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The continuous accumulation of atmospheric CO2 requires the development of new technologies for its mitigation. Carbon capture and utilization (CCU) technologies aim to convert CO2 into precious compounds like chemicals and fuels. Biological fixation is an attractive CCU strategy in terms of cost, sustainability and variety of products. Chemoautotrophic microorganisms such as methanogens and acetogens are able to reduce CO2 into acetate and methane, respectively. Acetogens bacteria are able to use CO2 for cell growth through the Wood Liujhundal pathway, moreover, the final precursor (i.e. Acetyl-CoA) of the autotrophic metabolism, is also used in energy metabolism with acetate production as a waste product. Furthermore, it is possible to obtain multicarbon products of autotrophic origin starting from acetyl-CoA and acetate. The biotechnological use of these microorganisms requires the presence of H2 as substrate, which is used as an electron donor in the pathway. This reaction can be sustained by a biocathode in a microbial electrosynthesis cell, in which the reducing power is generated by a polarized electrode. This study proposes the use of a microbial electrosynthesis cell for conversion to acetate in H-cells by either a mixed culture enriched with Acetobacterium woodii or a pure culture of Acetobacterium woodii, to observe the difference in terms of acetate production and reducing power consumption efficiency. The mixed culture was obtained from a mixture of activated sludge and anaerobic digestate, treated by a protocol capable to select acetogenic microorganisms without the use of specific chemical inhibitors (2-Bromoethanesulfonate). Both inoculums were tested at room temperature (25°C) in the cathodic chamber of the H-cell at potentials in the range of -0.7 to -1.1 V vs SHE. The obtained results showed that the enriched mixed culture produced at -0.7 vs SHE a mixture of volatile fatty acids including C4 and C5 molecules with an overall coulombic efficiency of 50%, while at the potential of -0.9 vs SHE methane constituted the main product of the biocathode. The pure culture, on the other hand, showed a specific production of acetate with a coulombic efficiency of 44% at -0.9 vs SHE and 63% at -1.1 vs SHE. Furthermore, a drastic decrease in biocathode biomass was observed in pure culture, suggesting a higher tendency to form biofilms on the electrode unlike the mixed culture, which showed a standard growth profile in the bulk. [ABSTRACT FROM AUTHOR]

The role of the electroactive surface area (EASA) and of the non-electroactive surface area (nEASA) was studied to better understand electroactive biofilm's (EAB) growth and performance in four different systems. Those systems consisted in four 1L glass bottles filled with mineral medium and substrates, a stainless-steel cathode and a bioanode. Four different types of bioanode were assembled in order to study the EASA and nEASA role. A potentiostat controlled the anodic potential, which was fixed in every system at + 0.2 V vs SHE (standard hydrogen electrode). To measure the EASA of every system, cyclic voltammetries (CVs) were carried out at different scan rates. Comparing them with the one obtained with a reference system, each EASA is easily calculated. The nEASA, instead, was measured calculating the geometric volume. The obtained results demonstrate the fundamental role of the EASA and, moreover, the necessity to reduce as much as possible the nEASA in order to enhance the performance. [ABSTRACT FROM AUTHOR]

Innovative treatment and utilization of waste biomass streams are crucial for increase environmental sustainability of human activities. Sewage sludge from the biological degradation of biomass can be valorized for the selection of biocatalysts capable to convert CO2 into valuable products. Indeed, chemoautotrophic microorganisms, like methanogens and acetogens, respectively, are able to convert CO2 into CH4 or acetate by using hydrogen as electron donor, i.e., their utilization for several bio-based CO2 reutilization processes has been widely proposed by several authors. Chemoautothrophic acetogens are widely present in waste streams deriving from the organic matter degradation, however, due to the syntrophic relationship between acetogens and acetoclastic methanogens in anaerobic environments, autothropihc acetate results immediately converted into methane. Therefore, the selection of an acetogenic inoculum which allow to obtain CO2 reduction into acetate, requires methanogens inhibition. Among the different methanogen's inhibition strategies, the most common method is the use of BES (bromo-ethane sulphonate) which results a not scalable technique for large scale application. A most promising and sustainable approach is offered by the adoption of a thermal treatment which allows to the selection of an acetogenic inoculum, thanks to the sporogenous capacity of acetogenic bacteria. This work presents the results obtained in the thermal pre-treatment of different type of waste biomasses coming from pilot and full-scale biological processes for the selection of an acetogenic inoculum able to convert CO2 into acetate. Each waste biomass was treated by a thermal shock procedure that consisted in the treatment of the dried biomass at 120°C for 2 hours. Acetogenic inoculums obtained by the thermal pre-treatment of an acidogenic fermentate, an activated sludge and a mesophilic anaerobic digestate, were tested under hydrogenophilic conditions in comparison with blank tests and raw inoculums. The results clearly indicate the effectiveness of the thermal pre-treatment in the selection of the acetogenic microorganisms [ABSTRACT FROM AUTHOR]

An innovative strategy to control the metabolism of microorganisms is offered by bioelectrochemical systems in which a graphite‐based cathode can be used as electron donor or acceptor. An advanced microbial electrolysis cell is developed to combine CO2 removal from a synthetic biogas in a biocathode and the organic matter oxidation in a bioanode. A novel biogas upgrading approach is presented in which an electron recycle concept is obtained by the combination of CO2 reduction and oxidation. While the bioelectrochemical anodic chemical oxygen demand oxidation provides the electrons necessary for the cathodic CO2 reduction into methane and acetate, the acetate produced by acetogenic microorganisms migrates from the cathode to the anode being oxidized again by the bioanode. [ABSTRACT FROM AUTHOR]

In this study, a lab-scale microbial electrolysis cell (MEC) aimed to the biogas upgrading through a methanogenic biocathode has been integrated with an adsorption column to test the possible increase of the biocathode CO2 removal capacity. In the adopted MEC configuration, the oxidation of the organic matter by an anodic biofilm was utilized to partially sustain the energy demand of the bioelectromethanogenesis reaction in the cathodic chamber. Anodic and cathodic biofilms were characterized by cyclic voltammetry (CV) technique which allowed the electron transfer mechanisms characterization in the anodic and cathodic bioelectrochemical reactions. More in detail, while the anodic biofilm showed the presence of a potential direct electron transfer, the cathodic CV suggests a hydrogen mediated mechanism for the CO2 reduction into CH4. The integration of a sorption column and the MEC biocathode showed a negligible effect in the overall biocathode CO2 removal, suggesting the control of the CO2 sorption by a chemical reaction through the alkalinity generation mechanism instead of the gas-liquid mass transfer. [ABSTRACT FROM AUTHOR]

Objective: Fluid responsiveness is the ability to increase the cardiac output in response to a fluid challenge. Only about 50% of patients receiving fluid resuscitation for acute circulatory failure increase their stroke volume, but the other 50% may worsen their outcome. Therefore, predicting fluid responsiveness is needed. In this purpose, in recent years, the assessment of the inferior vena cava (IVC) through ultrasound (US) has become very popular. The aim of our work was to systematically review all the previously published studies assessing the accuracy of the diameter of IVC or its respiratory variations measured through US in predicting fluid responsiveness. Data Sources: We searched in the MEDLINE (PubMed), Embase, Web of Science databases for all relevant articles from inception to September 2017. Study Selection: Included articles specifically addressed the accuracy of IVC diameter or its respiratory variations assessed by US in predicting the fluid responsiveness in critically ill ventilated or not, adult or pediatric patients. Data Extraction: We included 26 studies that investigated the role of the caval index (IVC collapsibility or distensibility) and 5 studies on IVC diameter. Data Synthesis: We conducted a meta-analysis for caval index with 20 studies: The pooled area under the curve, logarithmic diagnostic odds ratio, sensitivity, and specificity were 0.71 (95% confidence interval [CI]: 0.46-0.83), 2.02 (95% CI: 1.29-2.89), 0.71 (95% CI: 0.62-0.80), and 0.75 (95% CI: 0.64-0.85), respectively. Conclusion: An extreme heterogeneity of included studies was highlighted. Ultrasound evaluation of the diameter of the IVC and its respiratory variations does not seem to be a reliable method to predict fluid responsiveness. [ABSTRACT FROM AUTHOR]

An innovative bioelectrochemical reductive/oxidative sequential process was developed and tested on a laboratory scale to obtain the complete mineralization of perchloroethylene (PCE) in a synthetic medium. The sequential bioelectrochemical process consisted of two separate tubular bioelectrochemical reactors that adopted a novel reactor configuration, avoiding the use of an ion exchange membrane to separate the anodic and cathodic chamber and reducing the cost of the reactor. In the reductive reactor, a dechlorinating mixed inoculum received reducing power to perform the reductive dechlorination of perchloroethylene (PCE) through a cathode chamber, while the less chlorinated daughter products were removed in the oxidative reactor, which supported an aerobic dechlorinating culture through in situ electrochemical oxygen evolution. Preliminary fluid dynamics and electrochemical tests were performed to characterize both the reductive and oxidative reactors, which were electrically independent of each other, with each having its own counterelectrode. The first continuous-flow potentiostatic run with the reductive reactor (polarized at −450 mV vs. SHE) resulted in obtaining 100% ± 1% removal efficiency of the influent PCE, while the oxidative reactor (polarized at +1.4 V vs. SHE) oxidized the vinyl chloride and ethylene from the reductive reactor, with removal efficiencies of 100% ± 2% and 92% ± 1%, respectively. [ABSTRACT FROM AUTHOR]