Bioelectrochemical systems (BESs) towards conversion of carbon monoxide/syngas: A mini-review

Microbial conversion of carbon monoxide (CO)/syngas has been extensively investigated. The microbial conversion of CO/syngas offers numerous advantages over chemically catalyzed processes e.g. the specificity of the biocatalysts, the operation at ambient conditions and high conversion efficiencies. Bioelectrochemical systems (BESs) exploit the capacity of electrochemically active bacteria (EAB) to use insoluble electron acceptors or donors to produce electricity or added-value compounds. Electricity production from different organic sources in BESs has been broadly demonstrated, whereas electricity production from CO/syngas has been very little reported. Acetate oxidation by a consortium of carboxydotrophic and CO-tolerant EAB has been suggested to be the main pathway responsible for indirect electricity generation from CO/syngas. Although electricity production in BESs from several organic sources has been widely investigated, the interest on BESs research is currently moving to the production of added-value compounds by electro-fermentation (EF) processes. EF allows to modify redox balances by the use of electric circuits to fine tune metabolic pathways towards obtaining products with high economic value. Although EF has been widely studied, the potential of use CO-rich gas streams as substrate has been under explored. This review presents and discusses current advances on microbial conversion of CO/syngas in BESs.This study was supported by the Portuguese Foundation for Science and Technology (FCT), within the scope of the project “INNOVsyn - Innovative strategies for syngas fermentation” (POCI-01-0145-FEDER- 033177). This study was also supported by the FCT under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte oper-ation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Carbon nanomaterials for electrode modification in CH4-producing bioelectrochemical systems

Introduction: Unprecedented environmental phenomena have led to emerging and challenging plans to tackle global threats for the humanity namely intensive use of fossil resources and global warming. CO2 emission to the atmosphere is one of the major driver of global climate change. In this context, the development of alternative technologies for carbon capture and utilization has attracting more and more attention. Electrochemically assisted CO2 conversion in bioelectrochemical systems (BESs) for CH4 production is a new and emerging technology. This innovative approach allows the storage of electrical renewable energy in the form of CH4 that can, when needed, be reconverted, but also the simultaneous CO2 capture contributing to mitigate the climate change and the global warming. However, this technology has limitations mainly related to the electrons transference between the electrode and the biocatalysts. Previous results, obtained within the research group, demonstrated that it is possible to increase the efficiency of the process by improving the electrode surface area which, in turn, improved the microbial attachment. Methodology: This work aimed to investigate the effect of the presence of carbon nanomaterials (carbon nanotubes (CNTs)) at the cathode, on the CH4 production via CO2 reduction. It was hypothesized that the presence of carbon nanomaterials will improve the electrode surface area, thus increasing the electron transfer between the electrode and the biocatalysts. The production of CH4 was analyzed in two BESs, one working with a modified electrode (BES-CNT) and another one that works as a control with a non-modified electrode (BES-CTRL). The potential of CNTs to improve CH4 production was investigated under different electrochemical control modes, potentiostatic and galvanostatic. In addition, the microbial community developed at the biocathode was also investigated. Results: The results demonstrated that for both electrochemical control modes, the production of CH4 was higher in the presence of CNTs compared to the control assay. The study of the microbial community developed at the biocathode under galvanostatic control demonstrated a clear enrichment of methanogens compared to the initial inoculum, however no significant differences were observed between both BES. Conclusions: In conclusion, this work contributed with preliminary insights on the effect of carbon nanomaterials, namely CNTs, to improve the biocathode performance on BESs for CH4 production from CO2.This study was supported by the Portuguese Foundation for Science and Technology(FCT) under the scope of the strategic funding of UIDB/04469/2020 unit.info:eu-repo/semantics/publishedVersio

CH4 production at moderate H2/CO2 pressures insights on the use of anaerobic granular sludge as biocatalyst

Introduction: The continuous increase in energy consumption and the intensive use of fossil fuels, lead to the emission of greenhouse gases (GHG) and, in particular, to an increase in the concentration of CO2 in the atmosphere. In this context, the improvement in global awareness and the demand for sustainable technologies and products strongly contribute to laid plans to combat climate change. CO2-to-CH4 conversion represents a cutting-edge solution for CO2 capture and use, contributing to the reduction of GHG emission. Catalytic conversion of CO2-to-CH4 have been investigated, however, the high cost associated to the catalysts employed limits their use on a large scale. Biological CO2 methanation can overcome the significant technical and economic challenges of catalytic CO2 methanation. The biological production of CH4 using CO2-rich gases together with H2 is a promising strategy for the production of bioproducts. Hydrogenotrophic methanogens have a crucial role on the direct conversion of CO2+H2 into CH4, hence the importance to study the specific hydrogenotrophic methanogenic activity (SHMA). Methodology: In this work, the effect of initial substrate (H2/CO2) pressure, from 100 to 500 kPa, on the SHMA, on CH4 production rate and on developed microbial communities were evaluated. Two different pressurized bioreactors were studied using anaerobic granular sludge as the biocatalyst and H2/CO2 (80:20, v/v) as sole carbon and energy source. Gaseous compounds were analyzed by GC and archaeal diversity within granular sludge was monitored by 16S r-RNA based techniques. Results: The results showed an increase in the SHMA as well as in the CH4 production rate with the increase of the initial H2/CO2 pressure. This results are very interesting since no inhibitory effects were observed on the microbial activity, demonstrating the resistance of the anaerobic granular sludge. The Illumina results showed that Methanosarcinales, Methanobacteriales and Methanomicrobiales were the three orders that prevailed in the pressurized system, for all the pressures tested. However, hydrogenotrophic methanogens from Methanobacterium and Methanospirillum genera slightly increased their relative abundance, varying from 38% (100 kPa) to 41% (500 kPa) and from 8% (100 kPa) to 12% (500 kPa), respectively. Conclusions: In conclusion, the archaeal community seems to be very stable when submitted to increasing H2/CO2 pressures, highlighting the potential of the anaerobic granular sludge as an efficient microbial platform for the production of added-value compounds from gaseous carbon waste streams.Portuguese Foundation for Science and Technology (FCT): POCI-01-0145-FEDER-031377; strategic funding of UIDB/04469/2020 unit; BioTecNorte operation (NORTE-01-0145-FEDER-000004); FCT doctoral grant PD/BD/128030/2016.info:eu-repo/semantics/publishedVersio

CH4 production at moderate H2/CO2 pressures - insights on the specific hydrogenotrophic methanogenic activity

CO2 is one of the main contributors to greenhouse gases (GHGs), being its emission to the atmosphere one of the major driver of global climate change. Biological methanation of CO2 using renewable H2 provides a promising approach to use of superplus renewable electrical power to produce a gaseous fuel. CH4 is considered an important renewable energy carrier, that has a wide range of applications such as natural gas for distribution. Hydrogenotrophic methanogens are key elements in the CO2/H2 methanation process. Thus the importance to study the specific hydrogenotrophic methanogenic activity (SHMA). The effect of the initial substrate (H2/CO2) pressure on the SHMA was investigated in two different pressurized bioreactors. The results suggest that in addition to the increase of the initial substrate pressure, also the bioreactor configuration influence the SHMA, which is crucial for the success of biological CO2 methanation technologies but also in anaerobic bioreactors treating wastewaters.info:eu-repo/semantics/publishedVersio

Bioelectrochemically-assisted recovery of valuable resources from urine

Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Source separated urine is highly concentrated in nutrients and biodegradable compounds. This work explores the potential of combining nutrient recovery from urine with simultaneous energy production in bioelectrochemical systems (BES), under the FP7 project "ValueFromUrine". Non-spontaneous phosphorus (P) recovery by struvite precipitation was analysed by adding three different magnesium (Mg) sources (magnesium chloride (MgCl2), magnesium hydroxide (Mg(OH)2) and magnesium oxide (MgO)). A statistical design of experiments was used to evaluate the effect of Mg:P molar ratio (1:1, 1.5:1 and 2:1) combined with stirring speed (30, 45 and 60 rpm) for each Mg source tested. MgO at 2:1 molar ratio and a stirring speed of 30 rpm allowed to achieve the highest P recovery efficiency (99 %) with struvite crystals size of 50 to 100 μm [1]. Urine obtained after P recovery, showed high concentration of biodegradable compounds being subsequently fed as substrate in a microbial fuel cell (MFC). Microbial acclimation to urine was performed in a MFC resulting in an anaerobic community successfully enriched in “urine-degrading” electroactive microorganisms. When compared to the control assay operated without preliminary microbial enrichment (81±9 mA m-2), the acclimation method achieved significantly higher current density (455 mA m-2) (p<0.05). Tissierella and Paenibacillus were the dominant genus identified in the adapted microbial community. Tissierella can convert creatinine to acetate, whereas bacterial species belonging to the Paenibacillus genus are known to function as exoelectrogens. Corynebacterium that comprise urea-hydrolysing bacteria was also detected in the developed biofilms. [...]info:eu-repo/semantics/publishedVersio

Effect of different carbon materials on the performance of microbial electrolysis cells (MECs) operated on urine and their microbial composition

ISMET 6 - General Meeting of the International Society for Microbial Electrochemistry and TechnologyUrine is rich in nitrogen and phosphorous and can considerably reduce domestic wastewater treatment requirements if collected separately. Source separated urine has been shown to be suitable for energy production and nutrients recovery in bioelectrochemical systems. However, there are still several challenges to overcome mainly related to organics conversion into electrical energy. In this study, anode performance of three microbial electrolysis cells (MECs) fed with urine using different carbon anodes, Keynol (phenolic-based), C-Tex (cellulose-based) and PAN (polyacrylonitrilebased) was compared. Two strategies were used to supply energy to the MECs; cell potential control (1' 1 assay) and anode potential control (2"d assay). In both assays, the C-Tex MEC outperformed MECs using Keynol and PAN. The C-Tex MEC with anode potential control at -0.300 V generated the highest current density of 904 mA m·2 , which was almost 3-fold higher than the MEC with Keynol, and 8-fold higher than the MEC with PAN. Analysis of anodes textural, chemical and electrochemical characteristics suggest that the higher external surface area of C-Tex enabled the higher current density generation compared to Keynol and PAN. The microbial composition on each anode and its correlation with the generated current was also investigated. No significant differences were observed in microbial diversity of the biofilm present in the studied anodes. Nonetheless, C-Tex had higher dominance of bacteria belonging to Luctobucillu/es and Enterobucteriules suggesting its relation with higher current generation.info:eu-repo/semantics/publishedVersio

Influence of carbon anode properties on performance and microbiome of Microbial Electrolysis Cells operated on urine

"Available online 15 February 2018"Anode performance of Microbial Electrolysis Cells (MECs) fed with urine using different anodes, Keynol (phenolic-based), C-Tex (cellulose-based) and PAN (polyacrylonitrile-based) was compared under cell potential control (1st assay) and anode potential control (2nd assay). In both assays, C-Tex MEC outperformed MECs using Keynol and PAN. C-Tex MEC under anode potential control (0.300V vs. Ag/AgCl) generated the highest current density (904mAm2), which was almost 3-fold higher than the Keynol MEC and 8-fold higher than the PAN MEC. Analysis of anodes textural, chemical and electrochemical characteristics suggest that the higher external surface area of C-Tex enabled higher current density generation compared to Keynol and PAN. Anodes properties did not influence significantly the microbial diversity of the developed biofilm. Nonetheless, C-Tex had higher relative abundance of bacteria belonging to Lactobacillales and Enterobacteriales suggesting its correlation with the higher current generation.This study was supported by the European Union's Seventh Programme for research, technological development and demonstration [Grant number 308535] and by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 [POCI-01- 0145-FEDER-006684], of Project RECI/BBB-EBI/0179/2012 [FCOMP01-0124-FEDER-027462], POCI-01-0145-FEDER-007679 [UID/CTM/ 50011/2013], and by BioTecNorte operation [NORTE-01-0145- FEDER-000004] funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. This work is a result of project “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) and of Project POCI-01-0145- FEDER-006984 e Associate Laboratory LSRE-LCM funded by ERDF through COMPETE2020 - Programa Operacional Competitividade e Internacionalizaçao (POCI) e and by national funds through FCT. The authors also would like to acknowledge the support of Wetsus, European Centre of Excellence for Sustainable Water Technology.info:eu-repo/semantics/publishedVersio

Understanding the interactions of imidazolium-based ionic liquids with cell membrane models

Cell membrane models have been used to evaluate the interactions of various imidazolium-based ionic liquids (ILs) with Langmuir monolayers of two types of phospholipids and cholesterol. Data from surface pressure isotherms, Brewster angle microscopy (BAM) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) pointed to significant effects on the monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol, used to mimic the membranes of eukaryotic cells, for ILs containing more than 6 carbon atoms in the alkyl chain (i.e. n > 6). For ILs with less hydrophobic tails (n ≤ 6) and low concentrations, the effects were almost negligible, therefore, such ILs should not be toxic to eukaryotic cells. The hydrophobicity of the anion was also proved to be relevant, with larger impact from ILs containing tetrafluoroborate ([BF4]-) than chloride (Cl-). Molecular dynamics simulations for DPPC monolayers at the surface of aqueous solutions of alkylimidazolium chloride ([Cnmim]Cl) confirm the penetration of the IL cations with longer alkyl chains into the phospholid monolayer and provide information on their location and orientation within the monolayer. For monolayers of dipalmitoylphosphatidyl glycerol (DPPG), which is negatively charged like bacteria cell membranes, the ILs induced much larger effects. Similarly to the results for DPPC and cholesterol, effects increased with the number of carbon atoms in the alkyl chain and with a more hydrophobic anion [BF4]-. Overall, the approach used can provide relevant information of molecular-level interactions behind the toxicity mechanisms and support the design of (quantitative) structure-activity relationship models, which may help design more efficient and environmentally friendly ILs.publishe

Opposite Modulation of RAC1 by Mutations in TRIO Is Associated with Distinct, Domain-Specific Neurodevelopmental Disorders

The Rho-guanine nucleotide exchange factor (RhoGEF) TRIO acts as a key regulator of neuronal migration, axonal outgrowth, axon guidance, and synaptogenesis by activating the GTPase RAC1 and modulating actin cytoskeleton remodeling. Pathogenic variants in TRIO are associated with neurodevelopmental diseases, including intellectual disability (ID) and autism spectrum disorders (ASD). Here, we report the largest international cohort of 24 individuals with confirmed pathogenic missense or nonsense variants in TRIO. The nonsense mutations are spread along the TRIO sequence, and affected individuals show variable neurodevelopmental phenotypes. In contrast, missense variants cluster into two mutational hotspots in the TRIO sequence, one in the seventh spectrin repeat and one in the RAC1-activating GEFD1. Although all individuals in this cohort present with developmental delay and a neuro-behavioral phenotype, individuals with a pathogenic variant in the seventh spectrin repeat have a more severe ID associated with macrocephaly than do most individuals with GEFD1 variants, who display milder ID and microcephaly. Functional studies show that the spectrin and GEFD1 variants cause a TRIO-mediated hyper- or hypo-activation of RAC1, respectively, and we observe a striking correlation between RAC1 activation levels and the head size of the affected individuals. In addition, truncations in TRIO GEFD1 in the vertebrate model X. tropicalis induce defects that are concordant with the human phenotype. This work demonstrates distinct clinical and molecular disorders clustering in the GEFD1 and seventh spectrin repeat domains and highlights the importance of tight control of TRIO-RAC1 signaling in neuronal development.<br/

Intricate macrophage-colorectal cancer cell communication in response to radiation

Both cancer and tumour-associated host cells are exposed to ionizing radiation when a tumour is subjected to radiotherapy. Macrophages frequently constitute the most abundant tumour-associated immune population, playing a role in tumour progression and response to therapy. The present work aimed to evaluate the importance of macrophage-cancer cell communication in the cellular response to radiation. To address this question, we established monocultures and indirect co-cultures of human monocyte-derived macrophages with RKO or SW1463 colorectal cancer cells, which exhibit higher and lower radiation sensitivity, respectively. Mono- and co-cultures were then irradiated with 5 cumulative doses, in a similar fractionated scheme to that used during cancer patients' treatment (2 Gy/fraction/day). Our results demonstrated that macrophages sensitize RKO to radiation-induced apoptosis, while protecting SW1463 cells. Additionally, the co-culture with macrophages increased the mRNA expression of metabolism- and survival-related genes more in SW1463 than in RKO. The presence of macrophages also upregulated glucose transporter 1 expression in irradiated SW1463, but not in RKO cells. In addition, the influence of cancer cells on the expression of pro- and anti-inflammatory macrophage markers, upon radiation exposure, was also evaluated. In the presence of RKO or SW1463, irradiated macrophages exhibit higher levels of pro-inflammatory TNF, IL6, CCL2 and CCR7, and of anti-inflammatory CCL18. However, RKO cells induce an increase of macrophage pro-inflammatory IL1B, while SW1463 cells promote higher pro-inflammatory CXCL8 and CD80, and also anti-inflammatory VCAN and IL10 levels. Thus, our data demonstrated that macrophages and cancer cells mutually influence their response to radiation. Notably, conditioned medium from irradiated co-cultures increased non-irradiated RKO cell migration and invasion and did not impact on angiogenesis in a chicken embryo chorioallantoic membrane assay. Overall, the establishment of primary human macrophage-cancer cell co-cultures revealed an intricate cell communication in response to ionizing radiation, which should be considered when developing therapies adjuvant to radiotherapy