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Poster De Conférence Année : 2012

Estimation of kinetic parameters for bioethanol production from xylose by Pichia stipitis NRRL-Y7124.

Résumé

Efficient conversion of xylose by P. stipitis is necessary for commercially viable ethanol production. The accurate description of the kinetics parameters and a mathematical model of biotechnological processes can only be achieved by incorporation reliable methodologies to easily update the model when there are changes in operational conditions. The aim of this work was established to develop a mathematical model considering the effect of inhibiting the initial substrate concentration (S0) and the accumulated product in the conversion of xylose to ethanol on reaction kinetics. The microorganism used was Pichia stipitis NRRL-Y7124 and the culture media, synthetic xylose. To obtain the experimental data and kinetic parameters involved two stages. Firstly, the effects of substrate inhibition were evaluated by batch experiments. The initial substrate concentration ranged from 2.5 g.L-1 to 150 g.L-1 to obtain the parameters KS, máx e KI. P. stipitis was able to consume xylose and to produce ethanol in all fermentation performed. It was observed that the xylose was completely consumed in nearly all concentrations, except for experiments performed at higher concentrations (125.2 and 145.6 g.L-1), in which the xylose present was not totally consumed, with the residual concentration of this substrate. However, it was observed in assays with high concentrations of xylose does not affect the production of ethanol, and the highest concentration of ethanol obtained was 54.9 g.L-1 for the condition of initial substrate concentration of 119.8 g.L-1 for a period of 237 hours with a yield of 90% and productivity 0.26 g.L-1h-1, suggesting that this cell, despite the low growth rate, has a good tolerance to ethanol. Moreover, the rate of substrate consumption in these experiments was slowly, indicating the presence of inhibitory effect by ethanol by addition of substrate inhibition. Thus, the behavior of  as a function of substrate concentration was assessed and by linearization of these values by Lineweaver-Burk method were obtained values KS = 1.67 g.L-1 and máx = 0.23 h-1. Through these values and applying the Andrews equation was possible to obtain the value of KI = 24.4 g.L-1. In the second step, continuous experiments were performed at different dilution rates (0.008 a 0.150 h-1) in order to evaluate the effect of inhibition by the accumulated product. Therefore, it was proposed a mathematical model mix of Andrews-Levenspiel and the value obtained for the model was Pmáx = 53 g.L-1, which is the product concentration when cell growth stop and n = 3.5, which is the parameter inhibition model for the product. This indicate that although the kinetic parameters obtained in fermentation processes with P. stipitis is a time consuming task, because this microorganism to grow very slowly, it was possible to accurately describe the process through the proposed model.
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Dates et versions

hal-04366615 , version 1 (29-12-2023)

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  • HAL Id : hal-04366615 , version 1

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Daniele Farias, Francisco Maugeri Filho. Estimation of kinetic parameters for bioethanol production from xylose by Pichia stipitis NRRL-Y7124.. 15th European Congress on Biotechnology and 9th European Symposium on Biochemical Engineering Science, Sep 2012, Istambul, Turkey. ⟨hal-04366615⟩
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