Simultaneous characterization of porous and non-porous electrodes in microbial electrochemical systems

Adequate electrochemical characterization of electrode material/biofilms is crucial for a comprehensive understanding and comparative performance of bioelectrochemical systems (BES). However, their responses are greatly affected by the metabolic activity and growth of these living entities and/or the interference of electrode wiring that can act as an electroactive surface for growth or constitute a source of contamination by corrosion. This restricts the meaningful comparison of the performance of distinct electrode materials in BES. This work describes a methodology for simultaneous electrochemical control and measurement of the microbial response on different electrode materials under the same physicochemical and biological conditions. The method is based on the use of a single channel potentiostat and one counter and reference electrodes to simultaneously polarize several electrode materials in a sole bioelectrochemical cell. Furthermore, various strategies to minimize wiring corrosion are proposed. The proposed methodology, then, will enable a more rigorous characterization of microbial electrochemical responses for comparisons purposes.The authors thank the MINECO and FEDER (RYC-2017-23618) for financial support. This investigation has received funding from the European Union's Horizon 2020 research and innovation programme under the grant agreements No. 642190 (Project “iMETLAND”; http://www.imetland.eu) and No. 826244 (Project “ELECTRA”; http://www.electra.site). Amanda Prado de Nicolás was funded by the “Formación de Personal Investigador (FPI)” PhD fellowship programme from the University of Alcalá

Strategies for Reducing the Start-up Operation of Microbial Electrochemical Treatments of Urban Wastewater

Microbial electrochemical technologies (METs) constitute the core of a number of emerging technologies with a high potential for treating urban wastewater due to a fascinating reaction mechanism—the electron transfer between bacteria and electrodes to transform metabolism into electrical current. In the current work, we focus on the model electroactive microorganism Geobacter sulfurreducens to explore both the design of new start-up procedures and electrochemical operations. Our chemostat-grown plug and play cells, were able to reduce the start-up period by 20-fold while enhancing chemical oxygen demand (COD) removal by more than 6-fold during this period. Moreover, a filter-press based bioreactor was successfully tested for both acetate-supplemented synthetic wastewater and real urban wastewater. This proof-of-concept pre-pilot treatment included a microbial electrolysis cell (MEC) followed in time by a microbial fuel cell (MFC) to finally generate electrical current of ca. 20 A·m−2 with a power of 10 W·m−2 while removing 42 g COD day−1·m−2. The effective removal of acetate suggests a potential use of this modular technology for treating acetogenic wastewater where Geobacter sulfurreducens outcompetes other organisms.Research was supported by the European Union through the Bacwire FP7 Project (Contract #NPM4-SL-2009-229337)

Electroactive biochar outperforms highly conductive carbon materials for biodegrading pollutants by enhancing microbial extracellular electron transfer

The development and full-scale application of microbial electrochemical technologies (METs) for wastewater treatment demand massive amounts of electroconductive carbon materials to promote extracellular electron transfer (EET) and biodegradation. While the potential capability of these materials and their properties to design efficient systems is still in their infancy, the state-of-the-art METs are based on highly-conductive fossil-derived carbons. In this work we evaluate the performance of different electroconductive carbon materials (graphite, coke, biochar) for supporting microbial EET and treating urban wastewater. Our results reveal that the electroconductive biochar was the most efficient biofilter-material, enabling to stimulate bioremediation at anodic potential as high as 0.6 V (maximum removal efficiency (92%) and degradation rate (185 g-COD m−3d−1)), and to fulfill the discharge limits under conditions where the other materials failed. A deep materials characterization suggests that, despite electroconductivity is necessary, the optimal EET on biochar can be mainly assigned to its large number of electroactive surface oxygen functionalities, which can reversibly exchange electrons through the geobattery mechanism. We propose the modulation of quinone-like e-acceptors by anodic polarization to promote the biodegradation capability of carbon materials. Because of its great efficiency and sustainability, electroactive biochar will greatly expand the applicability of METs at large scale.This investigation has received funding from the European Union’s Horizon 2020 research and innovation programme under the grant agreement No. 642190 (Project “iMETLAND”; http://www.imetland.eu). Amanda Prado de Nicolás was funded by the “Formación de Personal Investigador (FPI)“ PhD fellowship programme from the University of Alcalá. The authors thank the MINECO and FEDER (IJCI-2014-20012) for financial support

Insights into the effect of a biocathode on driving mixed-culture fermentations under low electron recovery

4th EU-ISMET 2018, Newcastle upon Tyne (United Kingdom) from 12th to 14th September 2018This activity is supported by the Spanish Ministry of Education through the FPU scholarship (FPU14/05457)This activity is supported by the Spanish Ministry of Education through the FPU scholarship (FPU14/05457

Bioelectrochemical removal of indigo dye in wastewater.

ABSTRACTMotivation: Textile sector is one of the main industrial consumers of water and, consequently, is generating a significant amount of wastewater loaded with metals, salts, acids, nitrate and organic pollutants such as dyes. Such dyes are carcinogenic and exhibit toxicity for plants and microorganism after disccharge [1]. Indeed, indigo dye is broadly commercialised as blue dye in the denim industry. It has a very strong blue colour and its complex structure make it difficult to degrade.Microbial electrochemical technologies (MET) are a promising option for the treatment of different organic pollutants present in wastewater. These technologies exploit the ability of some microorganisms (electroactive bacteria) to exchange electrons with electroconductive material in order to stimulate the oxidative metabolism [2]. Among the electroactive bacteria reported so far, Purple Phototrophic Bacteria (PPB) are one of the most versatile and diverse group of microorganisms that are capable of tdegrading complex structures as well [3].In this work we propose a electrobioremediation strategy based on activating PPB by means of electrodes to degrade indigo dye present in textile wastewater. Besides, the influence of the electrode in the microbial population will also be studied to evaluate the polarization effect in the wastewater treatment.Methods: We used a PPB culture enriched from brewery wastewater. To simulate real wastewater conditions we made asynthetic textile wastewater with indigo as the sole carbon source. The PPB were grown heterotrophically at 30ºC and illuminated with infrared light. Firstly, we study the response of PPBs to indigo dye in two different reactors with 0.1 g/L and 0.5 g/L of dye.Secondly, we compared the impact of i) open circuit polarization (ocp) and ii) polarization at +0.4V (vs. Ag/AgCl) using aelectrochemical cell in media supplemented with 0.1 g/L of indigo. The working electrode was graphite, a platinized titanium was used as counter electrode and a Ag/AgCl as reference electrode. We carried a polarized negative control with the synthetic wastewater and 0,1 g/L of indigo without PPB.We measured the optical density (A590) of the culture of PPB, variations in the colour of the indigo dye (A610) and the chemical oxygen demand (COD). The electrochemical analyses consisted in chronoamperometries and cyclic voltammetries during the course of the assay

Electrochemically-assisted growth of purple phototrophic bacteria for PHB production

Motivation:Purple Phototrophic Bacteria (PPB) are considered one of the most versatile microorganisms ever found. They have autotrophic, heterotrophic and photoheterotrophic metabolism in order to adapt the diferent conditions in the environment. This characteristics altogether with the capacity of produce and accumulate bioplastics such as polyhydroxybutyrate (PHB) make PPB an interesting choice for biotechnological proccesses (Monroy & Buitrón, 2020).The microbial electrochemical technologies (METs) have been succesfully used in the last few years as an alternative to conventional wastewater treatment. With the development of this technologies a wide range of applications have been discovered. For example, in Microbial Electrochemical Synthesis (MES), we can modulate the metabolism of the microorganisms attached to the electrode with the application of an electric current and, in consequence, altering the redox power inside the cell (Guzman et al., 2019).The main purpose of this work consists in combining the qualities of the PPB together with METs to study the influence of the latter in bacterial metabolism and PHB biosynthesis. Furthermore, the production and quantification of the biopolymer will be optimized to increase the PHB yield.Methods:The enrichment of PPB culture was carried out from brewery wastewater. Near infrarred light was used to activate PPB growth. Four different reactors were built, one half was polarized, the other ona was kept in open circuit. Microorganisms were cultured with acetate as carbon source, and ammonium chloride as nitrogen source under various [Acetate]:[ammonia] ratios to test efficiency in PHB synthesis. To induce PHB production the "feast and famine" technique was conducted, in which, the nitrogen source is retired so that the microrganisms get stressed (Padovani, Emiliani, Giovanelli, Traversi, & Carlozzi, 2018).Growth was measured by spectrophotometry, acetate consumption was analysed by chemical oxygen demand, the ammonia assimilation was quantified by ionic chromatograph and the PHB production was studied with the indirect measurement of crotonic acid in the High Performance Liquid Chromatograhy (HPLC).The reactors were poised using a potentiostat, the electrodes used in this work were graphite for the working electrode; platinized titanium for the counter electrode and a reference electrode.Electric current was measured every second and cyclic voltammetries were performed to prove electroactivity

Electroactive Biochar for Large-Scale Environmental Applications of Microbial Electrochemistry

Large-scale environmental applications of microbial electrochemical technologies (MET), such as wastewater treatment, bioremediation, or soil improvement, would be more feasible if bioelectrodes could be fabricated with simpler materials. Biochar with potentially improved electroactive properties (e-biochar) can be an ideal candidate for this scope, being at the same time widely available, biocompatible, and fully recyclable at its end-of-life as a soil amendment. Here we review the application of biochar to MET, to set benchmarks aimed at tuning the electroactive properties of such materials from the point of view of MET. The precursor biomass, thermochemical process conditions, and pre-, in situ-, and/or post-treatments should tailor optimized combinations of electrical conductivity, capacitance, superficial redox-active and electroactive functional groups, porosity distribution, and capacity to host electroactive microbial communities. We also discuss methods to rigorously characterize e-biochar properties and the most relevant multidisciplinary research challenges toward its application in large-scale MET.This work has been financed by the Italian Ministry of University and Research (MIUR), within the SIR2014 Grant, project RBSI14JKU3. Dr. R. Berenguer also thanks the Spanish Ministerio de Economía y Competitividad and FEDER funds (RYC-2017-23618 and CTM2015-71520-C2-1-R) for financial support. Ricardo Louro and Catarina Paquete thank Fundação para a Ciência e a Tecnologia (FCT) Portugal [PTDC/BBBBQB/4178/2014 and PTDC/BIA-BQM/30176/2017], by Project LISBOA-01-0145-FEDER-007660 (Microbiologia Molecular, Estrutural e Celular) funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI), and by ITQB research unit GREEN-it “Bioresources for sustainability” (UID/Multi/04551/2013). This work has also received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810856. This investigation has also received funding from the European Union’s Horizon 2020 research and innovation programme under the grant agreement No. 642190 (Project “iMETLAND”; http://www.imetland.eu)

Assessing METland® Design and Performance Through LCA: Techno-Environmental Study With Multifunctional Unit Perspective

Conventional wastewater treatment technologies are costly and energy demanding; such issues are especially remarkable when small communities have to clean up their pollutants. In response to these requirements, a new variety of nature-based solution, so-called METland®, has been recently develop by using concepts from Microbial Electrochemical Technologies (MET) to outperform classical constructed wetland regarding wastewater treatment. Thus, the current study evaluates two operation modes (aerobic and aerobic–anoxic) of a full-scale METland®, including a Life Cycle Assessment (LCA) conducted under a Net Environmental Balance perspective. Moreover, a combined technical and environmental analysis using a Net Eutrophication Balance (NEuB) focus concluded that the downflow (aerobic) mode achieved the highest removal rates for both organic pollutant and nitrogen, and it was revealed as the most environmentally friendly design. Actually, aerobic configuration outperformed anaero/aero-mixed mode in a fold-range from 9 to 30%. LCA was indeed recalculated under diverse Functional Units (FU) to determine the influence of each FU in the impacts. Furthermore, in comparison with constructed wetland, METland® showed a remarkable increase in wastewater treatment capacity per surface area (0.6 m2/pe) without using external energy. Specifically, these results suggest that aerobic–anoxic configuration could be more environmentally friendly under specific situations where high N removal is required. The removal rates achieved demonstrated a robust adaptation to influent variations, revealing a removal average of 92% of Biology Oxygen Demand (BOD), 90% of Total Suspended Solids (TSS), 40% of total nitrogen (TN), and 30% of total phosphorus (TP). Moreover, regarding the global warming category, the overall impact was 75% lower compared to other conventional treatments like activated sludge. In conclusion, the LCA revealed that METland® appears as ideal solution for rural areas, considering the low energy requirements and high efficiency to remove organic pollutants, nitrogen, and phosphates from urban wastewater

Alteration in the Culex pipiens transcriptome reveals diverse mechanisms of the mosquito immune system implicated upon Rift Valley fever phlebovirus exposure

Rift Valley fever phlebovirus (RVFV) causes an emerging zoonotic disease and is mainly transmitted by Culex and Aedes mosquitoes. While Aedes aegypti-dengue virus (DENV) is the most studied model, less is known about the genes involved in infection-responses in other mosquito-arboviruses pairing. The main objective was to investigate the molecular responses of Cx. pipiens to RVFV exposure focusing mainly on genes implicated in innate immune responses. Mosquitoes were fed with blood spiked with RVFV. The fully-engorged females were pooled at 3 different time points: 2 hours post-exposure (hpe), 3- and 14-days post-exposure (dpe). Pools of mosquitoes fed with non-infected blood were also collected for comparisons. Total RNA from each mosquito pool was subjected to RNA-seq analysis and a de novo transcriptome was constructed. A total of 451 differentially expressed genes (DEG) were identified. Most of the transcriptomic alterations were found at an early infection stage after RVFV exposure. Forty-eight DEG related to immune infection-response were characterized. Most of them were related with the RNAi system, Toll and IMD pathways, ubiquitination pathway and apoptosis. Our findings provide for the first time a comprehensive view on Cx. pipiens-RVFV interactions at the molecular level. The early depletion of RNAi pathway genes at the onset of the RVFV infection would allow viral replication in mosquitoes. While genes from the Toll and IMD immune pathways were altered in response to RVFV none of the DEG were related to the JAK/STAT pathway. The fact that most of the DEG involved in the Ubiquitin-proteasome pathway (UPP) or apoptosis were found at an early stage of infection would suggest that apoptosis plays a regulatory role in infected Cx. pipiens midguts. This study provides a number of target genes that could be used to identify new molecular targets for vector control.info:eu-repo/semantics/publishedVersio

Electroactive biofilms: new means for electrochemistry

This work demonstrates that electrochemical reactions can be catalysed by the natural biofilms that form on electrode surfaces dipping into drinking water or compost. In drinking water, oxygen reduction was monitored with stainless steel ultra-microelectrodes under constant potential electrolysis at )0.30 V/SCE for 13 days. 16 independent experiments were conducted in drinking water, either pure or with the addition of acetate or dextrose. In most cases, the current increased and reached 1.5–9.5 times the initial current. The current increase was attributed to biofilm forming on the electrode in a similar way to that has been observed in seawater. Epifluorescence microscopy showed that the bacteria size and the biofilm morphology depended on the nutrients added, but no quantitative correlation between biofilm morphology and current was established. In compost, the oxidation process was investigated using a titanium based electrode under constant polarisation in the range 0.10–0.70 V/SCE. It was demonstrated that the indigenous micro-organisms were responsible for the current increase observed after a few days, up to 60 mA m)2. Adding 10 mM acetate to the compost amplified the current density to 145 mA m)2 at 0.50 V/SCE. The study suggests that many natural environments, other than marine sediments, waste waters and seawaters that have been predominantly investigated until now, may be able to produce electrochemically active biofilm