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PubMed1993

In vitro metabolism of radiolabeled carbohydrates by protective cecal anaerobic bacteria.

Cecal anaerobic bacteria from adult broilers were cultured in media containing .25% glucose or .25% lactose. Media also contained either [14C]-labeled lactose, glucose, galactose, or lactic acid as metabolic tracers. Cultures were analyzed at 4, 8, and 12 h for pH, radiolabeled and unlabeled volatile fatty acids, and lactic acid. The pH values of cultures containing .25% lactose were significantly (P < .05) higher than the pH values of cultures containing .25% glucose. Lactose cultures reached their lowest pH more slowly than glucose cultures. Concentrations of unlabeled volatile fatty acids increased and lactic acid decreased during incubation of the cultures. Radiolabeled sugars and lactic acid were more readily metabolized to volatile fatty acids in media containing lactose than in media containing glucose. The preferred metabolism of [14C]substrates, independent of media carbohydrate, was in the following order: lactic acid > galactose, lactose > glucose. The volatile fatty acids in which radiolabel was most concentrated were acetic acid, propionic acid, or butyric acid.

Animals↗

PubMed1982

Influence of dietary fibers on fermentation in the human large intestine.

Fiber sources were fed to 24 men to evaluate the effect of fiber on large intestinal microflora. The diets were low fiber basal or the basal diet supplemented with coarse bran, fine bran, cabbage, or cellulose (Solka floc). Twelve subjects (Group 1) were fed all fiber sources using a latin square design with 2-week experimental periods followed by a 3-week period on the basal diet. Group 2 made one diet change after the first experimental period, then remained on that diet throughout the experiment; during the last period their fiber intake was double (to approximately 26 g/day). A microbial culture system was utilized with fecal microflora to measure cell wall indigestibility and volatile fatty acid (VFA) production. Volatile fatty acids were also measured in fresh feces. The in vitro substrates were alfalfa, coarse bran, cabbage, or cellulose. In this system, dietary fiber had a significant (P less than .05) effect on resultant cell wall indigestibility and VFA level. Previous diet in group 1 subjects significantly (P less than .05) affected in vitro VFA. In groups 2 significant (P less than .05) period and subject effect were present for the in vitro VFA data. The VFA concentrations in feces of humans were significantly affected by the fiber consumed.

Brassica↗

PubMed1976

Alterations in volatile free fatty acids of blood after hepatectomy.

Volatile free fatty acids (VFA) in blood increased approximately twofold in dogs subjected to total hepatectomy. The average total plasma VFA preoperatively was 1,585 mug percent and shortly before death, postoperatively, was 2,798 mug percent. The corresponding red cell concentrations were essentially the same. Acetic acid was 81 percent of the total VFA, propionic acid 7 percent, isobutyric acid 4 percent, butyric acid one percent, and isovaleric acid 5 percent. There was little or no isovalerate in red cells. The increments in the individual fatty acids after hepatectomy were highly variable, but the average increase with time was almost linear. The increase in VFA probably reflects an increased utilization of the branched-chain aminoacids by extrahepatic tissues.

Acetates↗

PubMed2004

Effect of short-chain acids on the carboxymethylcellulase activity of the ruminal bacterium Ruminococcus albus.

The addition of 100-300 mmol/L of acetic, propionic, butyric or lactic acids (short-chain acids), or of acetic, propionic, and butyric acids (volatile fatty acids, VFA) mixtures increased the degradation of carboxymethyl cellulose (CMC) by R. albus (7.5 to 46 and 6 to 39 %, respectively). Differences among individual acids were observed at 300 mmol/L whereas VFA mixtures differed at 100 mmol/L. When assayed at the same concentration, CMCase activity was increased less by NaCl than by the short-chain acids, whereas ethylene glycol decreased the activity. Since osmolarity and/or ionic strength changes in the medium cannot completely account for the observed increases of carboxymethylcellulase (CMCase) activity, it is suggested that the anions of short-chain acids produce changes in the reaction media polarity that contribute to the effects observed. Alterations in the media could also bring about conformational changes in CMCase leading to increased rates of reaction and subsequent increases in CMC degradation. Finally, explanations for the observed phenomena based on the direct effect of the compounds tested on the cellulosome complex, its domains, and/or its component enzymes are proposed.

Acetates↗

PubMed2005

Effect of culture conditions on production of butter flavor compounds by Pediococcus pentosaceus and Lactobacillus acidophilus in semisolid maize-based cultures.

Two series of 120 h mixed cultures of Pediococcus pentosaceus MITJ-10 and Lactobacillus acidophilus Hansen 1748 were grown in semisolid maize-based media, applying an orthogonal factorial design in order to establish the most adequate parameters to get compounds related to butter-like flavor. Conditions of maize pre-treatment established in the first series were hot lime-treatment for 20 min, grinding and sieving to 0.0165 in., partial defatting and cooking for 25 min. While the culture conditions established for the second series were the addition of yeast extract (0.2% w/w), and culture starting with 2x10(6) CFU g(-1) and a ratio of P. pentosaceus and L. acidophilus, 3:1. The fermentation profile was studied in a last culture. Lactic acid bacteria (LAB) prevailed over the native microorganisms, with a specific growth rate of 0.47 h(-1). Diacetyl production correlated (r2=0.9972) with the 12 h exponential growth phase of LAB. The concentration of diacetyl at that time was 779.56 mg kg(-1). The contents of lactic acid and volatile fatty acids were low at 12 h, 665 and 1312 mg kg(-1), respectively. During the long stationary phase, they increased up to 4800 and 1886 mg kg(-1), respectively. This procedure might be useful to prepare naturally aromatized raw materials for the food industry.

Bacteriological Techniques↗

PubMed2001

Breaking through the acid barrier: an orchestrated response to proton stress by enteric bacteria.

The ability of enteropathogens such as Salmonella and Escherichia coli to adapt and survive acid stress is fundamental to their pathogenesis. Once inside the host, these organisms encounter life-threatening levels of inorganic acid (H+) in the stomach and a combination of inorganic and organic acids (volatile fatty acids) in the small intestine. To combat these stresses, enteric bacteria have evolved elegant, overlapping strategies that involve both constitutive and inducible defense systems. This article reviews the recent progress made in understanding the pH 3 acid tolerance systems of Salmonella and the even more effective pH 2 acid resistance systems of E. coli. Focus is placed on how Salmonella orchestrates acid tolerance by modulating the activities or levels of diverse regulatory proteins in response to pH stress. The result is induction of overlapping arrays of acid shock proteins that protect the cell against acid and other environmental stresses. Most notable among these pH-response regulators are RpoS, Fur, PhoP and OmpR. In addition, we will review three dedicated acid resistance systems of E. coli, not present in Salmonella, that allow this organism to survive extreme (pH 2) acid challenge.

Acids, Noncarboxylic↗

PubMed1990

Dietary modification of potential vitamin K supply from enteric bacterial menaquinones in rats.

Rats given a low-fibre diet based on boiled white rice developed symptoms of severe vitamin K deficiency within 23 d. Inclusion of autoclaved black-eye beans (Vigna unguiculata) in the diet prevented the bleeding syndrome. To test the hypothesis that deficiency resulted from low phylloquinone intake exacerbated by inadequate production of menaquinones by the enteric bacteria, a follow-up experiment was carried out in which groups of rats were given an all-rice diet, a rice + beans diet or a stock diet. Rats on the all-rice diet had significantly lower faecal concentrations of the main menaquinone-producing bacterial species (Bacteroides fragilis and Bacteroides vulgatus) than animals on either of the other two diets. This coupled with the much lower faecal output on this diet suggests that total menaquinone production was low for the all-rice diet. The alterations in faecal flora were associated with several significant changes in caecal metabolism. Rats given the stock diet had much shorter caecal transit times and a considerably greater proportion of butyric acid in volatile fatty acid end-products than did rats on either of the other two diets.

Animals↗

PubMed1997

[Fermentation process during the ensiling of green forage low in nitrate. 1. Fermentation process in untreated green forage].

The fermentation process of ensiling green forage, low in nitrate, was proved in 8 experiments with ryegrass, ochardgrass and grass-legumes mixture. It was demonstrated that also in easily fermentable green forage the absence of nitrate promote the occurrence of butyric acid simultaneously with the lactic acid fermentation even at an early stage of fermentation. It is supposed that the lack of nitrate as a natural inhibitor of clostridia leads to early formation of butyric acid. The evolution of clostridia in the beginning of the fermentation process was more rapid than expected. It seems that easily soluble carbohydrates are the substrates of butyric acid formation. That is why in green forage, low on nitrate, clostridia act as food competitors for lactic acid bacteria. Amino acids were not degraded in the early stage of fermentation. In spite of the high content of butyric acid the amount of ammonia was low. Apart from n-butyric acid volatile fatty acids > or = C4 did not occur. The lactic acid formation reached only a restricted extent, also in green forage with a high content of sucrose. It was assumed that there are differences in ensilability of carbohydrate fractions between forage plants.

Ammonia↗

PubMed1986

Using density rather than mass to express the concentration of gastrointestinal tract constituents.

This experiment had two objectives: to develop an analytical technique to measure the density of digesta and fecal samples; to determine whether this measurement is physiologically relevant. To address the latter question, rats were provided with one of five high-fiber diets or a fiber-free control diet, and density determinations were made on samples from the cecum, proximal and distal colon, and from a passed fecal pellet. The density of colonic contents varied with the fiber component of the diet. The fiber-free control diet produced the densest stool at all sites studied (P less than 0.01), whereas wheat bran produced the least dense stool at every site (P less than 0.01). There were also density differences among bowel positions within diet treatments: the stool from those animals consuming the fiber-free, guar and pectin diets became denser as it moved distally; wheat bran, on the other hand, produced the opposite effect--the more distal the stool traveled, the less dense it became. Since the density of colonic contents varied with respect to both diet and anatomical site, these data suggest that the traditional technique of expressing the concentration of a constituent of interest (e.g., bile acid, volatile fatty acid) per gram of digesta or fecal matter may not always be appropriate. This is particularly true if exposure of the intestinal mucosal cells to a substance in the digesta or fecal stream is of interest, since density, rather than mass, reflects the diluting potential of the diet.

Animals↗

PubMed1996

The acid tolerance response of Salmonella typhimurium provides protection against organic acids.

Salmonella typhimurium encounters a variety of acid stress situations during pathogenesis and in the natural environment. These include the extreme low pH encountered in the stomach and a less acidic intestinal environment containing large amounts of organic weak acids (volatile fatty acids). The acid tolerance response (ATR) is a complex defence system that can minimize the lethal effects of extreme low pH (pH3). The data presented illustrate that the ATR can also defend against weak acids such as butyric, acetic or propionic acids. Although an acid shock of pH 4.4 induced the ATR, growth in subinhibitory concentrations of weak acids did not. Various mutations shown to affect tolerance to extreme acid conditions (pH 3) were tested for their effects on tolerance to weak acids. An rpoS mutant lacking the alternative sigma factor sigma s failed to protect cells against weak acids as well as extreme acid pH. The fur (ferric uptake regulator) and atp (Mg(2+)-dependent ATPase) mutants defective in extreme acid tolerance showed no defects in their tolerance to weak acids. Curiously, the atbR mutant that exhibits increased tolerance to extreme acid pH proved sensitive to weak acids. Several insertions that rendered cells sensitive to organic acids were isolated, all of which proved to be linked to the rpoS locus.

Acids↗

PubMed1984

Tension receptors with vagal afferent fibres in the proximal duodenum and pyloric sphincter of sheep.

Single-unit afferent activity was recorded from the hepatic-duodenal branch of the vagus nerve of chloralose-anaesthetized sheep during acute electrophysiological experiments. The impulse activity of sixty-seven slowly adapting mechanoreceptors situated in the muscularis externa of the proximal duodenum and pyloric sphincter was synchronous with alterations in electromyographic and tension records. Afferent units were excited during passive distension, compression and drug-induced increases in muscle tension, thus satisfying the criteria for 'in series' tension receptors (Iggo, 1955). From the responses to compression some evidence was found for the existence of separate populations of tension receptors with different mechanical thresholds. Two fibre populations were found: non-myelinated (0.70 +/- 0.26 S.D. ms-1) and myelinated (7.6 +/- 1.6 S.D. m s-1). Mucosal application of solutions of hydrochloric acid, volatile fatty acids, alkali and amino acids, and mucosal probing modified the activity of most units. These changes were reduced by anaesthesia of the mucosa. It is concluded that tension receptors in the sheep duodenum occupy a position 'in series' with longitudinal muscle, and that their activity can be modified by the particulate and chemical composition of chyme by a mechanism involving local nerve plexuses. The activity of tension receptors is compared with that of two other mechanoreceptor classes located serosally (five units) and in the lesser omentum (eleven units). Receptors in neither of these two classes were directly excited by active contraction of the duodenum.

Action Potentials↗

PubMed1981

Gas-liquid chromatography in routine processing of blood cultures for detecting anaerobic bacteraemia.

Gas-liquid chromatography was performed on 233 positive blood cultures and findings were compared with culture results. Obligate anaerobic bacteria were recovered from 78 out of 79 blood cultures containing butyric or iso-valeric acids, or both; from 28 out of 69 blood cultures containing succinic acid; and from only one out of 41 blood cultures containing succinic but not butyric or iso-valeric acid. Good correlations (88%) were found for the recovery of anaerobic bacteria and the detection of butyric and/or iso-valeric acids. Detecting volatile fatty acids by gas-liquid chromatography performed on blood cultures at the first signs of growth can therefore provide an early and reliable indication of the presence of anaerobic bacteria.

Anaerobiosis↗

PubMed1984

Faecal weight, constituents, colonic motility, and lactose tolerance in the irritable bowel syndrome.

Lactose intolerance and faecal characteristics were compared in 16 patients with symptomatic irritable bowel syndrome and in age- and sex-matched controls. Faecal stool weight was increased in the irritable bowel syndrome patients, whereas faecal bile acids, fat, volatile fatty acids, and neutral sterols were not significantly different. No lactose intolerance was found in irritable bowel syndrome subjects. Measurements of colonic motility showed only modest activity for both basal and food-stimulated activity. There was a weak correlation between the concentration of total bile acids, deoxycholic acid, lithocholic acid and the motility index.

Adolescent↗

PubMed1979

How concentrate feeding affects glucoregulatory hormones in ruminants: implications in bovine ketosis.

Twenty-four feedlot steers and four sheep were fed roughage or grain rations while three other sheep received intraduodenal infusions of amino acids, glucose, volatile fatty acids, and proteins to determine whether the release of plasma glucagon-like immunoreactivity is influenced by dietary factors and the composition of duodenal chyme. Plasma glucagon-like immunoreactivity rose in both cattle and sheep as the proportion of grain in their rations was increased. In response to intraduodenal infusions, only glucose stimulated glucagon-like immunoreactivity release. These experiments demonstrate that plasma glucagon-like immunoreactivity concentrations change in cattle and sheep in response to the amount of grain consumed and that glucagon-like immunoreactivity release is triggered by glucose in intestinal chyme.

Amino Acids↗

PubMedDate not supplied

[Comparative characteristics of some products of decomposition of lactic protein and fat in cheeses produced with addition of boar pepsin].

The influence of a mixture of pig pepsin with renin (in a ratio of 1:1), used instead of renin in making natural cheeses according to the method proposed by the authors, on the content of some products secondary to decomposition of lactic protein and fat because of a dissimilar nutritional value of the latter, was studied. It has been found that cheeses prepared by using the above mixture do not differ from the control ones in the content of soluble forms of nitrogen, essential amino acids, volatile fatty acids, the sum-total of higher fatty acids and differ but slightly (except for butanone-2) in the proportion of various carbonyl compounds. Hence, an inference is drawn on the suitability of using the renin and pig pepsin mixture in making cheeses according to the method proposed by the authors, since the composition and the quantitative content of products secondary to decompesition of lactic protein and fat in test specimens of the cheese did not differ from the control ones which, in turn, points to the identity of the nutritional value of the finished products in either of these cases.

Amino Acids↗

PubMedDate not supplied

[A psychrotolerant Caulobacter sp. from Russian polar tundra soil].

Strain Z-0024, a psychrotolerant aerobic heterotrophic representative of the prosthecate bacteria of the genus Caulobacter, was isolated from a methanotrophic enrichment obtained from Russian polar tundra soil. The cells of the new isolate are vibrios (0.5-0.6 x 1.3-1.8 microm) with a polar stalk. The organism grows in a temperature range from 5 to 36 degrees C, with an optimum at 20 degrees C. The pH range for growth is from 4.5 to 7.0 with an optimum at pH 6.0. Strain Z-0024 utilizes a wide range of organic compounds: sugars, amino acids, volatile fatty acids, and primary alcohols. It tolerates a NaCl concentration in the medium of up to 15 g/l. The G + C content of DNA is 66.6 mol %. The 16S rRNA gene sequence analysis revealed that strain Z-0024 belongs to the cluster of Caulobacter species, showing a 98.8-99.2% sequence similarity to them. DNA-DNA hybridization revealed a low level of homology (24%) between strain Z-0024 and C. vibrioides ATCC 15252. The new isolate is described as Caulobacter sp. Z-0024.

Base Composition↗

PubMed1982

Ovine blood chemistry values measured during ammonia toxicosis.

Venous blood values were determined on 19 Southdown sheep (9 adult ewes and 10 wether lambs). Principal sheep were given 12.5 ml of 3.3M urea solution/kg of body weight, which produced acute ammonia toxicosis. Whole blood ammonium-nitrogen was determined by ion exchange; venous blood gases and pH were measured with a pH blood gas analyzer; and 23 serum chemical analyses were obtained with a sequential multiple autoanalyzer computer. Analysis of variance for the data revealed significant changes for 20 values. The values are presented and discussed with regard to those that changed beyond acceptable limits (whole blood ammonium-nitrogen, venous blood pH, serum glucose, serum lactate dehydrogenase, serum alkaline phosphatase, serum creatine kinase, serum urea nitrogen, serum inorganic phosphorus, serum sodium, and serum potassium), those that changed within acceptable limits (PVo2, PVco2, serum triglycerides, serum free fatty acids, plasma volatile fatty acids, serum aspartate aminotransferase, serum total protein, serum albumin, serum creatinine, urea nitrogen-creatinine ratio, serum uric acid, serum cholesterol, serum low-density lipoproteins, serum calcium, serum iron and serum chloride), and those with no change (total and direct serum bilirubin and albumin-globulin ratio). Metabolic consequences of ammonia toxicosis are considered with regard to energy, lipid , protein, and acid-base and electrolyte balances. Blood values having possible laboratory diagnosis value and considerations for therapeutic adjustment are discussed.

Acidosis↗

PubMedDate not supplied

[Control of the fermentation activity during ensilage of Lolium italicum A. Br. and Medicago sativa L].

Samples with different dry matter contents of Lolium italicum A. Br., Medicago sativa L., have been ensiled in hermetically sealed containers, in order to study the evolution of microflora and its activity. The principal microbial groups (coliforms, proteolytics , lactic acid bacteria, clostridia, yeasts) have been detected and enumerated, in anaerobic atmosphere, after ensiling periods of 3, 6, 10, 13, 20, 100 days. At the same time, the samples were chemically analyzed for the detection of: pH, moisture, ashes, total and ammoniacal nitrogen, total reducing sugars, lactic acid, volatile fatty acids, short chain alcohols. The relations found between chemical and microbiological data, show that a strong lactic fermentation is not enough for the inhibition of silage spoiling microorganisms, such as coliforms, yeasts, and (less) proteolytics . This phenomenon may be related to the "quality" of the lactic acid microflora, more than to the characteristics of the environment.

Animal Feed↗