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See detailCOMPARISON BETWEEN CONTINUOUS AND BATCH PROCESSING TO PRODUCE XYLANASE BY Penicillium canescens 10-10c
Bakri, Y.; Akeed, Y.; Thonart, Philippe ULg

in Brazilian Journal of Chemical Engineering (2012), 29(3), 441-447

Penicillium canescens 10-10c strain was cultivated on barley straw hydrolysate as a soluble nutrient source and as inducer for xylanase production. Barley straw hydrolysate was obtained by treatment of ... [more ▼]

Penicillium canescens 10-10c strain was cultivated on barley straw hydrolysate as a soluble nutrient source and as inducer for xylanase production. Barley straw hydrolysate was obtained by treatment of barley straw with NaOH or hot water. In shake flask cultures, NaOH treatment was found to increase the biomass production, but was not accompanied by an increase in xylanase production. The best xylanase production (54 U/ml) was observed on hydrolyzed extract from barley straw treated with hot water (100 ºC) for 3 hours. Enzyme production was further improved by scaling up the cultivation process to a 3-L stirred tank bioreactor. For batch cultivations in the bioreactor, the maximum xylanase productivity reached 1.31 and 0.46 U/ml/h, respectively, after 96 and 168 hours of cultivation. However, xylanase productivity reached 3.46 U/ml/h in the continuous culture. These results suggest that xylanase can be produced efficiently by Penicillium canescens 10-10c in continuous culture from an inexpensive source such as barley straw hydrolysate. [less ▲]

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See detailFermentative hydrogen production from glucose and starch using pure strains and artificial co-cultures ofClostridium spp.
Masset, Julien; Calusinska, Magdalena ULg; Hamilton, Christopher et al

in Biotechnology for biofuels (2012), 5(1), 35

ABSTRACT: BACKGROUND: Pure bacterial strains give better yields when producing H2 than mixed, natural communities. However the main drawback with the pure cultures is the need to perform the fermentations ... [more ▼]

ABSTRACT: BACKGROUND: Pure bacterial strains give better yields when producing H2 than mixed, natural communities. However the main drawback with the pure cultures is the need to perform the fermentations under sterile conditions. Therefore, H2 production using artificial co-cultures, composed of well characterized strains, is one of the directions currently undertaken in the field of biohydrogen research. RESULTS: Four pure Clostridium cultures, including C. butyricum CWBI1009, C. pasteurianum DSM525, C. beijerinckii DSM1820 and C. felsineum DSM749, and three different co-cultures composed of (1) C. pasteurianum and C. felsineum, (2) C. butyricum and C. felsineum, (3) C. butyricum and C. pasteurianum, were grown in 20 L batch bioreactors. In the first part of the study a strategy composed of three-culture sequences was developed to determine the optimal pH for H2 production (sequence 1); and the H2-producing potential of each pure strain and co-culture, during glucose (sequence 2) and starch (sequence 3) fermentations at the optimal pH. The best H2 yields were obtained for starch fermentations, and the highest yield of 2.91 mol H2/ mol hexose was reported for C. butyricum. By contrast, the biogas production rates were higher for glucose fermentations and the highest value of 1.5 L biogas/ h was observed for the co-culture (1). In general co-cultures produced H2 at higher rates than the pure Clostridium cultures, without negatively affecting the H2 yields. Interestingly, all the Clostridium strains and co-cultures were shown to utilize lactate (present in a starch-containing medium), and C. beijerinckii was able to re-consume formate producing additional H2. In the second part of the study the co-culture (3) was used to produce H2 during 13 days of glucose fermentation in a sequencing batch reactor (SBR). In addition, the species dynamics, as monitored by qPCR (quantitative real-time PCR), showed a stable coexistence of C. pasteurianum and C. butyricum during this fermentation. CONCLUSIONS: The four pure Clostridium strains and the artificial co-cultures tested in this study were shown to efficiently produce H2 using glucose and starch as carbon sources. The artificial co-cultures produced H2 at higher rates than the pure strains, while the H2 yields were only slightly affected. [less ▲]

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See detailLa production de biohydrogène à partir de substrats carbohydratés : état de l'art
Hiligsmann, Serge ULg; Beckers, Laurent ULg; Masset, Julien ULg et al

in Récents progrès en génie des procédés (2011, December 01)

Hydrogen is being considered as an ideal and clean energy carrier. The recent advances to produce biohydrogen from renewable sources such as biomass and particularly by fermentation of carbohydrate-rich ... [more ▼]

Hydrogen is being considered as an ideal and clean energy carrier. The recent advances to produce biohydrogen from renewable sources such as biomass and particularly by fermentation of carbohydrate-rich substrates from agriculture and agro-industries appear promising. Such a process enables both organic waste treatment and renewable energy production to be coupled. The paper presents the state of the art about the different hydrogen-producing microorganisms and the parameters that have been investigated in order to improve the hydrogen production yields and rates. [less ▲]

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See detailEffets de la pression partielle en hydrogène sur la production anaérobie de bioH2 par une bactérie chimiotrophe du genre Clostridium dans un nouveau réacteur à cylindre horizontal rotatif.
Beckers, Laurent ULg; Hiligsmann, Serge ULg; Hamilton, Christopher ULg et al

in Récents Progrès en Génie des Procédés (2011, December), 101

Hydrogen is widely considered as the most promising energetic carrier. At an industrial scale, steam reforming of methane is currently the major hydrogen producing process. But it may also be produced ... [more ▼]

Hydrogen is widely considered as the most promising energetic carrier. At an industrial scale, steam reforming of methane is currently the major hydrogen producing process. But it may also be produced from renewable biomass. Indeed, the fermentative production of hydrogen from renewable biomass using anaerobic bacteria could at least partially reduce our dependence on fossil fuel, decrease the carbon dioxide emissions and produce “green” energy. It offers the potential production of usable hydrogen from a variety of renewable resources such as carbohydrates wastes from agriculture or agro-food industries. This technology is based on anaerobic fermentation, called dark fermentation, by chemotrophic bacteria. The investigations carried out at CWBI involve selection and characterization of bacteria strains able to produce biohydrogen efficiently and with a wide range of substrate. The selected strains at the laboratory has been characterised as Clostridium sp. In order to produce hydrogen at high yields and production rates, the biotechnological process needs to be further optimized and efficient bioreactors must be designed. At CWBI, a new reactor called “horizontal rotating cylinder bioreactor” allows the production of biohydrogen from glucose with our Clostridium sp. strain with a high yield and production rate. This reactor, working continuously, has an internal volume of 2.3l but a working volume (liquid phase) of 300ml. Firstly, it enhances the hydrogen production rate by partially fixing the bacteria on the porous cylinder and thus increasing the cell concentration in the bioreactor. Secondly, the rotative cylinder enables efficient gas transfer (mainly hydrogen) from the liquid phase where it is produced by the bacteria. This is an important way to enhance hydrogen production yield by allowing the bacteria metabolism to shift in a fermentation type that produces more hydrogen. This was confirmed by increasing or decreasing the total pressure in the bioreactor and observing the influence of hydrogen production. The liquid to gas hydrogen transfer is possibly an important factor to enhance the biogas production. Our investigation confirmed this by testing different liquid to gas transfer condition in BHP test (batch fermentation in 250ml serum bottles).This was made either by decreasing total and partial pressure or by increasing the mixing state of the media. Our work concludes the importance of providing good liquid to gas transfers in the biohydrogen producing reactors to enhance the hydrogen production and reach higher yields and production rates. [less ▲]

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See detailEffects of hydrogen partial pressure on fermentative biohydrogen production by a chemotropic Clostridium bacterium in a new horizontal rotating cylinder reactor
Beckers, Laurent ULg; Hiligsmann, Serge ULg; Hamilton, Christopher ULg et al

Poster (2011, December)

The fermentative production of hydrogen using chemotrophic anaerobic bacteria offers a new way to produce “green” energy from a large variety of renewable resources and organic wastes. In order to produce ... [more ▼]

The fermentative production of hydrogen using chemotrophic anaerobic bacteria offers a new way to produce “green” energy from a large variety of renewable resources and organic wastes. In order to produce hydrogen at high yields and production rates, efficient bioreactors must be designed. A new reactor called “horizontal rotating cylinder bioreactor” allows the production of biohydrogen from glucose with the selected Clostridium sp. strain at high yields (1,9molH2·molglucose-1) and production rates (48,6mmolH2·lmilieu-1.molhexose-1·h-1). The rotative cylinder where the bacteria are fixed enables efficient gas transfer (mainly hydrogen) from the liquid phase where it is produced by the bacteria. This is an important way to allow the bacteria metabolism to shift in a fermentation pathway that produces more hydrogen. This was confirmed by varying the total pressure in the bioreactor. An increase of the total pressure 0,18bar lowered the yields of 19,5% while a decrease of 0,11bar increased the yields of 7%. Our work concludes the importance of providing good liquid to gas transfers in the biohydrogen-producing reactors in order to reach higher yields and production rates. [less ▲]

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See detailModèle hybride Euler-Lagrange pour la description des hétérogénéités dans les bioréacteurs.
Delafosse, Angélique ULg; Delvigne, Frank ULg; Collignon, Marie-Laure ULg et al

in SFGP (Ed.) Récents Progrès en Génie des Procédés - N° 101 - Des procédés au service du produit au coeur de l'Europe - Actes du XIIIème Congrès de la société Française de Génie des Procédés - Du 29 Nov. au 1er Décembre 2011 - Lille Grand Palais, FRANCE (2011, November 29)

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See detailSynthesis by the sol-gel process of visible light sensitive-TiO2 for the degradation of pollutants and microorganisms
Tasseroul, Ludivine ULg; Lambert, Stéphanie ULg; Páez Martínez, Carlos ULg et al

in Récents Progrès en Génie des Procédés, Lavoisier Technique et Documentation, Volume 101, 6 p. (CD-ROM) (2011, November 29)

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR ... [more ▼]

To stabilize the TiO2-dye interaction, free metal tetra(4-carboxyphenyl)porphyrin and nickel tetra(4-carboxyphenyl)porphyrin were introduced into the TiO2 matrix by cogelation rather than by grafting. DR and FT-IR spectroscopies were performed to establish the interaction between porphyrins and TiO2. Cristallinity and specific surface area were performed by XRD and nitrogen adsorption-desorption measurements. The photoactivity of doped-TiO2 xerogels was evaluated for p-nitrophenol and Escherichia coli degradation. Under visible light, the samples allowed the degradation of 40% of p-nitrophenol in 6 h and the elimination of 108 CFU/mL of E. coli in 48 h. [less ▲]

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See detailStratégies de production de 6-amyl-α-pyrone produit par Trichoderma spp. par culture en milieu semi-solide aspergé
Musoni, Michel ULg; Delvigne, Frank ULg; Destain, Jacqueline ULg et al

Conference (2011, November 29)

La biosynthèse de la 6-amyl-α-pyrone (arôme de noix de coco) à partir de l'espèce de Trichoderma a été étudiée dans différents bioréacteurs. L’étude compare la production du volatile dans un réacteur ... [more ▼]

La biosynthèse de la 6-amyl-α-pyrone (arôme de noix de coco) à partir de l'espèce de Trichoderma a été étudiée dans différents bioréacteurs. L’étude compare la production du volatile dans un réacteur classique submergé et un réacteur adapté avec plateau aspergé. La source de carbone était le glucose et l’huile de ricin, ce dernier et reconnu être le précurseur de la formation des lactones dans la biotransformation. Les milieux seront submergé et semi-solide, le volume de travail de 6, 12 et 16 litres. Il ressort des résultats obtenus au cours de l’étude que le composé aromatique est produit par la souche utilisé à partir du deuxième (133.8 mg/l) jour dans l’espace de tête et dans le milieu quand la culture est réalisé avec du glucose jusqu’au quatrième jour, alors qu’avec l’huile de ricin il est retrouvé dans le milieu uniquement (342,23 mg/l). La biomasse produite dans le réacteur de 6 l avec l’huile de ricin est de 279,6 g/l alors que pour le glucose est de 139,75, dans celui de 12 l il de 61,71 g/l avec l’huile de ricin et de 6,37 g/l avec le glucose, et celui de 16 l, 115,66 g/l et le glucose 7,4 g/l, ainsi, plus le volume est petit plus la production est meilleure. Il en va de même pour la concentration du volatile qui était de 2,42 g/l avec l’huile de ricin sur plateau et de 0,28 g/l avec le glucose. Dès lors, Il convient de noter que le système de production du volatile par le réacteur adapté avec plateau aspergé permet l’augmentation de la production de celui-ci, il présente la facilité d’aménagement, avec les contours possible, il offre la possibilité d’être extrapolable. En se référant à la possibilité de renouveler le milieu de culture en faisant circuler le milieu frais, compte tenue du fait que la biomasse est déposée sur les plateaux et qu’à la fin de culture la solution est translucide, retirable après un certain temps, il y découlerait l’amélioration de la productivité. [less ▲]

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See detailPrise en compte l'état de la membrane cellulaire sur la réponse de biocapteurs fluorescents pour la détection de défaut d'écoulement au niveau des bioréacteurs : vers une intégration du "sécrétome" dans la problématique de l'extrapolation
Delvigne, Frank ULg; Brognaux, Alison ULg; Gorret, Nathalie et al

Conference (2011, November 29)

Malgré les nombreuses approches envisagées à ce jour, la dynamique du stress microbien en conditions de culture intensive (procédé fed-batch) est encore un aspect mal maîtrisé. Au cours de ce travail ... [more ▼]

Malgré les nombreuses approches envisagées à ce jour, la dynamique du stress microbien en conditions de culture intensive (procédé fed-batch) est encore un aspect mal maîtrisé. Au cours de ce travail, deux biocapteurs microbiens basés sur le principe de la protéine fluorescente verte (Green Fluorescent Protein ou GFP) ont été mis en œuvre dans des réacteurs scale-down permettant de reproduire les défauts d'écoulement rencontrés dans les bioréacteurs industriels. Les promoteurs de stress associés à la synthèse de la GFP ont été choisis suivant leur sensibilité à la limitation en source de carbone, condition standard qui est rencontrée dans les processus fed-batch ou l'apport en substrat carboné est limité afin d'éviter des déviations du métabolisme microbien (promoteurs rpoS et csiE). Les résultats obtenus montrent clairement que l'exposition des biocapteurs à des hétérogénéités locales de substrat entraîne une diminution de l'expression de la GFP. L'intensité de fluorescence a été mesurée à l'échelle cellulaire par cytométrie en flux. Durant les cultures, une chute significative du niveau de GFP intracellulaire a été observée pour les deux conditions scale-down considérées et pour les deux types de promoteur. Cette chute de fluorescence peut être attribuée à des phénomènes de répression des promoteurs suite à la levée locale de la limitation en carbone, mais également au relargage de la GFP dans le milieu extracellulaire. Ce relargage a été observé dans toutes les conditions opératoires considérées, comme le montrent les analyses des surnageants de culture par SDS-PAGE. L'intensité du relargage est néanmoins plus forte dans les conditions standard de culture (c'est-à-dire dans des réacteurs classiques sans approche scale-down). En effet, la coloration par l'iodure de propidium des biocapteurs cultivés en conditions standards est plus élevée que dans les conditions scale-down, suggérant une perméabilité membranaire plus élevée. Ces résultats offrent des potentialités intéressantes pour l'analyse simultanée de la viabilité cellulaire et de la détection des défauts d'écoulement par l'emploi de biocapteurs microbiens. De plus, les analyses par SDS-PAGE ont montre une grande diversité de protéines relargée en cours de procédé. Cette observation est étonnante du fait de l'emploi de milieux minéraux définis dans toutes les conditions étudiées. L'analyse de ce sécrétome offre des potentialités intéressantes pour la caractérisation des conditions de stress encourues par les micro-organismes au cours des procédés. [less ▲]

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See detailEvolution de la viabilité cellulaire dans les procédés de production de ferments lactiques : effet du type de bactérie sur l'évaluation par cytométrie en flux
Delvigne, Frank ULg; Thiry, Christophe ULg; Pierart, Céline ULg et al

Conference (2011, November 29)

La cytométrie en flux est une technique permettant d'effectuer des analyses au niveau des cellules individuelles. Cette technique a été développée à l'origine pour l'analyse de cellules animales dans des ... [more ▼]

La cytométrie en flux est une technique permettant d'effectuer des analyses au niveau des cellules individuelles. Cette technique a été développée à l'origine pour l'analyse de cellules animales dans des applications à finalité médicale. Ce n'est que dans les années 90 que cette technique a été considérée dans le cadre des cellules microbiennes procaryotes et eucaryotes. Grâce à l'évolution des technologies (laser à l'état solide, progrès dans la maîtrise des micro-écoulements,…), plusieurs développeurs proposent actuellement des cytomètres en flux pour des budgets abordables (environ 30.000 euros). Cette évolution entraîne actuellement un engouement des industriels pour la mise en oeuvre de cette technique pour le suivi de l'évolution des populations microbiennes dans divers procédés : brasserie, vinaigrerie, production de starters pour la boulangerie, production de starters lactiques,… L'intérêt manifesté pour cette technique est simple à comprendre si on considère les techniques actuelles pour l'estimation de la viabilité cellulaire. En effet, celles-ci reposent souvent sur la revification des cellules sur milieu gélosé et comptage des colonies après un temps d'incubation. Le problème fondamental de cette technique repose sur l'utilisation de conditions de culture qui ne sont pas forcément identiques à celle rencontrée au niveau du processus de production. Ce phénomène entraîne une sous-estimation des cellules microbiennes actives rassemblées sous le terme de "viables mais non cultivables". A cela s'ajoutent des problèmes techniques imposés par le temps de remise en culture et l'obtention des résultats bien après que le processus de production soit terminé, ainsi que par des procédures de laboratoire coûteuses en personnel et en consommables. La cytométrie s'impose donc comme une technique de choix qui permet d'analyser les cellules microbiennes individuelles sans étape de remise en culture et avec un débit expérimental élevé. En effet, 30.000 cellules peuvent être analysées en 30 secondes immédiatement après la prise d'échantillon, ce qui permet éventuellement de corriger les conditions de procédés en fonction de l'état des micro-organismes. L'utilisation de fluorochromes spécifiques permet l'analyse de caractéristiques cellulaires. Dans le cas des bactéries lactiques, l'utilisation du couple de colorant "carboxyfluorescéine diacétate" / "iodure de propidium" (cFDA/PI) est mis en oeuvre en routine pour la détermination de la viabilité cellulaire. L'iodure de propidium pénètre dans les cellules ayant une membrane endommagée et les colore en rouge, tandis que le cFDA est un composé non fluorescent qui diffuse au travers de toutes les membranes cellulaires et est hydrolysées par les activités estérases intracellulaires pour donner un composé fluorescent vert. Ces deux composantes de fluorescence peuvent être facilement caractérisées par analyse multi paramétrique au niveau d'un cytomètre en flux. La difficulté majeure que rencontre l'application de la cytométrie en flux au niveau industriel réside dans l'interprétation des résultats. Dans ce travail, trois souches de bactéries lactiques ayant des sensibilités différentes au stress de procédé ont été mise en oeuvre dans des schémas de production industriels faisant intervenir les étapes suivantes : production en bioréacteur agité de 2m³, récolte par centrifugation continue, congélation et lyophilisation. L'analyse par cytométrie en flux montre des tendances fondamentalement différentes pour les trois types de micro-organismes. Les deux souches microbiennes plus sensibles au stress de procédé du fait de leur caractère anaérobie strict ou microaérophile montrent des sous-populations bien distinctes au niveau des cytogrammes, tandis que la souche plus résistante ne montre qu'une seule population évoluant suivant les étapes du procédé. Ces observations sont utilisées pour une meilleure interprétation des cytogrammes pour l'estimation de la viabilité cellulaire en conditions de procédé. Une meilleure interprétation peut également être obtenue en considérant la possibilité de relargage des produits de dégradation fluorescents provenant de l'hydrolyse du cFDA en fonction de l'état de la membrane cellulaire. [less ▲]

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See detailDetermination of optimum conditions for preservation and reactivation of freeze-dried Acetobacter senegalensis used as vinegar starter
Shafiei, Rasoul ULg; Thonart, Philippe ULg

Poster (2011, November)

Availability of efficient starters is one of the most important elements during fermentation technology. Acetic acid bacteria (AAB) face extreme conditions (low pH, high acetic acid concentration (>7 ... [more ▼]

Availability of efficient starters is one of the most important elements during fermentation technology. Acetic acid bacteria (AAB) face extreme conditions (low pH, high acetic acid concentration (>7%), ethanol and high temperature) during vinegar fermentation. In spite of introduction of broth media contained viable AAB as starter by some companies; traditional methods for initiation of vinegar fermentation are still used even in modern factories, therefore there is a long Lag phase for initiation of fermentation. In recent studies in CWBI, a kind of lyophilized starter has been produced by using an isolated thermotolerant bacterium: Acetobacter senegalensis. The aim of this study is to determine the best media for revitalization and the optimum temperature for preservation of the freeze-dried cells. To produce biomass, glucose was used as carbon source in batch culture under regulated conditions. The cells harvested when they reached to stationary phase. Harvested cells suspended in spent growth medium (final supernatant of fermentation). Maltodextrin (10%), manitol (20%) and spent growth medium were used as protestants. After freeze-drying they were subjected to storage test at -20° C, 4° C and 35° C for six months. The viability of cells determined by using spread plate technique using three different media: YG (yeast extract, glucose) and YGE (yeast extract, glucose, ethanol) and YGEA (yeast extract, glucose, ethanol, acetic acid). According to residual viable cells, manitol and maltodextrin showed higher protective functions rather than spent growth medium (92.3%, 88.2% and 82.1% survival, respectively) during freeze-drying process. Viability of cells during rehydration is completely dependent to the composition of the broth media used for this purpose. Adding ethanol (>0.5%) or acetic acid (>1%) to rehydration medium caused 40-45% reduction in viable cell numbers in comparison to YG broth. The composition of culture media can also influence the growth of bacteria after rehydration. In YG, much higher cell growth (about 1 log unit) was observed in comparison to YGE and YGEA. Addition of glucose (20 g/l) to YGE can neutralize the adverse effect of ethanol considerably but it cannot improve the growth in YGEA. This can be partially explained according to the activity of alcohol dehydrogenase and acetaldehyde dehydrogenase. It was revealed that freeze-dried cells had very low activities for these two enzymes. Analysis of total soluble protein contents of lyophilized cells during storage at different conditions revealed that the soluble protein content of cells reduced by increasing the storage temperature. At 35° C after 15 days, there were 4.87 log units reduction in the viability of cells, and also about 14% less soluble protein was detectable under this condition whereas keeping of cells at -20 or + 4° C had no influences on protein and viability of cells. Storage of cells at +4° C in darkness for six month showed that about 79.2% and 68.3% viability of cells remained for cells protected by manitol and maltodextrin, respectively. To assess the real activity of lyophilized cells as starters, they were introduced to broth media (YGE contained 20g/l of glucose). It was seen that 6 months old lyophilized cells (with maltodextrin or manitol as protectants) were able to grow and consume 5 v/v of ethanol in 48 hr in the presence of initial acetic acid concentration (0.5%) at 30° C. In conclusion, the mentioned methods for preservation and reactivation of freeze-dried Acetobacter senegalensis can provide a promising tool for decreasing the lag phase of vinegar fermentation. [less ▲]

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See detailUse of Bacillus subtilis S499 to control mould growth during malting of red sorghum from the D.R. of Congo
Bwanganga Tawaba, Jean-Claude ULg; Destain, Jacqueline ULg; Bera, François ULg et al

Poster (2011, November)

In this work, moulds growth was monitored during malting of a red sorghum from D.R. of Congo. Results obtained with chemical treatments [diluted alkalines: NaOH 0.2% (T1) and Ca(OH)2 0.1% (T2)] were ... [more ▼]

In this work, moulds growth was monitored during malting of a red sorghum from D.R. of Congo. Results obtained with chemical treatments [diluted alkalines: NaOH 0.2% (T1) and Ca(OH)2 0.1% (T2)] were compared with those of biocontrols [use of Bacillus subtilis S499 108 cells / mL: supernatant + cells (T3), cells (T4) and cells-free supernatant (T5)]. Chemical treatments have shown the highest fungal contamination levels, the highest malting loss, but better enzyme activities (α and β-amylases, limit-dextrinase, α-glucosidase and β-glucanase). The inhibition tests showed that the concentration of lipopeptides is correlated with the reduction of moulds growth. Malting trials with starters of Bacillus subtilis S499 showed that culture dilution affects the growth of moulds during red sorghum malting. The combination of a chemical treatment such as diluted NaOH with a biocontrol could be used to improve sorghum malts quality in terms of different enzymes activities and by reducing the level of fungal contamination. Key words: Bacillus subtilis S499, mould, sorghum malting [less ▲]

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See detailFermentative biohydrogen production in a novel biodisc bioreactor: Principle and Improvement
Beckers, Laurent ULg; Hiligsmann, Serge ULg; Masset, Julien ULg et al

in Bozhou, Li (Ed.) Low Carbon Earth Summit 2011 Proceeding (2011, October 23)

In order to produce hydrogen at high yields and production rates, the biotechnological process needs to be further optimized and efficient bioreactors must be designed. A biodisc bioreactor has been ... [more ▼]

In order to produce hydrogen at high yields and production rates, the biotechnological process needs to be further optimized and efficient bioreactors must be designed. A biodisc bioreactor has been design and investigated to produce biohydrogen from glucose by the Clostridium butyricum CWBI1009 strain at a high yield and production rate. This reactor, working continuously, has an internal volume of 2.3l but a working volume (liquid phase) of 300ml. Firstly, it enhances the hydrogen production rate (by about 3 times more than a completely stirred bioreactor) by partially fixing the bacteria on the porous support and thus increasing the cell concentration in the bioreactor (decoupling of HRT and SRT). Secondly, the rotating biodisc design enables efficient gas transfer (hydrogen and carbon dioxyde) from the liquid phase where it is produced by the bacteria to the headspace. Indeed, this is an important way to increase hydrogen production yields (by about 25% compared to a completely stirred bioreactor) by allowing the bacteria to focus on the metabolites pathways that produce more hydrogen. Other reactors designs have shown such good results by increasing the interfacial surface. [less ▲]

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See detailChanges in termites feeding diets for gut micro-organisms selection and further cultivation
Bauwens, Julien ULg; Brasseur, Catherine ULg; Matteotti, Christel ULg et al

Poster (2011, October 02)

Termites gut may overcome important dietary perturbations, initial diversity acting as key point buffering effects on host, although termites possess their own enzymatic system. Some artificial diets ... [more ▼]

Termites gut may overcome important dietary perturbations, initial diversity acting as key point buffering effects on host, although termites possess their own enzymatic system. Some artificial diets permitted a simplification of the lower termites gut symbiotic system, which could be used as first step in symbionts isolation and cultivation. Preliminary assay of cultivation actually gave encouraging results. Proteomic proved to be suitable tool to investigate such a complex system. Nevertheless, for some symbionts very few genes are sequenced, which should lead to more targeted proteomic studies. Protein chromatography will allow to split up the proteome and more accurate analysis. [less ▲]

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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 detailMICRO-H2 – Microbiological production of hydrogen: study of microalgal and bacterial processes
Calusinska, Magdalena ULg; Joris, Bernard ULg; Wilmotte, Annick ULg et al

Poster (2011, September 07)

The project MICRO-H2 aims to study and exploit the microbial (bacterial and algal) production of hydrogen (H2). In addition to building a competence centre around the H2 production by microorganisms and ... [more ▼]

The project MICRO-H2 aims to study and exploit the microbial (bacterial and algal) production of hydrogen (H2). In addition to building a competence centre around the H2 production by microorganisms and the molecular monitoring of the processes, this project tries to address two main socio-economic issues. First, transport and many economic activities will be based on hydrogen energy in the near future. Secondly, many researches and technology developments deal with renewable resources. Therefore, a new integrated technology for a sustainable development should be promoted. Photofermentation and dark-fermentation are the most promising ways to produce biohydrogen. The main advantage of the first process is the complete conversion of substrate, if any, to hydrogen. However, present H2-production rates by microalgae remain low. Therefore, a better understanding of the microalgal hydrogen metabolism and rate improvements by genetic engineering are needed. On the other hand, dark-fermentation achieves at present far higher H2-production rates, but improvements are expected through monitoring and optimisation of bacterial diversity and activity. The objectives about bacterial H2 production were to increase knowledge, stability potentialities and investigation skills about the consortia of bacteria involved in bioreactors treating wastewater rich in carbohydrates to produce biohydrogen. The project focused mainly on the study of the potentialities of different consortia, with a focus on Clostridium strains. Concerning the microalgal production of H2, the objectives were to increase knowledge on the metabolic interactions that determine H2 evolution at the cellular level and to produce new strains with increased ability for H2 production in the two-stage process. [less ▲]

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Peer Reviewed
See detailMicroorganisms from aphid honeydew attract natural enemies and tending ants
Verheggen, François ULg; Leroy, Pascal; Fischer, Christophe ULg et al

Conference (2011, August)

Aphids are some of the most serious pests of cultivated crops worldwide, causing major yield and economic losses. Previous works have demonstrated ants and natural enemies (including ladybeetles and ... [more ▼]

Aphids are some of the most serious pests of cultivated crops worldwide, causing major yield and economic losses. Previous works have demonstrated ants and natural enemies (including ladybeetles and hoverflies) to be able to use aphid volatile chemicals to locate aphid colonies. Here, we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which produces kairomones used by the aphidophagous hoverfly Episyrphus balteatus and the Asian Ladybeetle Harmonia axyridis during their search for prey colonies. Some specific semiochemicals produced by S. sciuri were identified as attractants and ovipositional stimulants. Similarly, we have shown scouts of the aphid tending ant species, Lasius niger, to orientate their foraging behaviour toward an Aphis fabae infested plant and we have demonstrated that the odours released by this aphid honeydew were attractive for ant scouts. Again, bacteria were involved in the production of these honeydew semiochemicals. Interestingly, ant scouts were also able to discriminate honeydew odour from A. fabae (usually attended by L. niger) and A. pisum (unattendedby L. niger). Comparison of the volatile and bacteria composition of both aphid species honeydew were attended. [less ▲]

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See detailEarthworms use odor cues to locate and feed on microorganisms in soil
Zirbes, Lara ULg; Mark, Mescher; Vrancken, Véronique ULg et al

in PLoS ONE (2011), 6(7), 21927

Detailed reference viewed: 56 (13 ULg)