Influence of barley malting operating parameters on T-2 and HT-2 toxinogenesis of Fusarium langsethiae, a worrying contaminant of malting barley in Europe.

The fungus Fusarium langsethiae, exclusively described in Europe at present, seems to have taken the place of other Fusarium species in barley fields over the last 5 years. It has proved to be a highly toxic type-A trichothecene producer (T-2 and HT-2 toxins). The aim of this work was to study the ecotoxinogenesis of this fungus the better to identify and manage the health risk it may pose during the beer manufacturing process. The influence of temperature and water activity on its growth rate and production of toxins are particularly assessed from a macroscopic point of view. Different cultures were grown on sterilized rehydrated barley with a water activity between 0.630 and 0.997 and a temperature ranging from 5 to 35°C. Biomass specific to F. langsethiae and T-2 and HT-2 toxins were quantified by real-time polymerase chain reaction and liquid chromatography-mass spectrometry, respectively. It appears that the optimal temperature and water activity for F. langsethiae toxinogenesis are 28°C and 0.997. This fungus was able to produce 2.22 g kg−1 of these toxins in 16 days on barley in optimal production conditions. The malting process seems to be a critical step because, in its temperature range, specific production was six times higher than under optimal temperatures for fungus growth. In the short-term, this work will help redefine the process conditions for malting. In the medium-term, the results will contribute to the development of a molecular tool to diagnose the presence of this contaminant and the detection of the toxins in barley, from fields to the end product

Forming microbial anodes under delayed polarisation modifies the electron transfer network and decreases the polarisation time required.

Microbial anodes were formed from compost leachate on carbon cloth electrodes. The biofilms formed at the surface of electrodes kept at open circuit contained microorganisms that switched their metabolism towards electrode respiration in response to a few minutes of polarisation. When polarisation at -0.2 V/SCE (+0.04 V/SHE) was applied to a pre-established biofilm formed at open circuit (delayed polarisation), the bacteria developed an extracellular electron transport network that showed multiple redox systems, reaching 9.4 A/m(2) after only 3-9 days of polarisation. In contrast, when polarisation was applied from the beginning, bacteria developed a well-tuned extracellular electron transfer network concomitantly with their growth, but 36 days of polarisation were required to get current of the same order (6-8 A/m(2)). The difference in performance was attributed to the thinner, more heterogeneous structure of the biofilms obtained by delayed polarisation compared to the thick uniform structure obtained by full polarisation

Optimisation d’anodes microbiennes à partir de lixiviat de sol pour la conception de piles à combustible microbiennes

Les piles à combustible microbienne (PACMs) sont des piles capables de convertir l’énergie chimique de combustibles organiques directement en énergie électrique. Dans ces piles, l’oxydation du combustible est assurée par des micro-organismes dits "électro-actifs" qui forment des biofilms à la surface de l’anode et jouent le rôle de catalyseur des réactions électrochimiques. Les travaux qui font l’objet de ce manuscrit ont eu pour objectif d’optimiser des anodes microbiennes formées à partir de la flore bactérienne contenue dans des terreaux de jardin. Les expériences effectuées en chronoampérométrie avec un système à trois électrodes ont conduit à la première démonstration expérimentale que des densités de courant de 66 A/m2 pouvaient être obtenues en formant les anodes microbiennes sur des ultra-microélectrodes. Sur des électrodes de taille normale, la mise au point d’une nouvelle technique (polarisation retardée) pour la formation de biofilms microbiens a permis d’obtenir des densités de courant de 9,4 A/m2 après seulement 3 jours de polarisation tandis que le protocole conventionnel demandait quelques semaines pour obtenir 6 à 8 A/m2. L’étude de différents matériaux d’électrode a indiqué que l’acier inoxydable qui permit d’atteindre des densités de courant de 21 A/m2 présente un grand intérêt pour la formation de biofilms électro-actifs. En effet, les électrodes en tissu de carbone ont assuré jusqu’à 34,3 A/m2, voire 50 A/m2 en anaérobiose, mais elles bénéficiaient d’une structure tridimensionnelle. La mise en oeuvre des anodes microbiennes optimisées dans les PACMs a assuré la production de 6,0 W/m2. L’élaboration d’un nouveau prototype intégrant un système de cathode amovible a permis d’allonger la durée de vie initiale de la pile de 2 semaines à plus de 2 mois

Stainless steel is a promising electrode material for anodes of microbial fuel cells.

The abilities of carbon cloth, graphite plate and stainless steel to form microbial anodes were compared under identical conditions. Each electrode was polarised at −0.2 V vs. SCE in soil leachate and fed by successive additions of 20 mM acetate. Under these conditions, the maximum current densities provided were on average 33.7 A m−2 for carbon cloth, 20.6 A m−2 for stainless steel, and 9.5 A m−2 for flat graphite. The high current density obtained with carbon cloth was obviously influenced by the three dimensional electrode structure. Nevertheless, a fair comparison between flat electrodes demonstrated the great interest of stainless steel. The comparison was even more in favour of stainless steel at higher potential values. At +0.1 V vs. SCE stainless steel provided up to 35 A m−2, while graphite did not exceed 11 A m−2. This was the first demonstration that stainless steel offers a very promising ability to form microbial anodes. The surface topography of the stainless steel did not significantly affect the current provided. Analysis of the voltammetry curves allowed two groups of electrode materials to be distinguished by their kinetics. The division into two well-defined kinetics groups proved to be appropriate for a wide range of microbial anodes described in the literature

Electroanalysis of microbial anodes for bioelectrochemical systems: basics, progress and perspectives

Over about the last ten years, microbial anodes have been the subject of a huge number of fundamental studies dealing with an increasing variety of possible application domains. Out of several thousands of studies, only a minority have used 3-electrode set-ups to ensure well-controlled electroanalysis conditions. The present article reviews these electroanalytical studies with the admitted objective of promoting this type of investigation. A first recall of basics emphasises the advantages of the 3-electrode set-up compared to microbial fuel cell devices if analytical objectives are pursued. Experimental precautions specifically relating to microbial anodes are then noted and the existing experimental set-ups and procedures are reviewed. The state-of-the-art is described through three aspects: the effect of the polarisation potential on the characteristics of microbial anodes, the electroanalytical techniques, and the electrode. We hope that the final outlook will encourage researchers working with microbial anodes to strengthen their engagement along the multiple exciting paths of electroanalysis

Towards an engineering-oriented strategy for building microbial anodes for microbial fuel cells.

The objective of the work was to give some first insight into an engineering-oriented approach to MFC design by focusing on anode optimisation. The effect of various parameters was firstly investigated in half cell set-ups under well-controlled conditions. Microbial anodes were formed from soil leachate under polarisation at -0.2 V vs. SCE with different concentrations of substrate, salt and buffer. It was shown that non-turnover CV could be used to assess the electroactive maturity of the anodes during polarisation. This first phase resulted in the definition of a set of optimal parameter values. In the second phase, an optimal anode was formed in a half-cell under the defined optimal conditions. A numerical approach was then developed to calculate the theoretical maximum power that the anode could provide in an ideal MFC. The concept of "ideal MFC" introduced here allowed the theoretical maximum power to be calculated on the sole basis of the kinetic characteristics of the anode. Finally, a MFC designed in the aim of approaching such ideal conditions generated stable power densities of 6.0 W m(-2), which were among the highest values reported so far. The discrepancy between the theoretical maximum (8.9 W m(-2)) and the experimental results pointed out some limit due to the source of inoculum and suggested possible paths to improvement

Optimisation d'anodes microbiennes à partir de lixiviat de sol pour la conception de piles à combustible microbiennes

Les piles à combustible microbienne (PACMs) sont des piles capables de convertir l'énergie chimique de combustibles organiques directement en énergie électrique. Dans ces piles, l'oxydation du combustible est assurée par des micro-organismes dits "électro-actifs" qui forment des biofilms à la surface de l'anode et jouent le rôle de catalyseur des réactions électrochimiques. Les travaux qui font l'objet de ce manuscrit ont eu pour objectif d'optimiser des anodes microbiennes formées à partir de la flore bactérienne contenue dans des terreaux de jardin. Les expériences effectuées en chronoampérométrie avec un système à trois électrodes ont conduit à la première démonstration expérimentale que des densités de courant de 66 A/m2 pouvaient être obtenues en formant les anodes microbiennes sur des ultra-microélectrodes. Sur des électrodes de taille normale, la mise au point d'une nouvelle technique (polarisation retardée) pour la formation de biofilms microbiens a permis d'obtenir des densités de courant de 9,4 A/m2 après seulement 3 jours de polarisation tandis que le protocole conventionnel demandait quelques semaines pour obtenir 6 à 8 A/m2. L'étude de différents matériaux d'électrode a indiqué que l'acier inoxydable qui permit d'atteindre des densités de courant de 21 A/m2 présente un grand intérêt pour la formation de biofilms électro-actifs. En effet, les électrodes en tissu de carbone ont assuré jusqu'à 34,3 A/m2, voire 50 A/m2 en anaérobiose, mais elles bénéficiaient d'une structure tridimensionnelle. La mise en oeuvre des anodes microbiennes optimisées dans les PACMs a assuré la production de 6,0 W/m2. L'élaboration d'un nouveau prototype intégrant un système de cathode amovible a permis d'allonger la durée de vie initiale de la pile de 2 semaines à plus de 2 moisMicrobial fuel cells (MFC) are devices capable to convert chemical energy from organic fuels directly into electrical energy. In these cells, the fuel oxidation is provided by micro-organisms known as "electro-active"; these microorganism form biofilms on the surface of the anode and act as a catalyst for electrochemical reactions. The aim of this work was the optimisation of microbial anodes formed from bacterial flora contained in garden soils. The chronoamperometric experiments performed in a three-electrode system showed for the very first time in these systems that current densities of 66 A/m2 could be obtained by forming microbial anodes on ultra-microelectrodes. On electrode of normal size, the development of a new technique (delayed polarisation) for designing microbial biofilms produced current densities of 9.4 A/m2 after 3 days of polarisation, while the conventional protocol asked a few weeks for obtaining 6 to 8 A/m2. The study of different electrode materials indicated that stainless steel allowed reaching current densities up to 21 A/m2, which makes it a suitable candidate for designing electro-active biofilms. Indeed, the carbon electrodes provided up to 34.4 A/m2, even 50 A/m2 in anaerobic conditions, but the electrodes benefited of a three-dimensional structure contrasting the stainless steel electrode. The use of optimised microbial anodes in MFCs insured the production of 6 W/m2. In addition, the development of a new prototype containing a removable cathode allowed extending the lifetime of the initial MFC from 2 weeks to over 2 monthsTOULOUSE-INP (315552154) / SudocSudocFranceF

Experimental and theoretical characterization of microbial bioanodes formed in pulp and paper mill effluent in electrochemically controlled conditions

Microbial bioanodes were formed in pulp and paper effluent on graphite plate electrodes under constant polarization at -0.3 V/SCE, without any addition of nutriment or substrate. The bioanodes were characterized in 3-electrode set-ups, in continuous mode, with hydraulic retention times from 6 to 48 h and inlet COD from 500 to 5200 mg/L. Current densities around 4 A/m2 were obtained and voltammetry curves indicated that 6 A/m2 could be reached at +0.1 V/SCE. A theoretical model was designed, which allowed the effects of HRT and COD to be distinguished in the complex experimental data obtained with concomitant variations of the two parameters. COD removal due to the electrochemical process was proportional to the hydraulic retention time and obeyed a Michaelis–Menten law with respect to the COD of the outlet flow, with a Michaelis constant KCOD of 400 mg/L. An inhibition effect occurred above inlet COD of around 3000 mg/L

Pregătirea asistentelor medicale cu studii superioare – Un imperativ al timpului

În lucrare este descrisă necesitatea pregătirii asistentelor medicale cu studii superioare, care a devenit un imperativ al timpului pe piaţa muncii în domeniul nursingului. Ea va oferi mai multe oportunităţi în ceea ce priveşte parcurgerea traseului profesional în sistemul de sănătate

Garden compost inoculum leads to microbial bioanodes with potential-independent characteristics

International audienceGarden compost leachate was used to form microbial bioanodes under polarization at 0.4, 0.2 and +0.1 V/SCE. Current densities were 6.3 and 8.9 A m2 on average at 0.4 and +0.1 V/SCE respectively, with acetate 10 mM. The catalytic cyclic voltammetry (CV) showed similar electrochemical characteristics for all bioanodes and indicated that the lower currents recorded at 0.4 V/SCE were due to the slower interfacial electron transfer rate at this potential, consistently with conventional electrochemical kinetics.RNA- and DNA-based DGGE evidenced that the three dominant bacterial groups Geobacter, Anaerophaga and Pelobacter were identical for all bioanodes and did not depend on the polarization potential. Only non-turnover CVs showed differences in the redox equipment of the biofilms, the highest potential promoting multiple electron transfer pathways. This first description of a potential-independent electroactive microbial community opens up promising prospects for the design of stable bioanodes for microbial fuel cells