917 resultados para RUMEN FERMENTATION


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Ruminal acidosis is due to excessive ingestion of carbohydrates of rapid fermentation without previous adaptation of the microorganisms, causing severe metabolic disturbances to the animals. The objective of the present study was to assess the neutrophilic oxidative metabolism in sheep treated with sodium monensin in experimentally induced ruminal lactic acidosis. A total of 18 male sheep, half-bred (ideal x Merino), fistulated in the rumen, were used; nine of them received 33 mg/kg of the ionophore diet per day, for 30 days; the others were controls. The acidosis was induced by supplying 15g of sucrose/kg of body weight. The clinical evaluation and the rumen and blood samples were obtained before (0h) and at 6, 12, 24 and 48 hours post-induction. In both groups, all the animals presented clinical manifestations of ruminal lactic acidosis 6 hours after the induction. From this period on, a significant pH decrease (P<0.05) was observed in the ruminal fluid, which reached levels below 5. There were relevant differences (P<0.05) between the groups 12 hours after the induction, when the sheep treated with monensin had higher values than those of the control group. During this period, the oxidative metabolism of the neutrophils remained inhibited, and the reestablishment of this function only occurred in the sheep which received monensin. Blood pH, plasmatic glucose and the ionizable calcium suffered alterations within its levels. The seric cortisol concentration rose significantly (P<0.05) in both groups, although differences (P<0.05) between them were found at the end of the observation period. The treatment with monensin did not influence the oxidative metabolism of the neutrophils inhibited by the lactic acidosis; however, a faster recovery of this metabolism was verified in the animals treated with the ionophore.

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Cyclodextrin glucanotransferase production from Bacillus clausii E16, a new bacteria isolated from Brazilian soil samples was optimized in shake-flask cultures. A 2 4 full-factorial central composite design was performed to optimize the culture conditions, using a response surface methodology the combined effect among the soluble starch concentration, the peptone concentration, the yeast extract concentration, and the initial pH value of the culture medium was investigated. The optimum concentrations of the components, determined by a 2(4) full-factorial central composite design, were 13.4 g/L soluble starch, 4.9 g/L peptone, 5.9 g/L yeast extract, and initial pH 10.1. Under these optimized conditions, the maximum cyclodextrin glucanotransferase activity was 5.9 U/mL after a 48-h fermentation. This yield was 68% higher than that obtained when the microorganism was cultivated in basal culture medium.

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Rhizopus stolonifer was cultivated in wheat bran to produce a cellulase-free alkaline xylanase. The purified enzyme obtained after molecular exclusion chromatography in Sephacryl S-200 HR showed optimum temperature as 45 degrees C and hydrolysis pHs optima as pH 6.0 and 9.0. Xylanase presented higher Vmax at pH 9.0 (0.87 mu mol/mg protein) than at pH 6.0 and minor Km at pH 6.0 (7.42 mg/mL)than at pH 9.0.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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This work studied the influence of nitrogen source and sucrose concentration in the feeding medium for biomass and inulinase production by Kluyveromyces marxianus var. bulgaricus. The results show that the best nitrogen source was a combination of 5 g/L of yeast extract and 10 g/L of peptone. Both cellular growth and enzymatic activity increased with sucrose concentration in the feeding medium (from 200 to 500 g/L). When the sucrose concentration reached 600 g/L, both cellular growth and enzymatic activity decreased.

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The use of sugarcane bagasse and grass as low cost raw material for xylanase production by Bacillus circulans D1 in submerged fermentation was investigated. The microorganism was cultivated in a mineral medium containing hydrolysate of bagasse or grass as carbon source. High production of enzyme was obtained during growth in media with bagasse hydrolysates (8.4 U/mL) and in media with grass hydrolysates (7.5 U/mL). Xylanase production in media with hydrolysates was very close to that obtained in xylan containing media (7.0 U/ mL) and this fact confirm the feasibility of using this agro-industrial byproducts by B. circulans D1 as an alternative to save costs on the enzyme production process. (c) 2005 Elsevier Ltd. All rights reserved.

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