References of "Thonart, Philippe"
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See detailEliciteurs dérivés de rhamnolipides : synthèses, modélisations et activités biologiques
Mayon, Patrick; Ait Barka, Essaid; Baillieul, Fabienne et al

Poster (2013, July 04)

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See detailSuitability of the Weibull 4-parameters model to predict the induction phase of α-amylase production during red sorghum malting when a steep in dilute NaOH is used prior to a resteep in a Bacillus subtilis-S499 based treatment
Bwanganga Tawaba, Jean-Claude ULg; Benjamin Pondo Kouadio; Malumba Kamba, Paul ULg et al

in Journal of the Institute of Brewing (2013)

In previous studies, Bacillus subtilis has been used to control mould growth during red sorghum malting. The use of this biocontrol in steeping liquor has been optimized with some success and the combined ... [more ▼]

In previous studies, Bacillus subtilis has been used to control mould growth during red sorghum malting. The use of this biocontrol in steeping liquor has been optimized with some success and the combined use of a 0.2% NaOH steep, followed by a resteep in a Bacillus subtilis-based biocontrol, has been proposed. The sharpness and variability of the β-amylase peak and the higher levels of β-glucanase obtained in the presence of B. subtilis cells were highlighted. In this work, the suitability of the Weibull 4 Parameters Model to predict sorghum malt α-amylase activity during the enzyme induction stage of red sorghum germination has been compared with those of a 2nd Order Polynomial Model and a General Linear Model. Results obtained showed that the Weibull 4 Parameters Model could be used to predict α-amylase activity, with significant goodness of fit when compared to the 2nd Order Polynomial Model and to the General Linear Model. The effects of steeping treatment (combined use of 0.2% NaOH and Bacillus subtilis S499 starters) and the germination temperature are presented. When the Bacillus subtilis culture used as a starter was diluted, the treatment efficacy to develop α-amylase activity was lost. This study also showed that the germination temperature affected the α-amylase activity rate increase during the induction phase. [less ▲]

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See detailIsolation and Cultivation of a Xylanolytic Bacillus subtilis Extracted from the Gut of the Termite Reticulitermes santonensis
Tarayre, Cédric ULg; Brognaux, Alison ULg; Brasseur, Catherine ULg et al

in Applied Biochemistry and Biotechnology (2013)

The aim of this work was the isolation of xylanolytic microorganisms from the digestive tract of the termite Reticulitermes santonensis. The reducing sugars released after the hydrolysis of xylans can be ... [more ▼]

The aim of this work was the isolation of xylanolytic microorganisms from the digestive tract of the termite Reticulitermes santonensis. The reducing sugars released after the hydrolysis of xylans can be further fermented to provide bioethanol. A xylanolytic strain of Bacillus subtilis was isolated from the hindgut of the termite and displayed amylase and xylanase activities. The bacterium was grown on media containing agricultural residues: wheat bran, wheat distiller’s grains, and rapeseed oil cake. Wheat bran led to the highest induction of xylanase activity, although the development of the strain was less fast than in the other media. It was possible to reach maximal xylanase activities of 44.3, 33.5, and 29.1 I.U./ml in the media containing wheat bran, wheat distiller’s grains, and rapeseed oil cake, respectively. Mass spectrometry identified a wide range of xylose oligomers, highlighting an endoxylanase activity. The enzyme was stable up to 45 °C and displayed an optimal pH close to 8. [less ▲]

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See detailPhysiological response of yeast to process perturbations: A mini-bioreactor approach
Lejeune, Annick ULg; Delvigne, Frank ULg; Thonart, Philippe ULg

in Cerevisia : Belgian Journal of Brewing and Biotechnology (2013), 38(1), 15-19

Large-scale production of yeast (Saccharomyces cerevisiae) is difficult to control, considering the drop of mixing and mass transfer efficiency during scale-up. The drop of hydrodynamic efficiency in ... [more ▼]

Large-scale production of yeast (Saccharomyces cerevisiae) is difficult to control, considering the drop of mixing and mass transfer efficiency during scale-up. The drop of hydrodynamic efficiency in large-scale bioreactors induces the formation of heterogeneities, i.e. mainly substrate and dissolved oxygen in process conditions. These extracellular fluctuations have several impacts at the level of the physiology of microorganisms, from metabolic shift to specific gene expression (stress response). Microbial cell responses to extracellular fluctuations are actually not fully understood. In this work, we propose to reproduce the main extracellular fluctuations at the level of a mini bioreactor platform. These mini-reactors are shake flasks equipped with dissolved oxygen probes. The cultures are realized with different fed-batch control strategies. A scale-down approach has been developed by considering slow release techniques and intermittent feeding, in order to reproduce the glucose and dissolved oxygen fluctuations experienced in large-scale reactors. The mini-reactor has been used to screen the response of several green fluorescent protein (GFP) reporter strains (adh2, tps2, pdc6 and hxt2). The GFP content of cells has been determined by flow cytometry in order to take into account population heterogeneity. In front of these results, the methodology presented in this work can be proposed as a scale-down tool. [less ▲]

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See detailIsolation and cultivation of cellulolytic and xylanolytic bacteria and molds extracted from the gut of the termite Reticulitermes santonensis (3DV.1.14)
Tarayre, Cédric ULg; Bauwens, Julien ULg; Mattéotti, Christel et al

Poster (2013, June)

Biofuel production can be based on the use of agro-residues, consisting in a complex lignocellulosic structure which is not easily hydrolysable. The digestive tract of the termite Reticulitermes ... [more ▼]

Biofuel production can be based on the use of agro-residues, consisting in a complex lignocellulosic structure which is not easily hydrolysable. The digestive tract of the termite Reticulitermes santonensis contains a diversified microflora able to hydrolyze the wood components. Bacteria, molds and protists form efficient consortia, able to break the lignocellulosic complex by producing enzymes, such as xylanases and cellulases. Our purpose is the isolation of microbial strains from termite guts in order to evaluate their potential for hydrolysis of lignocellulosic materials. Termites were fed using different diets chosen to improve the xylanolytic and cellulolytic microflora: wood, microcristalline cellulose (added with lignin or not), α-cellulose (added with lignin or not) and birchwood xylan. Then, dissections were realized to isolate the potential xylanolytic and cellulolytic strains. This approach led us to isolate and to study several strains of bacteria (Bacillus sp. strain CTGx and Chryseobacterium sp. strain CTGx) and molds (Trichoderma virens strain CTGx and Sarocladium kiliense strain CTGx). These microorganisms were able to hydrolyze starch, xylan, cellulose, carboxymethylcellulose, esculin, β-glucan and Whatman® filter paper. They can produce glucose and xylose monomers and oligomers which can be further fermented to produce bioethanol. [less ▲]

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See detailResearch of New Enzyme Producing Strains in the Gut of the Termite Reticulitermes santonensis
Tarayre, Cédric ULg; Bauwens, Julien ULg; Mattéotti, Christel et al

Poster (2013, June)

Termites contain a complex microflora inside of their guts. Inferior termites contain bacteria, mycetes and protists that interact to degrade vegetable components. These strains act as consortia to break ... [more ▼]

Termites contain a complex microflora inside of their guts. Inferior termites contain bacteria, mycetes and protists that interact to degrade vegetable components. These strains act as consortia to break natural materials by secreting various enzymes. Our aim was the isolation and cultivation of microorganisms in order to produce new enzymes that can be further used in green chemistry. Termites were fed with different diets: pinewood, microcristalline cellulose (added with lignin or not), α-cellulose (added with lignin or not) and birchwood xylan. Then, dissections were realized to isolate interesting strains. All the microorganisms were subjected to enzyme assays. That technique allowed us to isolate and to cultivate various strains of bacteria, molds and protists. Three strains of bacteria, two strains of molds and one strain of protist were isolated and displayed different enzymatic activities. The bacteria Bacillus subtilis strain ABGx, Bacillus sp. strain CTGx and Chryseobacterium sp. strain CTGx displayed amylase, cellulase and xylanase activities. The molds Trichoderma virens strain CTGx and Sarocladium kiliense strain CTGx were also able to produce those enzymes. However, the protist Poterioochromonas sp. was found to produce only amylase. In conlusion, the termite gut is a complex culivation medium that provides a habitat for many microorganisms that show interesting enzymatic activities. [less ▲]

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See detailChange in viability of Acetobacter senegalensis cells during gluconic acid fermentation at high temperature
Zarmehrkhorshid, Raziyeh ULg; Shafiei, Rasoul ULg; Thonart, Philippe ULg

Poster (2013, June)

Introduction: Gluconic acid (GA) is a multifunctional carbonic acid with versatile applications in food, beverage and pharmaceutical industries. Although the production of GA and its derivative dating ... [more ▼]

Introduction: Gluconic acid (GA) is a multifunctional carbonic acid with versatile applications in food, beverage and pharmaceutical industries. Although the production of GA and its derivative dating backs decades, but use of this acid and its derivatives due to high prices is currently restricted. Using a thermotolerant bacterium in production of this acid at high temperature can provide a new option for industrially cost effective production. However, fermentation productivity may be negatively affected by factors (such as high temperature) leading to loss of cell viability. Objectives: In this study, the ability of a thermotolerant bacterium, Acetobacter senegalensis, in gluconic acid production at high temperature and its survival responses to some factors including temperature and carbon sources were evaluated. Materials and Method: Different batch fermentation processes were carried out at 38 °C, and then cell viability (total dehydrogenase activity) and culturability were assessed using flow cytometry and plate counting techniques, respectively. Results: A. senegalensis oxidized 95 g/L of glucose to gluconic acid at 38 °C. In exponential growth phase, cells were less subjected to damages; but upon transition of cells to stationary phase, cell viability and culturability reduced. Consequently, due to the lack of dehydrogenase activity the specific rate of glucose consumption and gluconic acid production decreased dramatically. High temperature (38 °C), oxidation of high amount of glucose and accumulation of inhibitory compounds (possibly gluconic acid) were dominant inducers leading cells into a viable but non-culturable state (VBNC) during the course of stationary phase. In contrast, presence of ethanol accompanied with glucose, and low incubation temperature assisted in resuscitation of senescent cells of stationary phase. Conclusions: A. senegalensis is able to produce gluconic acid at 38 °C. But, due to entrance of cells into VBNC state during stationary phase, the performance of batch fermentation is adversely affected. [less ▲]

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See detailEffect of the use of dilute alkaline prior to Bacillus subtilis-based biocontrol steeping and germination conditions on red sorghum malt β-glucanase activities and residual β-glucans
Bwanganga Tawaba, Jean-Claude ULg; Destain, Jacqueline ULg; Malumba Kamba, Paul ULg et al

in Journal of Cereal Science (2013)

Malting is the ideal stage to deal with β-glucans. Their hydrolysis is very important as the diffusion of both hormones and hydrolytic enzymes in the endosperm of germinated grain depend on it. A high ... [more ▼]

Malting is the ideal stage to deal with β-glucans. Their hydrolysis is very important as the diffusion of both hormones and hydrolytic enzymes in the endosperm of germinated grain depend on it. A high malt β-glucanase activity is not a guarantee of an extensive hydrolysis of β-glucans. When Bacillus subtilis is used to control mould growth, red sorghum malt β-glucanase activity (measured using carboxymethylcellulose as the substrate) was improved without significantly affecting the hydrolysis of malt β-glucans. Thus, in order to reduce the residual β-glucans content, soaking in 0.2% NaOH was combined with a biocontrol. Soaking in 0.2% NaOH is recognized as capable of improving grain hydration by opening-up the endosperm cell walls. The combined use of 0.2% NaOH with Bacillus subtilis-based biocontrol treatments during red sorghum malting, leads to malt with increased β-glucanase activity and a significant reduction of residual β-glucans when compared with the 16 h biocontrol steeping without prior steeping in 0.2% NaOH. β-glucanase activity increases with increased germination temperature and time while, conversely, the residual β-glucans content of the malts decreases. Indeed, while the level of β-glucanase was not vastly different between the malts obtained after steeping in distilled water and those obtained after 8 h steeping in 0.2% NaOH followed by 8 h resteeping in distilled water (NaOH+H2O treatment), their residual β-glucans levels differ significantly. Bacillus subtilis-based treatment leads to malt with improved β-(1-3)- and β-(1-4)-glucanase activities without significantly improved malt β-(1-3),(1-4)-glucanase activity. While malts obtained after 84 h germination weren’t significantly different in terms of malt β-(1-3),(1-4)-glucanase activities for all steeping treatments, the use of 0.2% NaOH steeping prior to resteeping led to malts with improved β-glucans content. Combining the steeping in dilute alkaline and biocontrol enables taking advantage of the dilute alkaline effect on residual β-glucans content, due probably to the opening-up the cell walls and the improvement of water uptake, and that of the biocontrol (improvement of β-glucanase synthesis). [less ▲]

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See detailOptimisation de la production de Pseudomonas fluorescens BTP1 en fermenteur.
Mputu Kanyinda, Jean-Noël; Thonart, Philippe ULg

in International Journal of Microbiology Research (2013), 5(1), 370-373

The optimisation of production and freeze-drying of P. fluorescens used as a bio-control agent was investigated. P. fluorescens BTP1 was produced in a bioreactor with different against-pressure value (0.1 ... [more ▼]

The optimisation of production and freeze-drying of P. fluorescens used as a bio-control agent was investigated. P. fluorescens BTP1 was produced in a bioreactor with different against-pressure value (0.1 and 0.3 bar for bioreactor 1 and 2 respectively) and cells were harvested during the stationary phase (2 h and 4 h for bioreactor 1 and 2 respectively). A mixture of protective compounds were tested for freeze-drying, and the highest result was found for glycerol and maltodextrine (26%) followed by glycerol, maltodextrine and ascorbic acid (18.9%) and glycerol with ascorbic acid (8.5%). We observed that the survival rate is better at 4°C than at room temperature and those powders with protective compounds have a survival rate greater than the powder without protective compounds during storage. [less ▲]

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See detailFlow-cytometric assessment of damages to Acetobacter senegalensis during freeze-drying process and storage
Shafiei, Rasoul ULg; Delvigne, Frank ULg; Thonart, Philippe ULg

in Acetic Acid Bacteria (2013), 2(2(s1)), 10

Downstream processes have great influences on bacterial starter production. Different modifications occur to cellular compounds during freeze-drying process and storage of bacterial starters. Consequently ... [more ▼]

Downstream processes have great influences on bacterial starter production. Different modifications occur to cellular compounds during freeze-drying process and storage of bacterial starters. Consequently, viability and culturability (multiplication capacity) undergo some changes. In this study, the effects of freeze-drying process and storage conditions were examined on cell envelope integrity, respiration and culturability of Acetobacter senegalensis. <br />Freezing of cells protected with mannitol (20% w/w) did not affect cell multiplication and respiration considerably; however, 19% of cells showed compromised cell envelope after freezing. After drying, 1.96×1011 CFU/g were enumerated, indicating that about 34% of the <br />cells could survive and keep their culturability. Drying of the cells induced further leakage in cell envelope and finally 81% of cells appeared as injured ones; however, 87% of the dried cells maintained their respiration capacity. Storage temperature had significant effect on cell multiplication ability; higher storage temperature (35°C),caused 8.59-log reduction in cell culturability after nine-month period of storage. Collapse of cell envelop integrity and respiration wasobserved at 35°C. At lower storage temperature (4°C), the culturability <br />decreased about one-log reduction after nine months. Cell envelope integrity was subjected to minor changes during a period of nine month-storage at 4°C whereas a heterogeneous population of cells with different respiration capacity emerged at 4°C. These results indicate that a major part of cells undergone drying process and storage entered into viable but non-culturable state. In addition, usage of different culture media didn’t improve resuscitation. Besides, it seems that sub-lethal damages to cell envelope caused uptake of propidium iodide, however these kinds of injuries could not impress cell multiplications and respiration. [less ▲]

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See detailEvaluation of viability and growth of Acetobacter senegalensis under different stress conditions
Shafiei, Rasoul ULg; Thonart, Philippe ULg; Delvigne, Frank ULg et al

in International Journal of Food Microbiology (2013)

Acetic acid bacteria (AAB) are used in production of vinegars. During acetic acid fermentation, AAB encounter various aggressive conditions which may lead to a variety of cellular disorders. Previous ... [more ▼]

Acetic acid bacteria (AAB) are used in production of vinegars. During acetic acid fermentation, AAB encounter various aggressive conditions which may lead to a variety of cellular disorders. Previous researches mainly studied the influences of different carbon sources on tolerance of AAB to ethanol and acetic acid. In this study, different techniques were used comparatively to investigate the effects of preadaptation on the ability of A. senegalensis to tolerate ethanol and acetic acid. In general, the carbon sources used for preadaptation of A. senegalensis exhibited significant effects on the tolerance of cells to stressors. Flow-cytometric assessments of preadapted cells in ethanol showed that 87.3% of the cells perform respiration after exposure to a stress medium containing 5% (v/v) ethanol and 3% (w/v) acetic acid. However, 58.4% of these preadapted cells could keep their envelope integrity under the stress condition. They could also grow rapidly (μmax = 0.39/h) in the stress medium (E5A3) with a high yield (>80%). A. senegalensis grown in glucose exhibited a low tolerance to acetic acid. Analysis of their respiration capacity, membrane integrity and culturability revealed that almost all the population were dead after exposure to 5% (v/v) ethanol and 3% (w/v) acetic acid. In contrast, exposure of A. senegalensis preadapted in a mixture of glucose and acetic acid to a stress medium containing 5% (v/v) ethanol and 3% (w/v) acetic acid, exhibited an intact respiration system and cellular membrane integrity in 80.3% and 50.01% of cells, respectively. Moreover, just 24% of these cells could keep their culturability under that stress condition. [less ▲]

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