Acetogenic inoculum selection for acetate production from waste biomasses via thermal shock treatment

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 ot 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 microorg

Hydrogenophilic and bioelectrochemical production of acetate with a pure culture of Acetobacterium Woodii

In recent years there has been a growing interest in the potential use of autotrophic acetogenic bacteria to produce compounds of interest through CO2 fixation, representing an alternative solution to currently used CO2 storage technologies. This group of microorganisms are ubiquitous in nature and they are characterised by a Wood-Ljungdahl pathway that combines CO2 fixation with adenosine triphosphate (ATP) synthesis by using H2 as electron donor. In this work the autotrophic production of acetate by a pure colture of Acetobacterium woodii has been tested under hydrogenophilic or bioelectrochemical conditions. More in details, the hydrogenophilic tests were conducted at two different pH values (5.5 and 7.5) with an H2 partial pressure of 0.52 atm, while bioelectrochemical tests were performed at an applied cathodic potential of -0.90 V vs. SHE (Standard Hydrogen Electrode). The bioelectrochemical tests were set up in H-type reactors (250 mL), in which graphite rods were used as electrodic material and an anion exchange membrane served to separate the anodic and cathodic chambers while allowing anions migration for electroneutrality maintenance. The hydrogenophilic tests resulted in different kinetics depending on the applied pH value. The bioelectrochemical tests, performed at a pH value of 7.5, reached an acetate production rate 2 times higher than in the hydrogenophilic experiments at pH 7.5, as well as an increase in the efficiency of using the reducing power, suggesting an improvement in hydrogen uptake. At pH 5.5, on the other hand, production is improved by increasing the partial pressure of H

Production of short-chain fatty acid from CO2 through mixed and pure culture in a microbial electrosynthesis cell

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

Bioelectrochemical chlorinated aliphatic hydrocarbons reduction in synthetic and real contaminated groundwaters

The widespread contamination of chlorinated aliphatic hydrocarbons (CAHs) as Perchloroethylene (PCE) and Trichloroethylene (TCE) over the past recent years and their uncorrected disposal and storing brought these substances to become one of the most common contaminants of subsoils and groundwater in the world. In recent years, more sustainable remediation and cost-effective technologies involving groundwater’s indigenous microorganism such as the dehalorespiring microorganisms. Dehalorespiring microorganisms can reduce PCE and TCE via reductive dechlorination (RD) while aerobic dechlorinating microorganisms oxidized low chlorinated compound such as cis-dichloroethylene (cDCE) and vinyl chloride (VC) into non harmful products. The integration of reductive dechlorination and aerobic dechlorination results in an efficient approach for the complete mineralization of high chlorinated compounds, which usually led to a build-up of VC. Bioelectrochemical systems, which exploit the capability of microorganisms to interact with a polarized electrode, provide an effective strategy to promote reductive and oxidative environments by the regulation of the applied potentials. Indeed, the complete mineralization of high chlorinated CAHs, can be obtained by a sequential reductive/oxidative bioelectrochemical process which allows for the optimization of the reductive and oxidative dechlorinating conditions. In this study the performances of the reductive reactor, devoted to the reductive dechlorination has been presented with three different contaminated feeding solutions. The three different feeding solutions included an optimized mineral medium, a synthetic groundwater (constituted by tap water added with nitrate and sulphate) and a real contaminated groundwater. Moreover, different operating conditions like hydraulic retention time (HRT) and applied cathodic potential have been investigated to assess the performance of the reductive dechlorination and on side reactions. The analysis of the coulombic efficiencies for the reductive dechlorination in the reductive reactor showed an important effect of the feeding solution composition and operating conditions (applied potential and HRT), namely strongly decreasing under when using real contaminated groundwater. Despite the progressive decrease of the coulombic efficiency obtained using more complex matrixes, the CAHs removal rates along with the energetic consumption of the process showed an advantageous perspective in the adoption of the bioelectrochemical process for the stimulation of the reductive dechlorination reaction

Chromate fate and effect in bioelectrochemical systems for remediation of chlorinated solvents

A continuous-flow bioelectrochemical reactor was developed in a previous study to address the bioremediation of groundwater contaminated by trichloroethene (TCE). The present report investigated the applicability of the same system in the presence of Cr(VI) and its possible inhibitory effect on dehalorespiring bacterial populations. Preliminary batch tests were performed at the optimal cathodic reducing potential for the reductive dechlorination (RD) of TCE (-0.65 V vs. the standard hydrogen electrode) with two different dechlorinating microorganism consortia. The results demonstrated that Cr(VI) removal efficacy was increased by microorganisms that had been previously acclimatised to Cr(VI). Specifically, Cr(VI) was completely reduced only in the presence of acclimated microorganisms. The presence of chromate negatively affected RD performance, by either (i) limiting the TCE transformation to cis-dichloroethene at lower concentrations, or (ii) completely inhibiting RD at higher concentrations. In contrast, after the acclimation period, RD was extended down to vinyl chloride, which is the main TCE daughter product. Finally, the continuous flow reactor was fed by synthetic groundwater contaminated with TCE (50 μM) and Cr(VI) (45 μM), and the experimental results showed that Cr(VI) was completely reduced under RD conditions. Moreover, TCE removal was complete, with vinyl chloride and ethene as the main intermediates, thus indicating that chromate inhibition was decreased by Cr(VI) removal

Occurrence of <i>Chromadorita regabi</i> sp. nov. (Nematoda: Adenophorea), a nematode egg predator of <i>Alvinocaris muricola</i> (Crustacea: Decapoda: Caridea: Alvinocarididae) from a deep cold seep area of the Gulf of Guinea

Several individuals belonging to a new species of the genus Chromadorita (Nematoda: Adenophorea) were collected in a cold-seep area in the Gulf of Guinea during two French cruises: BIOZÄIRE 2 (2001) and BIOZAÏRE 3 (2003–2004) on board the R/V L’Atalante. In this area, rich chemosynthetic benthic communities have been discovered at 3150 m depth in the large pockmark field named Regab. Chromadorita regabi sp. nov. was found among the eggs in ovigerous specimens of the shrimp Alvinocaris muricola. The combination of long size (1500–2200&nbsp;µm), nine strong preanal papillae and relatively small dorsal tooth with weak musculature distinguishes this species from all known congeneric ones. An identification key to all known species of Chromadorita is provided

Novel risk calculator performance in athletes with arrhythmogenic right ventricular cardiomyopathy

Background: Disease progression and ventricular arrhythmias (VAs) in arrhythmogenic right ventricular cardiomyopathy (ARVC) are correlated with physical exercise, and clinical detraining and avoidance of competitive sport practice are suggested for ARVC patients. An algorithm assessing primary arrhythmic risk in ARVC patients was recently developed by Cadrin-Tourigny et al. Data regarding its transferability to athletes are lacking. Objective: The purpose of this study was to assess the reliability of the Cadrin-Tourigny risk prediction algorithm in a cohort of athletes with ARVC and to describe the impact of clinical detraining on disease progression. Methods: All athletes undergoing clinical detraining after ARVC diagnosis at our institution were enrolled. Baseline and follow-up clinical characteristics and data on VA events occurring during follow-up were collected. The Cadrin-Tourigny algorithm was used to calculate the a priori predicted VA risk, which was compared with the observed outcomes. Results: Twenty-five athletes (age 36.1 \ub1 14.0 years; 80% male) with definite ARVC who were undergoing clinical detraining were enrolled. Over median (interquartile range) follow-up of 5.3 (3.2\u20136.6) years, a reduction in premature ventricular complex (PVC) burden (P = .001) was assessed, and 10 VA events (40%) were recorded. The a priori algorithm-predicted risk seemed to fit with the observed cohort arrhythmic risk [mean observed\u2013predicted risk difference over 5 years \u20130.85% (interquartile range \u20134.8% to +3.1%); P = .85]. At 1-year follow-up, 11 patients (44%) had an improved stress ECG response, and no significant changes in right ventricular ejection fraction were observed. Conclusion: Clinical detraining is associated with PVC burden reduction in athletes with ARVC. The novel risk prediction algorithm does not seem to require any correction for its application to ARVC athletes

High environmental stress and productivity increase functional diversity along a deep‐sea hydrothermal vent gradient

peer reviewedProductivity and environmental stress are major drivers of multiple biodiversity facets and faunal community structure. Little is known on their interacting effects on early community assembly processes in the deep sea (>200 m), the largest environment on Earth. However, at hydrothermal vents productivity correlates, at least partially, with environmental stress. Here, we studied the colonization of rock substrata deployed along a deep‐sea hydrothermal vent gradient at four sites with and without direct influence of vent fluids at 1,700‐m depth in the Lucky Strike vent field (Mid‐Atlantic Ridge [MAR]). We examined in detail the composition of faunal communities (>20 μm) established after 2 yr and evaluated species and functional patterns. We expected the stressful hydrothermal activity to (1) limit functional diversity and (2) filter for traits clustering functionally similar species. However, our observations did not support our hypotheses. On the contrary, our results show that hydrothermal activity enhanced functional diversity. Moreover, despite high species diversity, environmental conditions at surrounding sites appear to filter for specific traits, thereby reducing functional richness. In fact, diversity in ecological functions may relax the effect of competition, allowing several species to coexist in high densities in the reduced space of the highly productive vent habitats under direct fluid emissions. We suggest that the high productivity at fluid‐influenced sites supports higher functional diversity and traits that are more energetically expensive. The presence of exclusive species and functional entities led to a high turnover between surrounding sites. As a result, some of these sites contributed more than expected to the total species and functional β diversities. The observed faunal overlap and energy links (exported productivity) suggest that rather than operating as separate entities, habitats with and without influence of hydrothermal fluids may be considered as interconnected entities. Low functional richness and environmental filtering suggest that surrounding areas, with their very heterogeneous species and functional assemblages, may be especially vulnerable to environmental changes related to natural and anthropogenic impacts, including deep‐sea mining