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PubMedDate not supplied

Extractive fermentation for enhanced propionic acid production from lactose by Propionibacterium acidipropionici.

An extractive fermentation process using an amine extractant and a hollow-fiber membrane extractor to selectively remove propionic acid from the fermentation broth was developed to produce propionate from lactose. Compared to the conventional batch fermentation, the extractive fermentation had a much higher productivity ( approximately 1 g/(L.h) or 5-fold increase), higher propionate yield (up to 0.66 g/g or more than 20% increase), higher final product concentration (75 g/L or higher), and higher product purity ( approximately 90%). Meanwhile, acetate and succinate productions in the extractive fermentation were significantly reduced. The improved fermentation performance can be attributed to the reduced product inhibition and a possible metabolic pathway shift to favor more propionic but less acetic and succinic acid production. The process was stable and gave consistent long-term performance over the 1. 5-month period studied. The effects of propionate concentration, pH, and amine content in the solvent on the extractive fermentation were also studied and are discussed in this paper.

Fermentation↗
PubMed1997

Local and systemic effects of intraduodenal exposure to topical gallstone solvents ethyl propionate and methyl tert-butyl ether in the rabbit.

During topical dissolution of gallstones, solvent can escape to the duodenum causing toxic effects that have not yet been adequately quantified. We compared the local intestinal cytotoxic and systemic hepatotoxic effects of two gallstone solvents, methyl tert-butyl ether and ethyl propionate, on the rabbit's duodenum. Methyl tert-butyl ether, ethyl propionate, or saline (control) was infused intraduodenally for 3 hr in 32 male New Zealand rabbits. The solvents were infused either at a high infusion rate of 8.5 microl/min or at a low rate of 4.0 microl/min. Blood samples were collected for biochemical analysis from each animal before and after the 3-hr infusion period. A standardized histologic scoring system was used by a pathologist blinded to the treatments to quantify liver and intestinal tissue injury. None of the animals studied showed any significant changes in serum alkaline phosphatase, amylase, bilirubin, or their hepatic histology or histologic scoring for mucosal necrosis and ulceration. At the higher dose, methyl tert-butyl ether produced significantly more submucosal inflammation (P = 0.0017) and showed a trend of causing more submucosal edema than ethyl propionate, but ethyl propionate led to significantly higher elevations of aminotransferases than methyl tert-butyl ether as compared to saline. There were no detectable blood levels of methanol or ethanol in any of the animals studied. Ethyl propionate may be less damaging to the intestinal mucosa of the rabbit than methyl tert-butyl ether, but at the higher dose (equivalent to 60 ml/3 hr in a 70-kg human) it appears to produce more biochemical liver injury when administered intraduodenally.

Administration, Topical↗
PubMed1998

Haem propionates control oxidative and reductive activities of horseradish peroxidase by maintaining the correct orientation of the haem.

The role of haem propionates in oxidative and reductive reactions catalysed by horseradish peroxidase (HRP) was studied after successful reconstitution of ferric protoporphyrin IX dimethyl ester (PPDME) into the apoperoxidase. The reconstituted enzyme oxidizes neither guaiacol (aromatic electron donor) nor iodide or thiocyanate (inorganic donor). Although the reconstituted enzyme binds guaiacol with a similar Kd (13 mM) to that of the native enzyme (10 mM), the Kd for SCN- binding (5 mM) is decreased 20-fold compared with that of the native enzyme (100 mM). This indicates that haem propionates hinder the entry or binding of inorganic anion to the active site of the native HRP. However, the reconstituted enzyme is catalytically inactive as it does not form spectroscopically detectable compound II with H2O2. CD measurements indicate a significant loss of haem CD spectrum of the reconstituted enzyme at 409 nm, suggesting a loss of asymmetry of the haem-protein interaction. Thus the inability of the reconstituted enzyme to form catalytic intermediates results from the change in orientation of the haem due to loss of interactions via the haem propionates. HRP also catalyses reductive reactions such as reduction of iodine (I+) in the presence of EDTA and H2O2. The reconstituted enzyme cannot catalyse I+ reduction because of the loss of I+ binding to the haem propionate. Since I+ reduction requires formation of the catalytically active enzyme-I+-EDTA ternary complex, the loss of reductive activity is primarily due to the loss of active enzyme formation. Haem propionates thus play a vital role in the oxidative and reductive reactions of HRP by favouring the formation of catalytic intermediates with H2O2 by maintaining the correct orientation of the haem with respect to the surrounding residues.

Apoenzymes↗
PubMed1997

Conversion of DL-threonine, D-threonine and 2-oxobutyrate into propionate and 2-hydroxybutyrate by Fusobacterium species.

The present investigation examined DL-threonine, D-threonine and 2-oxobutyrate conversion into propionate and 2-hydroxybutyrate by various type strains and clinical isolates of Fusobacterium. Except for Fus. naviforme, the type strains were able to produce varying degrees of propionate and/or 2-hydroxybutyrate from DL-threonine. Additionally, D-threonine was converted into an equimolar amount of propionate by Fus. necrophorum subsp. necrophorum, Fus. nucleatum subsp. nucleatum and Fus. varium, and to a lower but significant amount by Fus. mortiferum and Fus. perfoetens. However, the level of propionate remained unchanged for Fus. nucleatum subsp. fusiforme, Fus. nucleatum subsp. vincentii, Fus. naviforme, Fus. necrophorum subsp. funduliforme, Fus. gonidiaforme and Fus. russii. 2-Oxobutyrate was fermented to propionate by all type strains, although Fus. russii reduced it mainly to 2-hydroxybutyrate. Thus, an attempt was made to make use of these features in order to identify clinical isolates.

Fusobacterium↗
PubMedDate not supplied

The effect of supplemental propionate on insulin responsiveness to glucose and tissue responsiveness to insulin in relation to feeding in sheep.

Two glucose clamp techniques were performed for 6 h starting 2 h before the initiation of feeding to investigate the effect of dietary propionate supplementation on insulin responsiveness to glucose and tissue responsiveness to insulin in relation to feeding in rams. The rams were fed alfalfa hay without (Cont diet) and with 10 mmol.kg BW-1.d-1 of calcium propionate (Prop diet) for 4 weeks in randomized order. With the hyperglycemic clamp, the ratio of plasma insulin increment to glucose infusion rate did not differ between the diets, but for the Prop diet the ratio was less during the pre-feeding period. With the hyperinsulinemic euglycemic clamp, the glucose infusion rate was lower (P < 0.05) for the Prop diet than the Cont diet, and increased (P < 0.05) after feeding. In rams supplemented propionate tissue responsiveness to insulin was reduced. Propionate supplementation may either impair glucose utilization in response to insulin infusion or enhance glucose production from propionate.

Animals↗
PubMedDate not supplied

Propionate supplementation did not increase whole body glucose turnover in growing lambs fed rye grass.

The objective of the present study was to investigate the effects of propionate supplementation on whole body glucose turnover in growing lambs fed frozen rye-grass at 1.5 x maintenance using [1-13C]-glucose. Intraruminal infusion of propionate (0.55 and 0.91 mol x d(-1)) increased the ruminal molar proportions of propionate from 25% with the control to 40% with the highest propionate treatment. It did not however modify glucose turnover (26 mmol x d(-1) x kg(-1)), nor the conversion of its carbon into L-lactate (21%) and alanine (21%), nor glucose recycling (9%). All of the results suggest that in the present conditions glucose turnover and metabolism were not influenced by the supply of propionate.

Animal Nutritional Physiological Phenomena↗
PubMed2001

Studies of propionate toxicity in Salmonella enterica identify 2-methylcitrate as a potent inhibitor of cell growth.

Salmonella enterica serovar Typhimurium LT2 showed increased sensitivity to propionate when the 2-methylcitric acid cycle was blocked. A derivative of a prpC mutant (which lacked 2-methylcitrate synthase activity) resistant to propionate was isolated, and the mutation responsible for the newly acquired resistance to propionate was mapped to the citrate synthase (gltA) gene. These results suggested that citrate synthase activity was the source of the increased sensitivity to propionate observed in the absence of the 2-methylcitric acid cycle. DNA sequencing of the wild-type and mutant gltA alleles revealed that the ATG start codon of the wild-type gene was converted to the rare GTG start codon in the revertant strain. This result suggested that lower levels of this enzyme were present in the mutant. Consistent with this change, cell-free extracts of the propionate-resistant strain contained 12-fold less citrate synthase activity. This was interpreted to mean that, in the wild-type strain, high levels of citrate synthase activity were the source of a toxic metabolite. In vitro experiments performed with homogeneous citrate synthase enzyme indicated that this enzyme was capable of synthesizing 2-methylcitrate from propionyl-CoA and oxaloacetate. This result lent further support to the in vivo data, which suggested that citrate synthase was the source of a toxic metabolite.

Acyl Coenzyme A↗
PubMed1975

Metabolism of propionate in the tissues of the sheep gut.

1. The extent of propionate metabolism during absorption from the gut and the amounts of L-lactate formed and glucose utilized by the portal-drained viscera were determined in conscious sheep from measurements of portal venous blood flow and portal venous and aortic metabolite concentrations. The sheep were fasted overnight and given primed continuous intraruminal infusions of volatile fatty acids (VFA) at two rates, supplying propionate at 40.0 and 79.9 mmol/h. Measurements were made during the 5th and 6th hours of the infusion, when rumen liquor VFA concentrations were constant. 2. The rate of L-lactate formation by the portal-drained viscera was not affected by the VFA infusions and accounted for approximately 15% of the probably total lactate entry rate. 3. Considerable amounts of glucose were taken up by the portal-drained viscera, amounting to approximately 35% of the probable glucose entry rate. If this glucose was metabolized through the glycolytic pathway, this would at all times have accounted for the amounts of L-lactate formed. 4. Portal venous blood flow was positively correlated with VFA infusion rates and with the net amount of propionate appearing in the portal blood. 5. It is concluded that although propionate may be metabolized by the rumen epithelium, the unique pathway of L-lactate formation from propionate is of limited quantitative significance to the animal, although it may be of importance to the rumen epithelium itself.

Animals↗
PubMed1985

Gluconeogenesis from caecal propionate in the horse.

The production of propionate in the caecum of the horse has been measured in two Shetland-type ponies fitted with caecal and colonic cannulas and fed on hay or on hay and wheat bran. A continuous intracaecal infusion of 14C-labelled sodium propionate was used and samples were obtained from a cannula at the origin of the right ventral colon. A simultaneous intravenous infusion of [2-3H]glucose was used to measure total glucose entry. On a hay diet which provided 177 kJ/kg body-weight per d, mean caecal propionate production was 19.6 (range 17.2-21.2) mg/h per kg body-weight and on a hay and wheat bran diet, which provided 187 kJ/kg body-weight per d, mean caecal propionate production was 34.0 (range 28.9-38.3) mg/h per kg body-weight. Mean total glucose production (mg/h per kg body-weight) in one pony was 104 (range 100-110) and in the other 135 (range 123-153). Rates were not influenced by diet. About 7% of total glucose production was derived from propionate produced in the caecum and this percentage was unaffected by diet or by individual animals.

Animals↗
PubMed2005

Propionate precursors and other metabolic intermediates as possible alternative electron acceptors to methanogenesis in ruminal fermentation in vitro.

Fifteen potential precursors of propionate were tested for their ability to decrease CH4 production by ruminal fluid in vitro. Sodium acrylate and sodium fumarate produced the most consistent effects in batch cultures, with 50 % of the added precursors being fermented to propionate and CH4 production decreasing by between 8 and 17 %, respectively. Additives were more effective when added as free acids, but this also decreased the pH and may have inhibited fibre digestion. Changing the dietary substrate from predominantly grass hay to predominantly concentrate had no influence on the effectiveness of acrylate and fumarate. In an in vitro fermentor (the rumen simulating technique, Rusitec) with a grass hay-concentrate (50:50, w/w) diet as substrate, both compounds were again fermented to propionate (33 and 44 % conversion to propionate, respectively). However, fumarate appeared more effective as a H2 sink compound. It was calculated to capture 44 % of the H2 previously used for CH4 formation compared with a 22 % capture of H2 with acrylate. Fumarate also caused a stimulation in fibre digestion. Thus, sodium fumarate was the preferred propionate precursor for use as a feed ingredient to decrease CH4 emissions from ruminants.

Acids↗
PubMed1996

Effect of acetate and propionate on calcium absorption from the rectum and distal colon of humans.

To determine the effects of acetate and propionate on calcium absorption from the human distal colon and rectum, six healthy human subjects were given rectal infusions containing 50 mmol CaCl2/L on four separate occasions. Addition of 56.3 mmol acetate/L, 18.7 mmol propionate/L, or acetate and propionate together increased calcium disappearance (expressed as the change in the ratio of calcium to polyethylene glycol) from -5.5 +/- 1.4 to -22.6 +/- 2.8, -23.2 +/- 3.2, and -19.7 +/- 4.6, respectively; P < 0.05. To determine the effects of different acetate and propionate concentrations, six different subjects were studied further. The effects of 18.7 or 56.3 mmol acetate/L on calcium absorption were the same as those of 18.7 mmol propionate/L (-15.7 +/- 1.4), and less than those of 56.3 mmol propionate/L (-20.3 +/- 2.4, P < 0.05). We conclude that both acetate and propionate enhance calcium absorption from the human distal colon, but that propionate has a greater effect at higher concentrations. Further studies are needed to determine the mechanism of calcium absorption from the colon.

Acetates↗
PubMed1978

Effects of monensin on in vivo rumen propionate production and blood glucose kinetics in cattle.

Four rumen-fistulated steers (154 to 253 kg), fed two different diets in succession, were used to determine effects of monensin on rumen propionate production rates and blood glucose kinetics as determined by single-injection isotope-dilution techniques. A high-roughage and a high-grain diet, with and without 150 mg of monensin daily, were fed isoenergetically at 2-hour intervals. Monensin increased rumen propionate pool sizes from 32 to 57 g for the high-roughage diet and from 37 to 66 g for the high-grain diet and increased rumen propionate production rates from 441 to 659 g/day for the high-roughage diet and from 510 to 899 g/day for the high-grain diet. Molar percentages of rumen propionate were increased significantly by monensin in the high-grain diet. Blood glucose pool sizes were not changed significantly by either monensin or isoenergetic diets. Monensin increased irreversible losses of glucose from 582 to 677 g/day for the high-grain diet. Monensin tended to increase glucose total entry rates for both diets and to increase irreversible loss of glucose for the high-roughage diet but the differences were not significant. Thus, increases in glucose kinetics are minor in contrast to major increases of rumen propionate production caused by monensin.

Animals↗
PubMed1989

Effect of carnitine on propionate metabolism in the vitamin B-12--deficient rat.

Acyl-CoA thioesters are generated during the oxidation of organic acids in mammalian systems. Vitamin B-12 deficiency is associated with decreased L-methylmalonyl-CoA mutase activity, and consequent accumulation of propionyl-CoA and methylmalonyl-CoA. The formation of propionylcarnitine from propionyl-CoA and carnitine provides an alternative pathway to remove propionyl-CoA from cells. Hepatocytes isolated from vitamin B-12--deficient rats metabolized propionate (1 mM) to CO2 and glucose at only 23% and 12%, respectively, of the rates observed in hepatocytes from control animals. In contrast, no difference was seen in rates of pyruvate metabolism by hepatocytes from control and vitamin B-12--deficient rats. Addition of carnitine (10 mM) to hepatocyte incubations increased the rate of propionylcarnitine formation 10- to 20-fold without altering conversion of propionate to CO2 or glucose. The rate of propionylcarnitine formation was not affected by vitamin B-12 deficiency. When carnitine (10 mM) was added, propionylcarnitine generation represented 65-71% of total propionate utilization in hepatocytes isolated from vitamin B-12--deficient rats. Gluconeogenesis from [1-14C]pyruvate was inhibited by 1 mM propionate in hepatocytes from vitamin B-12--deficient rats. No effect of 1 mM propionate on glucose formation from pyruvate was seen using hepatocytes from control rats. Intraperitoneal administration of L-carnitine resulted in a significant increase in urinary propionylcarnitine excretion from vitamin B-12--deficient rats, but not from control animals. The results demonstrate that exogenous carnitine can significantly enhance propionyl-group utilization via the formation of acylcarnitines under the conditions of impaired acyl-CoA metabolism associated with vitamin B-12 deficiency.

Animals↗
PubMed1990

Effects of propionate on lipid biosynthesis in isolated rat hepatocytes.

The effects of propionate, a product of intestinal fiber fermentation, on fatty acid and sterol synthesis were studied in isolated rat hepatocytes. Fatty acid synthesis, as measured by tritium incorporation from 3H2O, was inhibited in the presence of 1 mmol/L propionate with no substrate additions or additions of acetate, butyrate, lactate or oleate. Incorporation of [1-14C]acetate into fatty acids was also inhibited in the presence of propionate. Although propionate markedly depressed [1-14C]acetate incorporation into sterols in hepatocyte preparations, tritium incorporation from 3H2O into sterols was not inhibited, indicating that overall sterol synthesis was not affected. Thus, in vitro, the effect of propionate on lipid metabolism is apparently limited to inhibition of de novo fatty acid synthesis.

Acetates↗
PubMed1992

Changes in pig serum lipids, nutrient digestibility and sterol excretion during cecal infusion of propionate.

Dietary water-soluble fiber supplementation elicits hypolipidemic effects. Propionate, the 3-carbon short-chain fatty acid derived from colonic fiber fermentation, has previously exhibited inhibition of cholesterol synthesis in vitro and may contribute to serum lipid lowering. This study examines the effect of colonic propionate absorption on serum lipids, sterol excretion and nutrient digestibility. Nine barrows were surgically cannulated at the distal ileum and cecum. Pigs received for 16 d continuous cecal infusions of either propionate (36 mmol/kg 0.75 daily) or saline (control) in a crossover design. Propionate infusion did not lower serum lipids, but increased total serum cholesterol by 15% (P less than 0.05) and LDL cholesterol by 15% (P less than 0.05). Differences in sterol excretion, ileal and fecal nutrient digestibilities, and weight gain were not detected between infusion treatments. The results suggest that propionate absorption does not result in decreased serum lipids and is not responsible for the serum lipid-lowering effects of water-soluble fibers.

Animals↗
PubMed1992

Inhibition of human endothelial cell proliferation in vitro in response to n-butyrate and propionate.

The study aimed to investigate the effects of n-butyrate and propionate on the proliferation and viability of human endothelial cells in culture. Proliferation was assessed by a 24-hour bromodeoxyuridine pulse labelling and immunoperoxidase method and viability was assessed by a colorimetric viability (MTT) assay. Endothelial cells were isolated from human umbilical vein by collagenase digestion. Experiments were performed on 96-well plates and cultures were exposed to different concentrations of n-butyrate and propionate for 2 days. n-butyrate and propionate caused significant reductions in the proliferation of endothelial cells at concentrations of 1.25 mM and 10 mM respectively (p less than 0.05); the reduction in proliferation was dose-dependent for both agents. n-butyrate was a more potent inhibitor of proliferation than propionate. However, there were no significant effects on the viability of the cells with both agents up to the highest concentrations tested (25 mM). The data indicate that n-butyrate and propionate inhibit endothelial cell proliferation which may contribute to the pathogenic effects of dental plaque in periodontal disease.

Analysis of Variance↗
PubMed1992

Vitamin B12-dependent propionate production by the ruminal bacterium Prevotella ruminicola 23.

When Prevotella ruminicola 23 was grown in a defined medium containing a vitamin mixture, significant amounts of propionate were formed. Succinate and acetate were the major fermentation acids produced when vitamins were omitted, and further experiments demonstrated that propionate formation was dependent on vitamin B12. When the organism was grown in continuous culture at dilution rates of less than 0.20 h-1, propionate and acetate were the predominant fermentation products and little succinate was formed when vitamin B12 was present. However, at higher dilution rates, propionate formation declined and succinate accumulated. Since cell protein yields were reduced 15 to 25% in the absence of vitamin B12, the pathway for propionate formation may contain an energy-conserving step.

Acetates↗
PubMed2000

Energetics of syntrophic propionate oxidation in defined batch and chemostat cocultures.

Propionate consumption was studied in syntrophic batch and chemostat cocultures of Syntrophobacter fumaroxidans and Methanospirillum hungatei. The Gibbs free energy available for the H(2)-consuming methanogens was <-20 kJ mol of CH(4)(-1) and thus allowed the synthesis of 1/3 mol of ATP per reaction. The Gibbs free energy available for the propionate oxidizer, on the other hand, was usually >-10 kJ mol of propionate(-1). Nevertheless, the syntrophic coculture grew in the chemostat at steady-state rates of 0.04 to 0. 07 day(-1) and produced maximum biomass yields of 2.6 g mol of propionate(-1) and 7.6 g mol of CH(4)(-1) for S. fumaroxidans and M. hungatei, respectively. The energy efficiency for syntrophic growth of S. fumaroxidans, i.e., the biomass produced per unit of available Gibbs free energy was comparable to a theoretical growth yield of 5 to 12 g mol of ATP(-1). However, a lower growth efficiency was observed when sulfate served as an additional electron acceptor, suggesting inefficient energy conservation in the presence of sulfate. The maintenance Gibbs free energy determined from the maintenance coefficient of syntrophically grown S. fumaroxidans was surprisingly low (0.14 kJ h(-1) mol of biomass C(-1)) compared to the theoretical value. On the other hand, the Gibbs free-energy dissipation per mole of biomass C produced was much higher than expected. We conclude that the small Gibbs free energy available in many methanogenic environments is sufficient for syntrophic propionate oxidizers to survive on a Gibbs free energy that is much lower than that theoretically predicted.

Culture Media↗