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philippe thonart

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See detailDépolution des sédiments d’une mangrove de l’estuaire du Wouri : évaluation du potentiel de microflores.
Semboung Lang, Firmin ULiege

Doctoral thesis (2017)

L’importance des écosystèmes de mangroves n’est plus à démontrer dans l’équilibre naturel des côtes des régions tropicales. Elles constituent un écosystème particulier et jouent un rôle important dans la ... [more ▼]

L’importance des écosystèmes de mangroves n’est plus à démontrer dans l’équilibre naturel des côtes des régions tropicales. Elles constituent un écosystème particulier et jouent un rôle important dans la production de la biomasse. Mais l’exploitation excessive du bois des palétuviers, les pollutions diverses suite à l’exploitation pétrolière et gazière, sont autant de facteurs qui contribuent à la dégradation des forêts de mangroves. Ainsi, entre 1980 et 2000, environ 35% de la superficie mondiale des mangroves a disparu. La pollution a entraîné une dégradation considérable des mangroves. Une quantité grandissante de déchets résultant des activités urbaines, industrielles et agricoles et de l’exploitation en mer du pétrole et du gaz est rejetée sans aucun traitement dans la mer et se retrouve au niveau des mangroves. Les déversements accidentels d’hydrocarbures en mer entraînent une grave pollution des mangroves et la pollution marine provenant des navires est une menace qui va sans doute s’accroître avec le développement de l’exploitation pétrolière. L’objectif de cette thèse était de mettre au point une méthode de dépollution par voie biologique des sédiments de mangroves pollués par les hydrocarbures. Il s’agissait plus précisément d’évaluer les capacités intrinsèques de dégradation de la microflore spécifique endogène, de comparer le potentiel de dégradation de cette microflore avec d’autres souches pures connues pour leur capacité à dégrader les hydrocarbures et enfin d’évaluer les différentes techniques de biodégradation adaptées pour l’élimination des hydrocarbures dans les sédiments de mangroves. Des procédés biologiques adaptés ont été mis en œuvre au cours de ce travail pour restaurer les écosystèmes de mangroves. Différentes techniques de traitements biologiques impliquant la microflore spécifique endogène ont été mises en œuvre. L’évaluation du potentiel de dégradation de cette microflore a été réalisée par rapport à trois souches pures exogènes. Les résultats obtenus ont montré que le potentiel de dégradation de la microflore spécifique est comparable à celui de Rhodococcus erythropolis lorsqu’on augmente sa concentration dans les sédiments (107 CFU.g-1 de matière sèche). La croissance de cette microflore est accélérée avec la présence des nutriments tels l’azote et le phosphore. Ce qui relève davantage le taux de dégradation des hydrocarbures. Le taux de dégradation obtenu en combinant les traitements par bioaugmentation de la microflore spécifique endogène et biostimulation (86%) nous ont amené à proposer cette méthode pour dépolluer les sédiments de mangroves. L’utilisation de la microflore spécifique endogène évite de travailler avec des souches exogènes qui nous exposent aux problèmes écologiques et éthiques liés à leur utilisation. [less ▲]

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See detailApplication des biotechnologies post-récolte pour la valorisation des produits de terroirs marocains par des microorganismes sélectionnés impliqués dans la fermentation de fruits : cas du vinaigre
Mounir, Majid ULiege

Doctoral thesis (2016)

Dans cette étude, de nouvelles souches microbiennes (levures et bactéries acétiques) ont été isolées, sélectionnées, identifiées et caractérisées pour évaluer leur usage comme starters pour la production ... [more ▼]

Dans cette étude, de nouvelles souches microbiennes (levures et bactéries acétiques) ont été isolées, sélectionnées, identifiées et caractérisées pour évaluer leur usage comme starters pour la production industrielle de vinaigre de fruits. Dans un premier temps, la levure Saccharomyces cerevisiae YS-DN1 a été isolée à partir de dattes locales et étudiée pour ces pouvoirs de fermentation des sucres et de résistance aux différents facteurs de stress (éthanolique, thermique et osmotique). Cette souche s’est distinguée comme étant la plus performante dans la production d’éthanol en comparaison à deux autres souches industrielles de référence. En effet, YS-DN1 était la seule souche capable de se développer à une température entre 35 et 40°C en présence d’un taux alcoolique élevé (>8% éthanol) et une pression osmotique agressive (>18 °Brix). Dans un deuxième temps, deux souches de bactéries acétiques CV01 et AF01, identifiées par des techniques moléculaires comme étant affiliées à l’espèce Acetobacter pasteurianus, ont été isolées respectivement de cactus et de pommes. A l’issue des caractérisations physiologiques et des cinétiques de fermentation réalisées en erlens et en bioréacteurs (6 L, 20 L et 500 L), ces deux souches ont montré des pouvoirs de thermotolérance et d’acétification notables. L’étude enzymatique réalisée sur les enzymes membranaires ADH et ALDH formant le complexe enzymatique impliqué dans le processus d’oxydation de l’éthanol a révélé que, contrairement aux souches de référence, ces enzymes maintiennent une activité normale à haute température (38°C). L’étude cinétique en bioréacteur 20 L a montré que la souche CV01 était moins sensible à la variation de la composition du milieu de fermentation et a pu produire plus d’acide acétique (10 g/L) que la souche AF01. Durant le même cycle de fermentation, la souche CV01 était notablement la seule souche capable d’orienter son mécanisme métabolique pour la production de l’acide gluconique simultanément avec l’acide acétique. Par ailleurs, la méthode des surfaces de réponse (RSM) a été utilisée pour l’optimisation de la production en biomasse de la souche CV01. Les valeurs optimales des facteurs influents, à savoir l’éthanol, l’acide acétique, le glucose et le pH, permettant d’obtenir le maximum de biomasse cellulaire (2.21 g/L) étaient de 28.18 g/L, 10.12 g/L, 15.15 g/L et 5.33, respectivement. Dans une troisième partie, la souche A. pasteurianus CV01 a été évaluée pour sa capacité à résister aux conditions de stress thermique en bioréacteur. Les résultats obtenus montrent une habilité de cette souche à contrecarrer l’augmentation excessive de température (>35°C) au cours d’un cycle de fermentation sans refroidissement. En outre, un protocole de démarrage de fermentation en mode semi-continu a été proposé et adopté pour la production de vinaigre de fruits en bioréacteur 500 L. La caractérisation aromatique du vinaigre de pomme produit à l’échelle pilote moyennant la technique de l’espace de tête – microextraction en phase solide (HS-SPME) – a permis d’identifier dans la composition de son arôme des molécules associées à des descripteurs généralement appréciés . Ces souches, caractérisées pour leur thermotolérance notable, pourront être utilisées comme starters pour la production à grande échelle de vinaigre de fruits. [less ▲]

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See detailThe Effect of Nutrients on the Degradation of Hydrocarbons in Mangrove Ecosystems by Microorganisms
Semboung Lang, Firmin ULiege; Tarayre, Cédric ULiege; Destain, Jacqueline ULiege et al

in International Journal of Environmental Research (2016), 10(4), 583-592

Mangrove ecosystems are areas prone to various types of pollution, especially hydrocarbons. These hydrocarbons mostly stem from human activities such as spills coming from offshore oil operations, runoff ... [more ▼]

Mangrove ecosystems are areas prone to various types of pollution, especially hydrocarbons. These hydrocarbons mostly stem from human activities such as spills coming from offshore oil operations, runoff from surrounding urban areas or atmospheric deposition. This pollution causes the decline of mangroves, which results in an imbalance in the functioning of this particular ecosystem with damages to the microbiota. Biodegradation allows to restore these ecosystems. This biodegradation can only be effective in specific environmental conditions. The presence of nutrients, which stimulate bacterial growth and promote biodegradation, is a key parameter to be considered. During this experiment, we achieved biodegradation tests to assess the effect of nitrogen and phosphorus on the process. The results showed that the biodegradation rates were strongly bound to the presence of nutrients. The degradation rates depended on the medium. The treatment that reached the best rate of degradation of diesel after 10 days was the one using 20% of a nutrient solution (MSM) containing nitrogen and phosphorus. This treatment led to a maximal degradation of 84.7% ± 4.7% obtained in the flasks containing 20% of a nutrient solution (MSM) containing nitrogen and phosphorus. [less ▲]

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See detailSemi-continuous fermentation of a thermotolerant and high acetic acid producing Acetobacter pasteurianus bacterium
Mounir, Majid ULiege; Thonart, Philippe; Ismaili Alaoui, Mustapha et al

Conference (2016, September 14)

Among 63 strains isolated from fruits and homemade vinegars from different ecosystems of Morocco, a thermotolerant bacterium with high production of acetic acid was selected and evaluated for its ability ... [more ▼]

Among 63 strains isolated from fruits and homemade vinegars from different ecosystems of Morocco, a thermotolerant bacterium with high production of acetic acid was selected and evaluated for its ability to perform efficient acetous fermentation at high temperature in a bioreactor. CV01 strain, isolated from cactus (Opuntia ficus-indica), was considered to be an Acetobacter pasteurianus sp. according to phylogenetic study based on 16s rDNA gene sequence analysis. An optimal culture medium containing initial concentrations of acetic acid and ethanol of 1% (v/v) and 4% (v/v), respectively, was used. The growth kinetics of this isolate were monitored in flasks and compared with those of the wild type LMG 1625 mesophilic strain and the thermoresistant Acetobacter senegalensis reference strain. The CV01 strain exhibited abundant growth along with high amount of produced acetic acid at high temperature (41°C). Subsequently, a 20-L stirred tank bioreactor was used to assess thermotolerance and acidoresistance properties of the selected strain during semi-continuous acetic acid fermentation at 38°C. Interestingly, a total amount of 13.4% (w/v) acetic acid was yielded at the end of fermentation. Moreover, this bacterium could produce during the same fermentation process a final concentration of 11.2 g/L gluconic acid, a sensory quality indicator in vinegar production. Finally, the enzymatic study showed that CV01 strain exhibited high ADH and ALDH enzyme activity at 38°C compared with the mesophilic reference strain LMG 1632, which was significantly susceptible to thermal inactivation. [less ▲]

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See detailBiodegradation of Polycyclic Aromatic Hydrocarbons in Mangrove Sediments Under Different Strategies: Natural Attenuation, Biostimulation, and Bioaugmentation with Rhodococcus erythropolis T902.1
Semboung Lang, Firmin ULiege; Destain, Jacqueline ULiege; Delvigne, Frank ULiege et al

in Water, Air & Soil Pollution (2016)

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that occur in mangrove sediments. Their removal by bacteria often depends on specific characteristics as the number of benzene rings they possess and ... [more ▼]

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that occur in mangrove sediments. Their removal by bacteria often depends on specific characteristics as the number of benzene rings they possess and their solubility. Their removal also depends on environmental factors, such as pH, temperature, oxygen, and the ability of the endogenous or exogenous microflora to metabolize hydrocarbons.With the aim of treating mangrove sediments polluted by hydrocarbons in a biological way, a biodegradation experiment was conducted using mangrove sediments artificially contaminated with a mixture of four PAHs. The study used Rhodococcus erythropolis as an exogenous bacterial strain in order to assess the biodegradation of the PAH mixture by natural attenuation, biostimulation, bioaugmentation, and a combination of biostimulation and bioaugmentation. The results showed that the last three treatments were more efficient than natural attenuation. The biostimulation/bioaugmentation combination proved to be the most effective PAH degradation treatment. [less ▲]

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See detailHydrocarbon biostimulation and bioaugmentation in organic carbon and clay-rich soils
Masy, Thibaut ULiege; Demanèche, Sandrine; Tromme, Olivier et al

in Soil Biology & Biochemistry (2016), 99

Hydrocarbon-contaminated organic carbon-rich clayey soils are challenging for bioremediation stakeholders since the pollutant is heterogeneously distributed and poorly bioavailable due to its strong ... [more ▼]

Hydrocarbon-contaminated organic carbon-rich clayey soils are challenging for bioremediation stakeholders since the pollutant is heterogeneously distributed and poorly bioavailable due to its strong adsorption on clay and organic particles. In addition, biodegradation rates are restricted by limited diffusion of oxygen and nutrients to hydrocarbon-degrading aerobes. This study assessed the benefits of bioaugmentation with the strain Rhodococcus erythropolis T902.1 versus those from biostimulation and anaerobic natural attenuation in terms of hydrocarbon (HC) degradation efficiency and changes in the bacterial community structure in a diesel-polluted clay-rich soil. Three soil samples with a similar total organic content but with a different HC concentration (0.2, 1.0 and 6.5 g/kg) were compared in a microcosm experiment. Despite a limitation in oxygen transfer, R. erythropolis T902.1 enhanced a greater HC degradation compared to the biostimulation treatment. However, this advantage decreased with time as the proportion of Rhodococci declined from 25% initially to 1% of the global community after 80 days of treatment. Similarly, the alkB gene proportion in bioaugmented soils decreased to levels close to those of biostimulated soils. Consequently, further engineering was suggested to improve the resilience of the inoculum to ensure its long-term presence and activity in such polluted environments. [less ▲]

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See detailStable biofilms of Rhodococcus erythropolis T902.1 in draining pavement structures for runoff water decontamination
Masy, Thibaut ULiege; Bertrand, Christelle ULiege; Paul-Marie, Xavier et al

in International Biodeterioration & Biodegradation (2016), 112

Permeable Pavement Systems (PPS) are sustainable devices designed to collect, store and treat urban stormwater before its release into the ground. However, this system must sufficiently retain pollutants ... [more ▼]

Permeable Pavement Systems (PPS) are sustainable devices designed to collect, store and treat urban stormwater before its release into the ground. However, this system must sufficiently retain pollutants brought by water runoff in order to comply with the current legislation. This study aims at evaluating the implementation in PPS of a hydrocarbonoclastic bacterium, Rhodococcus erythropolis T902.1, in terms of resilience and improvement of the degrading capacity. First results revealed that this strain could durably colonize the different gravels used in the construction of PPS. A 15-month experience in a real parking area showed that this biofilm remained viable without any replenishment of nutrients or bacteria. During accelerated pollution tests at a pilot scale, the structure bioaugmented with pre-coated biofilms was more efficient than a non-inoculated structure to limit hydrocarbon leaching below 50 μg L−1 and to degrade hydrocarbons adsorbed to the gravels. Over the long term, this innovative assembly should maintain the degrading capacity of PPS and ensure an effective treatment of stormwater before its infiltration into the soil. [less ▲]

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See detailMaîtrise de la fermentation alcoolique sous stress éthanolique, thermique et osmotique de la souche Saccharomyces cerevisiae YSDN1 en vue de la préparation du vinaigre de fruits
Mounir, Majid ULiege; Belgrire, Malika; Lahnaoui, Safaa et al

in Revue Marocaine des Sciences Agronomiques et Veterinaires (2016), 4(2), 86-95

La présente étude a pour but d’isoler, d’identifier et de caractériser de nouvelles souches de levures d’intérêt industriel. Un total de 54 levures ont été isolées et identifiées à partir de produits ... [more ▼]

La présente étude a pour but d’isoler, d’identifier et de caractériser de nouvelles souches de levures d’intérêt industriel. Un total de 54 levures ont été isolées et identifiées à partir de produits agricoles brutes et de sous-produits de l’industrie agro-alimentaire. Parmi ces isolats, quatre souches ont été retenues, purifiées et testées pour leur performance de fermentation sur un jus de dattes de variété Bouslikhène. D’après le séquençage du gène 18S de l’ADN ribosomal, les deux souches YS-DN1 et YS-M isolées respectivement à partir des dattes et de la mélasse ont été identifiées appartenant à l’espèce Saccharomyces cerevisiae. Par ailleurs, les deux autres souches YS-OPM et YS-G isolées des olives et des raisins appartiennent respectivement aux espèces Kluyveromyces marxianus, avec 78% d’homologie et Candida utilis à 89% d’homologie. D’autre part, la souche YS-DN1, s’est identifiée comme la plus performante dans la production d’éthanol en comparaison à deux autres souches industrielles de référence. La levure YS-DN1 était l’unique souche capable de croitre à une température entre 35 et 40°C en présence d’un taux alcoolique élevé et une pression osmotique agressive. Finalement, la production de la biomasse cellulaire de la souche YS -DN1 a été améliorée par optimisation des facteurs température, Brix et pH fixés respectivement à 29.75°C, 15.7% et 4.15. Ces valeurs ont permis d’obtenir un maximum de cellules de l’ordre de 8.4x108 UFC/ml. Il a été conclu que cette souche pourrait bien s’adapter à des usages industriels pour la production du vinaigre de fruits à grande échelle. [less ▲]

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See detailRhodococcus erythropolis T902.1 as a bioaugmentation starter: mechanisms, constrains and potentialities for the hydrocarbon degradation
Masy, Thibaut ULiege

Doctoral thesis (2016)

Since the advent of the industrial revolution in the 19th century, anthropogenic activities and lack of environmental concern gave birth to numerous contaminated areas. Amongst released pollutants ... [more ▼]

Since the advent of the industrial revolution in the 19th century, anthropogenic activities and lack of environmental concern gave birth to numerous contaminated areas. Amongst released pollutants, hydrocarbons (HC) are the most widespread in the environment but they can also constitute a carbon source for numerous microorganisms. Therefore, bioremediation (i.e. the use of microorganisms to degrade pollutants) appears as an ecologically- and cost-effective technique compared to chemical or physical treatments. This biotreatment technology often relies either on stimulating indigenous microorganisms already present in soil (biostimulation) or on adding specific microbial degraders (bioaugmentation) to enhance the natural attenuation of contaminants. However, there is a need for improved understanding of the causes that can lead to its failure or its low efficiency, such as diverse environmental constraints or poor adaptation ability of laboratory-cultivated microorganisms. Amongst bacteria studied, Rhodococcus sp. has been previously described as a potential candidate for bioaugmentation due to its ability to degrade a broad range of organic pollutants, to produce biosurfactants, which improves pollutant bioavailability, and to rapidly adapt to many environmental stresses (e.g. desiccation, low temperature, high salinity). The main objective of this work is thus to assess the potentiality and limitations in the use of a specific strain, Rhodococcus erythropolis T902.1, to degrade HC (from simple n-alkanes to polyaromatic) in diverse field conditions. The factors limiting such a process have to be identified and, as much as possible, overcome. A first bioaugmentation experiment in microcosms aimed at identifying these constrains in carbon and clay-rich soils contaminated with heating oil. This treatment was successful in strongly polluted soil, since the addition of the strain T902.1 helped in redirecting the limited quantity of available oxygen towards a higher HC degradation and also correlated with a higher proportion of degrading genes in bioaugmented soils, compared to biostimulated and control ones. However, this effect decreased with time as T902.1 development was curtailed by competition and potentially predation from the endogenous flora. In addition, HC were heterogeneously distributed and this hampered the detection of a real degradation in lowest polluted soils. As a result, inoculation should be targeted to highly polluted areas (e.g. contaminant source zones), but it requires controlling soil heterogeneity.   We thus resorted to electrical resistivity tomography (ERT), to describe this heterogeneity and to monitor bacterial HC degradation activity. This geophysical tool could discriminate lithological heterogeneities that were artificially introduced in a 2 m³ pilot. Compared to a first insufficient biostimulation phase, the introduction of R. erythropolis T902.1 in this pilot led to a HC depletion of almost 80% (6900 to 1600 ppm) in 3 months in the injection zone, where pollutants were less bioavailable. Simultaneously, HC mineralization and biosurfactant production were deduced from the monitoring of ERT, biological and physicochemical parameters. In another study, R. erythropolis T902.1 could form stable biofilms on the materials constituting draining pavement structures, which allowed its long-term survival in a real parking lot and improved the decontamination of runoff water drained through this structure during pollution tests carried out at a pilot scale. This indicates that the strain could be widely used in other decontaminating systems and not only in soil. Furthermore, this biofilm formation could be triggered by an appropriate pre-adaptation of the cells before their injection in the polluted environment, to ensure a higher ecological robustness of the inoculum, compared to the one observed in the microcosm experiment. A third constrain is the poor or slow degrading activity toward some recalcitrant compounds, such as polyaromatic HC (PAH). Metallic nanoparticles synthesized by a sol-gel process were considered as potential catalysts for the improvement of degradation kinetics. Iron nanoparticles boosted the bacterial catalytic activity of the strain T902.1 in liquid cultures containing biphenyl as the sole carbon source. Following results suggested that the iron encapsulated in the porous silica matrix, was progressively attracted by siderophores (heterobactins) produced by the strain. However, this hypothesis has still to be confirmed by further analyses. From these experiments, R. erythropolis T902.1 globally proved to compete and improve degradation rates in highly polluted soils compared to biostimulation, even under low oxygen and nutrient contents. Notably, the production of trehalolipidic biosurfactants enhances HC bioavailability for their further uptake by the strain and surrounding microorganisms. Furthermore, this strain forms stable biofilms on several supports, which increases its lifespan and paves the way for many applications in bioremediation systems. Finally, it can also be used in synergy with sol-gel iron nanoparticles to treat recalcitrant compounds such as PAH and some chlorinated aromatics, but this combination needs to be further tested in more complex media, such as soil or waste water. [less ▲]

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See detailOptimization of biomass production of Acetobacter pasteurianus KU710511 as a potential starter for fruit vinegar production
Mounir, Majid ULiege; Shafiei, Rasoul; Zarmehrkhorshid, Raziyeh ULiege et al

in African Journal of Biotechnology (2016), 15(27), 1429-1441

The objective of the present work was first the isolation of novel acetic acid bacteria strains from natural Moroccan habitats, and then, the evaluation of their ability to produce microbial starters for ... [more ▼]

The objective of the present work was first the isolation of novel acetic acid bacteria strains from natural Moroccan habitats, and then, the evaluation of their ability to produce microbial starters for vinegar production on a large scale. The strains were isolated from figs, dates, cactus, and traditional fruit vinegars. Four strains, selected from a total of 63 isolates, were confirmed as belonging to Acetobacter species according to biochemical and molecular studies based on 16s rRNA sequence analysis. Acetous fermentation tests, performed on date and apple fermented juices using selected Acetobacter strains, showed a high capacity of acidification. The most efficient strain KU710511, isolated from Morrocan cactus (Opuntia ficus-indica), was identified as Acetobacter strain closely related to A. pasteurianus and yielded 42.5 g/L acidity in apple juice. Cell growth optimization was carried out for KU710511 using response surface methodology (RSM). The linear, quadratic, and interaction effects of four factors—ethanol, acetic acid, glucose concentrations and pH—were studied by the application of a central composite design. Thirty experiments were designed to predict the maximum concentration of cell biomass. The optimal calculated values of ethanol, acetic acid, glucose and pH allowing the prediction of the maximum biomass production (2.21 g/L) were 28.18 g/L, 10.12 g/L, 15.15 g/L and 5.33, respectively. Subsequently, further batch fermentations were carried out in a 6-L lab-bioreactor at optimal and thermal stress conditions. The results were in line with the predicted values. It can be concluded that the studied strain is well suited to be used as a parental strain to prepare a starter for fruit vinegar production. [less ▲]

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See detailImproving probiotic viability and functionality by bioreactors engineering
Nguyen, Huu Thanh ULiege

Doctoral thesis (2016)

There is a growing market for probiotic bacteria, but their production is still the subject to technical limitations, i.e. susceptibility to the stress conditions found during upstream and downstream ... [more ▼]

There is a growing market for probiotic bacteria, but their production is still the subject to technical limitations, i.e. susceptibility to the stress conditions found during upstream and downstream operations. In this work, we have investigated the effect of cultivation and drying conditions on Bifidobacterium bifidum MG 25628, a probiotic bacteria being particularly sensitive to bioprocessing conditions. Previous results have shown that microbial physiology, and the ability of microbes to cope with stress, is dependent of the growth rate and the growth phase. It is also known that the preliminary exposure of microbial cells to sub-lethal stress enhance its robustness. Accordingly, the effect of the exposure of B. bifidum in a two-compartment reactor designed in order to expose the strain to different temperature conditions was investigated. We found that the exposure of B. bifidum at 42°C for 1h at the onset of the stationary phase enhanced significantly survival after freeze-drying. It appeared that the increase in cell survival was attributed to the induction of the synthesis and an exopolysaccharide layer surrounding the cells. The method involving the exposure of the strain to sub-lethal temperature stress was further successfully scaled-up to a bioreactor volume of 2000 L. EPS synthesis can also be stimulated by sparing the bioreactor with carbon dioxide. In this context, we investigated the EPS yield in two specific bioreactor designs for the intensification of the CO2 gas-liquid mass transfer, i.e. a trickle bed and a falling-film microreactor. Depending of the operating conditions, these two bioreactor configurations led to a significant improvement in EPS synthesis (around 21 g/L). Extensive comparative proteomic analysis confirmed the impact on CO2 mass transfer on cell physiology, notably by enhancing the intracellular concentration of two key enzymes implied in carbonate uptake, i.e. phosphoenolpyruvate carboxylase and carbamoyl phosphate synthase. Taken altogether, these results point out that biochemical engineering parameters can be used as a very efficient strategy for improving probiotic robustness. Additionally, this non-GMO approach is more suited to the consumer expectations. [less ▲]

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See detailOXIDATION OF ß-D-GLUCAN EXTRACTED FROM BAKER’S YEAST SACCHAROMYCES CEREVISIAE: PHYSICOCHEMICAL AND STRUCTURAL PROPERTIES
BORCHANI, Chema; FONTEYN, Fabienne; JAMIN, Guilhem et al

Conference (2016, March 21)

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See detailEnhanced biomass production of a novel Acetobacter strain isolated from Moroccan biotopes using response surface methodology approach
Mounir, Majid ULiege; Hamas, Khadija; Tamraoui, Khadija et al

Conference (2016, March 21)

The objective of this work was first the isolation of novel acetic acid bacteria strains from natural Moroccan habitats, and then, the evaluation of their ability to produce microbial starters for vinegar ... [more ▼]

The objective of this work was first the isolation of novel acetic acid bacteria strains from natural Moroccan habitats, and then, the evaluation of their ability to produce microbial starters for vinegar production in large-scale. The isolation was made from figs, dates, cactus, and traditional fruit vinegars. Four strains, selected from a total of 63 isolates were confirmed to be belonged to Acetobacter species according to biochemical tests and molecular study based on 16s rDNA sequence analysis. Acetic acid fermentation tests, performed on date and apple fermented juices by the selected Acetobacter strains, showed high capacity of acidification. The most efficient strain, isolated from cactus vinegar, yielded an acidity of about 42.5 g/L on apple juice. A cell growth optimization was carried out on the most efficient strain using the response surface methodology (RSM). The linear, quadratic and interaction effects of four factors; ethanol, acetic acid, glucose and pH were studied by the application of a central composite design. 30 experiments were designed to predict the maximum concentration of cell biomass. The optimal calculated values of ethanol, acetic acid, glucose and pH allowing the prediction of the maximum biomass production (2.2 g/L) were 28.18 g/L, 10.12 g/L, 15.15 g/L and 5.33, respectively. Subsequently, further batch fermentations were carried out in a 6 L lab-bioreactor using the optimased culture medium. The results were in line with the predict values. It was concluded that the studied strain is well suited to be used as parental strain to prepare a starter for vinegar fruit production. [less ▲]

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See detailExpression des propriétés biologiques des substances humiques de lixiviats sur le développement racinaire de ligneux
Tahiri, Abdelghani ULiege

Doctoral thesis (2016)

Humic substances (HS) are a dark-colored heterogeneous organic compounds originated from microbial decomposition and chemical degradation of organic matter. The exact structure and composition of HS ... [more ▼]

Humic substances (HS) are a dark-colored heterogeneous organic compounds originated from microbial decomposition and chemical degradation of organic matter. The exact structure and composition of HS macromolecules are not totally elucidated due to their complexity and their structural heterogeneity. They have long been recognized as plant growth promoting substances, particularly with regard to influencing nutrient uptake, root growth and architecture and by improving soil structure. However, the molecular mechanisms through which HS influence plant physiology are not well understood and must be deepened. The aim of this doctoral thesis is to obtain deeper understanding of the biological activity exerted by HS extracted from landfill leachates in comparaison to a commercial formulation extracted from leonardite on roots growth of woody plants in relation to their chemical characterization and mechanisms of action. Three experimental approach have been carried out. The first one concerns a comparative chemical characterization of total HS and derived fractions, separated in function of their solubility and molecular weight, was performed using elemental analysis, UV-vis, FT-IR and 1H NMR spectroscopy and MALDI-TOF mass spectrometry. Obtained results indicate that HS of both origins were basically similar regarding the presence of their chemical structures but, differ mainly in their relative abundance. The second, concerns the development of an in vitro culture model to study the biological activity of HS on the development of root system of two woody pioneer species. The data obtained showed that the effect of HS depends on plant species, concertation, mode of application and source of HS. If the high molecular weight fraction (HA) was effective at promoting root development, the lower ones (FA and OM) inhibit it in function of the concentration used. Finally, a molecular approach was investigated to study some molecular mechanisms that plant act in response to HS comparing the expression of four genes (ABCB1, ABCB19, GS and ADH) implicated respectively in auxin, nitrogen and carbon metabolisms. Obtained data show that HS and their HA fractions influence root growth and development apparently by influencing different mechanism of regulation associated with polar auxin transport, the incorporation of inorganic nitrogen as glutamate, carbon metabolism and abiotic stress responses. Results presented in this thesis showed that landfill leachates HS especially their HA fraction can be valued as bio-stimulant of plant growth. [less ▲]

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See detailComparison of explant responses treated with leachate and leonardite sources of humic substances during in vitro rooting of woody plants.
Tahiri, Abdelghani ULiege; Destain, Jacqueline ULiege; Thonart, Philippe ULiege et al

in Communications in Agricultural and Applied Biological Sciences (2016), 81(1), 158-165

As heterogeneous mixtures of compounds resulting from the physical, chemical and microbiological transformations of organic residues, humic substances (HS) are mostly recognized for their biostimulation ... [more ▼]

As heterogeneous mixtures of compounds resulting from the physical, chemical and microbiological transformations of organic residues, humic substances (HS) are mostly recognized for their biostimulation of plant growth that firstly involve the root development and architecture before further putative improvement of nutrients uptakes. To avoid the interferences currently reported from external origins, the successive steps of rooting have been carried out using shoots and isolated leaves of birch and alder vitro-plants. Extracts issued from landfill leachate (LHS) has been compared to a stable formulation from leonardite ("Humifirst" 12% humic acid 3% and fulvic acid) commercialized by TRADECORP company's (HHS). Chemical analysis showed that LHS source typically contain much higher N (mainly as ammonium (93%) and chloride concentration than HHS. Used at low concentration (10 ppm) during root induction/initiation phase, both HS sources may be slightly unfavorable to the root formation (21% of reduction in primary root number) of alder but not of birch. While, in root elongation phase, there is an increase in the primary root length and lateral root number. The direct effects of HS on in vitro root development vary from one species to another depending on the root treatment stage. Results showed that both explants type response are equivalent in the development of a complete rooting system. [less ▲]

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See detailLeachate and leonardite Humic substances effect on in vitro root initiation and elongation of woody species
Tahiri, Abdelghani ULiege; Destain, Jacqueline ULiege; Thonart, Philippe ULiege et al

Poster (2016, February 05)

Arise from the chemical and biological degradation of plant and animal residues and from the synthetic activities of microorganisms in the soil, humic substances (HS) are natural heterogeneous aromatic ... [more ▼]

Arise from the chemical and biological degradation of plant and animal residues and from the synthetic activities of microorganisms in the soil, humic substances (HS) are natural heterogeneous aromatic and organic compounds. These substances are chemically complex with no clearly defined chemical structure, although generalized models have been proposed. Present everywhere in the nature; they take part in basic functionalities in any ecosystems involving soils, sediments, water and landfills. They have long been recognized as plant growth promoting substances, particularly with regard to influencing nutrient uptake, root growth and architecture. They influence plant productivity directly by the stimulation of biochemical and metabolic processes or indirectly through the modification of soil characteristics and microflora activities. All together, these properties mainly affect root architecture by inducing root hairs proliferation, differentiating root cells and enhancing lateral root emergence. Experiments targeting the rooting stages in absence of interferences were conducted in vitro using HS extracted from landfill leachate and a stable commercial formulation (“Humifirst” from TRADECORP company: 12% humic acid and fulvic acid 3%) issued from leonardite. Shoots and leaves explants of silver birch (Betula pendula Roth) and black alder (Alnus glutinosa L. Gaertn) explants were treated with 10 ppm of leachate and leonardite HS for 5 days during the rooting induction/initiation phase or during rooting elongation phase. The results obtained show that treatment with a low concentration (10 ppm) during induction/initiation phase may be slightly unfavorable to the formation of roots in alder but not in birch. While, in root elongation phase, there is an increase in the number of roots per shoot only in birch. The direct effects of leachate and leonardite HS on root development vary from one species to another. [less ▲]

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See detailSimultaneous production of acetic and gluconic acids by a thermotolerant Acetobacter strain during acetous fermentation in a bioreactor
Mounir, Majid ULiege; shafiei, rasoul; Zarmehrkhorshid, Raziyeh et al

in Journal of Bioscience & Bioengineering (2016), 121(2), 166-171

The activity of bacterial strains significantly influences the quality and the taste of vinegar. Previous studies of acetic acid bacteria have primarily focused on the ability of bacterial strains to ... [more ▼]

The activity of bacterial strains significantly influences the quality and the taste of vinegar. Previous studies of acetic acid bacteria have primarily focused on the ability of bacterial strains to produce high amounts of acetic acid. However, few studies have examined the production of gluconic acid during acetous fermentation at high temperatures. The production of vinegar at high temperatures by two strains of acetic acid bacteria isolated from apple and cactus fruits, namely AF01 and CV01, respectively, was evaluated in this study. The simultaneous production of gluconic and acetic acids was also examined in this study. Biochemical and molecular identification based on a 16s rDNA sequence analysis confirmed that these strains can be classified as Acetobacter pasteurianus. To assess the ability of the isolated strains to grow and produce acetic acid and gluconic acid at high temperatures, a semi-continuous fermentation was performed in a 20-L bioreactor. The two strains abundantly grew at a high temperature (41°C). At the end of the fermentation, the AF01 and CV01 strains yielded acetic acid concentrations of 7.64% (w/v) and 10.08% (w/v), respectively. Interestingly, CV01 was able to simultaneously produce acetic and gluconic acids during acetic fermentation, whereas AF01 mainly produced acetic acid. In addition, CV01 was less sensitive to ethanol depletion during semi-continuous fermentation. Finally, the enzymatic study showed that the two strains exhibited high ADH and ALDH enzyme activity at 38°C compared with the mesophilic reference strain LMG 1632, which was significantly susceptible to thermal inactivation. [less ▲]

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See detailCharacterization and Evaluation of the Potential of a Diesel-Degrading Bacterial Consortium Isolated from Fresh Mangrove Sediment
Semboung Lang, Firmin ULiege; Destain, Jacqueline ULiege; Delvigne, Frank ULiege et al

in Water, Air & Soil Pollution (2016)

Hydrocarbons are ubiquitous and persistent organic pollutants in the environment. In wetlands and marine environments, particularly in mangrove ecosystems, their increase and significant accumulation ... [more ▼]

Hydrocarbons are ubiquitous and persistent organic pollutants in the environment. In wetlands and marine environments, particularly in mangrove ecosystems, their increase and significant accumulation result from human activities such as oil and gas exploration and exploitation operations. Remediation of these ecosystems requires the development of adequate and effective strategies. Natural attenuation, biostimulation, and bioaugmentation are all biological soil treatment techniques that can be adapted to mangroves. Our experiments were performed on samples of fresh mangrove sediments from the Cameroon estuary and mainly from the Wouri River in Cameroon. This study aims to assess the degradation potential of a bacterial consortium isolated from mangrove sediment. The principle of our bioremediation experiments is based on a series of tests designed to evaluate the potential of an active indigenous microflora and three exogenous pure strains, to degrade diesel with/without adding nutrients. The experiments were conducted in laboratory flasks and a greenhouse in microcosms. In one case, as in the other, the endogenous microflora showed that it was able to degrade diesel. Under stress of the pollutant, the endogenous microflora fits well enough in the middle to enable metabolism of the pollutant. However, the Rhodococcus strain was more effective over time. The degradation rate was 77 and 90%in the vials containing the sterile sediments and non-sterile sediments, respectively. The results are comparable with those obtained in the microcosms in a greenhouse where only the endogenous microflora were used. The results of this study show that mangrove sediment contains an active microflora that can metabolize diesel. Indigenous and active microflora show an interesting potential for diesel degradation. [less ▲]

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