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Elqotbi M.,Laboratoire ProBioGEM EA 1026 | Vlaev S.D.,Bulgarian Academy of Science | Montastruc L.,Laboratoire ProBioGEM EA 1026 | Montastruc L.,National Polytechnic Institute of Toulouse | Nikov I.,Laboratoire ProBioGEM EA 1026
Computers and Chemical Engineering | Year: 2013

An advanced study of a bioreactor system involving a Navier-Stokes based model has been accomplished. The model allows a more realistic impeller induced flow image to be combined with the Monod bioreaction kinetics reported previously. The time-course of gluconic acid production by Aspergillus niger strain is simulated at kinetic conditions proposed in the literature. The simulation is based on (1) a stepwise solution strategy resolving first the fluid flow field, further imposing oxygen mass transfer and bioreaction with subsequent analysis of flow interactions, and (2) a segregated solution of the model replacing the multiple iterations per grid cell with single iterations. The numerical results are compared with experimental data for the bioreaction dynamics and show satisfactory agreement. The model is used for assessment of the viscosity effect upon the bioreactor performance. A 10-fold viscosity rise results in 2-fold decrease of KLa and 25% decrease of the specific gluconic acid production rate. The model allows better understanding of the mechanism of the important bioprocess. © 2012.

Montastruc L.,Laboratoire ProBioGEM EA 1026 | Montastruc L.,Laboratoire Of Genie Chimique | Tao L.,East China University of Science and Technology | Nikov I.,Laboratoire ProBioGEM EA 1026 | And 2 more authors.
Chinese Journal of Chemical Engineering | Year: 2011

The study is focused on modeling of separation process and optimization. An adsorption separation process is simulated. The surfactin production process by Bacillus subtilis ATCC 21332 followed by surfactin adsorption in a fixed-bed column packed with commercial active carbon is studied in laboratory. The adsorption column achieves high surfactin recovery (94%) by up-flow methanol elution at 25 °C. The adsorption column is simulated with a complex one-dimensional plug flow dispersion model coupled with nonlinear adsorption equilibrium, based on the assumption that the adsorption of surfactin is monomolecular layer and no micelle is formed. The molecular diffusion coefficient of surfactin in water solution with electric neutrality is estimated to be 0.428×10 -5 cm 2.s -1 by molecular dynamics simulation. The model developed can describe the complex interplay of adsorption kinetics, fluid dynamics, and mass-transfer phenomena based on the assumption of no radial temperature and concentration gradients, and is of adequate precision. The work involved in this paper is valuable for the optimization of the production process of surfactin.

Hadrich B.,University of Sfax | Dimitrov K.,Laboratoire ProBioGEM EA 1026 | Kriaa K.,Gabes University
Journal of Food Processing and Preservation | Year: 2016

Kinetics of aqueous extraction of polyphenols from carob (Ceratonia siliqua L.) have been performed in different conditions (Temperature=40 and 60C; solid-liquid ratio=1:3 and 1:19 and without and with ultrasonic assistance (100W)). The effects of various parameters were studied using an experimental design. The final yield was modelled as a first order polynomial model: Y = 42.688+7.997×T (p<0.10). An HPLC analysis showed that the major component is the galic acid and ultrasound assistance has no effect on degradation of phenols. Eight models (theoretical, empirical and semi-empirical) were tested to fit all kinetics [Y=f(t)] performed in all experiment conditions. Patricelli model showed the best fitting result and was retained to simulate all extraction conditions. Then polyphenols extraction from carob is based on two stages: an instant washing step followed by a slow diffusion step. Practical Applications: We test both conventional and acoustic extraction of polyphenols from carob (Ceratonia siliqua L.). Increasing temperature increase final yield extraction. Highest values of final yield extraction were obtained with ultrasound application. Major component is the galic acid. Ultrasound assistance has no effect on degradation of phenols. Eight models were tested to describe extraction phenomenon and Patricelli Model was the best one. © 2016 Wiley Periodicals, Inc.

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