Reactors for microbial electrobiotechnology

From the first electromicrobial experiment to a sophisticated microbial electrochemical process - it all takes place in a reactor. Whereas the reactor design and materials used strongly influence the obtained results, there are no common platforms for MES reactors. This is a critical convention gap, as cross-comparison and benchmarking among MES as well as MES vs. conventional biotechnological processes is needed. Only knowledge driven engineering of MES reactors will pave the way to application and commercialization. In this chapter we first assess the requirements on reactors to be used for bioelectrochemical systems as well as potential losses caused by the reactor design. Subsequently, we compile the main types and designs of reactors used for MES so far, starting from simple H-cells to stirred tank reactors. We conclude with a discussion on the weaknesses and strengths of the existing types of reactors for bioelectrochemical systems that are scored on design criteria and draw conclusions for the future engineering of MES reactors. [GRAPHICS]

Syntrophy drives the microbial electrochemical oxidation of toluene in a continuous-flow "bioelectric well"

Microbial electrochemical technologies (MET) are promising for the remediation of groundwater pollutants such as petroleum hydrocarbons (PH). Indeed, MET can provide virtually inexhaustible electron donors or acceptors directly in the subsurface environment. However, the degradation mechanisms linking contaminants removal to electric current flow are still largely unknown, hindering the development of robust design criteria. Here, we analysed the degradation of toluene, a model PH, in a bioelectrochemical reactor known as "bioelectric well"operated in continuous-flow mode at various influent toluene concentrations. With increasing concentration of toluene, the removal rate increased while the current tended to a plateau, hence the columbic efficiency decreased. Operation at open circuit confirmed that the bioelectrochemical degradation of toluene proceeded via a syntrophic pathway involving cooperation between different microbial populations. First of all, hydrocarbon degraders quickly converted toluene into metabolic intermediates probably by breaking the aromatic ring upon fumarate addition. Subsequently, fermentative bacteria converted these intermediates into volatile fatty acids (VFA) and likely also H2, which were then used as substrates by electroactive microorganisms forming the anodic biofilm. As toluene degradation is faster than subsequent conversion steps, the increase in intermediate concentration could not result in a current increase. This work provides valuable insights on the syntrophic degradation of BTEX, which are essential for the application of microbial electrochemical system to groundwater remediation of petroleum hydrocarbons

Pollutant dispersion in a developing valley cold-air pool

Pollutants are trapped and accumulate within cold-air pools, thereby affecting air quality. A numerical model is used to quantify the role of cold-air-pooling processes in the dispersion of air pollution in a developing cold-air pool within an alpine valley under decoupled stable conditions. Results indicate that the negatively buoyant downslope flows transport and mix pollutants into the valley to depths that depend on the temperature deficit of the flow and the ambient temperature structure inside the valley. Along the slopes, pollutants are generally entrained above the cold-air pool and detrained within the cold-air pool, largely above the ground-based inversion layer. The ability of the cold-air pool to dilute pollutants is quantified. The analysis shows that the downslope flows fill the valley with air from above, which is then largely trapped within the cold-air pool, and that dilution depends on where the pollutants are emitted with respect to the positions of the top of the ground-based inversion layer and cold-air pool, and on the slope wind speeds. Over the lower part of the slopes, the cold-air-pool-averaged concentrations are proportional to the slope wind speeds where the pollutants are emitted, and diminish as the cold-air pool deepens. Pollutants emitted within the ground-based inversion layer are largely trapped there. Pollutants emitted farther up the slopes detrain within the cold-air pool above the ground-based inversion layer, although some fraction, increasing with distance from the top of the slopes, penetrates into the ground-based inversion layer.Peer reviewe

Preparation and surface functionalization of MWCNTs: study of the composite materials produced by the interaction with an iron phthalocyanine complex

Carbon nanotubes [CNTs] were synthesized by the catalytic vapor decomposition method. Thereafter, they were functionalized in order to incorporate the oxygen groups (OCNT) and subsequently the amine groups (ACNT). All three CNTs (the as-synthesized and functionalized) underwent reaction with an iron organometallic complex (FePcS), iron(III) phthalocyanine-4,4",4",4""-tetrasulfonic acid, in order to study the nature of the interaction between this complex and the CNTs and the potential formation of nanocomposite materials. Transmission electronic microscopy, N2 adsorption at 77 K, thermogravimetric analysis, temperature-programmed desorption, and X-ray photoelectron spectroscopy were the characterization techniques employed to confirm the successful functionalization of CNTs as well as the type of interaction existing with the FePcS. All results obtained led to the same conclusion: There were no specific chemical interactions between CNTs and the fixed FePcS

Casting for a sovereign role:Socialising an aspirant state in the Scottish independence referendum

This article examines international reactions to Scotland’s 2014 bid for independence as an instance of socialisation of an aspirant state, what we term ‘pre-socialisation’. Building on and contributing to research on state socialisation and role theory, this study proposes a nexus between roles and sovereignty. This nexus has three components: sovereignty itself is a role casted for by an actor; the sovereign role is entangled with the substantive foreign policy roles the actor might play; and the sovereign role implicates the substantive foreign policy roles of other actors. The Scottish debate on independence provides an effective laboratory to develop and explore these theoretical dimensions of pre-socialisation, revealing the contested value and meaning of sovereignty, the possible roles that an independent Scotland could play, and the projected implications for the role of the UK and other international actors. Our analysis of the Scottish case can provide insights for other cases of pre-socialisation and is more empirically significant following the UK’s 2016 referendum to leave the European Union.PostprintPeer reviewe

Potential implications of differential preservation of testate amoeba shells for paleoenvironmental reconstruction in peatlands

Testate amoebae are now commonly used in paleoenvironmental studies but little is known of their taphonomy. There is some experimental evidence for differential preservation of some testate amoeba shell types over others, but it is unclear what, if any impact this has on palaeoenvironmental reconstruction. To investigate this issue we looked at palaeoecological evidence for the preservation of different shell types. We then investigated the possible impact of selective preservation on quantitative palaeoenvironmental inference. We first used existing palaeoecological data sets to assess the vertical patterns of relative abundance in four testate amoeba shell types: (1) shells made of secreted biosilica plates (idiosomes, e.g. Euglypha), (2) idiosomes with thick organic coating (Assulina), (3) proteinaceous shells (e.g. Hyalosphenia), (4) shells built from recycled organic or mineral particles (xenosomes) (e.g. Difflugia, Centropyxis). In three diagrams a clear pattern of decay was only observed for the idiosome type. In order to assess the implications of differential preservation of testate amoeba taxa for paleoenvironmental reconstruction we then carried out simulations using three existing transfer functions and a wide range of scenarios, downweighting different test categories to represent the impact of selective test decomposition. Simulation results showed that downweighting generally reduced overall model performance. However downweighting a shell type only produced a consistent directional bias in inferred water table depth where that shell type is both dominant and shows a clear preference along the ecological gradient. Applying a scenario derived from previous experimental work did not lead to significant difference in inferred water table. Our results show that differential shell preservation has little impact on paleohydrological reconstruction from Sphagnum-dominated peatlands. By contrast, for the minerotrophic peatlands data-set loss of idiosome tests leads to consistent underestimation of water table depth. However there are few studies from fens and it is possible that idiosome tests are not always dominant, and/or that differential decomposition is less marked than in Sphagnum peatlands. Further work is clearly needed to assess the potential of testate amoebae for paleoecological studies of minerotrophic peatlands

Quality of life after sleeve gastrectomy and adjustable gastric banding

Abstract Background: With the addition of laparoscopic vertical sleeve gastrectomy (SG) to the bariatric surgery procedural toolkit, patients desiring a restrictive bariatric procedure often choose between adjustable gastric banding (LAGB) and SG. One study compared quality of life after these 2 procedures and found no difference. The purpose of our study was to re-evaluate the postoperative quality of life in LAGB and SG patients at a military teaching hospital in the United States. Methods: A retrospective review of 108 consecutive laparoscopic restrictive bariatric procedures performed within 15 months at a Department of Defense hospital was conducted. Of these 108 patients, 69 had undergone laparoscopic vertical SG and 39 LAGB. A validated quality of life questionnaire (Bariatric Quality of Life) was conducted a mean of 9.3 Ϯ 3.2 months (range 5-16) postoperatively. The weight loss and standard laboratory parameters were measured at 0, 1, 3, 6, and 12 months. Results: The quality of life assessment revealed significantly better scores after SG than after LAGB (66.5 versus 57.9, P ϭ .0002). The excess weight loss and excess body mass index loss at 3, 6, and 12 months postoperatively were significantly greater in the laparoscopic SG group. The patients demonstrated a clear preference over time for SG once it was offered. Conclusion: Early postoperative quality of life was superior after SG than after LAGB. SG also resulted in superior early excess weight loss. In a practice not constrained by reimbursement, these findings were associated with increased patient choice of SG after it began to be offered. (Surg Obes Relat Dis 2012;8:31-40.

Long-term performance of a plant microbial fuel cell with Spartina anglica

The plant microbial fuel cell is a sustainable and renewable way of electricity production. The plant is integrated in the anode of the microbial fuel cell which consists of a bed of graphite granules. In the anode, organic compounds deposited by plant roots are oxidized by electrochemically active bacteria. In this research, salt marsh species Spartina anglica generated current for up to 119 days in a plant microbial fuel cell. Maximum power production was 100 mW m−2 geometric anode area, highest reported power output for a plant microbial fuel cell. Cathode overpotential was the main potential loss in the period of oxygen reduction due to slow oxygen reduction kinetics at the cathode. Ferricyanide reduction improved the kinetics at the cathode and increased current generation with a maximum of 254%. In the period of ferricyanide reduction, the main potential loss was transport loss. This research shows potential application of microbial fuel cell technology in salt marshes for bio-energy production with the plant microbial fuel cell