Enhancing thermophilic dark fermentative hydrogen production at high glucose concentrations via bioaugmentation with Thermotoga neapolitana

The aim of the present study was to investigate the effect of gradually increasing glucose concentrations (from 5.6 to 111 mmol L−1) on the fermentative H2 production with and without bioaugmentation. A stirred tank reactor (STR) was operated at 70 °C and inoculated with a hyperthermophilic mixed culture or a hyperthermophilic mixed culture bioaugmented with Thermotoga neapolitana. With both the unaugmented (control) and augmented cultures, the H2 production rate was improved when the initial glucose concentration was increased. In contrast, the highest H2 yield (1.68 mol H2 mol−1 glucose consumed) was obtained with the augmented culture at the lowest glucose concentration of 5.6 mmol L−1 and was 37.5% higher than that obtained with the unaugmented culture at the same feed glucose concentration. Overall, H2 production rates and yields were higher in the bioaugmented cultures than in the unaugmented cultures whatever the glucose concentration. Quantitative polymerase chain reaction targeting T. neapolitana hydA gene and MiSeq sequencing proved that Thermotoga was not only present in the augmented cultures but also the most abundant at the highest glucose concentrations.acceptedVersionPeer reviewe

Analyse des écoulements dans les cuves agitées

National audienc

Structure de l'hydrodynamique générée par une turbine de Rushton

L'hydrodynamique 3D générée par une turbine de Rushton est analysée expérimentalement à l'aide de la technique de mesure P.I.V.. Une technique de moyenne de phase est mise en œuvre pour extraire les mouvements moyen, turbulent et organisé lié au passage périodique des pales de l'agitateur. Les résultats sont tout d'abord validés par rapport aux nombreuses données de la bibliographie. La technique de décomposition triple est utilisée pour quantifier les échanges d'énergie cinétique entre les trois mouvements ; les termes présents dans les équations de bilan d'énergie cinétique des trois mouvements sont calculés et le taux de dissipation visqueux de l'énergie cinétique turbulente est estimé. Une définition objective des tourbillons est mise en place pour localiser les vortex traînants et leur trajectoire dans la cuve : les interactions entre ces structures et les mouvements moyen et turbulent sont quantifiées. Nous terminons par la caractérisation des structures de la turbulence en termes d'échelles (Kolmogorov, Taylor, macro-échelle) et d'anisotropieThe 3D hydrodynamic generated by a Rushton turbine is analyzed by P.I.V. technique. Phase average acquisition is performed in order measure mean velocity field, turbulent motion and organized flow induced by the impeller blade (trailing vortices). Results are compared firstly to previous works. Triple decomposition method enables to quantify kinetic energy exchanges between the three motions. Moreover, one can calculate the terms that constitute the kinetic energy balance of the three motions: in particular, the viscous dissipation rate of turbulent kinetic energy is estimated. An objective definition of vortex is used to locate the trailing vortices and their trajectories through the tank: interactions between organized structure and mean and turbulent flows are outlook. Finally, the structure of turbulence is defined in terms of length-scales (Kolmogorov, Taylor, macro scale) and anisotropyTOULOUSE-INSA (315552106) / SudocSudocFranceF

Management strategies of the heat provided by a fireplace or an insert

International audienc

Gestion de la chaleur fournie par une cheminée ou un insert

International audienc

Lien entre paramètres opératoires, micro-organismes et performances de la digestion anaérobie par voie sèche

La digestion anaérobie est un processus de transformation de la matière organique en biogaz riche en méthane. Les déchets solides sont le plus souvent traités par une technologie par voie sèche qui est caractérisée par des teneurs en matières sèches supérieures à 20%. Du fait de la faible teneur en eau, la digestion sèche présente de nombreuses inconnus scientifiques, tant au niveau microbiologique et physico-chimique. Le but de cette thèse est de comprendre l'influence des parametres opératoires spécifiques à la digestion anaérobie par voie sèche sur les performances et le comportement des communautés microbiennes de ce processus. Les résultats obtenus montrent que l'augmentation de la teneur en matières sèches au-delà de 30% et la diminution de la surface spécifique d'échange ont un effet négatif sur le processus de digestion anaérobie. En effet lorsque la teneur en matière sèche est supérieure à 30%, le transfert des gaz dissous du milieu réactionnel vers le ciel gazeux peut limiter la méthanisation. L'analyse des populations microbiennes montre la présence de bio-indicateurs bactériens liés au non fonctionnement de la digestion anaérobie. Ces bio-indicateurs sont des clostridium et sont présents quel que soit l'inoculum utilisé. L'étude des populations méthanogènes montre une sensibilité de ces microorganismes à leur environnement : des shifts de populations méthanogènes ont été observés en fonction de la concentration en matières sèches. Ce travail a permis d'accroître les connaissances dans le domaine de la digestion anaérobie sèche, ces connaissances pouvant contribuer à améliorer les performances des procédés.Anaerobic digestion is the transformation of organic matter into biogas rich in methane. Solid waste is treated by dry anaerobic digestion process with a total solid content higher than 20%. The high solids content make the process difficult to control. The aim of this work is to study the influence of operating parameters specific to dry anaerobic digestion on performances and behavior of microbial communities. The results show that increasing the solids content higher than 30% and decreasing the specific surface area of change have a negative effect on the anaerobic digestion process. Indeed, when the solids content exceeds 30%, the transfer of dissolved gas from the reaction mixture to the headspace can limit anaerobic digestion. The analysis of microbial populations demonstrates the presence of bacterial bio-indicators related to no-functioning anaerobic digestion. These bio-indicators correspond to the clostridium genus and are present regardless of the inoculum source. The study of methanogenic Archaea shows a sensitivity of these microorganisms. Shifts in the methanogenic populations related to the concentration of total solids were observed. This work has improved the fundamental knowledge of dry anaerobic digestion which can help improve the performance of this process.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Influence of abrasion on biofilm detachment: evidence for stratification of the biofilm

International audienceThe objective of this paper was to understand the detachment of multispecies biofilm caused by abrasion. By submitting a biofilm to different abrasion strengths (collision of particles), stratification of biofilm cohesion could be highlighted and related to stratification of biofilm bacterial communities using the PCR-SSCP fingerprint method. The biofilm comprised a thick top layer, weakly cohesive and composed of one dominant species, and a thin basal layer, strongly cohesive and composed of a more diverse population. These observations suggest that microbial composition of biofilms may be an important parameter in understanding biofilm detachment

Dry Discontinuous Anaerobic Percolation Digestion DDAPD

International audienceAnaerobic digestion is a natural process based on the synergy of several microbial species taking place in anaerobic and reducing environmental conditions. During that process, in which organic matter (OM) is slowly decomposed to simpler compounds, a big part of the energy contained in it is transferred in very energetic molecules like methane CH4 [1], [2]. Broadly studied over the past 50 years, Anaerobic Digestion (AD) is a very known and appreciated process because of its unique common response to several actual problems: waste management, human pollution and energy source differentiation. Technologies based on this process have never stopped to change and improve their performances since the start. If, originally, AD was created to treat liquid effluent mainly, nowadays many AD plants are designed to treat waste in their natural dry form (MSW, rural waste, green waste, etc). Dry AD is overtaking Wet Anaerobic Digestion (WAD) in last years because of some important advantages: smaller reactor size, less mechanical parts and lower investment [3]. Dry Discontinuous Anaerobic Digestion Percolation digestor (DDAPd), a reactor where the solid phase is static and the liquid one is percolating through the bulk, seems to answer better than other to the need of farmers in treating animal wastes which are often under dry form. Moreover, manure, a mixture of feces, urine and straw, is a very common resource in French farms and anaerobic digestion responds to the manure environmental disposal obligations on one side and the need in energy and good quality fertilizer on the other side. DDAPd, and in particular the adaptation of this technology to manure, is not something well studied and a lot of scientific parameters, often set empirically by industries, need nowadays to find a scientific support in order to improve their performances. Two parameters play a major role in DDAPD : first the recirculation which controls the mass transfer, and second the microbial seedling. Since the mass transfer is the major problem in dry reactor, parameters like the recirculation frequencies and the flows as well as variations of these during the digestion or the technical ways to perform it are crucial [4]–[6]. The seedling on the other side can influence the kinetics of the process; so the inoculum state (liquid or solid), the way of mixing it to fresh substrate and its origin are important to be defined [6]–[8]. A third parameter, whose role is on one side to overcome the limitation of batch reactors, a discontinuous biogas production, and on the other side the poorer performances due to nonoptimal conditions, is the coupling strategies of several reactors in what is called a multi-stage process [9], [10]. Through the study of the evoked parameters this work aims at giving a scientific base at the setting and at the process control of AD plants utilizing DDAPD technology for manure digestion

Control of start-up and operation of anaerobic biofilm reactors: An overview of 15 years of research

International audienceAnaerobic biofilm reactors have to be operated in a way that optimizes on one hand the start-up period by a quick growth of an active biofilm, on the other hand the regular operation by an active control of the biofilm to avoid diffusion limitations and clogging. This article is an overview of the research carried out at INRA-LBE for the last 15 years. The start-up of anaerobic biofilm reactors may be considerably shortened by applying a short inoculation period (i.e. contact between the inoculum and the support media). Then, the increase of the organic loading rate should be operated at a short hydraulic retention time and low hydrodynamic constraints in order to favor biofilm growth. After the start-up period, biofilm growth should be controlled to maintain a high specific activity and prevent clogging. This can be done in particulate biofilm systems by using hydrodynamics to increase or decrease shear forces and attrition but is much more difficult in anaerobic fixed bed reactors