Assisted reverse electrodialysis : a novel technique to decrease reverse osmosis energy demand

Assisted reverse electrodialysis (ARED) was introduced as a pre-desalination technique for seawater reverse osmosis (RO) for drinking water production. ARED is comparable to an additional applied pressure along the osmotic pressure in pressure assisted osmosis; a small voltage is applied in the same direction as the open cell voltage to increase the desalination speed compared to reverse electrodialysis (RED). This decreases the required membrane area. The concentration of the dilute compartment increases significantly during ARED operation due to the increased speed of desalination. This results in an overall decrease in total cell resistance. Although the energy demand for ARED is higher than for RED, the ARED-RO process still achieves a decrease in overall energy requirements at higher RO recoveries when compared to stand-alone RO. However, ion-exchange membrane prices will have to come down to 1-10 €/m² for the ARED-RO hybrid to become economically viable at current energy prices

The electron donating capacity of biochar is dramatically underestimated

Biochars have gathered considerable interest for agronomic and engineering applications. In addition to their high sorption ability, biochars have been shown to accept or donate considerable amounts of electrons to/from their environment via abiotic or microbial processes. Here, we measured the electron accepting (EAC) and electron donating (EDC) capacities of wood-based biochars pyrolyzed at three different highest treatment temperatures (HTTs: 400, 500, 600 °C) via hydrodynamic electrochemical techniques using a rotating disc electrode. EACs and EDCs varied with HTT in accordance with a previous report with a maximal EAC at 500 °C (0.4 mmol(e−).gchar−1) and a large decrease of EDC with HTT. However, while we monitored similar EAC values than in the preceding study, we show that the EDCs have been underestimated by at least 1 order of magnitude, up to 7 mmol(e−).gchar−1 for a HTT of 400 °C. We attribute this existing underestimation to unnoticed slow kinetics of electron transfer from biochars to the dissolved redox mediators used in the monitoring. The EDC of other soil organic constituents such as humic substances may also have been underestimated. These results imply that the redox properties of biochars may have a much bigger impact on soil biogeochemical processes than previously conjectured

Hydrodynamic chronoamperometry for probing kinetics of anaerobic microbial metabolism : case study of Faecalibacterium prausnitzii

Monitoring in vitro the metabolic activity of microorganisms aids bioprocesses and enables better understanding of microbial metabolism. Redox mediators can be used for this purpose via different electrochemical techniques that are either complex or only provide non-continuous data. Hydrodynamic chronoamperometry using a rotating disc electrode (RDE) can alleviate these issues but was seldom used and is poorly characterized. The kinetics of Faecalibacterium prausnitzii A2-165, a beneficial gut microbe, were determined using a RDE with riboflavin as redox probe. This butyrate producer anaerobically ferments glucose and reduces riboflavin whose continuous monitoring on a RDE provided highly accurate kinetic measurements of its metabolism, even at low cell densities. The metabolic reaction rate increased linearly over a broad range of cell concentrations (9 x 10(4) to 5 x 10(7) cells. mL(-1)). Apparent Michaelis-Menten kinetics was observed with respect to riboflavin (K-M = 6 mu M; k(cat) = 5.3x10(5) s(-1), at 37 degrees C) and glucose (K-M = 6 mu M; k(cat) = 2.4 x 10(5) s(-1)). The short temporal resolution allows continuous monitoring of fast cellular events such as kinetics inhibition with butyrate. Furthermore, we detected for the first time riboflavin reduction by another potential probiotic, Butyricicoccus pullicaecorum. The ability of the RDE for fast, accurate, simple and continuous measurements makes it an ad hoc tool for assessing bioprocesses at high resolution

Electrochemical upgrading of bio-oil: A proof-of-principle investigation

Fast pyrolysis is an advanced thermochemical conversion technology developed to produce bio-oil from biomass. With lignocellulosic biomass, high product yields (65-75 wt.%) can be attained. Yet, certain unfavorable characteristics of bio-oil impede its utilization prospects. High water content, high oxygen content, together with instability and acidity are the recognized adverse features of bio-oil. Tackling these issues is possible by reducing the oxygen content and/or steering the oxygen functionality of bio-oils. Electrochemical hydrogenation (ECH) is a recently proposed approach targeting the reduction of the reactive compounds in bio-oil (aldehydes, ketones etc.) to their corresponding alcohols, diols [1]. In this attractive approach, the water present in bio-oil acts as the hydrogen source for reduction reactions. Production of alcohols/diols leads to an upgraded/stabilized bio-oil product. Performing the upgrading at ambient temperature, pressure and providing a means to store intermittently available renewable energy (e.g. solar, wind) are clear advantages of the ECH process. In this work, we have investigated electrochemical upgrading of bio-oil using water soluble bio-oil (WSBO) as feed. The ECH experiments, carried out in an electrochemical reactor at a current density of 44 mA cm-2, focused on comparison of several cathode materials. Separated by a cation exchange membrane, cathode and anode chambers of the reactor were filled with WSBO (ca. 20 wt.% bio-oil in aqueous solution) and 1M H2SO4, respectively. The tested cathode materials included Ti, Ru-coated Ti (Ru), Pt-coated Ti (Pt), stainless steel (SS) and CuZn (brass) electrodes. All electrodes converted the carbonyl groups present in bio-oil to a certain extent following the order CuZn\u3e\u3eSS\u3eTi\u3ePt\u3eRu. The trend is explained in close relation with the hydrogen evolution reaction, the preferred pathway especially with Pt and Ru electrodes. Despite the high conversions achieved for some compounds, the selectivity towards desired alcohols and diols was not very high (e.g. 15 – 49% ethylene glycol selectivity for glycolaldehyde conversion) for the electrodes tested in this study. Low Faradaic efficiencies obtained are considered as another challenge keeping the conversion costs high. Nevertheless, electrochemical hydrogenation appears to be a promising technology to upgrade/stabilize bio-oil that deserves further investigation. Next to the experimental results obtained, possible future improvements in catalytic cathode selection and processing options will be discussed as well. References [1] Z. Li, S. Kelkar, L. Raycraft, M. Garedew, J.E. Jackson, D.J. Miller, C.M. Saffron, Green Chem., 2014, 16, 844

Electrical current is more than hydrogen during microbial electrosynthesis and electrofermentation

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Electroactivity across the cell wall of Gram-positive bacteria

Funding Information: This work was supported by national funds through FCT? Funda??o para a Ci?ncia e a Tecnologia, I.P. Project UIDB/04612/2020, UIDP/04612/2020 and PTDC/BIA-BQM/30176/2017, and by the European Union's Horizon 2020 research and innovation programme under grant agreement No 810856. Funding Information: This work was supported by national funds through FCT– Fundação para a Ciência e a Tecnologia, I.P., Project UIDB/04612/2020, UIDP/04612/2020 and PTDC/BIA-BQM/30176/2017, and by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810856. Publisher Copyright: © 2020 The Author(s) Copyright: Copyright 2021 Elsevier B.V., All rights reserved.The growing interest on sustainable biotechnological processes for the production of energy and industrial relevant organic compounds have increased the discovery of electroactive organisms (i.e. organisms that are able to exchange electrons with an electrode) and the characterization of their extracellular electron transfer mechanisms. While most of the knowledge on extracellular electron transfer processes came from studies on Gram-negative bacteria, less is known about the processes performed by Gram-positive bacteria. In contrast to Gram-negative bacteria, Gram-positive bacteria lack an outer-membrane and contain a thick cell wall, which were thought to prevent extracellular electron transfer. However, in the last decade, an increased number of Gram-positive bacteria have been found to perform extracellular electron transfer, and exchange electrons with an electrode. In this mini-review the current knowledge on the extracellular electron transfer processes performed by Gram-positive bacteria is introduced, emphasising their electroactive role in bioelectrochemical systems. Also, the existent information of the molecular processes by which these bacteria exchange electrons with an electrode is highlighted. This understanding is fundamental to advance the implementation of these organisms in sustainable biotechnological processes, either through modification of the systems or through genetic engineering, where the organisms can be optimized to become better catalysts.publishersversionpublishe

Demonstration of the First Prototype of RUGBI, Design and Deployment of a Grid for Bioinformatics

présenté par N. Jacq, proceedings publiés par "Studies in health technology and informatics" seriesInternational audienceRUGBI is an industrial and academic project to design and deploy on top of existing technologies a computing grid offering a set of grid and bioinformatics services to analyse proteins. It aims to support life sciences SMEs for computing and storage, to deploy an interregional grid for bioinformatics and to create a biologists community in a grid environment. The proposed demonstration presents the first prototype of RUGBI architecture and bioinformatics services