Use of microbial reactors: Comparison with chemical reactors

This paper is aimed at raising the specificities and similarities between microbiological bioreactors on the one hand and chemical reactors in the other hand. In order to do so, the technological evolutions of bioreactors and engines are compared.Cet article établit une comparaison entre, d'une part, les moteurs à combustion pour ce qui est des réactions chimiques et, d'autre part, les différents modes de culture microbiens de façon à mettre en exergue leurs similitudes et particularités de mise en oeuvre

Batch fermentation of d-glucose/cellobiose mixtures by clostridium acetobutylicum atcc 824: energetic and carbon source regulation

Lignocellulosic biomass presents an interesting alternative to fossil carbon sources as a source of renewable energy that respects the environment. Indeed, this abundant resource can be converted by a wide range of thermal, chemical and biological techniques to compounds that can be used as substrate in anaerobic fermentation to produce biofuels and building blocks. As a general rule, micro-organisms possess regulation mechanisms that ensure the sequential use of the carbon and energy sources present in their environment. These regulations may consequently play a vital role in biomass to energy and building blocks conversion performances. Clostridium acetobutylicum, a promising biomass transformation organism, has the capacity to utilize a wide variety of compounds as carbon and energy sources. These compounds may be present in a complex mixture produced from cellulose conversion. Therefore it is of high importance to understand the potential synergy or inhibiting effects of the cellulose-derived products. The aim of this work is to study this regulation mechanism by using glucose and cellobiose as model substrates, provided alone and in mixtures to Clostridium acetobutylicum. Our experiments show a total consumption of both substrates, alone or in mixtures, with an increment of 30% of microbial growth production of cellobiose over glucose. A diauxic growth (cell growth in two phases) occurs in the presence of different mixtures of D-glucose and cellobiose. In general, D-glucose is the preferred substrate and after its complete consumption, when exhausted, the growth kinetics exhibits an adaptation time, of approximately 1-2 hours, before to be able to use cellobiose (figure 1). This adaptation is probably due to an induction stage that is also accompanied of acid consumption (lactic acid). This study provides a first approach to understand the metabolic changes related to substrate utilization in Clostridia. Please click Additional Files below to see the full abstract

Vers un changement de pratique dans une filière céréalière : apport de la modélisation de l’environnement

National audienceProject management, especially in the field of sustainable development, requires to take into account not only the working environment stricto sensu, but also supra components of environmental, social, economic, legislative, etc. Ergonomists and psychologists are then led to be interested in, and to develop modeling frameworks to better understand and to make more intelligible this complex environment. The study presented here, which requires taking into account this environment, aims at setting up a novel practice for improving the food safety of a cereal chain in a global context of sustainable development: protection of the environment (flora and fauna) and the health of farmers and consumers. As part of this study, a quick fungal contamination diagnostic tool and a corresponding decontamination process have been developed for an application in the barley-malt-beer food chain. However, the use of these processes may change the agricultural practices in antifungal treatments with the regular and high dose treatments replaced by fine targeted applications only where and when necessary. In relation with this technological development, the challenge is to identify the components of the environment that may become brakes and levers to the implementation of this new practice. In this scope, this investigation mobilizes the modeling of the environment of Thatcher and Yeow (2016). This paper is consequently aimed at presenting the underlying process to this construction, and this in relation with the characteristics of the study. At last, a discussion is initiated concerning the further use of such modelling practices for purposes other than the decision-making processes on ergonomic intervention purposes.L’intervention ergonomique dans le champ du développement durable requiert la prise en compte d’un environnement dépassant largement l’environnement de travail afin d’y intégrer des composants relevant de dimensions environnementales, économique, législative, etc. Les ergonomes et psychologues ergonomes sont alors conduits à développer des cadres de modélisation permettant d’appréhender et de rendre davantage intelligible cet environnement complexe. L’étude sur laquelle nous nous basons ici s’inscrit dans ce cadre et vise l’identification des freins et leviers à la mise en place d’une nouvelle pratique en matière de traitement antifongique pour la filière orge-malt-bière. Pour cette investigation, nous nous référons notamment à la modélisation de Thatcher et Yeow (2016). L’enjeu est de présenter le processus de recueil et d’analyse sous-jacente à la modélisation et de poursuivre par une réflexion quant à l’emploi de ces formes de modélisation au cours d’un processus d’intervention

Recombinant pediocin in Lactococcus lactis:increased production by propeptide fusion and improved potency by co-production with PedC

We describe the impact of two propeptides and PedC on the production yield and the potency of recombinant pediocins produced in Lactococcus lactis. On the one hand, the sequences encoding the propeptides SD or LEISSTCDA were inserted between the sequence encoding the signal peptide of Usp45 and the structural gene of the mature pediocin PA-1. On the other hand, the putative thiol-disulfide oxidoreductase PedC was coexpressed with pediocin. The concentration of recombinant pediocins produced in supernatants was determined by enzyme-linked immunosorbent assay. The potency of recombinant pediocins was investigated by measuring the minimal inhibitory concentration by agar well diffusion assay. The results show that propeptides SD or LEISSTCDA lead to an improved secretion of recombinant pediocins with apparently no effect on the antibacterial potency and that PedC increases the potency of recombinant pediocin. To our knowledge, this study reveals for the first time that pediocin tolerates fusions at the N-terminal end. Furthermore, it reveals that only expressing the pediocin structural gene in a heterologous host is not sufficient to get an optimal potency and requires the accessory protein PedC. In addition, it can be speculated that PedC catalyses the correct formation of disulfide bonds in pediocin.</p

Production d'arômes laitiers par des lactocoques : recherche de la voie de synthèse du diacétyle et d'une mise en œuvre en réacteur continu à haute densité cellulaire

Not availableCe travail de recherche portant sur les bactéries lactiques productrices d'aromes laitiers Lactococcus lactis subsp. lactis biovar. diacetylactis comprend deux parties. La première partie est consacrée au mode de production du diacétyle par ce microorganisme, et, en particulier, à l'étude de la réaction de décarboxylation oxydative de l'alpha-acetolactate en diacétyle. Les résultats cinétiques obtenus montrent que cette réaction peut être à l’origine de la production microbiologique du diacétyle, et ce, même dans des conditions physico-chimiques défavorables pour une décarboxylation oxydative. De plus, le siège de cette réaction a été déterminé comme étant intracellulaire, avec un mécanisme faisant intervenir un ou des composés thermolabiles. La deuxième partie de ce travail consiste en une étude prospective pour la mise en œuvre de Lactococcus lactis subsp. lactis biovar. diacetylactis en culture continue à haute densité cellulaire. Deux modes de mise en œuvre sont évalués : la culture continue en réacteur à recyclage cellulaire et la culture continue de cellules immobilisées en réacteur à lit fixe. L’évaluation est établie en termes d'influence de ces modes de culture sur le métabolisme des cellules et de performances pour la production de biomasse et de diacétyle. Au niveau physiologique, cette étude permet de mettre en évidence des règles d'orientation du flux catabolique provenant des substrats carbonés lactose et citrate en fonction du taux de dilution et de révéler un mécanisme de régénération du NADH + H+ en conditions de fort co-métabolisme citrate/lactose. Pour ce qui est des performances, ces résultats montrent que ces deux modes de culture, comparés à des cultures discontinues, apportent des gains notables en productivité, tant pour la biomasse que le diacétyle

New insights in agar biorefinery with arylsulphatase activities

International audienceAgar is a major gelling agent used both in food and pharmaceutical applications. Traditional purification of agar is generally performed by sequential time consuming chemical and/or physical steps, leading to both poor recovery yields and low productivities. As a consequence, only 30% of the amount of agar produced is actually available under purified form to feed the world market. The current limiting factor for purification is the presence of sulphated compounds such as sulphated-agaropectin, which strongly affect the technological properties of the agar gel such as gel strength, melting and fusion temperatures and electroendosmosis. In this context, this communication aims at discussing about the development of a biorefining agar purification approach which allows overcoming the current limitations associated with traditional purification methods. More specifically, this article focuses on the potential role of arylsulphatases in agar purification processes to reduce the number of purification steps and to improve recovery yields. This review first presents the global gelling agents market before focusing on agar characteristics and production processes. Then, after a brief reminder of the sulphur metabolism, the roles, classes and properties of the different arylsulphatases are described to draw perspectives on their integration in current or new agar production processes

Etude de la production et de l'émanation de composés volatils malodorants sur textile à usage sportif

Si la sueur fraîchement émise par le corps humain est inodore, la dégradation de celle-ci par la flore bactérienne cutanée produit des composés volatils malodorants, responsables des odeurs de transpiration. Les odeurs de transpiration apparaissent également sur les vêtements au cours de leur utilisation, particulièrement sur les textiles réalisés en fibres synthétiques. Ce travail a pour but d améliorer la compréhension du phénomène d émanation d odeurs en étudiant l effet du sujet testé, l effet de la flore bactérienne et l effet du textile sur les émissions de composés volatils malodorants.L intérêt de ce travail réside dans l approche globale de la problématique des odeurs de transpiration et dans la diversité des méthodes de mesure mises en place, tant dans l étude de la flore microbiologique que dans les méthodes de mesures des composés odorants émis.Dans un premier temps, le dénombrement simultané de la flore bactérienne sur la peau et sur le vêtement a été réalisé sur un échantillon de 15 sujets à l issue d un exercice physique. Cette expérimentation a permis d évaluer le taux de transfert bactérien moyen lors d une activité sportive et d étudier son rôle dans l émission d odeurs. Ensuite, afin d affiner ces résultats, une méthode basée sur la biologie moléculaire a été mise en place pour réaliser le suivi qualitatif de la stabilité de la flore commensale axillaire d un sujet pendant 3 mois. Le transfert bactérien spécifique entre la peau du testeur et le vêtement a été étudié pour 4 matières textiles sélectionnées (dont le coton et le PET). Ceci a permis de déterminer le rôle du transfert bactérien spécifique dans l émission des odeurs à partir de textile.Enfin, le dernier chapitre est consacré à l étude de l émission de composés volatils et odorants à l aide de mesures olfactives et d un nez électronique au cours du temps par 8 composants textiles sélectionnés. Après traitement statistique par analyse en composante principale et étude détaillée des mesures, 9 composés chimiques ont été identifiés comme indicateurs d un comportement textile malodorant. Ces derniers pourraient être utilisés dans la mise en place d une méthode ciblée de mesure physico-chimique des mauvaises odeurs.Ce travail a permis de déterminer l impact de chacun des facteurs sujet, flore bactérienne et textile dans l émission d odeurs. En outre, ce travail ouvre des perspectives sur l étude des contaminations bactériennes par contact, mais également dans l étude des odeurs, sur les phénomènes de désorption de molécules volatiles à partir de différentes matrices textiles et sur les solutions pouvant être envisagées pour limiter les émissions odorantes à partir de textiles.Fresh human sweat is odorless. Odoriferous volatile compounds are produced by the metabolism of bacteria living on the skin, generating strong malodor. Sweaty body odors do also appear on clothes during use, and especially on synthetic fabrics. The aim of this document is to improve understanding of odor emission by investigating subject effect, microbiota effect and fabric effect on the emission of odoriferous volatile compounds.Odors of perspiration are hereby globally approached with a wide use of methods and experimental devices, for microbial flora study as well as for odoriferous volatile compounds emission study.First, microflora enumeration has been simultaneously processed on the skin and on the fabric after exercise for 15 subjects. This experiment allowed an evaluation of the average bacterial transfer yield during physical activity and the beginning of the investigation of its effect on odor emission.A molecular biology methodology has then been developed in order to refine these results. Monitoring of qualitative composition of the microbiota has been performed to study the stability of the armpit s ecosystem on a subject during 3 months. Specific microbial transfer from subject s skin to clothe has been performed for 4 textile fabrics (including cotton and PET). This leaded to characterize the effect of specific bacterial transfer on odor emission from fabric.The last chapter is dedicated to the study of the emission of odoriferous volatile compounds over time using olfactory measurements and electronic nose for 8 selected fabrics. Principal component analysis targeted 9 chemical compounds that have been selected as malodorous behavior indicators for a given fabric. Those 9 compounds could be used for setting up a fitted physicochemical method of malodor.To conclude, this study helped to understand the effect of 3 factors in odor perception from a fabric after sport : subject, microbial flora and fabric. Perspectives have been charted on contact microbial contamination, but also on odor, and especially on desorption of odoriferous volatile molecules from a textile or knitted matrix. The solutions that could be used to limit malodorous emission from fabrics have also been discussed.NANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

Selective extraction, structural characterisation and antifungal activity assessment of napins from an industrial rapeseed meal

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Diauxic growth of Clostridium acetobutylicum ATCC 824 when grown on mixtures of glucose and cellobiose

Abstract Clostridium acetobutylicum, a promising organism for biomass transformation, has the capacity to utilize a wide variety of carbon sources. During pre-treatments of (ligno) cellulose through thermic and/or enzymatic processes, complex mixtures of oligo saccharides with beta 1,4-glycosidic bonds can be produced. In this paper, the capability of C. acetobutylicum to ferment glucose and cellobiose, alone and in mixtures was studied. Kinetic studies indicated that a diauxic growth occurs when both glucose and cellobiose are present in the medium. In mixtures, d-glucose is the preferred substrate even if cells were pre grown with cellobiose as the substrate. After the complete consumption of glucose, the growth kinetics exhibits an adaptation time, of few hours, before to be able to use cellobiose. Because of this diauxic phenomenon, the nature of the carbon source deriving from a cellulose hydrolysis pre-treatment could strongly influence the kinetic performances of a fermentation process with C. acetobutylicum

Hydrothermal conversion of wood, organosolv and chlorite pulps

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