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See detailEstimation of bioreactor efficiency through structured hydrodynamic modeling case study of a Pichia pastoris fed-batch process.
Delvigne, Frank ULg; El Mejdoub, Thami ULg; Destain, Jacqueline ULg et al

in Applied Biochemistry and Biotechnology (2005), 121-124

In this article, two theories are unified to investigate the effect of hydrodynamics on a specific bioprocess: the network-of-zones (NOZ) hydrodynamic structured modeling approach (developed by several ... [more ▼]

In this article, two theories are unified to investigate the effect of hydrodynamics on a specific bioprocess: the network-of-zones (NOZ) hydrodynamic structured modeling approach (developed by several researchers but applied to only a few bioprocesses) and the effectiveness factor eta approach. Two process scales were investigated (20 and 500 L), and for each, hydrodynamics were quantified using an NOZ validated by homogeneity time measurements. Several impeller combinations inducing quite different hydrodynamics were tested at the 20-L scale. After this step, effectiveness factors were determined for each fermentation run. To achieve this, a perfectly mixed microbial kinetic model was evaluated by using simple Monod kinetics with a fed-batch mass balance. This methodology permitted determination of the effectiveness factor with more accuracy because of the relation with the perfect case deduced from the Monod kinetics. It appeared that for the small scale, eta decreased until reaching a value of approx 0.7 (30% from the ideal case) for the three impeller systems investigated. However, stirring systems that include hydrofoils seemed to maintain higher effectiveness factors during the course of the fermentation. This effect can be attributed to oxygen transfer performance or to homogenization efficiency exhibited by the hydrofoils. To distinguish the oxygen transfer from the homogenization component of the effectiveness factor, these phenomena were analyzed separately. After determining the evolution of etaO2 linked to oxygen transfer for each of the fermentation runs, the NOZ model was employed to quantify substrate gradient appearance. After this step, another effectiveness factor, etamix, related to mixing was defined. Consequently, it is possible to distinguish the relative importance of the mixing effect and oxygen transfer on a given bioprocess. The results have highlighted an important scale effect on the bioprocess that can be analyzed using the NOZ model. [less ▲]

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See detailThe two-phase water/silicon oil bioreactor prospects in off-gas treatment
Aldric, Jean-Marc ULg; Destain, Jacqueline ULg; Thonart, Philippe ULg

in Applied Biochemistry and Biotechnology (2005), 121(Spring), 707-719

Research was carried out to develop a biphasic biologic reactor able to clean the gas effluents polluted by volatile organic compounds. Initially, Rhodococcus erythropolis T 902.1 was selected on the ... [more ▼]

Research was carried out to develop a biphasic biologic reactor able to clean the gas effluents polluted by volatile organic compounds. Initially, Rhodococcus erythropolis T 902.1 was selected on the basis of its capacity to degrade isopropylbenzene (IPB). The effect of gas flow and IPB concentration on the biodegadation of IPB was evaluated. The results show that the use of silicon oil allows large quantities of IPB to be absorbed within the medium of biologic abatement. On the other hand, the biodegradation rate was directly correlated to the inlet flow of IPB. Thus, the reactor presents interesting opportunities for the biologic treatment of gas effluents. [less ▲]

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See detailXylanase Production By Penicillium Canescens 10-10c In Solid-State Fermentation
Bakri, Y.; Jacques, Philippe; Thonart, Philippe ULg

in Applied Biochemistry and Biotechnology (2003), 105

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See detailInfluence Of A New Axial Impeller On K(L)A And Xylanase Production By Penicillium Canescens 10-10c
Bakri, Yasser; Jacques, Philippe; Shi, Kui et al

in Applied Biochemistry and Biotechnology (2002), 98

The effects of a new axial impeller (HTPG4) on oxygen volumetric transfer coefficient, KLa, and xylanase production by Penicillium canescens 10-10c were studied and compared for dual-impeller systems, one ... [more ▼]

The effects of a new axial impeller (HTPG4) on oxygen volumetric transfer coefficient, KLa, and xylanase production by Penicillium canescens 10-10c were studied and compared for dual-impeller systems, one with one DT4 impeller below and one HTPG4 above (DT4-HTPG4) and one with two DT4 (DT4-DT4) impellers, in a 5-L bioreactor. The volumetric coefficient of oxygen transfer was measured in culture medium using a gassing-out method at different gassing rates and agitation speeds. We observed that the DT4-HTPG4 combination provided better KLa performance than the DT4-DT4 combination. The two combinations were also tested for their influence on xylanase production by a filamentous microorganism; P. canescens 10-10c. These experiments demonstrated that the DT4-HTPG4 combination impeller enhanced enzyme production up to 23% compared with the DT4-DT4 combination at an aeration rate of 1 vvm and an agitation speed of 600 rpm. The main cause for this difference is thought to be a higher shear stress generated by the DT4-DT4 combination, which damages the mycelium of P. canescens and decreases xylanase production. [less ▲]

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See detailPurification and characterization of a microbial dehydrogenase - A vanillin : NAD(P)(+) oxidoreductase
Bare, G.; Swiatkowski, T.; Moukil, A. et al

in Applied Biochemistry and Biotechnology (2002), 98-100(Spring), 415-428

Pseudomonas fluorescens (strain BTP9) was found to have at least two NAD(P)-dependent vanillin dehydrogenases: one is induced by vanillin, and the other is constitutive. The constitutive enzyme was ... [more ▼]

Pseudomonas fluorescens (strain BTP9) was found to have at least two NAD(P)-dependent vanillin dehydrogenases: one is induced by vanillin, and the other is constitutive. The constitutive enzyme was purified by ammonium sulfate fractionation, gel-filtration, and Q-Sepharose chromatography. The subunit Mr value was 55,000, determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The native M, value estimated by gel-filtration chromatography gave a value of 210,000. The enzyme made use of NAD(+) less effectively than NADP(+). Benzaldehyde, 4-hydroxybenzaldehyde, hexanal, and acetaldehyde were not oxidized at detectable rates in the presence of NAD(+) or NADP(+). The ultraviolet absorption spectrum indicated that there is no cofactor or prosthetic group bound. The vanillin oxidation reaction was essentially irreversible. The pH optimum was 9.5 and the pI of the enzyme was 4.9. Enzyme activity was not affected when assayed in the presence of salts, except FeCl2. The enzyme was inhibited by the thiol-blocking reagents 4-chloromercuribenzoate and N-ethylmaleimide. NAD(+) and NADP(+) protected the enzyme against such a type of inhibition along with vanillin to a lesser extent. The enzyme exhibited esterase activity with 4-nitrophenyl acetate as substrate and was activated by low concentrations of NAD(+) or NADP(+). We compared the properties of the enzyme with those of some well-characterized microbial benzaldehyde dehydrogenases. [less ▲]

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See detailDissemination of Catabolic Plasmids among Desiccation-Tolerant Bacteria in Soil Microcosms
Weekers, Frederic; Rodriguez, Christian; Jacques, Philippe et al

in Applied Biochemistry and Biotechnology (2001), 91-93(Spring), 219-32

The dissemination of catabolic plasmids was compared to bioaugmentation by strain inoculation in microcosm experiments. When Rhodococcus erythropolis strain T902, bearing a plasmid with trichloroethene ... [more ▼]

The dissemination of catabolic plasmids was compared to bioaugmentation by strain inoculation in microcosm experiments. When Rhodococcus erythropolis strain T902, bearing a plasmid with trichloroethene and isopropylbenzene degradation pathways, was used as the inoculum, no transconjugant was isolated but the strain remained in the soil. This plasmid had a narrow host range. Pseudomonas putida strain C8S3 was used as the inoculum in a second approach. It bore a broad host range conjugative plasmid harboring a natural transposon, RP4::Tn4371, responsible for biphenyl and 4-chlorobiphenyl degradation pathways. The inoculating population slowly decreased from its original level (10(6) colony-forming units [CFU]/g of dry soil) to approx 3 x 10(2) CFU/g of dry soil after 3 wk. Transconjugant populations degrading biphenyl appeared in constant humidity soil (up to 2 x 10(3) CFU/g) and desiccating soil (up to 10(4) CFU/g). The feasibility of plasmid dissemination as a bioaugmentation technique was demonstrated in desiccating soils. The ecologic significance of desiccation in bioaugmentation was demonstrated: it upset the microbial ecology and the development of transconjugants. [less ▲]

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See detailInfluence of culture conditions on lipopeptide production by Bacillus subtilis
Akpa, E.; Jacques, P.; Wathelet, Bernard ULg et al

in Applied Biochemistry and Biotechnology (2001), 91-3

Bacillus subtilis produces various families of lipopeptides with different homologous compounds. To produce "new molecules" with improved activities and to select strains that produced a reduced number of ... [more ▼]

Bacillus subtilis produces various families of lipopeptides with different homologous compounds. To produce "new molecules" with improved activities and to select strains that produced a reduced number of homologs or isomers, we studied the effects of different media on the nature of the synthesis of fatty; acid chains for each lipopeptide family. This study focused on two B. subtilis strains cultivated in flasks. Optimized medium for lipopeptide production and Landy medium modified by replacing glutamic acid with other alpha -amino acids were used. We found that the intensity of production of homologous compounds depends on the strain and the culture medium. Analysis of these lipopeptides by high-performance liquid chromatography showed that the strain R. subtilis NT02 yielded various homologous compounds when cultivated in Landy medium (L-Glu), but primarily one homologous product in hi,oh relative amounts when cultivated in the optimized medium. Mass spectrometric analysis and determination of the amino acid composition of this molecule enabled us to identify it as Bacillomycine L c15. [less ▲]

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See detailEffect of Temperature on Growth of Psychrophilic and Psychrotrophic Members of Rhodotorula Aurantiaca
Sabri, Ahmed ULg; Jacques, Philippe; Weekers, Frederic et al

in Applied Biochemistry and Biotechnology (2000), 84-86(Spring), 391-9

The thermo-dependence of growth kinetic parameters was investigated for the Antarctic psychrophilic strain Rhodotorula aurantiaca and a psychrotrophic strain of the same species isolated in Belgium ... [more ▼]

The thermo-dependence of growth kinetic parameters was investigated for the Antarctic psychrophilic strain Rhodotorula aurantiaca and a psychrotrophic strain of the same species isolated in Belgium (Ardennes area). Cell production, maximum growth rate (mu max), and half-saturation constant for glucose uptake (Ks) of both yeasts were temperature dependent. For the two yeasts, a maximum cell production was observed at about 0 degree C, and cell production decreased when temperature increased. The mu max values for both strains increased with temperature up to a maximum of 10 degrees C for the psychrophilic strain and 17 degrees C for the psychrotrophic strain. For both yeasts, Ks for glucose was relatively constant at low temperatures. It increased at temperatures above 10 degrees C for the psychrophilic strain and 17 degrees C for the psychrotrophic strain. Although its glucose affinity was lower, the psychrotrophic strain grew more rapidly than the psychrophilic one. The difference in growth rate and substrate affinity was related to the origin of the strain and the adaptation strategy of R. aurantiaca to environmental conditions. [less ▲]

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See detailImproving The Catabolic Functions Of Desiccation-Tolerant Soil Bacteria
Weekers, F.; Jacques, P.; Springael, D. et al

in Applied Biochemistry and Biotechnology (1999), 77-9

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See detailOptimization of biosurfactant lipopeptide production from Bacillus subtilis S499 by Plackett-Burman design
Jacques, P.; Hbid, C.; Destain, Jacqueline ULg et al

in Applied Biochemistry and Biotechnology (1999), 77-9

Bacillus subtilis S499 is well-known for its ability to produce two families of surfactant lipopeptides: Iturin A and Surfactin S1. Fermentation optimization for this strain was performed to amplify the ... [more ▼]

Bacillus subtilis S499 is well-known for its ability to produce two families of surfactant lipopeptides: Iturin A and Surfactin S1. Fermentation optimization for this strain was performed to amplify the surfactant production. Ten active variables were analyzed by two successive Plackett-Burman designs, consisting respectively of 12 and 16 experiments to give an optimized medium. The amount of biosurfactant lipopeptides in the supernatant of a culture carried out in this optimized medium was about five times higher than that obtained in nonoptimized rich medium. The analysis of the surfactant molecules produced in such optimized conditions has revealed the presence of a third family of lipopeptides: the fengycins. The time-dependent production of these three families of molecules in bioreactors showed that surfactin S1 is produced during the exponential phase and iturin A and fengycins during the stationary phase. [less ▲]

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See detailModification of the Thermoresistance to Spray-Drying of a Cold-Adapted Subtilisin by Genetic Engineering
Bare, G.; Diakiese, A.; Zgoulli, S. et al

in Applied Biochemistry and Biotechnology (1999), 77-79(Spring), 857-65

The thermoresistance of a cold-adapted subtilisin dried by spray-drying was studied. Proteolytic activity of this enzyme was measured before and after spray-drying. Without chemical additives, spray ... [more ▼]

The thermoresistance of a cold-adapted subtilisin dried by spray-drying was studied. Proteolytic activity of this enzyme was measured before and after spray-drying. Without chemical additives, spray-drying yields ranged from 2-13%. The use of arabic gum and lactose in the composition of the enzyme solutions allowed the strengthening of the enzyme structures and increased water mobility in the product. Increase of water mobility led to a shorter residence time of the product in the spray-drier and a net yield increase was obtained (yield higher than 50%). The effect of two selective mutations on the thermoresistance to spray-drying of the cold-adapted subtilisin was also investigated. Mutation T85D (introduction of an additional link with an ion Ca2+ necessary for enzyme activity, by substitution of Asp for Thr 85) had no effect on the thermoresistance of the subtilisin to spray-drying. Mutation H121W (introduction of an additional aromatic link by substitution of Trp for His 121) reduced the drying yield from 66% (not modified subtilisin) to 52%. This higher thermosensitivity could be explained by an increase of the hygroscopic character of the modified subtilisin (mutation H121W). [less ▲]

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See detailImprovement Of Lactic Cell Production
Desmons, S.; Krhouz, H.; Evrard, P. et al

in Applied Biochemistry and Biotechnology (1998), 70-2

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See detailEffect Of Drying On Bioremediation Bacteria Properties
Weekers, F.; Jacques, P.; Springael, D. et al

in Applied Biochemistry and Biotechnology (1998), 70-2

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See detailThe Degradation Of L-Tyrosine To Phenol And Benzoate In Pig Manure - The Role Of 4-Hydroxy-Benzoate
Antoine, P.; Taillieu, X.; Thonart, Philippe ULg

in Applied Biochemistry and Biotechnology (1997), 63-5

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See detailStudy on the Production of Xylanolytic complex from Pencillium canescens 10-10c.
Gaspar, A.; Cosson, T.; Roques, C. et al

in Applied Biochemistry and Biotechnology (1997), 67

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See detailInfluence of the production of two lipopeptides, Iturin A and Surfactin S1, on oxygen transfer during Bacillus subtilis fermentation
Hbid, Choukri; Jacques, Philippe; Razafindralambo, Hary ULg et al

in Applied Biochemistry and Biotechnology (1996), 57-8

Bacillus subtilis produces three types of lipopeptides: Iturins, Fengycins, and Surfactins. These amphiphilic molecules influence the volumetric oxygen transfer (K(L)a) like chemical surfactant. K(L)a ... [more ▼]

Bacillus subtilis produces three types of lipopeptides: Iturins, Fengycins, and Surfactins. These amphiphilic molecules influence the volumetric oxygen transfer (K(L)a) like chemical surfactant. K(L)a values were from two- to fivefold lower when both Iturin A and Surfactin S1 were coproduced, and from 0.57- to 0.8-fold lower when only Iturin A was produced. The addition of an oxygen vector (n-Dodecane) during fermentation increased K(L)a values (7.5-fold) and biomass production (twofold), and decreased Iturin A and Surfactin S1 production. However, at high stirring conditions and in the presence of n-Dodecane, Iturin A production was improved. [less ▲]

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See detailProduction of sulfur from gypsum as an industrial byproduct
Hiligsmann, Serge ULg; Deswaef, Sophie; Taillieu, Xavier et al

in Applied Biochemistry and Biotechnology (1996), 57-8

Biological sulfate reduction was investigated at the bench and pilot scales in order to determine optimum culture conditions. Efficient strains of sulfate-reducing bacteria (SRB) were selected by ... [more ▼]

Biological sulfate reduction was investigated at the bench and pilot scales in order to determine optimum culture conditions. Efficient strains of sulfate-reducing bacteria (SRB) were selected by classical microbiological methods and by mutagenesis. Improvement factors, including stripping, scale-up, sulfate,and organic substrate concentrations, have been studied in batch bioreactors. Two types of pilot-scale bioreactors have been adopted, the first being completely mixed with free cells and the second having two stages with immobilized cells on a fixed bed. An overall bioconversion capacity of 11 kg/m(3) . d of gypsum and 1.2 kg/m(3) . d of dissolved organic carbon has been achieved in the two-stage bioreactor. [less ▲]

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See detailBioconversion of vanillin into vanillic acid by Pseudomonas fluorescens strain BTP9
Bare, Ghislain; Delaunois, Valérie; Rikir, Rafaelle et al

in Applied Biochemistry and Biotechnology (1994), 45/46

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See detailBioconversion of vanillin into vanillic acid by Pseudomonas fluorescens, strain BTP9. I. Cell reactors and mutants study.
Baré, G.; Gerard, J.; Jacques, Ph. et al

in Applied Biochemistry and Biotechnology (1992), 34/35

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