982 resultados para KINETIC PARAMETERS


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The process of spermatic division and differentiation (spermatogenesis) occurs with intratesticular temperature lower that the corporal temperature and for that is essential that the testicular thermoregulation mechanism occurs properly. For evaluation of the scrotal surface temperature can be used the infrared thermography or testicular sensors, besides that, can be evaluated the blood flux in the spermatic cord through the Doppler ultrasonography. Thus, the aim of this study is to analyze the testicular thermoregulation in adult buffaloes through scrotal thermography and Doppler ultrasound of testicular artery and verify its effect on sperm quality. For that were used seven healthy buffaloes, with age of 3 and 4 years, of the Murrah breed. The animals were subjected to 3 semen collections using artificial vagina, with one day of interval. In addiction, the retal temperature measurement (RT) with dry bulb thermometer, the measurement of scrotal surface temperature (SST) and body surface temperature (BST) through infrared thermography and the pulsatility (PI) and resistivity (RI) index of testicular artery by Doppler ultrasonography, were performed using 2 distinct moments: animals previously placed to shade (M1) and animals subjected to 4 hours of sun (M2). All parameters were compared by T test and the correlations were performed by Pearson test using the In Stat Graph Pad 3 (R) program. The significant level considered was 5%. There was an increase (p<0,05) of RT, SST, SNT and RI in M2. increasing trend was observed (0,05>p>0,01) PI and RI between M1 and M2. There was a low correlation between SST and semen quality. The results of this study allow us to conclude that adult buffaloes have low ability to perform body and testicular thermoregulation in situations of enviromental heat stress. However, this low capacity of testicular temperature maintenance demonstrated no correlation with the sperm kinetic parameters and sperm morphological defects in buffalo spermatozoa.

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Pós-graduação em Química - IBILCE

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Levan is an extracellular polysaccharide (EPS), constituted by linked fructose units β (2,6), obtained by transfructosilation reaction during fermentation of microorganisms in a sucrose rich culture medium. The bacterial levan production is a good alternative of fructose source, besides having certain functional characteristics in the human body, such as a hypocholesterolemic and an anticarcinogenic agent. In the food industry, the levan can be used to fix colors and flavors, as well as to thickening and stabilizing agent in foods. This work aimed to analyze the kinetic parameters for levan production by Zymomonas mobilis CCT 4494, using submerged fermentation. The response surface methodology (RSM), was utilized to predict the optimization of medium for exopolymer production and the independent variables studied were: initial pH, incubation temperature, sucrose, KCl, K2SO4, MgSO4 and CaCl2. It was observed that the bacterium Z. mobilis CCT 4494 well adapted in medium containing high concentrations of sucrose.

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Pós-graduação em Biotecnologia - IQ

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Experiments of continuous alcoholic fermentation of sugarcane juice with flocculating yeast recycle were conducted in a system of two 0.22-L tower bioreactors in series, operated at a range of dilution rates (D (1) = D (2) = 0.27-0.95 h(-1)), constant recycle ratio (alpha = F (R) /F = 4.0) and a sugar concentration in the feed stream (S (0)) around 150 g/L. The data obtained in these experimental conditions were used to adjust the parameters of a mathematical model previously developed for the single-stage process. This model considers each of the tower bioreactors as a perfectly mixed continuous reactor and the kinetics of cell growth and product formation takes into account the limitation by substrate and the inhibition by ethanol and biomass, as well as the substrate consumption for cellular maintenance. The model predictions agreed satisfactorily with the measurements taken in both stages of the cascade. The major differences with respect to the kinetic parameters previously estimated for a single-stage system were observed for the maximum specific growth rate, for the inhibition constants of cell growth and for the specific rate of substrate consumption for cell maintenance. Mathematical models were validated and used to simulate alternative operating conditions as well as to analyze the performance of the two-stage process against that of the single-stage process.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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