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PubMed1986

Influence of lignin on digestibility of forage cell wall material.

One-hundred-ninety-four grass samples, representing eight species, were used to determine the relationships of in vitro forage dry matter, cell wall, hemicellulose and cellulose digestibilities with lignin concentration. Linear regressions indicated that dry matter digestion was inhibited to a lesser degree (P less than .05) by lignin concentration than was cell wall digestion. Results for linear regressions of hemicellulose and cellulose digestibilities as functions of lignin concentration showed a greater (P less than .05) effect of lignin on cellulose digestion. Smooth bromegrass and switchgrass were collected at both Clay Center and Mead, NE; for all digestibility measures, the Clay Center samples gave stronger (P less than .05) negative correlations with lignin. A comparison of linear and curvilinear models indicated that, for all digestion measurements, the curvilinear model was a better (P less than .05) description of relationships with lignin concentration. For all digestibility measures, lignin's inhibiting effect declined at higher lignin concentrations. The curvilinear models did not show significant differences among the digestibility measures for effect of lignin. The demonstration that the forage digestibility response to lignin's inhibitory effect is curvilinear in nature suggests that the mechanism of lignin's inhibition is complex.

Animal Feed↗
PubMed2002

Ammonia production by ruminal microorganisms and enumeration, isolation, and characterization of bacteria capable of growth on peptides and amino acids from the sheep rumen.

Excessive NH(3) production in the rumen is a major nutritional inefficiency in ruminant animals. Experiments were undertaken to compare the rates of NH(3) production from different substrates in ruminal fluid in vitro and to assess the role of asaccharolytic bacteria in NH(3) production. Ruminal fluid was taken from four rumen-fistulated sheep receiving a mixed hay-concentrate diet. The calculated rate of NH(3) production from Trypticase varied from 1.8 to 19.7 nmol mg of protein(-1) min(-1) depending on the substrate, its concentration, and the method used. Monensin (5 micro M) inhibited NH(3) production from proteins, peptides, and amino acids by an average of 28% with substrate at 2 mg/ml, compared to 48% with substrate at 20 mg/ml (P = 0.011). Of the total bacterial population, 1.4% grew on Trypticase alone, of which 93% was eliminated by 5 micro M monensin. Many fewer bacteria (0.002% of the total) grew on amino acids alone. Nineteen isolates capable of growth on Trypticase were obtained from four sheep. 16S ribosomal DNA and traditional identification methods indicated the bacteria fell into six groups. All were sensitive to monensin, and all except one group (group III, similar to Atopobium minutum), produced NH(3) at >250 nmol min(-1) mg of protein(-1), depending on the medium, as determined by a batch culture method. All isolates had exopeptidase activity, but only group III had an apparent dipeptidyl peptidase I activity. Groups I, II, and IV were most closely related to asaccharolytic ruminal and oral Clostridium and Eubacterium spp. Group V comprised one isolate, similar to Desulfomonas piger (formerly Desulfovibrio pigra). Group VI was 95% similar to Acidaminococcus fermentans. Growth of the Atopobium- and Desulfomonas-like isolates was enhanced by sugars, while growth of groups I, II, and V was significantly depressed by sugars. This study therefore demonstrates that different methodologies and different substrate concentrations provide an explanation for different apparent rates of ruminal NH(3) production reported in different studies and identifies a diverse range of hyper-ammonia-producing bacteria in the rumen of sheep.

Animals↗
PubMed1985

Stereochemistry and synthetic applications of products of fermentation of alpha,beta-unsaturated aromatic aldehydes by baker's yeast.

Baker's yeast fermenting on D-glucose converts 2-substituted C6-C3 alpha,beta-unsaturated aromatic aldehydes into the corresponding 3-phenylprop-2-en-1-ols and 3-phenylpropan-1-ols, and into the 4-substituted (2S,3R)-5-phenylpent-4-en-2,3-ols. The formation of the C6-C3 alcohols from the aldehydes by baker's yeast was already known, but the production of the methyl diols is new. The conversion of C6-C3 alpha,beta-unsaturated aldehydes into the C6-C5 methyl diols can be viewed as the overall consequence of two distinct chemical operations: (1) addition of a C2 unit equivalent to acetaldehyde onto the Si-face of the carbonyl carbon of the unsaturated aldehyde forms the (R)-alpha-hydroxy ketone in an acyloin-type condensation, and (2) reduction of this intermediate on the Re-face of the carbonyl gives the diol actually isolated. There is some tolerance by the enzymic system(s) involved in the reaction(s) leading from the C6-C3 alpha,beta-unsaturated aromatic aldehydes to the 4-substituted (2S,3R)-5-phenylpent-4-en-2,3-ols as far as the structure of the aromatic aldehydes and the substitutents in the alpha position are concerned, but acetaldehyde is the only aldehyde accepted as second terminus of the reaction. However, synthetic alpha-hydroxy ketones, prepared from aldehydes that cannot be directly converted by yeast into the corresponding methyl diols, are reduced by yeast. This indicates that the reason direct conversion of the aldehydes does not occur is that these materials probably cannot be accepted as substrates by the condensing enzyme(s). The (2S,3R)-diols can be used instead of natural carbohydrates as starting materials for the synthesis of optically active forms of natural products belonging to different structural classes. Applications of these diols in the synthesis of L-daunosamine, the natural form of vitamin E and other products are discussed.

Aldehydes↗
PubMed2000

Nitric oxide-mediated endothelium-dependent relaxation of rat thoracic aorta induced by aqueous extract of red rice fermented with Monascus ruber.

Vasodilatory effects of aqueous extract of red rice fermented with Monascus ruber IFO32318 were examined on the isolated rat aorta. The water phase of fermented rice with Monascus (WP/FRM, 0.1-10 mg/ml) caused a transient relaxation of the endothelium-intact rat aorta precontracted with norepinephrine (NE, 300 nM). The WP/FRM-induced relaxation was abolished by removal of endothelium or in the presence of N(G)-nitro-L-arginine (L-NNA, 10 microM), a nitric oxide (NO) synthase inhibitor. Neither atropine, a muscarinic receptor antagonist (10 microM), nor indomethacin, a cyclooxygenase inhibitor (10 microM), altered the WP/FRM-induced endothelium-dependent relaxation. gamma-Aminobutyric acid (GABA), one of the principle components of the extract, did not affect the muscle tension of the aorta with intact endothelium. In addition, WP/FRM increased the production of NO in primary cultured endothelial cells from human umbilical vein. The enhanced production of NO by WP/FRM was diminished by pretreatment with L-NNA (10 microM). In conclusion, WP/FRM induces relaxation of rat aorta by releasing NO from endothelium. There seem to be some unknown factor(s) other than acetylcholine (Ach) and GABA, in the aqueous extract of red rice, which stimulate vascular endothelial cells to produce and/or release NO leading to endothelium-dependent relaxation by WP/FRM.

Acetylcholine↗
PubMed2004

Effects of esculin and esculetin on the survival of Escherichia coli O157 in human faecal slurries, continuous-flow simulations of the rumen and colon and in calves.

The human pathogen Escherichia coli O157:H7 is thought to be spread by direct or indirect contact with infected animal or human faeces. The present study investigated the effects of the plant coumarin esculin and its aglycone esculetin on the survival of a strain of E. coli O157 under gut conditions. The addition of these compounds to human faecal slurries and in vitro continuous-flow fermenter models simulating conditions in the human colon and rumen caused marked decreases in the survival of an introduced strain of E. coli O157. When four calves were experimentally infected with E. coli O157 and fed esculin, the pathogen was detected in five of twenty-eight (18 %) of faecal samples examined post-inoculation, compared with thirteen of thirty-five (37 %) of faecal samples examined from five control calves not fed esculin. Coumarin compounds that occur naturally in dietary plants or when supplemented in the diet probably inhibit the survival of E. coli O157 in the gut.

Animals↗
PubMed2005

The SYNCAN project: goals, set-up, first results and settings of the human intervention study.

Experimental evidence on the anticancer properties of dietary prebiotics such as chicory inulin and oligofructose and dietary probiotics has accumulated in recent years. Various experimental models ranging from chemoprevention studies, tumour implantation models to genetically modified mice models, etc. have systematically shown the protective effects of these food ingredients. In some studies it appeared that synbiotics (combination of pre- and probiotics) exerted synergistic activity against processes of carcinogenesis. The logical next step in research was to find out if these observations also would be valid for human volunteers. This was the principal goal of the EU-sponsored SYNCAN project (QLK1-1999-346) which involved the integration of an in vitro study to select the most suitable synbiotic preparation, the application of this synbiotic in an in vivo rat model of chemically induced colon cancer, and, as the heart of the project, the investigation of the synbiotic effects in a human intervention study. The in vitro tests consisted of fermentation studies where the interaction of pre- and probiotics was studied. Cell-free supernatants were generated from various synbiotic combinations fermented by faecal slurry, which were then used to optimise a series of bioassays. In the rat study the anticarcinogenic effect of prebiotics and synbiotics but not of probiotics was demonstrated. Using tissue samples generated in this model, attempts were made to gain a better insight into the mechanisms underlying cancer development. The human intervention study consisted of two groups of volunteers. One group was composed of people at high risk (polypectomised subjects) for colon cancer and the other of volunteers (colon cancer subjects) who had previously undergone 'curative resection' for colon cancer but were not currently receiving treatment. The present paper describes the experimental design of the SYNCAN study, and demonstrates a functional effect of the synbiotic preparation (probiotic survival during gastrointestinal transit and modification of the intestinal flora). Detailed experimental outcome of the human intervention study will be reported elsewhere.

Animals↗
PubMed2000

Fermentation of carbohydrates and yield of microbial protein in mixed cultures of rabbit caecal microorganisms.

Fermentation pattern and yields of microbial protein were investigated in cultures of the rabbit caecal contents supplied with glucose, xylose, starch, pectin and xylan. Rabbits at the age of 4 weeks (before weaning) and 3 months were slaughtered, their caecal contents added at 1.1% to growth media and incubated anaerobically at 39 degrees C for 18 h. Caecal microorganisms of 4-week-old rabbits produced no methane and caproate, less butyrate, but more propionate than microorganisms of 3-month-old rabbits. In both groups of rabbits, fermentation of xylose produced significantly more propionate and less butyrate than fermentation of glucose. More propionate and less acetate was formed from starch than from pectin. In caecal cultures from 4-week-old rabbits with pectin, the molar percentages of acetate was significantly higher and percentages of other short-chain fatty acids (SCFA) lower than in cultures with starch or xylan. In cultures from 3-month-old rabbits, fermentation of pectin and xylan produced similar SCFA profiles, different from SCFA molar composition in cultures with starch. Average production of microbial protein was 129 mg per 1 g of carbohydrate digested (range 110 to 141 mg/g). Protein yields were the same on glucose and xylose, but nonsignificantly higher on starch than on pectin and xylan. It can be concluded that the characteristics of substrate affected fermentation pattern in mixed cultures of rabbit caecal microorganisms. Substrate effects on protein yields were not statistically significant, due to high variation.

Age Factors↗
PubMed1992

Effect of monensin on fermentation of hay and wheat bran investigated by the Rumen Simulation Technique (Rusitec). 1. Basal parameters of fermentation.

An experiment was performed with Rumen Simulation Technique (Rusitec) in which the fermentation of mixed ration of hay (12.8 g/d) and wheat bran (3.2 g/d) was compared with the fermentation of the same diet in the presence of 2, 5 and 10 mg of monensin/d. The duration of the experiment was 12 days. During the first six days the fermentation conditions in Rusitec were stabilized. Monensin significantly depressed the digestibility of dry matter and fibre digestion--neutral detergent fibre (NDF), acid detergent fibre (ADF) and cellulose but only after using 2 mg monensin/d. Addition of monensin depressed the production of VFAs--acetate, butyrate and isovalerate and acetate:propionate ratio. Production of propionate was increased and production of methane and CO2 was decreased in the presence of monensin. It can be explained by changes in the production of VFAs and redistribution of metabolic hydrogen. The recovery of nitrogen was satisfactory (about 100%) and its distribution in the effluent was increased by monensin. The recovery of protein (measured as alpha--NH2 groups) and distribution of protein in the effluent and residues was increased with the increasing dose of monensin.

Animal Feed↗
PubMed2001

Long-term anoxia tolerance in leaves of Acorus calamus L. and Iris pseudacorus L.

Mature green leaves of Acorus calamus and Iris pseudacorus have been shown to survive at least 28 d of total anoxia in the dark during the growing season, increasing up to 75 d and 60 d in overwintering leaves in A. calamus and I. pseudacorus, respectively. During the period of anaerobic incubation the glycolytic rate is reduced, carbohydrate reserves are conserved and ethanol levels in the tissues reached an equilibrium. Prolonged anoxia significantly suppressed leaf capacity for respiration and photosynthesis. After 28 d of anoxia, respiratory capacity was reduced in A. calamus and I. pseudacorus by 80% and 90%, respectively. The photosynthetic capacity of leaves decreased by 83% in A. calamus and by 97% in I. pseudacorus after 28 d of anoxia. This reduction in photosynthetic capacity was accompanied by a modification of the chlorophyll fluorescence pattern indicating damage to the PSII reaction centre and subsequent electron transport. Chlorophyll content was only slightly reduced after 28 d under anoxia and darkness in A. calamus, whereas there was a 50% reduction in I. pseudacorus. On return to air A. calamus leaves that endured 28 d of anoxia recovered full photosynthetic activity within 7 d while those of I. pseudacorus had a lag phase of 3-10 d. This well-developed ability to endure prolonged periods of oxygen deprivation in both these species is associated with a down-regulation in metabolic activity in response to the imposition of anaerobiosis. It is suggested that when leaf damage eventually does take place in these species after protracted oxygen deprivation, it is anoxic rather than post-anoxic stress that is responsible.

Acorus↗