References of "Crine, Michel"
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See detailPotential use of GFP microbial biosensors for the detection of mixing imperfections and cell viability in bioreactors
Delvigne, Frank ULg; Delafosse, Angélique ULg; Collignon, Marie-Laure ULg et al

Conference (2011, September 25)

The dynamics of microbial stress response in intensive cultivation conditions remains misunderstood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used as ... [more ▼]

The dynamics of microbial stress response in intensive cultivation conditions remains misunderstood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used as biosensors of the heterogeneities generated in a two-compartment scale-down reactor. The stress promoters have been chosen for their responsiveness to carbon limitation corresponding to the global substrate profiles encountered in intensive fed-batch cultures. From our results, it can be concluded that the exposure of microbial cells to substrates heterogeneities tends to decrease the GFP expression level in fed-batch mode. Fluorescence intensities have been monitored at the single cell level by using flow cytometry. During the course of the fed-batch culture, a drop at the level of the intracellular GFP content has been observed for the two scale-down operating conditions and for the two promoters sensitive to substrate limitation (rpoS and csiE). The fluorescence drop can be attributed to the repression of these promoters but also to the release of GFP to the extracellular medium according to the increase of the fluorescence level of the supernatant. This leakage has been observed for all the operating conditions, i.e. the scale-down reactors and the culture operating in the normal mode. Interestingly, GFP leakage is more pronounced in the case of the cultures operated in the normal mode. Indeed, staining by propidium iodide (PI) tends to be more elevated for the microbial cells cultured under the normal mode by comparison with those cultured in scale-down conditions, indicating a higher permeability of the membrane. These results are in accordance with previously published ones (Hewitt and co-workers) suggesting that microbial cells cultivated in heterogeneous bioreactors (scale-down and large-scale bioreactors) exhibits a higher viability level. These results suggest that GFP microbial biosensors could be used to detect simultaneously mixing imperfections and their impact on the viability of microorganisms. [less ▲]

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See detailX-ray CT study of the influence of liquid viscosity on fluid phase distribution in modular catalytic packings
Aferka, Saïd ULg; Viva, Aurora; Brunazzi, Elisabetta et al

in Chemical Engineering Transactions (2011), 24

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing Katapak-SP 11 is measured. Water and an ... [more ▼]

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing Katapak-SP 11 is measured. Water and an aqueous solution of glycerine, the viscosity of which equals 10 cP, are used as feed liquids. The estimation of liquid holdup is of great interest due to its strong influence on pressure drop, on solid wetting and on heat and mass transfer coefficients. The experimental technique used is high energy X-ray tomography, which is a unique technique to visualize the local liquid distribution inside the complex structure of packings and to quantify the liquid holdup at different scales. [less ▲]

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See detailCharacterization of the response of GFP microbial biosensors sensitive to substrate limitation in scale-down bioreactors
Delvigne, Frank ULg; Brognaux, Alison ULg; Gorret, Nathalie et al

in Biochemical Engineering Journal (2011), 55(2), 131-139

The dynamics of microbial stress response in intensive cultivation conditions remains not completely understood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used ... [more ▼]

The dynamics of microbial stress response in intensive cultivation conditions remains not completely understood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used as biosensors of the heterogeneities generated in a two-compartment scale-down reactor. The stress promoters have been chosen for their responsiveness to carbon limitation corresponding to the global substrate profiles encountered in intensive fed-batch cultures. From our results, it can be concluded that the exposure of microbial cells to substrates heterogeneities tends to decrease the GFP expression level in fed-batch mode. Fluorescence intensities have been monitored at the single cell level by using flow cytometry. During the course of the fed-batch culture, a drop at the level of the intracellular GFP content has been observed for the two scale-down operating conditions and for the two promoters sensitive to substrate limitation (rpoS and csiE). The fluorescence drop can be attributed to the repression of these promoters but also to the release of GFP to the extracellular medium according to the increase of the fluorescence level of the supernatant. This leakage has been observed for all the operating conditions, i.e. the scale-down reactors and the culture operating in the normal mode, i.e. in a well-mixed bioreactor. Interestingly, GFP leakage is more pronounced in the case of the cultures operated in the normal mode. Indeed, staining by propidium iodide tends to be more elevated for the microbial cells cultured under the normal mode by comparison with those cultured in scale-down conditions, indicating a higher permeability of the membrane. These results suggest that GFP microbial biosensors could be used to detect simultaneously mixing imperfections and their impact on the viability of microorganisms. [less ▲]

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See detailReply to "Comments on Collignon et al. (Chem. Eng. Sci. 65 (2010) 5929-5941)"
Collignon, Marie-Laure ULg; Delafosse, Angélique ULg; Crine, Michel ULg et al

in Chemical Engineering Science (2011), 6

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See detailEstimation of the turbulent kinetic energy dissipation in a culture cell stirred tank bioreactor
Delafosse, Angélique ULg; Collignon, Marie-Laure ULg; Dossin, Denis et al

in Chemical Engineering Science (2011), 66(8), 1728-1737

The turbulent dissipation rate is a key parameter in stirred tanks and its local values may have a strong influence on the performance of many processes. However, the local dissipation rate estimation is ... [more ▼]

The turbulent dissipation rate is a key parameter in stirred tanks and its local values may have a strong influence on the performance of many processes. However, the local dissipation rate estimation is far from easy in a stirred tank, especially near the impeller discharge where maximum values are encountered. The aim of this work is to estimate the dissipation rate in a vessel used for animal-cell cultures and stirred with a down-pumping axial impeller (Mixel TTP) from velocity fields measured by 2D-PIV. Special attention is paid to the assumptions necessary to estimate the dissipation rate from 2D measurements and to the influence of measurement spatial resolution on the estimated values. The analysis of isotropy ratios measured on vertical, horizontal and tangential planes shows that the turbulence in the impeller discharge is far from isotropic. Isotropy assumptions classically used to estimate the dissipation rate from 2D measurements may thus lead to erroneous values. Based on the measured isotropy ratios, a new relationship is proposed to estimate the dissipation rate in the impeller discharge. This relationship is then used to estimate the dissipation rate on a vertical plane located in the impeller discharge zone. In order to analyze the influence of the measurement spatial resolution on the estimated values of the dissipation, a total of 12 spatial resolutions are tested. Results show that if the spatial resolution is divided by a factor 2, the dissipation rate increases by 220%. For the smallest spatial resolution value used, the maximum dissipation rate estimated is 50 times higher than the mean overall dissipation rate and the corresponding minimum value of the Kolmogorov scale is nearly 3 times smaller than the Kolmogorov scale computed from the mean overall dissipation rate. [less ▲]

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See detailApplicability of GFP Microbial Whole Cell Biosensors to Bioreactor Operations : Mathematical Modeling and Related Experimental Tools
Delvigne, Frank ULg; Brognaux, Alison ULg; Gorret, Nathalie et al

in Biosensors : emerging materials and applications (2011)

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See detailSynthesis, characterization and photocatalytic properties of alkali metals doped tin dioxide
Benhebal, Hadj; Chaib, Messaoud; Léonard, Angélique ULg et al

in Journal of Molecular Structure (2011), 1004(1-3), 222-226

In order to improve the photocatalytic properties of tin dioxide, crystallized powders of SnO(2) photocatalysts doped by alkali metals (Li, Na and K) were synthesized by sol-gel process. The physical ... [more ▼]

In order to improve the photocatalytic properties of tin dioxide, crystallized powders of SnO(2) photocatalysts doped by alkali metals (Li, Na and K) were synthesized by sol-gel process. The physical properties of these materials were characterized by X-ray diffraction, nitrogen adsorption-desorption, Scanning electron microscopy and Ultraviolet-visible diffuse reflection spectroscopy. The photocatalytic tests under UV radiation conducted on four aromatic compounds (phenol, paranitrophenol, pentachlorophenol and benzoic acid) showed that tin dioxide modified by sodium possesses good photocatalytic activity; The Li-doped SnO(2) is moderately active, while modification by potassium does not improve this activity. (C) 2011 Elsevier B.V. All rights reserved. [less ▲]

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See detailGas Flow Simulations in a Structured Packing by Lattice Boltzmann Method
Beugre, Djomice; Calvo, Sébastien ULg; Crine, Michel ULg et al

in Chemical Engineering Science (2011), 66

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental ... [more ▼]

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental measurements and with known correlations. They are also compared with simulations using a classical CFD code. In all cases, the agreement is very good. [less ▲]

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See detailImpact of Storage Duration on the Gaseous Emissions during Convective Drying of Urban Residual Sludges
Fraikin, Laurent ULg; Salmon, Thierry ULg; Herbreteau, B. et al

in Chemical Engineering and Technology (2011), 34(7), 1172--1176

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See detailTomographic measurement of liquid hold up and effective interfacial area distributions in a column packed with high performance structured packings
Aferka, Saïd ULg; Viva, Aurora; Brunazzi, Elisabetta et al

in Chemical Engineering Science (2011), 66

In this paper, we report on the use of a high energy and high resolution X-ray tomograph to visualize and quantify the distribution of liquid hold up and of gas-liquid interfacial area in a 0.1m diameter ... [more ▼]

In this paper, we report on the use of a high energy and high resolution X-ray tomograph to visualize and quantify the distribution of liquid hold up and of gas-liquid interfacial area in a 0.1m diameter column filled with MellapakPlus 752.Y packing elements. A standard air-water system at room temperature and atmospheric pressure was used. Tomographic measurements have been carried out in a large number of packing cross sections situated at different heights between the top and the bottom of the packed column, giving access to the evolution of axial profiles of liquid hold up and of gas-liquid interfacial area as a function of the operating conditions. Gas-liquid interfacial area values were also measured by a chemical method (CO2 absorption from air into a caustic solution). For the first time, a whole set of gas-liquid interfacial area values evaluated from tomographic images are interestingly compared with values measured by a chemical method. A comparison is also presented with literature models. [less ▲]

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See detailDetermination of liquid hold-up and flow distribution inside modular catalytic structured packings
Viva, Aurora; Aferka, Saïd ULg; Toye, Dominique ULg et al

in Chemical Engineering Research & Design : Transactions of the Institution of Chemical Engineers Part A (2011), 89

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1m internal diameter column filled with catalytic structured packing Katapak-SP. Information ... [more ▼]

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1m internal diameter column filled with catalytic structured packing Katapak-SP. Information has been gathered at local scale by means of a non-intrusive high energy X-ray tomograph. Measurements have been carried out in a large number of packing cross sections situated at different heights between the top and bottom of the packed column, giving access to the evolution of axial profiles of liquid hold-up in the open channels (separation zone) and in the catalytic baskets (reaction zone) as a function of the liquid load. The total hold-up, evaluated by averaging local tomographic values over the packed volume, was compared with global hold-up data obtained by traditional methods, like draining and RTD measurements. A method was also proposed to deduce the distribution of liquid flowrate, between the reaction and the separation zones, from hold-up distribution measured by tomography. The methodology was validated by comparison with experimental data obtained by collecting separately the liquid flowing out of the two zones at the bottom of the packed bed. The obtained results are invaluable to improve the description of hydrodynamics in rate based performance models. [less ▲]

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See detailProcessing of X-ray tomographic images: a procedure adapted for the analysis of phase distribution in MellapakPlus 752.Y and Katapak-SP packings
Viva, Aurora; Aferka, Saïd ULg; Brunazzi, Elisabetta et al

in Flow Measurement & Instrumentation (2011), 22

We developed a simple practical methodology to face common problems encountered in the analysis of tomographic images to get quantitative information on phase distributions in gas liquid contacting ... [more ▼]

We developed a simple practical methodology to face common problems encountered in the analysis of tomographic images to get quantitative information on phase distributions in gas liquid contacting columns packed with complex metallic packings. In particular, the procedure (thresholding and normalisation) was developed and validated on images of geometrically well known Mellapak Plus 752 Y packings. The methodology was extended to images of Katapak-SP modular packings which are made of an alternation of Mellapak Plus 752 Y sheets and catalytic baskets. Global liquid hold-up, obtained by averaging tomographic results over the column height, were found in agreement with bed scale data measured on the same Mellapak Plus 752 Y and Katapak-SP (11 and 12) packings at a given liquid load. Moreover, gas-liquid interfacial area were calculated and reported to the installed geometric area. [less ▲]

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See detailAXIAL IMPELLER SELECTION FOR ANCHORAGE DEPENDENT ANIMAL CELL CULTURE IN STIRRED BIOREACTORS: METHODOLOGY BASED ON THE IMPELLER COMPARISON AT JUST-SUSPENDED SPEED OF ROTATION
Collignon, Marie-Laure ULg; Delafosse, Angélique ULg; Crine, Michel ULg et al

in Chemical Engineering Science (2010), 65(22), 5929-5941

Animal cells, which are nowadays essential for the industrial production of proteinic compounds, are commonly cultivated inside stirred tank bioreactors. In case of anchorage dependent cells, they are ... [more ▼]

Animal cells, which are nowadays essential for the industrial production of proteinic compounds, are commonly cultivated inside stirred tank bioreactors. In case of anchorage dependent cells, they are usually fixed on microcarriers. The choice of agitation conditions (impeller type, rotational speed…) in this type of process is not an easy task as it has to fulfil three potentially conflicting goals: (1) maintaining microcarriers in complete suspension, (2) homogenizing the culture medium, and (3) limiting mechanical constraints generated by the hydrodynamics on the cells. The aim of this study is to present an original methodology to select the most appropriate axial impeller for this specific application. Seven propellers are preselected on basis of their characteristics available in the literature. Instead of comparing impellers at a given rotational speed or a given power input, they are compared at their respective minimum impeller rotational speed that leads to a complete microcarrier suspension, i.e. at their respective just-suspended speed Njs. They are then compared at higher rotational speeds N, expressed as multiples of Njs. The impeller classification is based on the intensity of mechanical constraints they produced, evaluated from: (1) the macro-shear rate quantified by the spatial derivative of time average velocity fields measured by P.I.V, (2) the micro-shear rate characterized by the ratio between the microcarrier diameter to the average Kolmogorov scale computed from power input measurements, and (3) the impact of microcarrier collisions on cells described via the Turbulent Collision Severity index also computed from power input measurements. Results show that the 125 mm diameter TTP impeller (Mixel) and the 150 mm diameter Elephant Ear impeller (Applikon) produce the smallest mechanical constraints at their just-suspended speed (50 rpm and 20 rpm, respectively). Moreover, the mechanical constraints they produce increase more slowly with the N/Njs ratio than the mechanical constraints produced by other impellers. These propellers are thus even more advantageous if rotational speeds higher than the just-suspended speed have to be used. [less ▲]

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See detailX-ray tomography : a key for revealing local behavior of fluids in packed beds
Toye, Dominique ULg; Marchot, Pierre ULg; Crine, Michel ULg

Scientific conference (2010, October 28)

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See detailImpact of storage duration on the emissions of ammonia and VOC during the convective drying of urban residual sludges
Fraikin, Laurent ULg; Herbreteau, Benjamin; Chaucherie, Xavier et al

in Tsotsas, E.; Metzger, T.; Peglow, M. (Eds.) Proceedings of IDS 2010 - Drying 2010 (2010, October)

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See detailAspects pratico-techniques du séchage des boues d'épuration
Léonard, Angélique ULg; Crine, Michel ULg

Conference given outside the academic context (2010)

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See detailImpact of storage at 4°C on the study of sludge drying emissions
Fraikin, Laurent ULg; Herbreteau, Benjamin; Chaucherie, Xavier et al

Conference (2010, September)

Detailed reference viewed: 50 (22 ULg)