References of "Thonart, Philippe"
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See detailScalable temperature induced stress for the large-scale production of functionalized Bifidobacteria
Nguyen, Huu Thanh ULg; Razafindralambo, Hary; Richel, Aurore ULg et al

in Journal of Industrial Microbiology & Biotechnology (in press)

The application of sub-lethal stresses is known to be an efficient strategy to enhance survival of probiotic bacteria during drying processes. In this context, we previously showed that the application of ... [more ▼]

The application of sub-lethal stresses is known to be an efficient strategy to enhance survival of probiotic bacteria during drying processes. In this context, we previously showed that the application of heat stress upon the entry into stationary phase increased significantly the viability of Bifidobacterium bifidum. However, this heat shock has been considered only in small scale bioreactor and no information is available for a possible scaling-up strategy. Five different operating scales (0.2 L, 2 L, 20 L, 200 L and 2000 L) have thus been tested and the results showed that the viability of B. bifidum increases from 3.15 to 6.57 folds, depending on the scale considered. Our observations pointed out the fact that the heat stress procedure is scalable according to the main outcome, i.e. increases in cell viability, but other factors have to be taken into account. Among these factors, dissolved carbon dioxide seems to play a significant role since it explain the differences observed between the test performed at lab-scale and in industrial conditions. [less ▲]

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See detailPhysiological and bio-functional properties of gum arabic: a notable interest for certain human diseases
Eloundou Mballa, Pierre; Goffin, Dorothée ULg; Destain, Jacqueline ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (in press)

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See detailERT to monitor the bioremediation of hydrocarbons with Rhodococcus erythropolis T902.1 at a pilot scale
Masy, Thibaut ULg; Caterina, David; Tromme, Olivier et al

Conference (2015, June 30)

Petroleum hydrocarbons (HC) represent the most widespread contaminants in the world and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the ... [more ▼]

Petroleum hydrocarbons (HC) represent the most widespread contaminants in the world and in-situ bioremediation remains a competitive treatment in terms of cost and environmental concerns. However, the efficiency of such a technique (by biostimulation or bioaugmentation) strongly depends on numerous environmental characteristics (heterogeneities of the subsurface structure, soil moisture, oxygen and pollutants bioavailability, microbial niches…) and is still difficult to predict a priori. In order to lower these uncertainties, Electrical Resistivity Tomography (ERT) appears as a valuable non-invasive tool to detect soil heterogeneities and to monitor biodegradation. The main objective of this study was thus to isolate with ERT an electrical signature corresponding to an enhanced biodegrading activity, in an aged HC-contaminated clay loam soil. To achieve it, a pilot tank with metric dimensions (3.6 × 0.9 × 0.6 m) and a recirculating system (which is quite unique for this type of purpose) was built to mimic field conditions and to control the evolution of the bio-physico-chemical parameters (microbial concentration in soil and groundwater, temperature, pH, pO2, redox potential, bulk and fluid conductivities, water flow, hydrocarbon content) through time and space. Five panels of electrodes were placed at different locations in the tank to detect lithological heterogeneities and to monitor the bulk resistivity variations with time-lapse ERT. Compared to a first insufficient biostimulation phase with H2O2 and KNO3, bioaugmentation with Rhodococcus erythropolis T902.1 led to a HC depletion of almost 80% (6900 to 1600 ppm) in 3 months in the center of the contaminated clay, where pollutants were less bioavailable. Furthermore, lithological heterogeneities (clay, sand, gravels) and microbial activities (growth, degradation and biosurfactant production) were successfully discriminated by ERT images obtained during both remediation phases. In the future, this cost-effective technique should be transferred to the field in order to either (i) detect and forecast biodegradation processes before choosing an appropriate remediation technique, or (ii) monitor the efficiency of this biodegradation during an in-situ bioremediation. [less ▲]

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See detailIn vitro model to study the biological properties of humic fractions from landfill leachate and leonardite during root elongation of Alnus glutinosa L. Gaertn and Betula pendula Roth.
Tahiri, Abdelghani ULg; Destain, Jacqueline ULg; Thonart, Philippe ULg et al

in Plant Cell, Tissue & Organ Culture (2015), 122(3), 739-749

Humic substances (HS) are organic compounds resulting from the physical, chemical and microbiological transformations of organic residues. Our study aims to determine the main biological properties of HS ... [more ▼]

Humic substances (HS) are organic compounds resulting from the physical, chemical and microbiological transformations of organic residues. Our study aims to determine the main biological properties of HS comparing landfill leachate (LHS) source to a stable formulation extracted from leonardite (HHS), and using an in vitro system of root development from shoot and leaf explants of silver birch (Betula pendula Roth) and black alder (Alnus glutinosa L. Gaertn). Results showed that both explants of both species rooted closely to 100% when cultivated in absence of HS. The incorporation of HS or their fractions into the culture medium affect root growth, mainly lateral roots formation and primary root length. Applied at low concentration (10 ppm) HS stimulated especially primary root growth. But at high concentration (100 ppm), LHS inhibited root formation of alder, while birch was more tolerant. The application of 100 ppm of HHS, did not affect alder root growth but increased root growth in birch. Humic acids fractions (HA) were favorable and improved root growth while, fulvic acids (FA) and other molecules (OM) decreased significantly root growth, especially those extracted LHS. The root inhibition expressed at high LHS concentration may be due to the presence of different toxic molecules and root growth inhibitors in OM and FA fractions and that some of them remained in the OM fraction from leonardite. [less ▲]

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See detailMicrobial diversity and function during different bioremediation strategies of diesel-polluted soil
Masy, Thibaut ULg; Hiligsmann, Serge ULg; Thonart, Philippe ULg et al

Poster (2015, June 16)

In numerous hydrocarbon-polluted sites, oxygen and pollutant bioavailability constitutes the main limiting factors for biodegradation because of the strong adsorption of hydrocarbons on organic soil ... [more ▼]

In numerous hydrocarbon-polluted sites, oxygen and pollutant bioavailability constitutes the main limiting factors for biodegradation because of the strong adsorption of hydrocarbons on organic soil particles (clay and peat). Therefore, several strategies such as biostimulation (with air/H2O2 and/or nutrients) or bioaugmentation are used, but often without understanding the endogenous microflora degrading capacity. This lack of differentiation between indigenous and added microorganisms could lead to poor predictability of the biodegradation efficiency. In addition, anaerobic degradation remains less applied in industrial settings for such compounds (especially for saturated hydrocarbons) as this process remains slow. In this context, the main objective of our study was to understand how the bacterial community evolves, in terms of species and degrading gene diversities, during the application of three different bioremediation strategies in a heavily diesel-polluted clay soil: (i) anaerobic natural attenuation, (ii) bioventing and (iii) bioaugmentation with Rhodococcus erythropolis T902.1. In addition to the supply of new degrading genes, bioaugmentation with this biosurfactant-producing strain should facilitate the bioassimilation of desorbed hydrocarbons by the whole degrading microflora. This hypothesis is strengthened by previous results obtained during several microcosm- and pilot-scale experiments. Aerobic and anaerobic microcosms were set up with three different soil samples coming from the same polluted site. Initially, their global organic content was identical but their hydrocarbon and peat concentrations were different, which led to differential oxygen consumption. Soils were sampled every 10 days to extract the DNA to measure changes in bacterial populations (with RISA analysis and 16S rRNA gene sequencing) and function (with qPCR and sequencing of degrading genes). Further analyses of the hydrocarbon content by GC-MS and of the genetic diversity by MiSeq metagenomic analysis provided detailed chemical and functional microbial data related to compound degradation and relative gene increases. Initial results showed significant differences in the microbial community structure. Moreover, Rhodococci seem to be maintained in the soil after inoculation. [less ▲]

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See detailComparative biochemical analysis after steam pretreatments of lignocellulosic biomass from six combined morphological parts of Williams Cavendish banana plant (Triploid Musa AAA group)
Kamdem, Irenée ULg; Jacquet, Nicolas ULg; Tiappi Deumaga, Mathias Florian ULg et al

in Waste Management & Research : The Journal of the International Solid Wastes & Public Cleansing Association (2015)

The accessibility of fermentable substrates to enzymes is a limiting factor for the efficient bioconversion of agricultural wastes in the context of sustainable development. This paper presents the ... [more ▼]

The accessibility of fermentable substrates to enzymes is a limiting factor for the efficient bioconversion of agricultural wastes in the context of sustainable development. This paper presents the results of a biochemical analysis performed on Williams Cavendish Lignocellulosic Biomass (WCLB) after steam cracking (SC) and steam explosion (SE) pretreatments. Solid (S) and liquid (L) fractions (Fs) obtained from SC pretreatment performed at 180°C (SLFSC180) and 210°C (SLFSC210) generated, after diluted acid hydrolysis, the highest proportions of neutral sugar (NS) contents, specifically 52.82±3.51 and 49.78±1.39 %w/w WCLB’s dry matter (DM), respectively. The highest proportions of glucose were found in SFSC210 (53.56±1.33 %w/w DM) and SFSC180 (44.47±0.00 %w/w DM), while the lowest was found in unpretreated WCLB (22.70±0.71 %w/w DM). Total NS content assessed in each LF immediately after SC and SE pretreatments was less than 2 %w/w of the LF’s DM, thus revealing minor acid autohydrolysis consequently leading to minor NS production during the steam pretreatment. WCLB subjected to SC at 210°C (SC210) generated up to 2.7-fold bioaccessible glucan and xylan. SC and SE pretreatments showed potential for the deconstruction of WCLB (delignification, depolymerisation, decrystallization and deacetylation), enhancing its enzymatic hydrolysis. The concentrations of enzymatic inhibitors such as 2-furfuraldehyde and 5-(hydroxymethyl)furfural from LFSC210 were the highest (41 and 21 µg mL-1, respectively). This study shows that steam pretreatments in general and SC210 in particular are required for efficient bioconversion of WCLB. Yet, biotransformation through biochemical processes (e.g., anaerobic digestion) must be performed to assess the efficiency of these pretreatments. [less ▲]

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See detailMultiple analyses of microbial communities applied to the gut of the wood-feeding termite Reticulitermes flavipes fed on artificial diets
Tarayre, Cédric ULg; Bauwens, Julien ULg; Mattéotti, Christel et al

in Symbiosis (2015)

The purpose of this work was the observation of the differences between the microbial communities living in the gut of the termite Reticulitermes flavipes fed on different diets. The termites were fed on ... [more ▼]

The purpose of this work was the observation of the differences between the microbial communities living in the gut of the termite Reticulitermes flavipes fed on different diets. The termites were fed on poplar wood (original diet) and artificial diets consisting of crystalline cellulose (with and without lignin), α-cellulose (with and without lignin) and xylan. The termites were then dissected and the protist communities were analyzed through microscopy, leading to the conclusion that protist species are strongly influenced by diets. BIOLOG ECO Microplates® were used to assess the metabolic properties of the different types of consortia, highlighting strong differences on the basis of principal component analysis and calculation of similarity rates. The microorganisms were cultivated in liquid media corresponding to the artificial diets before being characterized through a metagenetic analysis of gut microbiota (16S ribosomal DNA). This analysis identified several phyla: Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Fibrobacteres, Firmicutes, Nitrospirae, OP9, Planctomycetes, Proteobacteria, Spirochaetes, TM6, Tenericutes, Verrucomicrobia and WS3. The OTUs were also determined and confirmed the abundance of Proteobacteria, Bacteroidetes, Firmicutes and Verrucomicrobia. It was possible to isolate several strains from the liquid media, and one bacterium and several fungi were found to produce interesting enzymatic activities. The bacterium Chryseobacterium sp. XAvLW produced α-amylase, β-glucosidase, endo-1,4-β-D-glucanase, endo-1,4-β-D-xylanase and filter paper-cellulase, while the fungi Sarocladium kiliense CTGxxyl and Trichoderma virens CTGxAviL generated the same activities added with endo-1,3-β-D-glucanase. [less ▲]

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See detailBacteria may enhance species association in an ant-aphid mutualistic relationship
Fischer, Christophe ULg; Lognay, Georges ULg; Detrain, Claire et al

in Chemoecology (2015)

The mutualistic relationships between certain ant and aphid species are well known, the primary benefits being protection for the aphids and carbohydrate-rich honeydew for the ants. Questions remain ... [more ▼]

The mutualistic relationships between certain ant and aphid species are well known, the primary benefits being protection for the aphids and carbohydrate-rich honeydew for the ants. Questions remain, however, as to the exact semiochemical factors that establish and maintain such relationships. In this study we used a series of treatments and associated controls placed at the end of a two-way olfactometer to determine the degree of attractiveness of a complete plant-aphid-honeydew system as well as individual components of that system. Both the olfactometer branch selected by the black garden ant (Lasius niger), and the linear speed with which ants moved through the device, were measured. Study results showed that ants were attracted not just to the complete plant system and the honeydew itself, but also to the microbial flora in the absence of plant or honeydew, and specifically to a bacterium from the black bean aphid (Aphis fabae) honeydew, Staphylococcus xylosus. This bacterium produces a blend of semiochemicals that attract the ant scouts. This information suggests the presence of a naturally-occurring, reliable biotic cue for detection of potential aphid partners. This would have to be confirmed in natural conditions by further field experiments. Rather than being opportunistic species that coincidentally colonize a sugar-rich environment, microorganisms living in aphid honeydew may be able to alter emissions of volatile organic compounds (VOCs), thus significantly mediating partner attraction. A bacterial involvement in this mutualistic relationship could alter the manner in which these and similar relationships are viewed and evaluated. Future studies into mutualism stability and function among macroscopic partners will likely need to transition from a two-partner perspective to a multiple-partner perspective, and consider the microbial component, with the potential for one or more taxa making significant contributions to the relationship [less ▲]

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See detailEffect of iron nanoparticles synthesized by a sol-gel process on Rhodococcus erythropolis T902.1 for biphenyl degradation
Wannoussa, Wissal ULg; Masy, Thibaut ULg; Lambert, Stéphanie ULg et al

in Journal of Water Resource and Protection (2015), 7

Nanoparticles (NPS) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NPS ... [more ▼]

Nanoparticles (NPS) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NPS encapsulated in porous silica (SiO2) on the biphenyl biodegradation by Rhodococcus erythropolis T902.1 (RT902.1). The iron NPS (major iron oxide FexOy form) were dispersed in the porosity of a SiO2 support synthesized by sol-gel process. These Fe/SiO2 NPS offer a stimulating effect on the biodegradation rate of biphenyl, an organic pollutant that is very stable and water-insoluble. This positive impact of NPS on the microbial biodegradation was found to be dependent on the NPS concentration ranging from 10−6 M to 10−4 M. After 18 days of incubation the cultures containing NPS at a concentration of 10−4 M of iron improved RT902.1 growth and degraded 35% more biphenyl than those without NPS (positive control) or with the sole SiO2 particles. Though the microorganism could not interact directly with the insoluble iron NPS, the results show that about 10% and 35% of the initial 10−4 M iron NPS encapsulated in the SiO2 matrix would be incorporated inside or adsorbed on the cell surface respectively and 35% would be released in the supernatant. These results suggest that RT902.1 would produce siderophore-like molecules to attract iron from the porous silica matrix. [less ▲]

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See detailManufacturing of Kivuguto milk and stability in storage under refrigeration
Karenzi, Eugène; Fauconnier, Marie-Laure ULg; Destain, Jacqueline ULg et al

in European Scientific Journal (2015), 11(3), 1-16

The kivugutomilk was processed in a 20 liters bioreactor with three bacteria previously selected in kivuguto traditional milk. The work aimed to study the association of three bacteria previously selected ... [more ▼]

The kivugutomilk was processed in a 20 liters bioreactor with three bacteria previously selected in kivuguto traditional milk. The work aimed to study the association of three bacteria previously selected in traditional kivuguto in order to reproduce it in a controlled fermentation, and thereafter to understand its stability during storage under refrigeration. Postacidification, viability, proteolysis, flavor compounds as well as rheological characteristics were monitored for 36 days. The ph decreases from 4.54 to 4.45 and the titratable acidity grew from 73°d to 79°d. The final biomass after storage was 0.60 108 cfu.g-1 which is far higher than the recommended 106 cells.g-1before consumption. The proteolysis was at a range of 3.0 to 7.0 mg.l-1of lysine equivalent, which is too low so that it can’t produce bitter peptides. The evolution of flavor compounds in storage showed that no change found with 3-methylbutan-1-ol, acetic acid and furan-2(5h)-one, whilst pentan-1-ol and furanmethan-2-ol increased slightly upon 24 days’ storage. The complex viscosity decreased from 4 - 5.3 pas before storage to 2.9 - 4.0 pas corresponding respectively to the ratio g''/g' of about 0.3-0.4 with a very low variation. These data allowed the production and the good preservation of kivuguto milk at 4°c on 36 days. [less ▲]

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See detailAmélioration de la biodégradation du biphényle par Rhodococcus erythropolis t902.1 en présence de Fe2O3 et de nanoparticules de fer encapsulées dans un xérogel de silice
wanoussa; Hiligsmann, Serge ULg; Tasseroul, Ludivine ULg et al

in Déchets Sciences et Techniques (2015), 69

In this work, the effect of iron oxide particles Fe2O3 and iron nanoparticles encapsulated in a porous silica matrix (xerogel Fe/SiO2) was investigated on biphenyl biodegradation by the strain Rhodococcus ... [more ▼]

In this work, the effect of iron oxide particles Fe2O3 and iron nanoparticles encapsulated in a porous silica matrix (xerogel Fe/SiO2) was investigated on biphenyl biodegradation by the strain Rhodococcus erythropolis T902.1. After 18 days of incubation biodegradation yields of 75% and 85% were achieved respectively in presence of non-autoclaved or autoclaved xerogel Fe/SiO2 at 10-5 M iron. These results are 42 and 60 % higher than in standard conditions without nanoparticles. They suggest that the autoclave procedure lead to the release of some iron less anchored in the silica matrix. This study highlights that siderophore production by Rhodococcus erythropolis T902.1 would be related to the presence of iron nanoparticles in the culture. It suggests that the production of these strong chelating compounds decreases with increase of iron release from xerogel Fe/SiO2. Moreover, most of the surfactants synthesized by Rhodococcus erythropolis T902.1 which are glycolipids containing trehalose (hexose), would be linked to cell surface and not excreted in the culture medium; the biomass hexose content also increased by 85% in presence of iron nanoparticles. [less ▲]

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See detailEffect of metal ions and metal nanoparticles encapsulated in porous silica on biodegradation kinetics for biphenyl
Wannoussa, Wissal; Hiligsmann, Serge ULg; Masy, Thibaut ULg et al

in Journal of Sol-Gel Science and Technology (2015), 75

Biodegradation of biphenyl was carried out by Rhodococcus erythropolis T902.1 in presence of nanometer-sized metallic (Co, Pd, Ag and Cu) nanoparticles (NPS) synthesized by the sol-gel process. In order ... [more ▼]

Biodegradation of biphenyl was carried out by Rhodococcus erythropolis T902.1 in presence of nanometer-sized metallic (Co, Pd, Ag and Cu) nanoparticles (NPS) synthesized by the sol-gel process. In order to prevent their agglomeration, the metallic NPs (1-2 nm diameter) were anchored inside microporous silica crystallites and named Co/SiO2, Pd/SiO2, Ag/SiO2 and Cu/SiO2 samples respectively. They were added at low concentrations of 10-6 M, 10-5 M and 10-4 M of metal in the culture medium and their impact was compared with that of the simple metal ions added as cobalt, palladium, silver or copper salts. The cultures containing Pd/SiO2 or Co/SiO2 samples at 10-4 M of metal achieved a 50% higher biphenyl degradation yield after 18 days of incubation and improved Rhodococcus erythropolis T902.1 growth compared with those without (positive control) or with silica particles only. The highest biodegradation performance, i.e. 107±3 ppm/day, which was about 85% higher than in control conditions without NPs, was recorded in 250 ml baffled flasks stirred at 150 rpm with Co/SiO2 sample at 10-4 M Co. Furthermore, the stimulating effect of NPs on biphenyl biodegradation seems to also depend on the thermal treatment conditions applied to NPs since the experimental results indicated that, after calcination, the cobalt oxide NPs at a concentration of 10-4 M were more effective than the reduced cobalt NPs with a degradation yield of 81±1% and 77±2% respectively after 18 days. On the other hand, the results showed that the addition of 10-4 M of Cu2+ or Ag+ ions or the addition of Cu/SiO2 or Ag/SiO2 samples at 10-4 M of metal have an inhibitory effect on biphenyl biodegradation. However, Cu+2 and Ag+ ions were more toxic to the Rhodococcus erythropolis T902.1 bacteria than the respective Cu or Ag NPS anchored inside silica particles. Moreover, this work showed that in these conditions, the activity of catechol 1, 2-dioxygenase (a critical enzyme in aromatic biodegradation pathway) was severely inhibited, whereas the presence of 10-4 M of Co2+ ions or Co/SiO2 sample stimulated the enzyme activity compared to the conditions without NPs. [less ▲]

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See detailLipopeptides as main ingredients for inhibition of fungal phytopathogens by Bacillus subtilis/amyloliquefaciens
Cawoy, H.; Debois, Delphine ULg; Franzil, Laurent ULg et al

in Microbial Biotechnology (2015), 8(2), 281-295

Summary: Some isolates of the Bacillus subtilis/amyloliquefaciens species are known for their plant protective activity against fungal phytopathogens. It is notably due to their genetic potential to form ... [more ▼]

Summary: Some isolates of the Bacillus subtilis/amyloliquefaciens species are known for their plant protective activity against fungal phytopathogens. It is notably due to their genetic potential to form an impressive array of antibiotics including non-ribosomal lipopeptides (LPs). In the work presented here, we wanted to gain further insights into the relative role of these LPs in the global antifungal activity of B.subtilis/amyloliquefaciens. To that end, a comparative study was conducted involving multiple strains that were tested against four different phytopathogens. We combined various approaches to further exemplify that secretion of those LPs is a crucial trait in direct pathogen ward off and this can actually be generalized to all members of these species. Our data illustrate that for each LP family, the fungitoxic activity varies in function of the target species and that the production of iturins and fengycins is modulated by the presence of pathogens. Our data on the relative involvement of these LPs in the biocontrol activity and modulation of their production are discussed in the context of natural conditions in the rhizosphere. © 2014 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology. [less ▲]

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See detailTechnological Features of Selected Kivuguto Strains during Milk Fermentation
Karenzi, Eugène; Fauconnier, Marie-Laure ULg; Destain, Jacqueline ULg et al

in Bioengineering and Bioscience (2015), 3(2), 13-22

Kivuguto milk is a traditional fermented milk of Rwanda. A previous study allowed for the selection of three bacteria involved in the fermentation process. The aim of the present work is the technological ... [more ▼]

Kivuguto milk is a traditional fermented milk of Rwanda. A previous study allowed for the selection of three bacteria involved in the fermentation process. The aim of the present work is the technological characterization of kivuguto strains for its production in the dairy industry. Acidification, proteolysis, the flavor compound profile, rheology and sensory analyses of fermented milks were assessed as important indicators of the starter culture formulation. Acidification showed that kivuguto milk ferments in 14 hours at 19°C with a titratable acidity of 73°D. The samples of CWBI-B1466 Lactococcus lactis and CWBI-B1470 Leuconostoc pseudomesenteroides had fermentation times of 14 h and 20 h, respectively. All samples were viscoelastic fluids, and the most important flavor compounds found were two alcohols, one ester and two furan derivative compounds. Proteolysis revealed low values ranging to 3.04-5.45 mg.L-1, which is very interesting in terms of taste acceptability. The three strains showed positive technological properties for kivuguto starter culture development and the data are fully in agreement with the preliminary results of the technological analyses. The findings revealed similarities between the formulated kivuguto and the traditional kivuguto as recognized by a tasting panel in a discrimination test. Ultimately, this study allowed for the formulation of kivuguto milk using three bacteria, prior to studying the stability of these properties during storage under refrigeration, which is the last stage before industrial production of kivuguto milk can begin. [less ▲]

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See detailEffect of metal ions and metal nanoparticles encapsulated in porous silica on biphenyl biodegradation by Rhodococcus erythropolis T902.1
Wannoussa, Wissal ULg; Hiligsmann, Serge ULg; Tasseroul, Ludivine ULg et al

in Journal of Sol-Gel Science and Technology (2015)

Biodegradation of biphenyl was carried out by Rhodococcus erythropolis T902.1 in presence ofnanometer-sized metallic (Co, Pd, Ag and Cu) nanoparticles (NPS) synthesized by the sol-gel process. In order to ... [more ▼]

Biodegradation of biphenyl was carried out by Rhodococcus erythropolis T902.1 in presence ofnanometer-sized metallic (Co, Pd, Ag and Cu) nanoparticles (NPS) synthesized by the sol-gel process. In order to prevent their agglomeration, the metallic NPs (1-2 nm diameter) were anchored inside microporous silica crystallites and named Co/SiO2, Pd/SiO2, Ag/SiO2 and Cu/SiO2 samples respectively. They were added at low concentrations of 10-6 M, 10-5 M and 10-4 M of metal in the culture medium and their impact was compared with that of the simple metal ions added as cobalt, palladium, silver or copper salts. The cultures containing Pd/SiO2 or Co/SiO2 samples at 10-4 M of metal achieved a 50% higher biphenyl degradation yield after 18 days of incubation and improved Rhodococcus erythropolis T902.1 growth compared with those without (positive control) or with silica particles only. The highest biodegradation performance, i.e. 107 ±3 ppm/day, which was about 85% higher than in control conditions without NPs, was recorded in 250 ml baffled flasks stirred at 150 rpm with Co/SiO2 sample at 10-4 M Co. Furthermore, the stimulating effect of NPs on biphenyl biodegradation seems to also depend on the thermal treatment conditions applied to NPs since the experimental results indicated that, after calcination, the cobalt oxide NPs at a concentration of 10-4 M were more effective than the reduced cobalt NPs with a degradation yield of 81 ±1% and 77 ±2% respectively after 18 days. On the other hand, the results showed that the addition of 10-4 M of Cu2+ or Ag+ ions or the addition of Cu/SiO2 or Ag/SiO2 samples at 10-4 M of metal have an inhibitory effect on biphenyl biodegradation. However, Cu2+ and Ag+ ions were more toxic to the Rhodococcus erythropolis T902.1 bacteria than the respective Cu or Ag NPS anchored inside silica particles. Moreover, this work showed that in these conditions, the activity of catechol 1, 2-dioxygenase (a critical enzyme in aromatic biodegradation pathway) was severely inhibited, whereas the presence of 10-4 M of Co2+ ions or Co/SiO2 sample stimulated the enzyme activity compared to the conditions without NPs. [less ▲]

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See detailComparative study of the methane production based on the chemical composition of Mangifera Indica and Manihot Utilissima leaves
Mambanzulua Ngoma, Philippe; Hiligsmann, Serge ULg; Sumbu Zola, Eric et al

in SpringerPlus (2015), 4(75), 1-8

Leaves of Mangifera Indica (MI, mango leaves) and Manihot Utilissima (MU, cassava leaves) are available in tropical regions and are the most accessible vegetal wastes of Kinshasa, capital of Democratic ... [more ▼]

Leaves of Mangifera Indica (MI, mango leaves) and Manihot Utilissima (MU, cassava leaves) are available in tropical regions and are the most accessible vegetal wastes of Kinshasa, capital of Democratic Republic of Congo. These wastes are not suitably managed and are not rationally valorized. They are abandoned in full air, on the soil and in the rivers. They thus pollute environment. By contrast, they can be recuperated and treated in order to produce methane (energy source), organic fertilizer and clean up the environment simultaneously. The main objective of this study was to investigate methane production from MI and MU leaves by BMP tests at 30°C. The yields achieved from the anaerobic digestion of up to 61.3 g raw matter in 1 l medium were 0.001 l/g and 0.100 l CH4/g volatile solids of MI and MU leaves, respectively. The yield of MU leaves was in the range mentioned in the literature for other leaves because of a poor presence of bioactive substrates, and low C/N ratio. This methane yield corresponded to 7% of calorific power of wood. By contrast, the methane yield from MI leaves was almost nil suggesting some metabolism inhibition because of their rich composition in carbon and bioactive substrates. Whereas classical acidogenesis and acetogenesis were recorded. Therefore, methane production from the sole MI leaves seems unfavorable by comparison to MU leaves at the ambient temperature in tropical regions. Their solid and liquid residues obtained after anaerobic digestion would be efficient fertilizers. However, the methane productivity of both leaves could be improved by anaerobic co-digestion. [less ▲]

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See detailGenome-wide transcriptional analysis suggests hydrogenase- and nitrogenase-mediated hydrogen production in Clostridium butyricum CWBI 1009
Calusinska, Magda; Hamilton, Christopher; Monsieurs, Pieter et al

in Biotechnology for Biofuels (2015), 8(27), 1-16

Background: Molecular hydrogen, given its pollution-free combustion, has great potential to replace fossil fuels in future transportation and energy production. However, current industrial hydrogen ... [more ▼]

Background: Molecular hydrogen, given its pollution-free combustion, has great potential to replace fossil fuels in future transportation and energy production. However, current industrial hydrogen production processes, such as steam reforming of methane, contribute significantly to the greenhouse effect. Therefore alternative methods, in particular the use of fermentative microorganisms, have attracted scientific interest in recent years. However the low overall yield obtained is a major challenge in biological H2 production. Thus, a thorough and detailed understanding of the relationships between genome content, gene expression patterns, pathway utilisation and metabolite synthesis is required to optimise the yield of biohydrogen production pathways. Results: In this study transcriptomic and proteomic analyses of the hydrogen-producing bacterium Clostridium butyricum CWBI 1009 were carried out to provide a biomolecular overview of the changes that occur when the metabolism shifts to H2 production. The growth, H2-production, and glucose-fermentation profiles were monitored in 20 L batch bioreactors under unregulated-pH and fixed-pH conditions (pH 7.3 and 5.2). Conspicuous differences were observed in the bioreactor performances and cellular metabolisms for all the tested metabolites, and they were pH dependent. During unregulated-pH glucose fermentation increased H2 production was associated with concurrent strong up-regulation of the nitrogenase coding genes. However, no such concurrent up-regulation of the [FeFe] hydrogenase genes was observed. During the fixed pH 5.2 fermentation, by contrast, the expression levels for the [FeFe] hydrogenase coding genes were higher than during the unregulated-pH fermentation, while the nitrogenase transcripts were less abundant. The overall results suggest, for the first time, that environmental factors may determine whether H2 production in C. butyricum CWBI 1009 is mediated by the hydrogenases and/or the nitrogenase. Conclusions: This work, contributing to the field of dark fermentative hydrogen production, provides a multidisciplinary approach for the investigation of the processes involved in the molecular H2 metabolism of clostridia. In addition, it lays the groundwork for further optimisation of biohydrogen production pathways based on genetic engineering techniques. [less ▲]

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See detailThermophilic and cellulolytic consortium isolated from composting plants improves anaerobic digestion of cellulosic biomass: toward a microbial resource management approach
Kinet, Romain ULg; Destain, Jacqueline ULg; Hiligsmann, Serge ULg et al

in Bioresource Technology (2015)

A cellulolytic consortium was isolated from a composting plant in order to boost the initial hydrolysis step encountered in anaerobic digestion. Improvement of the cellulose degradation, as well as biogas ... [more ▼]

A cellulolytic consortium was isolated from a composting plant in order to boost the initial hydrolysis step encountered in anaerobic digestion. Improvement of the cellulose degradation, as well as biogas production, was observed for the cultures inoculated with the exogenous consortium. Metagenomics analyses pointed out a weak richness (related to the number of OTUs) of the exogenous consortium induced by the selective pressure (cellulose as sole carbon source) met during the initial isolation steps. Main microbial strains determined were strictly anaerobic and belong to the Clostridia class. During cellulose anaerobic degradation, pH drop induced a strong modification of the microbial population. Despite the fact that richness and evenness were very weak, the exogenous consortium was able to adapt and to maintain the cellulolytic degradation potential. This important result point out the fact that simplified microbial communities could be used in order to increase the robustness of mixed cultures involved in environmental biotechnology. [less ▲]

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