Synthèse des connaissances sur la déshydratation osmotique

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(1), 129-142

Parmi les procédés de conservation des produits végétaux, la déshydratation osmotique présente un intérêt économique et nutritionnel certain. Cette technique, économe en énergie, est susceptible de ... [more ▼]

Parmi les procédés de conservation des produits végétaux, la déshydratation osmotique présente un intérêt économique et nutritionnel certain. Cette technique, économe en énergie, est susceptible de prolonger la période de disponibilité des produits alimentaires et leur confère des propriétés sensorielles nouvelles et appréciées. Elle permet ainsi aux acteurs de la filière agro-alimentaire d’écouler leurs productions à de meilleurs prix et aux consommateurs d’en disposer tout au long de l’année. Cette technique est un outil facile à mettre en place, surtout dans les pays en voie de développement, en raison de son faible cout. Le présent article a pour objectif de présenter une synthèse de la littérature concernant la technique de déshydratation osmotique afin d’en rappeler les bases théoriques et pratiques, mais aussi d’en préciser les nouvelles tendances et voies de recherches récentes. [less ▲]

La vision artificielle: une méthode d'avenir pour la reconnaissance automatisée des plantes adventices?

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(4), 597-610

Weeds compete with crop plants for sunlight, moisture and nutrients and can have a detrimental impact on crop yields and quality if uncontrolled. They are destroyed by chemical, non chemical and ... [more ▼]

Weeds compete with crop plants for sunlight, moisture and nutrients and can have a detrimental impact on crop yields and quality if uncontrolled. They are destroyed by chemical, non chemical and integrated methods. To perform a site-specific weeds destruction, combination of these techniques with ground-based machine vision technology has high potential. Several methods exist to differentiate weeds from soil, between the rows. The more complicated problem is encountered when weeds are mixed to crops within the rows. Algorithms based on colorimetric or shape features are widely dependant on the variability of weeds and crops and are difficult to transpose from one situation to another. Measurement of plant height is a promising method, since at low spatial scale, the growthing speed is more uniform for the plants than for the weeds. This growing speed is function of the height and of a characteristic time, such as the number of days after sowing. To implement this method, active stereoscopy combined to an accurate measurement of the soil microrelief is required. [less ▲]

In vitro culture of Jatropha curcas L (Culture in vitro de Jatropha curcas L.)

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(4), 567-574

Comparaison d’un modèle empirique et d’un modèle physique de séchage de grains de maïs en lit fluidisé

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(3), 389-398

Dans cet article, deux modèles prévisionnels de la température et de la teneur en eau de grains de maïs durant leur séchage en lit fluidisé sont comparés. Le premier modèle est un modèle empirique, où les ... [more ▼]

Dans cet article, deux modèles prévisionnels de la température et de la teneur en eau de grains de maïs durant leur séchage en lit fluidisé sont comparés. Le premier modèle est un modèle empirique, où les phénomènes physiques impliqués dans le processus ne sont pas décrits. Ses équations peuvent être résolues à l’aide de logiciels gratuits disponibles sur Internet. Le second est un modèle plus complexe, basé sur les lois physiques régissant les transferts de chaleur et de masse au sein du produit. Sa résolution nécessite l’utilisation de logiciels commerciaux de calcul par éléments finis. Les deux modèles sont paramétrés sur des séchages à température constante, puis validés sur des séchages à température variable et un séchage discontinu. Les deux modèles permettent de décrire avec une précision acceptable les évolutions de teneurs en eau au cours des séchages continus et de prévoir les évolutions de teneurs en eau lors des séchages à température variable et du séchage discontinu. Le modèle empirique ne permet pas de décrire l’évolution de la température des grains lors de séchages à température variable avec une précision meilleure qu’1 °C. Si cette précision est suffisante, l’exploitation du modèle empirique permettra de réduire considérablement les couts en temps et en licence de logiciels pour la modélisation du séchage du maïs en lit fluidisé. [less ▲]

From biologicalmembranes to biomimetic model membranes

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14

Recent insights into Protein Phosphatase 2A structure and regulation : The reason why PP2A is no longer considered as a lazy passive housekeeping enzyme

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(1), 243-252

Reversible protein phosphorylation is a major intracellular mechanism for controlling many important physiological activities. In the past, most of the attention was focused primarily on protein kinases ... [more ▼]

Reversible protein phosphorylation is a major intracellular mechanism for controlling many important physiological activities. In the past, most of the attention was focused primarily on protein kinases and on their regulation, mainly because phosphatases were then viewed as simple housekeeping enzymes. But advances in the understanding of phosphatases make now clear that protein phosphatases are dynamic and highly regulated enzymes and are as important as kinases in the regulation of cellular processes involving protein phosphorylation. Protein phosphatase 2A (PP2A) is a very abundant -it accounts for as much as 1% of total cellular protein-, ubiquitous and remarkably conserved enzyme. By dephosphorylating a plethora of cellular proteins, it is involved in the regulation of nearly all cellular activities. [less ▲]

Trehalose as a stress marker of the physiological impact of mixing on yeast production: scale-down reactors and mini-bioreactors investigations

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14

Development of a compartment model based on CFD simulations for mixing description in bioreactors

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(2), 517-522

Understanding and modelling the complex interactions between biological reaction and hydrodynamics is a key problem when dealing with bioprocesses. It is fundamental to be able to accurately predict the ... [more ▼]

Understanding and modelling the complex interactions between biological reaction and hydrodynamics is a key problem when dealing with bioprocesses. It is fundamental to be able to accurately predict the hydrodynamics behaviour of bioreactors of different size and its interaction with the biological reaction. CFD can provide detailed modelling about hydrodynamics and mixing. However, it is computationally intensive, especially when reactions are taken into account. Another way to predict hydrodynamics is the use of "Compartment" or "Multi-zone" model which are much less demanding in computation time than CFD. However, compartments and fluxes between them are often defined by considering global quantities not representative of the flow. To overcome the limitations of these two methods, a solution is to combine compartment modelling and CFD simulations. Therefore, the aim of this study is to develop a methodology in order to propose a compartment model based on CFD simulations of a bioreactor. The flow rate between two compartments can be easily computed from the velocity fields obtained by CFD. The difficulty lies in the definition of the zones in such a way they can be considered as perfectly mixed. The creation of the model compartments from CFD cells can be achieved manually or automatically. The manual zoning consists in aggregating CFD cells according to the user's wish. The automatic zoning defines compartments as regions within which the value of one or several properties are uniform with respect to a given tolerance. Both manual and automatic zoning methods have been developed and compared by simulating the mixing of an inert scalar. For the automatic zoning, several algorithms and different flow properties have been tested as criteria for the compartment creation. [less ▲]

Fermentative hydrogen production by Clostridium butyricum CWBI1009 and Citrobacter freundii CWBI952 in pure and mixed cultures

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(S2), 541-548

This paper investigates the biohydrogen production by two mesophilic strains, a strict anaerobe (Clostridium butyricum CWBI1009) and a facultative anaerobe (Citrobacter freundii CWBI952). They were ... [more ▼]

This paper investigates the biohydrogen production by two mesophilic strains, a strict anaerobe (Clostridium butyricum CWBI1009) and a facultative anaerobe (Citrobacter freundii CWBI952). They were cultured in pure and mixed cultures in serum bottles with five different carbon sources. The hydrogen yields of pure C. freundii cultures ranged from 0.09 molH2.molhexose-1 (with sucrose) to 0.24 molH2.molhexose-1 (with glucose). Higher yields were obtained by the pure cultures of Cl. butyricum ranging from 0.44 molH2.molhexose-1 (with sucrose) to 0.69 molH2.molhexose-1 (with lactose). This strain also fermented starch whereas C. freundii did not. However, it consumed the other substrates faster and produced hydrogen earlier than Cl. butyricum. This ability has been used to promote the growth conditions of Cl. butyricum in co-culture with C. freundii, since Cl. butyricum is extremely sensitive to the presence of oxygen which strongly inhibits H2 production. This approach could avoid the addition of any expensive reducing agents in the culture media such as L-cysteine since C. freundii consumes the residual oxygen. Thereafter, co-cultures with glucose and starch were investigated: hydrogen yields decreased from 0.53 molH2.molhexose-1 for pure Cl. butyricum cultures to 0.38 molH2.molhexose -1 for mixed culture with glucose but slightly increased with starch (respectively 0.69 and 0.73 molH2.molhexose-1). After 48 h of fermentation, metabolites analysis confirmed with microbial observation, revealed that the cell concentration of C. freundii dramatically decreased or was strongly inhibited by the development of Cl. butyricum. [less ▲]

Prevalence and sources of Campylobacter spp. contamination in free-range broiler production in the southern part of Belgium

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(2), 279-288

A one year epidemiological study was carried out between February 2005 and January 2006 in the southern part of Belgium to assess the Campylobacter prevalence in free-range broiler production. Three ... [more ▼]

A one year epidemiological study was carried out between February 2005 and January 2006 in the southern part of Belgium to assess the Campylobacter prevalence in free-range broiler production. Three successive broiler flocks from six Belgian farms were investigated for the presence of Campylobacter spp. during the rearing period. Each flock was visited four times, before and after the outdoor rearing period. During each visit, samples were taken in the broiler house (litter, cecal droppings, water-lines, feed, anteroom) as well as from the outer rearing environment (open-air range). The Campylobacter detection in all samples was carried out according to the ISO 10272 standard. Identification was based on colonial morphology, microscopic examination, and biochemical tests. PCR multiplex was used for genetic confirmation. Campylobacter jejuni was the main species isolated from all contaminated samples. Overall, mixed infections C. jejuni/C. coli represented 40.6%, while C. jejuni and C. coli represented 46.9% and 12.5% of chicken samples respectively. A 100% flock contamination was observed in the 6 farms during the summer/autumn period, whereas only 66.7% and 33.3% of the flocks became Campylobacter-positive in spring and winter respectively, at the end of the rearing period. Half of contaminated flocks were infected before chickens have access to the open-air range. Environmental samples, especially the open-air range soil, were found to be Campylobacter-positive before flock infection. The other potential sources of contamination were delivery tray, anteroom floor and water-lines. Other animal productions like cattle on the farm, no applied rodent control, no cleaning and disinfection of water-lines between flocks, no detergent used for cleansing and thinning were recorded as risk factors. In conclusion, the contact with the environment, particularly the access to an open-air range, appeared to be the major way of Campylobacter contamination of chickens in free-range broiler production. [less ▲]