http://hdl.handle.net/2268/140 Search this channel search http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/150764 Title: Contribution to the study of the resistance to drying of Pseudomonas fluorescens <br/> <br/>Author, co-author: Mputu Kanyinda, Jean-Noël <br/> <br/>Abstract: The objective of this thesis is to study the resistance to drying of Pseudomonas fluorescens. Freeze-drying is the most suitable method for drying P. fluorescens. However, freeze-drying induced loss of cell viability. This loss of viability is mainly due to membrane rupture, temperature and oxidation of fatty acids, membrane proteins and glutathione. For this purpose, the use of protective compounds during freeze-drying has allowed us to obtain a powder having a high viability. We then studied the impact of these protective compounds, oxygen and storage temperature on the viability of P. fluorescens during storage. Analyses of fatty acids, proteins, glutathione and the study of membrane integrity during the various manufacturing processes and storage have established a link between the degree of oxidation and cell death. The results of flow cytometry showed that the freeze-drying longer affects the viability of P. fluorescens rather than storage. We have increased the yield of the production in bioreactor of P. fluorescens and time of culture was halved. Tue, 18 Jun 2013 17:03:45 GMT http://hdl.handle.net/2268/150651 Title: On the Relevance of Sophisticated Structural Annotations for Disulfide Connectivity Pattern Prediction <br/> <br/>Author, co-author: Becker, Julien; Maes, Francis; Wehenkel, Louis <br/> <br/>Abstract: Disulfide bridges strongly constrain the native structure of many proteins and predicting their formation is therefore a key sub-problem of protein structure and function inference. Most recently proposed approaches for this prediction problem adopt the following pipeline: first they enrich the primary sequence with structural annotations, second they apply a binary classifier to each candidate pair of cysteines to predict disulfide bonding probabilities and finally, they use a maximum weight graph matching algorithm to derive the predicted disulfide connectivity pattern of a protein. In this paper, we adopt this three step pipeline and propose an extensive study of the relevance of various structural annotations and feature encodings. In particular, we consider five kinds of structural annotations, among which three are novel in the context of disulfide bridge prediction. So as to be usable by machine learning algorithms, these annotations must be encoded into features. For this purpose, we propose four different feature encodings based on local windows and on different kinds of histograms. The combination of structural annotations with these possible encodings leads to a large number of possible feature functions. In order to identify a minimal subset of relevant feature functions among those, we propose an efficient and interpretable feature function selection scheme, designed so as to avoid any form of overfitting. We apply this scheme on top of three supervised learning algorithms: k-nearest neighbors, support vector machines and extremely randomized trees. Our results indicate that the use of only the PSSM (position-specific scoring matrix) together with the CSP (cysteine separation profile) are sufficient to construct a high performance disulfide pattern predictor and that extremely randomized trees reach a disulfide pattern prediction accuracy of on the benchmark dataset SPX+, which corresponds to +3.2% improvement over the state of the art. A web-application is available at http://m24.giga.ulg.ac.be:81/x3CysBridge​s. Mon, 17 Jun 2013 09:38:47 GMT http://hdl.handle.net/2268/150618 Title: High-energy X-ray tomography analysis of a metal packing biofilm reactor for the production of lipopeptides by Bacillus subtilis <br/> <br/>Author, co-author: Zune, Quentin; Soyeurt, Delphine; Toye, Dominique; Ongena, Marc; Thonart, Philippe; Delvigne, Frank <br/> <br/>Abstract: BACKGROUND: Whereas multi-species biofilm reactors are commonly used for the treatment of liquid and solid wastes, new strategies are progressing for the development of single species biofilm for the production of high-value metabolites. Technically, this new concept relies on the design of bioreactors able to promote biofilm formation and on the identification of the key physico-chemical parameters involved in biofilm formation. RESULTS: An experimental setting comprising a liquid continuously recirculated on a metal structured packing has been used to promote Bacillus subtilis GA1 biofilm formation. The colonization of the packing has been visualized non-invasively by X-ray tomography. This analysis revealed an uneven, conical, distribution of the biofilm inside the packing. Compared with a submerged culture carried out in a stirred tank reactor, significant modification of the lipopeptide profile has been observed in the biofilm reactorwith the disappearance of fengycin and iturin fractions and an increase of the surfactin fraction. In addition, considering the biofilm reactor design, no foam formation has been observed during the culture. CONCLUSIONS: The configuration of this biofilm reactor set-up allows for a higher surfactin production by comparison with a submerged culture while avoiding foam formation. Additionally, scale-up could easily be performed by increasing the number of packing elements. Sun, 16 Jun 2013 16:00:22 GMT http://hdl.handle.net/2268/150257 Title: Le Munkoyo : une source d'amylases végétales pour une boisson fermentée traditionnelle <br/> <br/>Author, co-author: Foma Kibwega, Roland <br/> <br/>Abstract: In Africa, several sources of amylases are not well documented. Munkoyo roots are used as the source of amylases during the traditional preparation of a fermented beverage called munkoyo. These roots are unique as the synthesis and accumulation of amylases activities do not require germination. Despite this advantage, munkoyo roots are not well known as sources of amylases and they have not yet been introduced into industrial processes. Thus, the aim of this PhD project was to (1) promote munkoyo roots as sources of α- and β-amylases and to (2) propose pathways of optimization and industrialization of manufacturing munkoyo beverage. In the first part, purification, characterization and identification of α- and β-amylases from munkoyo roots was achieved. Amylases from roots of Eminia holubii, Eminia harmsiana, Rhynchosia insignis insignis and Rhynchosia insignis affinis were retained in our study. Compared to malted cereals, α- and β-amylases from munkoyo roots are more thermostable and their activities are optimal at high temperatures. However, these properties are closer to those of germinated cotyledons belonging to some Fabaceae family plants. Using LC-ESI MSMS analysis, this study showed significant matching of α- and β-amylases from munkoyo roots to germinated leguminous seeds. In the second part, the traditional production of munkoyo beverage was studied. The evolution of physicochemical parameters and ferments involved in spontaneous fermentation was investigated. Acidification is promoted by thermophilic and heterofermentative lactic acid bacteria. Alcohol production in munkoyo is due mainly to Saccharomyces cerevisiae. The study shows that knowledge of amylase properties and the use of an appropriate microbial starter will optimize the manufacturing process and the quality of munkoyo beverage.; En Afrique, plusieurs sources d'amylases utilisées ne sont pas bien documentées. C'est le cas des racines de munkoyo utilisées comme sources d'amylases lors de la préparation traditionnelle de la boisson munkoyo. Les racines de munkoyo sont spécifiques parce que la synthèse et l’accumulation des activités amylases ne nécessitent pas de germination. Malgré cet avantage, les racines de munkoyo ne sont pas bien connues comme sources d'amylases et elles ne sont pas encore intégrées dans des procédés industriels. Ainsi, les objectifs de cette thèse étaient de (1) promouvoir les racines de munkoyo comme sources d'α- et β-amylases et (2) de proposer des voies d'optimisation et d'industrialisation de la fabrication de la boisson munkoyo. Dans la première partie, la purification, la caractérisation et l'identification des amylases des racines de munkoyo ont été réalisées. Les amylases provenant des racines d’Eminia holubii, Eminia harmsiana, Rhynchosia insignis insignis et Rhynchosia insignis affinis ont été retenues dans notre étude. Comparativement aux céréales maltées, les α-et β-amylases des racines de munkoyo sont particulièrement thermostables et leurs activités sont optimales à des températures élevées. Ces propriétés sont cependant proches de celles des graines germées de certaines fabacées. Les analyses par LC-ESI-MSMS ont montré des correspondances significatives des α- et β-amylases des racines de munkoyo avec celles des graines germées de fabacées. Dans la deuxième partie, la production traditionnelle du munkoyo a été étudiée. L'évolution des paramètres physico-chimiques et des ferments impliqués dans la fermentation spontanée a été étudiée. Les bactéries lactiques thermophiles et hétérofermentaires sont responsables de l'acidification du munkoyo. La production d'alcool est principalement due à une souche de Saccharomyces cerevisiae. L'étude montre que la connaissance des propriétés des amylases des racines de munkoyo et l’emploi d’un starter microbien approprié optimiserait le procédé de fabrication et la qualité de la boisson munkoyo. Wed, 12 Jun 2013 12:35:03 GMT http://hdl.handle.net/2268/150186 Title: OPTIMIZATION OF THE LIPASE-CATALYZED SYNTHESIS OF SUGAR ESTERS IN PURE IL AND IN IL/ORGANIC SOLVENT MIXTURES VIA RESPONSE SURFACE METHODOLOGY (RSM) <br/> <br/>Author, co-author: Galonde, Nadine; Nott, Katherine; Richard, Gaetan; Brostaux, Yves; Debuigne, Antoine; Jérôme, Christine; Fauconnier, Marie-Laure Tue, 11 Jun 2013 10:28:24 GMT http://hdl.handle.net/2268/149826 Title: Physiological response of yeast to process perturbations: A mini-bioreactor approach <br/> <br/>Author, co-author: Lejeune, Annick; Delvigne, Frank; Thonart, Philippe <br/> <br/>Abstract: 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. Wed, 05 Jun 2013 09:03:54 GMT http://hdl.handle.net/2268/149562 Title: Change in viability of Acetobacter senegalensis cells during gluconic acid fermentation at high temperature <br/> <br/>Author, co-author: Zarmehrkhorshid, Raziyeh; Shafiei, Rasoul; Thonart, Philippe <br/> <br/>Abstract: 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. Fri, 31 May 2013 07:49:26 GMT http://hdl.handle.net/2268/149485 Title: Implementation of structured metal packing for the design of biofilm reactor : analysis by high energy X-ray tomography and application to the production of lipopeptides by Bacillus subtilis <br/> <br/>Author, co-author: Zune, Quentin; Soyeurt, Delphine; Ongena, Marc; Toye, Dominique; Thonart, Philippe; Delvigne, Frank <br/> <br/>Abstract: 1. Whereas multi-species biofilm reactors are commonly used for treatments of water and gas effluents, new strategies are arising for the development of mono-species biofilm reactors in order to produce high added value molecules. Thus, it is required to design new bioreactors able to promote the growth of the biomass on the form of a biofilm and to identify the key physico-chemical parameters involved in order to optimize the bioprocess. 2. Aim of this study was to investigate a pilot-scale biofilm reactor comprising a metal structured packing promoting growth of Bacillus subtilis as a biofilm for the production of lipopeptides, high added value compounds with high surface active properties. 3. In this work, the mechanical stirring system of a 20L stirred tank bioreactor has been removed and replaced by a metal structured packing positioned in the headspace of the vessel above a liquid phase. The culture medium is continuously recirculated on the packing thanks to a peristaltic pump and air supply is performed just above the liquid phase under the packing. High energy X-ray tomography was used to estimate non-invasively the biofilm distribution inside the packing and permitted to define parameters that affect scale-up. Performances of the biofilm reactor were compared with a submerged culture in a stirred tank reactor in terms of lipopeptides production. 4. After 72 hours of fermentation, 94 % of the total biomass adheres onto the metal packing on the form of a biofilm. The colonization of this latter has been visualized non-invasively by X-ray tomography directly inside the packing and shows a conical repartition of the biofilm mass (about 25% of the total volume of the packing) as well as the presence of clogging. However, unlike the submerged culture, no foam formation appeared during fermentation and surfactin yield reaches 345,4 ± 32,8 mg / L for the biofilm reactor against 277,3 ± 34,4 mg / L in the stirred tank reactor. 5. In conclusion, this experimental setting leads to a major technological progress avoiding foam formation and increasing surfactin production. Nevertheless, significant improvements are required at the level of the biofilm distribution in thin layers inside the packing in order to increase mass transfer and lipopeptides recoveries. Further investigations will be devoted to the optimization of the physico-chemical parameters involved in biofilm distribution. Thu, 30 May 2013 03:00:25 GMT http://hdl.handle.net/2268/149287 Title: Implementation of structured metal packing for the design of biofilm reactor : analysis by high energy X-ray tomography and application to the production of lipopeptides by Bacillus subtilis <br/> <br/>Author, co-author: Zune, Quentin; Soyeurt, Delphine; Ongena, Marc; Toye, Dominique; Thonart, Philippe; Delvigne, Frank <br/> <br/>Abstract: 1. Whereas multi-species biofilm reactors are commonly used for treatments of water and gas effluents, new strategies are arising for the development of mono-species biofilm reactors in order to produce high added value molecules. Thus, it is required to design new bioreactors able to promote the growth of the biomass on the form of a biofilm and to identify the key physico-chemical parameters involved in order to optimize the bioprocess. 2. Aim of this study was to investigate a pilot-scale biofilm reactor comprising a metal structured packing promoting growth of Bacillus subtilis as a biofilm for the production of lipopeptides, high added value compounds with high surface active properties. 3. In this work, the mechanical stirring system of a 20L stirred tank bioreactor has been removed and replaced by a metal structured packing positioned in the headspace of the vessel above a liquid phase. The culture medium is continuously recirculated on the packing thanks to a peristaltic pump and air supply is performed just above the liquid phase under the packing. High energy X-ray tomography was used to estimate non-invasively the biofilm distribution inside the packing and permitted to define parameters that affect scale-up. Performances of the biofilm reactor were compared with a submerged culture in a stirred tank reactor in terms of lipopeptides production. 4. After 72 hours of fermentation, 94 % of the total biomass adheres onto the metal packing on the form of a biofilm. The colonization of this latter has been visualized non-invasively by X-ray tomography directly inside the packing and shows a conical repartition of the biofilm mass (about 25% of the total volume of the packing) as well as the presence of clogging. However, unlike the submerged culture, no foam formation appeared during fermentation and surfactin yield reaches 345,4 ± 32,8 mg / L for the biofilm reactor against 277,3 ± 34,4 mg / L in the stirred tank reactor. 5. In conclusion, this experimental setting leads to a major technological progress avoiding foam formation and increasing surfactin production. Nevertheless, significant improvements are required at the level of the biofilm distribution in thin layers inside the packing in order to increase mass transfer and lipopeptides recoveries. Further investigations will be devoted to the optimization of the physico-chemical parameters involved in biofilm distribution. Mon, 27 May 2013 03:00:44 GMT http://hdl.handle.net/2268/148611 Title: Photobioreactors for efficient production of molecules with high added value, based upon an innovative technology for the production of porous materials <br/> <br/>Author, co-author: Tocquin, Pierre Thu, 16 May 2013 19:13:52 GMT http://hdl.handle.net/2268/148043 Title: Apply and develop multiplex PCR to detect Fasciola gigantica infection in Lymnaea viridis at different larval stages <br/> <br/>Author, co-author: Bui Thi, Dung <br/> <br/>Abstract: Multiplex PCR was used to detect Fasciola gigantica infection in Lymnaea viridis snail as intermediate host. In this study, snail Lymnaea viridis was experimentally infected with F.gigantica and used for DNA template. Fasciola specific primers was amplified a 124 bp fragment in multiplex PCR when the genomic DNA isolated from F.gigantica infected Lymnaea viridis snails was used as template and amplified a 500 - 600 bp fragment. Genomic DNA of the parasite was used as a positive control, which also gave an amplification of the 124 bp fragment. DNA isolated from non-infected snails was used as a negative control and no amplification of this sequence was observed. The developed diagnostic multiplex PCR will be of use for assessment of transmission of fascioliasis in snail as intermediate host in Vietnam. Tue, 07 May 2013 23:26:39 GMT http://hdl.handle.net/2268/148042 Title: Distribution of freshwater snails in family-based VAC ponds and associated waterbosied with special reference to intermediate hosts of fish-borne zoonotic trematides in Nam Dinh province, Vietnam <br/> <br/>Author, co-author: Bui Thi, Dung <br/> <br/>Abstract: Fish-borne zoonotic trematodes, such as Clonorchis sinensis, heterophyids and others, constitute a public health concern in parts of northern Vietnam and infections with these trematodes are often thought to be linked to fish culture. One common fish culture system is the integrated fish-livestock (VAC) ponds where individual households have 1 or more ponds. Fish fry, mainly of various carp species, pro-duced in hatcheries, not necessarily local, are introduced into nursery ponds and after approximately 6 weeks, juvenile fishes are transferred to household ponds, referred to as grow-out ponds. Grow-out ponds are usually fertilized with organic debris, including animal excreta, to stimulate algal growth and subsequently fish growth. This paper describes the distribution of freshwater snails and occurrence of trematode infections in these in VAC ponds and associated habitats as part of a major study on risk factors of FZT infections in cultured fish in two communes, Nghia Lac and Nghia Phu, Nghia Hung District, Nam Dinh Province. The area is under intense rice cultivation with an extensive canal network supplying fields and also household VAC ponds. A total of 16 snail species was found and four were widely distributed i.e. Angulyagra polyzonata, Melanoides tuberculata, Bithynia fuchsiana and Pomacea insularum. Snail diver-sity and counts were higher in nursery ponds than in grow-out ponds. Species of the families Thiaridae and Viviparidae were more abundant than other species in VAC ponds while species of the Bithyniidae, Stenothyridae and Planorbidae dominated in rice fields and small canals. Trematode infections were found in eight snail species and among these M. tuberculata had the highest overall prevalence of infec-tion (13.28%). No trematode infections were found in species of the Viviparidae and Ampullaridae except for metacercariae. Parapleurolophocercous and pleurolophocercous cercariae constituted the most com-mon type of cercariae recovered, contributing 40.6% of all infections followed by echinostome cercariae (35.0%) and xiphidiocercariae (17.3%). Bithynia fuschiana and M. tuberculata had the most diverse trema-tode fauna. C. sinensis was not recorded in this study. The VAC pond system in this area, is very important for transmission of minute intestinal trematodes while they play little role in transmission of C. sinensis as its intermediate hosts, bithynid snails, rarely occur in these ponds. From a public health perspective this is positive as the effects of infections with intestinal trematodes are considered mild. On the other hand it is possible that even such subtle effects could have importance in public health as transmission is very intense in the area. And this in combination with the aquaculture importance, reduced marketability of fishes with high metacercariae loads, warrants that control efforts against these trematodes are initiated to reduce transmission in this production system. Tue, 07 May 2013 23:17:27 GMT http://hdl.handle.net/2268/147889 Title: Valorisation des produits issus des feuilles de betteraves : extraction de molécules à note verte <br/> <br/>Author, co-author: Marlier, Michel; Thonart, Philippe; du Jardin, Patrick; Ongena, Marc; Fauconnier, Marie-Laure Fri, 03 May 2013 14:43:46 GMT http://hdl.handle.net/2268/147888 Title: Valorisation des produits issus des feuilles de betteraves : extraction de molécules à note verte - Rapport final <br/> <br/>Author, co-author: Wathelet, Jean-Paul; Thonart, Philippe; du Jardin, Patrick; Ongena, Marc; Fauconnier, Marie-Laure Fri, 03 May 2013 14:43:21 GMT http://hdl.handle.net/2268/147887 Title: Valorisation des produits issus des feuilles de betteraves : extraction de molécules à note verte <br/> <br/>Author, co-author: Wathelet, Jean-Paul; Thonart, Philippe; du Jardin, Patrick; Ongena, Marc; Fauconnier, Marie-Laure Fri, 03 May 2013 14:42:56 GMT http://hdl.handle.net/2268/147644 Title: THE RESPONSE OF ACETOBACTER SENEGALENSIS TO STRESSORS: A STUDY TOWARDS IMPROVEMENT OF VINEGAR STARTER PRODUCTION <br/> <br/>Author, co-author: Shafiei, Rasoul; Thonart, Philippe <br/> <br/>Abstract: Acetic acid bacteria encounter various harsh conditions during acetic acid fermentation. Ethanol as the main substrate and acetic acid as the major product at low pH can influence deeply on the cellular functions of acetic acid bacteria. In previous studies in CWBI, Acetobacter senegalensis was used for production of dried vinegar starters; however the impact of stressors (ethanol and acetic acid) on A. senegalensis remained unclear. In this study, different techniques such as flow cytometry, culturability on solid medium and 2-DiGE were used comparatively to investigate the effect of carbon sources of inoculum media on the tolerance of A. senegalensis to stressors. Analysis of respiration system by flow cytometric methods showed that the presence of 2% (v/v) acetic acid in inoculum medium, in one hand, causes 80% of cells to continue to do respiration after a sudden exposure to 1- 3% (v/v) acetic acid in stress media while 89.7% of cells grown in glucose appeared as dead cells after an abrupt exposure to 3%(v/v) of acetic acid. On the other hand, 59.2% and 49.33% of cells grown in the presence of 2% (v/v) of acetic acid could maintain their entire membrane integrity after exposure to 1% and 3% (v/v) of acetic acid, respectively. Inoculum medium contained 5% (v/v) of ethanol as a carbon source enabled about 90% of cells to keep their growing capacities after a sudden exposure to 3% acetic acid. In contrast, just 40% of cells grown in glucose as a carbon source maintained their culturability on solid medium after exposure to 1% acetic acid. A similar profile of culturability was observed for the cells grown in 5% (v/v) ethanol or 2% (v/v) of acetic acid. A proteomic approach (2-DiGE) was used to analyze proteins expressed in the presence of different carbon sources. Differentially expressed proteins were mainly associated with energy metabolism, carbohydrate metabolisms, folding, sorting and degradation processes. The relative abundance of proteins was extensively different for cell grown in glucose compared with protein contents of cells grown in ethanol or acetic acid. In conclusion, production of a cost effective vinegar starter needs a qualified biomass which tolerates ethanol and acetic acid. Tolerance of A. senegalensis to acetic acid depends to a great extent on the composition of the medium which cells grow in. In spite of low adaption to acetic acid for cell grown in glucose, using ethanol or acetic acid in inoculum media renders a physiological state in A. senegelensis which enables it to cope with higher concentration of acetic acid readily, this biomass has a potential to be used as a starter. Mon, 29 Apr 2013 13:21:35 GMT http://hdl.handle.net/2268/147643 Title: Flow-cytometric assessment of damages to Acetobacter senegalensis during freeze-drying process and storage <br/> <br/>Author, co-author: Shafiei, Rasoul; Delvigne, Frank; Thonart, Philippe <br/> <br/>Abstract: 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. 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 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 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. Mon, 29 Apr 2013 13:21:16 GMT http://hdl.handle.net/2268/147561 Title: Improvement of gluco-amylase B excretion by Aspergillus oryzae in a biofilm reactor <br/> <br/>Author, co-author: Zune, Quentin; Kinet, Romain; Toye, Dominique; Thonart, Philippe; Punt, Peter J; Delvigne, Frank Mon, 29 Apr 2013 09:23:08 GMT http://hdl.handle.net/2268/147402 Title: Potentiality of using microbial biosensors for the detection of sub-strate heterogeneities and the assessment of microbial viability in industrial bioreactors: a complete set of experiments in chemostat and scale-down reactors, and elaboration of a mini scale-down platform <br/> <br/>Author, co-author: Brognaux, Alison; Neubauer, Peter; Twizere, Jean-Claude; Thonart, Philippe; Delvigne, Frank Fri, 26 Apr 2013 10:21:55 GMT http://hdl.handle.net/2268/147401 Title: On-line flow cytometry profiling of Escherichia coli stress response <br/> <br/>Author, co-author: Brognaux, Alison; Han, Shanshan; Sorensen, Soren; Lebeau, Frédéric; Thonart, Philippe; Delvigne, Frank Fri, 26 Apr 2013 10:15:46 GMT