- INRA-LBE, Avenue des étangs, 11100 Narbonne, France
Nicolas BERNET
National Institute of Agricultural Research (INRA), LBE, Faculty Member
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I am a researcher at the Laboratoire de Biotechnologie de l’Environnement (LBE), French National Institute for Agric... moreI am a researcher at the Laboratoire de Biotechnologie de l’Environnement (LBE), French National Institute for Agricultural Research (INRA). My research is in the field of Environmental Biotechnology and Biorefinery including more recently microbial electrochemical technologies. edit
To move today’s agricultural and urban systems towards tomorrow’s circular economy and respond to climate change, it is imperative to turn organic residues and wastewater into resourceful assets. This article discusses the changes that... more
To move today’s agricultural and urban systems towards tomorrow’s circular economy and respond to climate change, it is imperative to turn organic residues and wastewater into resourceful assets. This article discusses the changes that are needed in research to drive this paradigm shift and to go from a “losses and waste” situation to a “resource and opportunities” ambition. The current lines of research aim to maximise the use and value of biomass or organic residues and wastewater and propose new organisational schemes driven by technical innovations. Exploring the pathways to a sustainable future through many domains let us identify five challenges to structure the research efforts and find circular bioeconomy solutions for organic residues and wastewater: (1) proposing innovative processes and integrated multi-process systems; (2) promoting the emergence of multi-scale and cross-sectoral organisations; (3) developing multi-performance evaluation methods, (4) rethinking research–...
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Recirculation of solid digestate through digesters has been demonstrated to be a potential simple strategy to increase continuous stirred-tank reactor biogas plant efficiency. This study extended this earlier work and investigated solid... more
Recirculation of solid digestate through digesters has been demonstrated to be a potential simple strategy to increase continuous stirred-tank reactor biogas plant efficiency. This study extended this earlier work and investigated solid digestate post-treatment using liquid isolated ligninolytic aerobic consortia in order to increase methane recovery during the recirculation. Based on sampling in several natural environments, an enrichment and selection method was implemented using a Lab-scale Automated and Multiplexed (an)Aerobic Chemostat system to generate ligninolytic aerobic consortia. Then, obtained consortia were further cultivated under liquid form in bottles. Chitinophagia bacteria and Sordariomycetes fungi were the two dominant classes of microorganisms enriched through these steps. Finally, these consortia where mixed with the solid digestate before a short-term aerobic post-treatment. However, consortia addition did not increase the efficiency of aerobic post-treatment o...
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This work proposes a new biotechnological route for an emerging environmental biorefinery technology handling table olive processing wastewater (TOPW). This wastewater is currently considered to be recalcitrant but can become a valuable... more
This work proposes a new biotechnological route for an emerging environmental biorefinery technology handling table olive processing wastewater (TOPW). This wastewater is currently considered to be recalcitrant but can become a valuable substrate for energy recovery via novel microbial electrochemical technologies (MET). MET are really promising since they possess a huge potential for application in many disciplines (bioremediation, wastewater treatment, biofuel and biochemical production). In a completely environmentally compatible way, they are regarded as a new sustainable and effective strategy for treatment of recalcitrant compounds in wastewater. TOPW is of major environmental concern since they are generated in large quantities and are characterized by a high organic content. About 15600 m of TOPW are indeed directly discharged into evaporation ponds each year while TOPW exhibits antimicrobial, ecotoxic and phytotoxic properties due the presence of phenolic compounds. This la...
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Microalgae can be cultivated on waste dark fermentation effluents containing volatile fatty acids (VFA) such as acetate or butyrate. These VFA can however inhibit microalgae growth at concentrations above 0.5-1 gC.L–1. This study used the... more
Microalgae can be cultivated on waste dark fermentation effluents containing volatile fatty acids (VFA) such as acetate or butyrate. These VFA can however inhibit microalgae growth at concentrations above 0.5-1 gC.L–1. This study used the model strain Chlorella sorokiniana to investigate the effects of acetate or butyrate concentration on biomass growth rates and yields alongside C:N:P ratios and pH control. Decreasing undissociated acid levels by raising the initial pH to 8.0 allowed growth without inhibition up to 5 gC.L–1 VFAs. However, VFA concentration strongly affected biomass yields irrespective of pH control or C:N:P ratios. Biomass yields on 1.0 gC.L–1 acetate were around 1.3-1.5 gC.gC–1 but decreased by 26-48% when increasing initial acetate to 2.0 gC.L–1. This was also observed for butyrate with yields decreasing up to 25%. This decrease in yield in suggested to be due to the prevalence of heterotrophic metabolism at high organic acid concentration, which reduced the amou...
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The conversion of H2 into methane can be carried out by microorganisms in a process so-called biomethanation. In ex-situ biomethanation H2 and CO2 gas are exogenous to the system. One of the main limitations of the biomethanation process... more
The conversion of H2 into methane can be carried out by microorganisms in a process so-called biomethanation. In ex-situ biomethanation H2 and CO2 gas are exogenous to the system. One of the main limitations of the biomethanation process is the low gas-liquid transfer rate and solubility of H2 which are strongly influenced by the temperature. Hydrogenotrophic methanogens that are responsible for the biomethanation reaction are also very sensitive to temperature variations. The aim of this work was to evaluate the impact of temperature on batch biomethanation process in mixed culture. The performances of mesophilic and thermophilic inocula were assessed at 4 temperatures (24, 35, 55 and 65 °C). A negative impact of the low temperature (24 °C) was observed on microbial kinetics. Although methane production rate was higher at 55 and 65 °C (respectively 290 ± 55 and 309 ± 109 mL CH4/L.day for the mesophilic inoculum) than at 24 and 35 °C (respectively 156 ± 41 and 253 ± 51 mL CH4/L.day)...
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Correction for ‘The environmental biorefinery: state-of-the-art on the production of hydrogen and value-added biomolecules in mixed-culture fermentation’ by Roman Moscoviz et al., Green Chem., 2018, 20, 3159–3179.
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The production of energy carriers and bulk chemicals by mixed-culture fermentation is quantitatively analysed and discussed in a biorefinery context.
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Biodegradable wastes produced seasonally need an upstream storage, because of the requirement for a constant feeding of anaerobic digesters. In the present article, the potential of co-ensiling biodegradable agro-industrial waste (sugar... more
Biodegradable wastes produced seasonally need an upstream storage, because of the requirement for a constant feeding of anaerobic digesters. In the present article, the potential of co-ensiling biodegradable agro-industrial waste (sugar beet leaves) and lignocellulosic agricultural residue (wheat straw) to obtain a mixture with low soluble sugar content was evaluated for long-term storage prior to anaerobic digestion. The aim is to store agro-industrial waste while pretreating lignocellulosic biomass. The dynamics of co-ensiling was evaluated in vacuum-packed bags at lab-scale during 180 days. Characterization of the reaction by-products and microbial communities showed a succession of metabolic pathways. Even though the low initial sugars content was not sufficient to lower the pH under 4.5 and avoid undesirable fermentations, the methane potential was not substantially impacted all along the experiment. No lignocellulosic damages were observed during the silage process. Overall, i...
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The effect of supplementing granular activated carbon and trace elements on the anaerobic digestion performance of consecutive batch reactors treating food waste was investigated. The results from the first batch suggest that addition of... more
The effect of supplementing granular activated carbon and trace elements on the anaerobic digestion performance of consecutive batch reactors treating food waste was investigated. The results from the first batch suggest that addition of activated carbon favored biomass acclimation, improving acetic acid consumption and enhancing methane production. Adding trace elements allowed a faster consumption of propionic acid. A second batch proved that a synergy existed when activated carbon and trace elements were supplemented simultaneously. The degradation kinetics of propionate oxidation were particularly improved, reducing significantly the batch duration and improving the average methane productivities. Addition of activated carbon favored the growth of archaea and syntrophic bacteria, suggesting that interactions between these microorganisms were enhanced. Interestingly, microbial analyses showed that hydrogenotrophic methanogens were predominant. This study shows for the first time ...
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Anaerobic digestion of food waste is a complex process often hindered by high concentrations of volatile fatty acids and ammonia. Methanogenic archaea are more sensitive to these inhibitors than bacteria and thus the structure of their... more
Anaerobic digestion of food waste is a complex process often hindered by high concentrations of volatile fatty acids and ammonia. Methanogenic archaea are more sensitive to these inhibitors than bacteria and thus the structure of their community is critical to avoid reactor acidification. In this study, the performances of three different inocula were compared using batch digestion tests of food waste and cardboard mixtures. Particular attention was paid to the archaeal communities in the inocula and after digestion. While the tests started with inocula rich in Methanosarcina led to efficient methane production, VFAs accumulated in the reactors where inocula initially were poor in this archaea and no methane was produced. In addition, higher substrate loads were tolerated when greater proportions of Methanosarcina were initially present in the inoculum. Independently of the inoculum origin, Methanosarcina were the dominant methanogens in the digestates from the experiments that effi...
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Microbial community structure of anodic biofilms plays a key role in bioelectrochemical systems (BESs). When ecosystems are used as inocula, many bacterial species having interconnected ecological interactions are present. The aim of the... more
Microbial community structure of anodic biofilms plays a key role in bioelectrochemical systems (BESs). When ecosystems are used as inocula, many bacterial species having interconnected ecological interactions are present. The aim of the present study was to identify these interactions for the conversion of single substrates into electrical current. Dual-chamber reactors were inoculated with activated sludge and fed in batch mode with acetate, lactate, butyrate and propionate at 80 mMe equivalents in quadruplicate. Analyses of biofilms and planktonic microbial communities showed that the anodic biofilms were mainly dominated by the Geobacter genus (62.4% of the total sequences). At the species level, Geobacter sulfurreducens was dominant in presence of lactate and acetate, while Geobacter toluenoxydans and Geobacter pelophilus were dominant with butyrate and propionate as substrates. These results indicate for the first time a specificity within the Geobacter genus towards the elect...
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The hydrogen (H) production efficiency in dark fermentation systems is strongly dependent on the occurrence of metabolic pathways derived from the selection of microbial species that either consume molecular Hor outcompete hydrogenogenic... more
The hydrogen (H) production efficiency in dark fermentation systems is strongly dependent on the occurrence of metabolic pathways derived from the selection of microbial species that either consume molecular Hor outcompete hydrogenogenic bacteria for the organic substrate. In this study, the effect of organic loading rate (OLR) on the Hproduction performance, the metabolic pathways, and the microbial community composition in a continuous system was evaluated. Two bacterial genera, Clostridium and Streptococcus, were dominant in the microbial community depending on the OLR applied. At low OLR (14.7-44.1 g/L-d), Clostridium sp. was dominant and directed the system towards the acetate-butyrate fermentation pathway, with a maximum Hyield of 2.14 mol/molobtained at 29.4 g/L-d. Under such conditions, the volumetric hydrogen production rate (VHPR) was between 3.2 and 11.6 L/L-d. In contrast, relatively high OLR (58.8 and 88.2 g/L-d) favored the dominance of Streptococcus sp. as co-dominant...
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Glycerol is currently an over-produced chemical that can be used as substrate for the production of high value products such as 1,3-propanediol (1,3-PDO) in fermentation processes. The aim of this study was to investigate the effect of... more
Glycerol is currently an over-produced chemical that can be used as substrate for the production of high value products such as 1,3-propanediol (1,3-PDO) in fermentation processes. The aim of this study was to investigate the effect of initial pH on a batch mixed culture fermentation of glycerol, considering both the bacterial community composition and the fermentation patterns. For pH values between 5 and 9, 1,3-PDO production yields ranged from 0.52 ± 0.01 to 0.64 ± 0.00 [Formula: see text], with the highest values obtained at pH 7 and 8. An Enterobacteriaceae member closely related to Citrobacter freundii was strongly enriched at all pH values. Within the less dominant bacterial species, two different microbial community structures were found, one at acid pH values and another at neutral to basic pH values. 1,3-PDO production was improved at pH values over 7. It was anti-correlated with lactate and ethanol production but positively correlated with acetate production. No direct co...
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Interspecies electron transfer is a common way to couple metabolic energy balances between different species in mixed culture consortia. Direct interspecies electron transfer (DIET) mechanism has been recently characterised with Geobacter... more
Interspecies electron transfer is a common way to couple metabolic energy balances between different species in mixed culture consortia. Direct interspecies electron transfer (DIET) mechanism has been recently characterised with Geobacter species which couple the electron balance with other species through physical contacts. Using this mechanism could be an efficient and cost-effective way to directly control redox balances in co-culture fermentation. The present study deals with a co-culture of Geobacter sulfurreducens and Clostridium pasteurianum during glycerol fermentation. As a result, it was shown that Geobacter sulfurreducens was able to grow using Clostridium pasteurianum as sole electron acceptor. C. pasteurianum metabolic pattern was significantly altered towards improved 1,3-propanediol and butyrate production (+37% and +38% resp.) at the expense of butanol and ethanol production (-16% and -20% resp.). This metabolic shift was clearly induced by a small electron uptake th...
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This study evaluated the influence of the co-substrate proportions (0-60% of cardboard in dry basis) and the initial total solid contents (20-40%) on the batch fermentation performance. Maximum hydrogen yields were obtained when... more
This study evaluated the influence of the co-substrate proportions (0-60% of cardboard in dry basis) and the initial total solid contents (20-40%) on the batch fermentation performance. Maximum hydrogen yields were obtained when mono-fermenting food waste at high solids contents (89mlH2·gVS(-1)). The hydrogen yields were lower when increasing the proportions of cardboard. The lower hydrogen yields at higher proportions of cardboard were translated into higher yields of caproic acid (up to 70.1gCOD·kgCODbio(-1)), produced by consumption of acetic acid and hydrogen. The highest substrate conversions were achieved at low proportions of cardboard, indicating a stabilization effect due to higher buffering capacities in co-fermentation. Clostridiales were predominant in all operational conditions. This study opens up new possibilities for using the cardboard proportions for controlling the production of high added-value products in dry co-fermentation of food waste.
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Electro-fermentation is a new technique that could be used to influence the global metabolism in mixed-culture fermentation. In this study, a mixed-culture cathodic electro-fermentation of glycerol was investigated. Both microbial... more
Electro-fermentation is a new technique that could be used to influence the global metabolism in mixed-culture fermentation. In this study, a mixed-culture cathodic electro-fermentation of glycerol was investigated. Both microbial community structure and metabolic patterns were altered when compared to standard fermentation. This microbial population shift was more significant when the working electrodes were pre-colonized by Geobacter sulfurreducens, before electro-fermentation. The electro-fermenting microbial community was more efficient for producing 1,3-propanediol with an improved yield of 10% when compared with fermentation controls. Such improvement did not require high energy and total electron input represented < 1% of the total electron equivalents provided only by glycerol. A linear model was developed to estimate the individual metabolic pattern of each operational taxonomic unit. Application of this model compared to the experimental results suggests that the change...
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Extracellular electron transfer (EET) is a mechanism that allows energetic coupling between two microorganisms or between a microorganism and an electrode surface. EET is either supported by direct physical contacts or mediated by... more
Extracellular electron transfer (EET) is a mechanism that allows energetic coupling between two microorganisms or between a microorganism and an electrode surface. EET is either supported by direct physical contacts or mediated by electron shuttles. So far, studies dealing with interspecies EET (so-called IET) have mainly focused on possible syntrophic interactions between microorganisms favoured by this mechanism. In this article, the case of fermentative bacteria receiving extracellular electrons while fermenting a substrate is considered. A thermodynamical analysis based on metabolic energy balances was applied to re-investigate experimental data from the literature. Results suggest that the observations of a decrease of cell biomass yields of fermentative electron-accepting species, as mostly reported, can be unravelled by EET energetics and correspond to parasitism in case of IET. As an illustration, the growth yield decrease of Propionibacterium freudenreichii (-14%) observed ...
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Chemistry, Biofilms, Modeling, Control, Microbial diversity, and 15 moreMedicine, Multidisciplinary, Dynamics, Biofilm, Computer Simulation, Nitrification, Bacteria, Nitrogen, Bioreactors, Microbial Diversity, Nitrogen Removal, Ammonia oxidizing bacteria, Autotrophic nitrogen removal, Oxygen concentration, and nitrite accumulation
Abstract Fixed-biomass reactors present the main advantage of increasing the hydrogen production rates by supporting high organic loading rates. However, the use of complex natural inoculum often precludes a long-term operation through... more
Abstract Fixed-biomass reactors present the main advantage of increasing the hydrogen production rates by supporting high organic loading rates. However, the use of complex natural inoculum often precludes a long-term operation through the rapid emergence of methanogens. In this study, an Anaerobic Sequencing Batch Biofilm Reactor (ASBBR) was inoculated with a simplified H 2 -producing culture to evaluate its influence on robustness and more particularly on methanogenic activity. An ASBBR was operated over 6 months with unsterile lactose-rich effluent and under Hydraulic Retention Time ranging from 1 to 34 h. Hydrogen performances in terms of productivity and yields ranged from 0.23 to 519 mmole H2 L −1 d −1 and 0.01 to 7.11 mole H2 mole lactose −1 , respectively. No significant methane production was observed all along the experimental procedure, showing that inoculating with a simplified and highly enriched preculture could increase substantially the robustness of the process. Specific preparation of the inoculum may represent a solution to sustain long-term operation of biofilm-based reactors.
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Little information exists on the fate of antibiotics, hormones and their associated endocrine activity during manure treatment processes. Thus, the aim of this study was to assess the fate of such emerging pollutants and multiple... more
Little information exists on the fate of antibiotics, hormones and their associated endocrine activity during manure treatment processes. Thus, the aim of this study was to assess the fate of such emerging pollutants and multiple endocrine activities during manure treatment coupling anaerobic digestion and aerobic/anoxic conditions under mesophilic conditions. The thermophilic anaerobic digestion was also studied. The endocrine activities tested include estrogenic (ER), dioxin-like (AhR), peroxisome proliferator receptor gamma (PPAR), pregnane X (PXR) and androgenic (AR) activities. Our results showed that antibiotics and steroid hormones were recalcitrant to biodegradation under anaerobic conditions in both mesophilic and thermophilic temperatures. In contrast, antibiotic and hormone removal reached between 76 to 95 % when anaerobic digestion was coupled to aerobic/anoxic treatment. In absence of anaerobic predigestion, hormone removal in aerobic/anoxic conditions was about 40 %; ...
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Dark fermentation of lignocellulosic residues is a process of interest producing simultaneously biohydrogen and valuable industrial endproducts (volatile fatty acids, organic acids or alcohols). Theoretically, wet (<15% Total Solid... more
Dark fermentation of lignocellulosic residues is a process of interest producing simultaneously biohydrogen and valuable industrial endproducts (volatile fatty acids, organic acids or alcohols). Theoretically, wet (<15% Total Solid (TS)) and dry (>20% TS) fermentation technologies can be operated at mesophilic (35°C) and thermophilic (55°C) temperatures [1]. Even though high temperatures favour substrate hydrolysis, high TS content processes could lead to microbial limitations [2]. The aim of this study was to assess the impact of water content reduction on dark fermentation processes at mesophilic and thermophilic temperatures. An experiment was set- up to study the impact of TS content from wet to dry conditions (10% to 34% TS) in discontinuous anaerobic batch tests operated with wheat straw as substrate and under mesophilic and thermophilic conditions. For both temperatures, more than 15 NmH2.gTS-1were obtained in wet fermentation, and the results indicated a decrease of su...
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ABSTRACT Dark fermentation is an intermediate microbial process occurring along the anaerobic biodegradation of organic matter. Saline effluents are rarely treated anaerobically since they are strongly inhibited by high salt... more
ABSTRACT Dark fermentation is an intermediate microbial process occurring along the anaerobic biodegradation of organic matter. Saline effluents are rarely treated anaerobically since they are strongly inhibited by high salt concentrations. This study deals with the characterization of microbial communities producing hydrogen under moderate halophilic conditions. A series of batch experiments was performed under anaerobic conditions, with glucose as substrate (5 g L−1) and under increasing NaCl concentrations ranging from 9 to 75 gNaCl L−1. A saline sediment of a lagoon collecting salt factory wastewaters was used as inoculum. Interestingly, a gradual increase of the biohydrogen production yield according to NaCl concentration was observed with the highest value obtained for the highest NaCl concentration, i.e. 75 gNaCl L−1, suggesting a natural adaptation of the sediment inoculum to salt. This work reports for the first time the ability of mixed culture to produce hydrogen in moderate halophilic environment. In addition, maximum hydrogen consumption rates decreased while NaCl concentration increased. A gradual shift of the bacterial community structure, concomitant to metabolic changes, was observed with increasing NaCl concentrations, with the emergence of bacteria belonging to Vibrionaceae as dominant bacteria for the highest salinities.
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... A4 on MMT A----A Bacterial growth; + --- Nitrile-hydratase activity ... Amaud, A., Galzy, P. and Jallageas, JC (1980) Production d&amp;#x27;acide a-amints sttrtospkifiques par ... World, 114,75-81 Brenon, M. (1982) Le traitement... more
... A4 on MMT A----A Bacterial growth; + --- Nitrile-hydratase activity ... Amaud, A., Galzy, P. and Jallageas, JC (1980) Production d&amp;#x27;acide a-amints sttrtospkifiques par ... World, 114,75-81 Brenon, M. (1982) Le traitement graphique des surfaces: un support rl I&amp;#x27;optimisation de processus ...
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This paper details a dynamic evaluation of a 1 m3 fixed bed anaerobic digestion reactor in response to organic overloads and toxicant shock loads. Raw industrial wine distillery wastewater was used as a reference substrate and several... more
This paper details a dynamic evaluation of a 1 m3 fixed bed anaerobic digestion reactor in response to organic overloads and toxicant shock loads. Raw industrial wine distillery wastewater was used as a reference substrate and several disturbances were applied to the process: (i) organic overloads with and without pH regulation in the feeding line, (ii) adding of ammonia in
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Up to date a few electroactive bacteria embedded in biofilms are described to catalyze both anodic and cathodic reactions in bioelectrochemical systems (i.e. bidirectional electron transfer). How these bacteria transfer electrons to or... more
Up to date a few electroactive bacteria embedded in biofilms are described to catalyze both anodic and cathodic reactions in bioelectrochemical systems (i.e. bidirectional electron transfer). How these bacteria transfer electrons to or from the electrode is still uncertain. In this study the extracellular electron transfer mechanism of bacteria within an electroactive biofilm was investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). First, a mature anodic electroactive biofilm was developed from an activated sludge sample (inoculum), acetate as electron donor and a poised electrode (+397mV vs. SHE). Later, this biofilm was &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;switched&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; to biocathodic conditions by feeding it with a medium containing nitrates and poising the electrode at -303mV vs. SHE. The electrochemical characterization indicated that both, acetate oxidation and nitrate reduction took place at a similar formal potential of -175±05 and -175±34mV vs. SHE, respectively. The biofilm was predominantly composed by Geobacter sp. at both experimental conditions. Taken together, the results indicated that both processes could be catalyzed by using the same electron conduit, and most likely by the same bacterial consortium. Hence, this study suggests that electroactive bacteria within biofilms could use the same electron transfer conduit for catalyzing anodic and cathodic reactions.
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The solid-state anaerobic digestion (SS-AD) of wheat straw was characterized under low inoculated batch tests during 244days. High levels of degradation of the cellulose (52%±1) and hemicelluloses (55%±2) were observed at the final stages... more
The solid-state anaerobic digestion (SS-AD) of wheat straw was characterized under low inoculated batch tests during 244days. High levels of degradation of the cellulose (52%±1) and hemicelluloses (55%±2) were observed at the final stages and associated to a methane yield of 204±16NmLgTS(-1). Ultrastructural observations, using transmission electronic microscopy, indicated that microorganisms degraded wheat straw from the central to the outer tissue (i.e. parenchyma to epidermis), depending on cell chemical, physical accessibility and the degree of lignification. Furthermore, major degradation of sclerenchyma secondary walls was observed. The bioaccessibility of lignocellulosic structures of wheat straw is mainly limited by the external waxy layer (cuticle), tertiary cell walls, high silica content and access to the cell lumen. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Invasion of non-native species can drastically affect the community composition and diversity of engineered and natural ecosystems, biofilms included. In this study, a molecular community fingerprinting method was used to monitor the... more
Invasion of non-native species can drastically affect the community composition and diversity of engineered and natural ecosystems, biofilms included. In this study, a molecular community fingerprinting method was used to monitor the putative establishment and colonization of allochthonous consortia in resident multi-species biofilms. To do this, biofilms inoculated with tap water or activated sludge were grown for 10 days in bubble column reactors W1 and W2, and S, respectively, before being exposed to non-native microbial consortia. These consortia consisted of fresh activated sludge suspensions for the biofilms inoculated with tap water (reactors W1 and W2) and of transplanted mature tap water biofilm for the activated sludge biofilm (reactor S). The introduction of virgin, unoccupied coupons into W1 and W2 enabled us to additionally investigate the competition for new resources (space) among the resident biofilm and the allochthonous consortia. CE-SSCP revealed that after the invasion event changes were mostly observed in the abundance of the dominant species in the native biofilms rather than their composition. This suggests that the resident communities within a bioreactor immediately outcompete the allochthonous microbes and shape the microbial community assemblage on both new coupons and already colonized surfaces for the short term. However, with time, latent members of the allochthonous community might grow up affecting the diversity and composition of the original biofilms.
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Agro-industries are facing many economic and environmental problems associated with seasonal generation of liquid and solid waste. In order to reduce treatment costs and to cope with seasonal variation, we have developed a hybrid... more
Agro-industries are facing many economic and environmental problems associated with seasonal generation of liquid and solid waste. In order to reduce treatment costs and to cope with seasonal variation, we have developed a hybrid anaerobic reactor operated sequentially by using lignocellulosic biomass (LB) as biofilm carrier support. Six LBs were tested to evaluate the treatment performance during a succession of two start-up periods, separated by a non-feeding period. After a short acclimation phase of several days, all the reactors succeeded in starting-up in less than 1month to reach an organic loading rate of 25gCODL(-1)d(-1). In addition, they restarted-up successfully in only 15days after a 3month non-feeding period, indicating that biofilms conserved their biological activities during this last phase. As a consequence, the use of LB as a biofilm support gives the potential to sustain seasonal variations of wastewater loads for industrial application.
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The effect of milling pretreatment on performances of Solid-State Anaerobic Digestion (SS-AD) of raw lignocellulosic residue is still controverted. Three batch reactors treating different straw particle sizes (milled 0.25 mm, 1 mm and 10... more
The effect of milling pretreatment on performances of Solid-State Anaerobic Digestion (SS-AD) of raw lignocellulosic residue is still controverted. Three batch reactors treating different straw particle sizes (milled 0.25 mm, 1 mm and 10 mm) were followed during 62 days (6 sampling dates). Although a fine milling improves substrate accessibility and conversion rate (up to 30% compared to coarse milling), it also increases the risk of media acidification because of rapid and high acids production during fermentation of the substrate soluble fraction. Meanwhile, a gradual adaptation of microbial communities, were observed according to both reaction progress and methanogenic performances. The study concluded that particle size reduction affected strongly the performances of the reaction due to an increase of substrate bioaccessibility. An optimization of SS-AD processes thanks to particle size reduction could therefore be applied at farm or industrial scale only if a specific managemen...