2.6 to 52 +/- 1.2% 16 h after the start at the highest rate of VFA infusion. Urinary Mg excretion increased during the first 4 h of infusion on all treatments but the increase was not sustained. The results are discussed in the context of limited knowledge of the importance of the large intestine in intake regulation and Mg absorption.

Animals↗

PubMed2002

Volatile fatty acids as electron donors for the reductive dechlorination of chloroethenes.

Uses of a mixture of six volatile fatty acids (VFAs) including acetic, propionic, butyric, isobutyric, valeric and isovaleric acids as electron donors for the reductive dechlorination of chloroethenes have been investigated by both microcosm and column studies. The fates of tetrachloroethene (PCE), cis-dichloroethene (cis-DCE) and vinyl chloride (VC) in the presence of VFAs and in the absence of VFAs were respectively documented. The results showed that VFAs stimulated complete reductive dechlorination of chloroethenes, either as direct substrates for the dechlorinating bacteria or via H2 formed during VFAs-degradation. There were sequential utilizations of different VFAs by fermenting bacteria. In the microcosm, propionic acid was the first to be used, followed by acetic, butyric, isobutyric, valeric, and isovaleric acids, and their mean first-order degradation rates obtained were 0.128, 0.048, 0.016, 0.027, 0.025 and 0.003 day(-1), respectively. In the column, propionic acid was the first to be used, followed by butyric and valeric acids, and their calculated first-order degradation rates were 0.833, 0.403 and 0.260 day(-1), respectively.

Carcinogens↗

PubMedDate not supplied

Methodological studies on the formation of CO2 and volatile fatty acids in porcine ileo-chyme and faeces.

As part of digestibility and energy metabolism studies in intact and ileorectostomized growing pigs model experiments were carried out on sampling techniques and the influence of storage conditions on CO2 and volatile fatty acid production in chyme. Results on the formation of CO2 and VFA in chyme and faeces are given. They indicate that chyme from the small intestine can be subjected to bacterial and enzymatic changes outside the animals and therefore must be stored in a cool place. In the chyme of IRA animals with closed colon descendens (end-to-end anastomosis) significantly reduced VFA contents were found in comparison to animals with open colon descendens (end-to-side anastomosis).

Anastomosis, Surgical↗

PubMed1998

Long-term competition between sulfate reducing and methanogenic bacteria in UASB reactors treating volatile fatty acids.

The competition between acetate utilizing methane-producing bacteria (MB) and sulfate-reducing bacteria (SRB) was studied in mesophilic (30 degrees C) upflow anaerobic sludge bed (UASB) reactors (upward velocity 1 m h-1; pH 8) treating volatile fatty acids and sulfate. The UASB reactors treated a VFA mixture (with an acetate:propionate:butyrate ratio of 5:3:2 on COD basis) or acetate as the sole substrate at different COD:sulfate ratios. The outcome of the competition was evaluated in terms of conversion rates and specific methanogenic and sulfidogenic activities. The COD:sulfate ratio was a key factor in the partitioning of acetate utilization between MB and SRB. In excess of sulfate (COD:sulfate ratio lower than 0.67), SRB became predominant over MB after prolonged reactor operation: 250 and 400 days were required to increase the amount of acetate used by SRB from 50 to 90% in the reactor treating, respectively, the VFA mixture or acetate as the sole substrate. The competition for acetate was further studied by dynamic simulations using a mathematical model based on the Monod kinetic parameters of acetate utilizing SRB and MB. The simulations confirmed the long term nature of the competition between these acetotrophs. A high reactor pH (+/-8), a short solid retention time (<150 days), and the presence of a substantial SRB population in the inoculum may considerably reduce the time required for acetate-utilising SRB to outcompete MB.

Acetates↗

PubMed1993

Dietary fat and fiber alter large bowel and portal venous volatile fatty acids and plasma cholesterol but not biliary steroids in pigs.

Male pigs were fed a low fiber beef diet (control) or that diet with additional fiber either as wheat bran, oat bran or baked beans. Total large bowel digesta and volatile fatty acid (VFA) pools were highest in pigs fed the diet with baked beans, intermediate in those fed the diets with oat bran and wheat bran and lowest in those fed the control diet. In all groups digesta mass and total VFA pools rose from the cecum and then fell to the distal colon, and incremental effects of diet were the same at all sampling sites. For acetate and propionate pools there was a significant interaction between diet and anatomical site, but data conversion to logarithms abolished this interaction, indicating that all dietary effects were proportionately the same across sections. Consumption of the diets with wheat bran, oat bran and baked beans increased the total large bowel butyrate pool compared with consumption of the control diet. Digesta H+ concentrations fell along the large bowel and correlated positively with VFA concentrations in the median colon. Portal venous VFA concentrations correlated with VFA in the proximal colon only. Plasma cholesterol and biliary steroids were unrelated to portal venous propionate concentrations.

Animals↗

PubMed1999

Effects of ruminal infusion of volatile fatty acids on plasma concentration of growth hormone and insulin in sheep.

In an initial experiment we observed postprandial changes in plasma concentrations of growth hormone (GH), insulin, glucagon, and somatostatin (SRIF) in sheep. We then examined whether increasing the rumen concentration of volatile fatty acids (VFA) by infusing a VFA mixture at three rates (53.5, 107, and 214 micromol/kg/min for 4 hr) mimicked the postprandial changes in hormone secretion. Feeding significantly (P < 0.05) suppressed the plasma GH concentration for 6 hr, whereas it significantly (P < 0.05) increased plasma concentrations of insulin, glucagon, and SRIF. Plasma glucose levels tended to decrease after feeding but then gradually increased over the prefeeding level (P < 0.05). Intraruminal infusion of the VFA mixture at 107 micromol/kg/min caused similar changes in ruminal VFA concentrations to those seen after feeding. The infusion significantly (P < 0.05) suppressed GH secretion in a dose-dependent manner, whereas it caused a significant (P < 0.05) increase in insulin and glucose concentrations without changing glucagon concentrations. From these results, we conclude that the postprandial change in ruminal VFA concentration may be a physiological signal which modifies GH and insulin secretion in sheep.

Animal Nutritional Physiological Phenomena↗

PubMed1980

Effect of fermentable carbohydrates on volatile fatty acids, ammonia and mineral absorption in the rat caecum.

The effects of poorly digested carbohydrates in the small intestine on caecal digestion and absorption have been studied in the rat. Even in diets lacking these carbohydrates, there was a noticeable production of volatile fatty acids (VFA) in the caecum. Except for cellulose, the carbohydrates (bran, pectin, guar-gum, crude potato-starch, lactose, lactulose) favoured considerable development of the caecum and enhanced the quantities of VFA present there. On reaching the caecum, they increased ammonia absorption as a result of a higher uptake of blood urea, even if a greater part of the urea nitrogen was used in bacterial protein synthesis. Arteriovenous differences in the caecum showed a considerable absorption of various electrolytes. VFA absorption seemed to be accompanied by a release of Cl- into the caecal contents and by absorption of the main cations, Na+ being absorbed along an unfavourable gradient between the plasma and the caecal contents.

Ammonia↗

PubMed1983

Volatile Fatty Acid production by the hindgut microbiota of xylophagous termites.

Acetate dominated the extracellular pool of volatile fatty acids (VFAs) in the hindgut fluid of Reticulitermes flavipes, Zootermopsis angusticollis, and Incisitermes schwarzi, where it occurred at concentrations of 57.9 to 80.6 mM and accounted for 94 to 98 mol% of all VFAs. Small amounts of C(3) to C(5) VFAs were also observed. Acetate was also the major VFA in hindgut homogenates of Schedorhinotermes lamanianus, Prorhinotermes simplex, Coptotermes formosanus, and Nasutitermes corniger. Estimates of in situ acetogenesis by the hindgut microbiota of R. flavipes (20.2 to 43.3 nmol . termite . h) revealed that this activity could support 77 to 100% of the respiratory requirements of the termite (51.6 to 63.6 nmol of O(2) . termite . h). This conclusion was buttressed by the demonstration of acetate in R. flavipes hemolymph (at 9.0 to 11.6 mM), but not in feces, and by the ability of termite tissues to readily oxidize acetate to CO(2). About 85% of the acetate produced by the hindgut microbiota was derived from cellulose C; the remainder was derived from hemicellulose C. Selective removal of major groups of microbes from the hindgut of R. flavipes indicated that protozoa were primarily responsible for acetogenesis but that bacteria also functioned in this capacity. H(2) and CH(4) were evolved by R. flavipes (usually about 0.4 nmol . termite . h), but these compounds represented a minor fate of electrons derived from wood dissimilation within R. flavipes. A working model is proposed for symbiotic wood polysaccharide degradation in R. flavipes, and the possible roles of individual gut microbes, including CO(2)-reducing acetogenic bacteria, are discussed.

Journal Article↗

PubMed1983

Effect of monensin on total volatile fatty acid production by steers fed a high grain diet.

Four rumen-fistulated steers, averaging 315 kg during two experimental periods were used in a replicated 2 X 2 Latin square study designed to determine the effects of monensin supplementation on rumen volatile fatty acid (VFA) production, pH and liquid volume. A 72% steam-flaked, sorghum grain diet was fed twice daily at 0700 and 1700 h at 2.0% of live body weight. Production rates were determined at 11 times during a 24-h feeding cycle by short-term in vitro incubations of whole rumen contents. Monensin increased moles/100 mol (P less than .05) and production rate (mumoles X liter-1 X min-1; P greater than .01) of propionate and depressed moles/100 mol (P less than .01) and production rate (P less than .05) of butyrate. Moles of acetate/100 mol were not affected (P greater than .05) by monensin. Daily propionate production (moles) was increased (P less than .01) by 37% by monensin. Monensin increased total production of acetate (11%) and total VFA production (16%), both nonsignificantly. Both rumen pH and liquid volumes were increased nonsignificantly by monensin.

Acetates↗

PubMed2001

Cecal volatile fatty acids and broiler chick susceptibility to Salmonella typhimurium colonization as affected by aflatoxins and T-2 toxin.

Four experiments were conducted using day-of-hatch, mixed-sex broiler chicks to evaluate the effects of aflatoxins and T-2 toxin on cecal volatile fatty acids (VFA) and the susceptibility to Salmonella colonization. All chicks in these experiments were challenged orally with 10(4) cfu of Salmonella typhimurium (ST) on Day 3. In Experiments 1 and 2, chicks were fed diets containing 0, 2.5, or 7.5 mg aflatoxins/kg of diet and were allowed to develop their microflora naturally. In Experiment 3, all chicks were orally gavaged on the day of hatch with a competitive exclusion (CE) culture (PREEMPT) and were fed diets containing 0, 2.5, or 7.5 mg T-2 toxin/kg. In Experiment 4, the chicks were fed diets containing 0, 7.5, or 15.0 mg T-2 toxin/kg and one-half of the chicks were orally gavaged on the day of hatch with the CE culture. In Experiments 1 and 2, with the exception of increased total VFA at 5 d in chicks fed the 7.5 mg T-2 aflatoxins/kg diet, there were no treatment effects on cecal propionic acid, total VFA, or incidence or severity of ST colonization. In Experiment 3, the only alteration in concentration of cecal propionic acid or total VFA was a significant reduction in total VFA at 5 d in chicks fed the 2.5 mg T-2 toxin/kg diet. No significant treatment differences were observed for numbers of Salmonella cecal culture-positive chicks or for numbers of ST in the cecal contents. In Experiment 4, with minor exceptions, the chicks treated with the CE culture had higher cecal concentrations of propionic acid and were less susceptible to Salmonella colonization than the non-CE-treated chicks. In the non-CE-treated chicks, T-2 toxin had no effect on any of the parameters, and 85 to 90% of the chicks were Salmonella cecal culture-positive. In the CE-treated chicks, there was a decrease in propionic acid concentration at 3 and 11 d and an increase in susceptibility to Salmonella colonization of the chicks fed the 15.0 mg T-2 toxin/kg diet. These results indicate that cecal concentrations of VFA can be affected by toxins, such as high concentrations of T-2 toxin, and that resistance to Salmonella colonization may be reduced. Further research is necessary to determine the biological significance of these changes.

Aflatoxins↗

PubMed1986

Effects of food restriction and starvation-refeeding on volatile fatty acid concentrations in the rat.

Adult male rats were fed either ad libitum or at levels of 19 or 15 g of nonpurified diet per rat daily or subjected to 48 h of starvation followed by 24 h of refeeding. Concentrations of total and individual volatile fatty acids (VFA) in cecal contents were higher in rats fed ad libitum than in those restricted to 19 or 15 g/d. Only butyrate concentration was lower in rats given 15 g/d than in those given 19 g/d. In starved animals all cecal VFA declined within 24 h of food removal, but the greatest change was in butyrate, which fell to less than 12% of the initial value. Acetate and propionate fell further after 48 h, but their concentrations were restored to control values within 24 h of refeeding while butyrate remained depressed by 50%. Cecal pH was closely related to total VFA concentration, although the highest degree of correlation was with butyrate. Hepatic portal venous plasma VFA concentrations generally reflected those in cecal digesta except that the proportion of butyrate was relatively lower in this blood vessel than in cecal contents. Under all conditions acetate was the only VFA found in arterial plasma and in the fully fed state was lower than in hepatic portal venous plasma. Food restriction and starvation did not alter arterial concentrations, indicating abolition of net uptake. We conclude that all VFA are affected by availability of fermentable material to the large bowel microflora but that the disproportionate changes in butyrate may reflect preferential use of this acid by cells of the large bowel wall.

Animals↗

PubMed1977

[Relationship between the volatile fatty acids (VFA) in the rumen and nitrogen secretion into isolated sheep's rumen].

Two sheep with a ruminal fistula and an isolated small rumen were studied for the secretion of ammonia nitrogen, urea nitrogen, and amino nitrogen into the isolated rumen at different levels of volatile fatty acids (VFA) (50, 133-97, and 97-66 M Mol 1(-1)) in the rumen. The VFA level in the rumen was found to exert a great influence on the quantitative secretion of endogenous nitrogen from the blood through the rumen wall into rumen content. When the VFA level in the rumen was increased by administration of a single dose of acetic, propionic, and butyric acid, the secretion of ammonia nitrogen and amino nitrogen abruptly dropped and the secretion of urea into the isolated rumen slightly increased. The over-all amount of nitrogen (NH3-N + urea-N + amino-N) that had passed into the isolated rumen in the course of an hour showed a highly significant correlation with the passage of nitrogen in the form of ammonia and amino nitrogen and was greatest before the application of VFA to the rumen, i.e. at the level of 50 m mol 1-1. Of the metabolites under study, which were passing to the isolated rumen, amino nitrogen shared the greatest proportion (45.38-46.54%). When the VFA level in the rumen was raised, the proportion of ammonia secreted to the isolated rumen decreased and the proportion of urea in the total amount of nitrogen increased.

Animals↗