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This study evaluated the combined impact of salinity (2.5, 13, and 19.3 g NaCl/L) and inoculum pretreatment (acid/alkali) on the genomic and metabolic profiles of mesophilic fermentative bacteria for hydrogen (H

Biotransformation of organic substrates via acidogenic fermentation (AF) to high-value products such as C1-C6 carboxylic acids and alcohol serves as platform chemicals for various industrial applications. However, the AF technology suffers from low product titers due to thermodynamic constraints. Recent studies suggest that augmenting AF redox potential can regulate the metabolic pathway and provide seamless electron flow by lowering the activation energy barrier, thus positively influencing the substrate utilization rate, product yield, and speciation. Hence, the augmented AF system with an exogenous electricity supply is termed as electro-fermentation (EF), which has enormous potential to strengthen the fermentation technology domain. Therefore, this critical review systematically discusses the current understanding of EF with a special focus on the extracellular electron transfer mechanism of electroactive bacteria and provides perspectives and research gaps to further improve the technology for green chemical synthesis, sustainable waste management, and circular bio-economy.

This study systematically evaluated and compared different inoculum pretreatment methods to quickly select dark fermentative bacteria from anaerobic sludge for the bioconversion of food waste. The hydrogen (H

Microalgae are a promising source of raw material (i.e., proteins, carbohydrates, lipids, pigments, and micronutrients) for various value-added products and act as a carbon sink for atmospheric CO

Capnophilic lactic fermentation (CLF) is a novel anaplerotic pathway able to convert sugars to lactic acid (LA) and hydrogen using CO2 as carbon enhancer in the hyperthermophilic bacterium Thermotoga neapolitana. In order to give further insightsinto CLF metabolic networks, we investigated the transcriptional modification inducedby CO2 using a RNA-seq approach. Transcriptomic analysis revealed 1601 differentially expressed genes (DEGs) in an enriched CO2 atmosphere over a total of 1938 genes of the T. neapolitana genome. Transcription of PFOR and LDH genes belonging to the CLF pathway was up-regulated by CO2 together with 6-phosphogluconolactonase (6PGL) and 6-phosphogluconate dehydratase (EDD) of the Entner–Doudoroff (ED) pathway. The transcriptomic study also revealed up-regulation of genes coding for the flavin-based enzymes NADH-dependent reducedferredoxin: NADP oxidoreductase (NFN) and NADferredoxin oxidoreductase (RNF) that control supply of reduced ferredoxin and NADH and allow energy conservation-based sodium translocation through the cell membrane. These results support the hypothesis that CO2 induces rearrangement of the central carbon metabolism together with activation of mechanisms that increase availability of the reducing equivalents that are necessay to sustain CLF. In this view, this study reportsa first rationale of the molecular basis of CLF in T. neapolitana and provides a list of target genes for the biotechnological implementation of this process. &nbsp

Microbial fuel cells (MFCs) technology have the potential to decarbonize electricity generation and offer an eco-friendly route for treating a wide range of industrial effluents from power generation, petrochemical, tannery, brewery, dairy, textile, pulp/paper industries, and agro-industries. Despite successful laboratory-scale studies, several obstacles limit the MFC technology for real-world applications. This review article aimed to discuss the most recent state-of-the-art information on MFC architecture, design, components, electrode materials, and anodic exoelectrogens to enhance MFC performance and reduce cost. In addition, the article comprehensively reviewed the industrial effluent characteristics, integrating conventional technologies with MFCs for advanced resource recycling with a particular focus on the simultaneous bioelectricity generation and treatment of various industrial effluents. Finally, the article discussed the challenges, opportunities, and future perspectives for the large-scale applications of MFCs for sustainable industrial effluent management and energy recovery.

Thermotoga neapolitana is a hyperthermophilic eubacterium that produces hydrogen by sugar fermentation. A lab strain of T. neapolitana DSMZ 4359(T) maintained in a CO2-enriched atmosphere showed a stable increase of lactic acid production under capnophilic lactic fermentation (CLF) conditions. The genotypic comparison between the putative mutant (TN-CMut) and the original strain DSMZ 4359(T) (WT4359) revealed 88.1 (+/- 2.4)% DNA homology. RiboPrint (R) and MALDI-TOF mass analyses support a genetic differentiation beyond subspecies level. The phenotypic characterization indicated a high correlation between the two strains, except for the lactic acid production. Under identical operating conditions, the lab mutant produced significantly more lactic acid than the parent strain without impairing the hydrogen yield. The highest divergence between TN-CMut and WT4359 was observed for fermentation of glucose or lactose at 80 degrees C. Based on these results, we propose that the lab strain is a new subspecies of the genus Thermotoga that is named T. neapolitana subsp. capnolactica with regards to its improved feature to produce lactic acid under capnophilic conditions. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This study investigated the effect of the salinity level, buffering agent and carbon source on the hydrogen (H2) and lactic acid synthesis under capnophilic (CO2-assisted) lactic fermentation (CLF) by Thermotoga neapolitana cf capnolactica (DSM 33003). Several series of batch fermentation experiments were performed either in 0.12 L serum bottles for selection of the best performing conditions or in a 3 L fermenter for the best possible combination of conditions. The serum bottle study revealed that change in the salinity level of the culture medium from 0 to 35 g L−1 NaCl increased lactic acid synthesis by 7.5 times without affecting the H2 yield. Use of different buffers (MOPS, TRIS or HEPES) did not affect the average H2 yield of 3.0 ± 0.24 mol H2 mol−1 of glucose and lactic acid synthesis of 13.7 ± 1.03mM when the cultures were sparged by CO2. Among the carbonsources investigated, glucose was found to be the best performing carbon source for the CLF fermentation with 35 g L−1 of NaCl and 0.01M of phosphate buffer. Hence, an up-scale experiment using a 3 L fermenter and the combination of the best performing conditions showed a 2.2 times more lactic acid synthesis compared to the 0.12 L serum bottle experiments. The study reveals the robustness and flexibility of the CLF-based technology using T. neapolitana cf capnolactica fermentation under various operating environmental conditions.

Varying pH and high levels of nitrite have major inhibitory effects on anaerobic ammonium oxidizing bacteria (AnAOB) and are known to interfere with the anaerobic ammonia oxidation (Anammox) process. In this study, we evaluated the effect of pH and nitrite on Anammox process performance through a predictive kinetic model. A series of batch experiments were performed in a stably operating Anammox sequencing batch reactor system with “Candidatus Brocadia” as the dominant AnAOB taxon (>95%), by varying the nitrite concentration from 40 to 378 mg/L and the pH from 6.7 and 8.5, while maintaining the NH4+-N concentration at 54.6 ± 5.6 mg/L. Dual substrate kinetics including a pH inhibition function was able to predict Anammox activity at higher NO2−-N concentrations, with a nitrite inhibition constant of 210 mg/L. A synergistic negative effect on Anammox activity was observed when combining pH and nitrite stressors. Anammox activity was completely lost at low (6.7) and high (8.5) pH conditions, but resumed after adjusting to an optimal pH (7.5 ± 0.2). We found that AnAOB bacteria are susceptible to both high nitrite concentrations and fluctuating pH levels. Based on experimental evidence and modeling, pH mediates nitrite inhibition in the Anammox process due to the accumulation of free nitrous acid. Our model can predict the outcome of different operating scenarios and help select optimal operational strategies for Anammox implementation.

Hydrogen is a clean energy vector that could help to face the current environmental issues of greenhouse gas emissions and, over a longer time scale, to replace the depleting nonrenewable fuels. Biological production by fermentation of waste and residues has the potential to surrogate the current technologies of production of this gas. In this chapter we report a summary of the fermentative pathways related to hydrogen production in the thermophilic microorganisms of the genera Thermotoga and Pseudothermotoga that embrace several marine species with the highest hydrogen yields among eubacteria. The contribution includes a brief review of dark fermentation (DF) and capnophilic lactic fermentation (CLF), the two processes related to hydrogen synthesis in these organisms, together with a discussion of new data concerning the distribution of CLF in these bacteria. The data show a varied scenario with different metabolic capabilities spread across the two genera. Under standard conditions, CLF is active only in few species of Thermotoga genus. The study underlines the great potential of these microbes in the valorization of agro-food waste and production of fuel and chemicals. In particular, the metabolic and biochemical diversity of Thermotoga and Pseudothermotoga species, together with their resilience to different environmental conditions, suggests the possibility to overtake many of the bottlenecks related to operational factors such as substrates, temperature, pH, hydraulic retention time, and hydrogen partial pressure.

In this present paper, we present a class of static, spherically symmetric charged anisotropic fluid models of super dense stars in isotropic coordinates by considering a particular type of metric potential, a specific choice of electric field intensity E and pressure anisotropy factor Δ which involve parameters K (charge) and α (anisotropy) respectively. The solutions so obtained are utilized to construct the models for super-dense stars like neutron stars and strange quark stars. Our solutions are well behaved within the following ranges of different constant parameters: 4

108The increased use of the activated sludge system to treat municipal and industrial wastewater has led to a considerable production of sludge, which is potentially harmful to both the environment and human beings. Anaerobic digestion (AD) of waste-activated sludge (WAS) is a widely accepted method for sludge stabilization and biogas production. The enhancement of the AD process has been studied by implementing different pretreatments of WAS, codigestion of WAS, and other substrates and applying multiphase systems. The current study applied compost material from aerobic composting of plant litter as inoculants to the WAS digesters. The studies were carried out in two phases. First, compost with different maturations was tested. During the process of compost production, the temperature and the microbial community evolve with time. The phases of composting are indicated by temperature difference. In this test, the compost was sampled at its initial, hot and stable phases, respectively. The stable compost was found to have the strongest stimulatory effect on the biogas production. The reactor with an inoculation of 0.1 g compost DW/g COD could achieve 42% more biogas production than the control reactor at the 10th day. Subsequent experiments further investigated this effect by distinguishing it into biological and nonbiological aspects. After 60 days, the biological aspects showed a stronger stimulatory effect of biogas production and a better removal of effluent chemical oxygen demand (COD) than the control. Furthermore, an addition of 0.1 g compost DW/g COD, with a thermo-alkaline pretreatment and kitchen waste as co-substrate, would give 19% more specific biogas production (mL biogas/g COD loaded) than the control.

Solid-liquid extraction (adsorption or ion exchange) is a promising approach for the in situ separation of organic acids from fermentation broths. In this study, a diluted concentration of lactic acid (< 10 g/L) separation from a model fermentation broth by granular activated carbon (GAC) as well as weak (Reillex (R) 425 or RLX425) and strong (Amberlite (R) IRA-400 or AMB400) base anion exchange resins under various operating conditions was experimentally investigated. Thermodynamic analysis showed that the best lactic acid adsorption performances were obtained at a pH below the pKa value of lactic acid (i. e., 3.86) for GAC and RLX425 by physical adsorption mechanism and above the pKa value for the AMB400 resin by an ion exchange mechanism, respectively. The adsorption capacity for GAC (38.2 mg/g) was the highest, followed by AMB400 (31.2 mg/g) and RLX425 (17.2 mg/g). As per the thermodynamic analysis, the lactic acid adsorbed onto GAC and RLX425 through a physical adsorption mechanism, whereas the lactic acid adsorbed onto AMB400 with an ion exchange mechanism. The Langmuir adsorption isotherm model (R-2 > 0.96) and the pseudo-second order kinetic model (R-2 similar to 1) fitted better to the experimental data than the other models tested. Postulating the conditions for the real fermentation broth (pH: 5.0-6.5 and temperature: 30-80 degrees C), the resin AMB400 represents an ideal candidate for the extraction of lactic acid during fermentation.

We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for perfect charged fluid, compatible with a super dense star modeling. The solution is well behaved for all the values of Schwarzschild parameter u lying in the range 0 < u < 0.1727 for the maximum value of charge parameter K = 0.08163. The maximum mass of the fluid distribution is calculated by using stellar surface density as ρ b = 4.6888×1014g cm−3. Corresponding to K = 0.08 and u max = 0.1732, the resulting well behaved solution has a maximum mass M = 0.9324M ⊙ and radius R = 8.00 and by assuming ρ b = 2×1014g cm−3 the solution results a stellar configuration with maximum mass M = 1.43M ⊙ and radius R b = 12.25 km. The maximum mass is found increasing with increasing K up to 0.08. The well behaved class of relativistic stellar models obtained in this work might has astrophysical significance in the study of internal structure of compact star such as neutron star or self-bound strange quark star like Her X-1.

A kinetic model of fermentative hydrogen (H-2) production was developed for the hyper-thermophilic marine bacterium Thermotoga neapolitana DSMZ 4359(T) using glucose as the substrate. The model was built based on anaerobic digestion model no.1 (ADM1) by IWA using Monod-like kinetic equations. Several series of pH controlled batch fermentation tests were performed under pure CO2 or N-2 atmosphere in serum bottles to evaluate the growth kinetic parameters. The kinetic parameters were estimated by applying the nonlinear least square method to Monod and Michaelis Menten kinetic equations. The experimentally estimated value of k, k(s), Y and k(d) were 0.839 h(-1), 1.42 g/L, 0.1204 and 0.0043 h(-1), respectively. The kinetic parameters were analyzed for sensitivities and subsequently calibrated and validated by a separate set of experimental results. The model was particularly effective in estimating the biomass growth, substrate consumption, and H-2 production except for acetate and lactate production, due to capnophilic condition (under CO2 atmosphere). Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The aim of the present study was to develop a kinetic model for a recently proposed unique and novel metabolic process called capnophilic (CO2-requiring) lactic fermentation (CLF) pathway in Thermotoga neapolitana. The model was based on Monod kinetics and the mathematical expressions were developed to enable the simulation of biomass growth, substrate consumption and product formation. The calibrated kinetic parameters such as maximum specific uptake rate (k), semi-saturation constant (k(S)), biomass yield coefficient (Y) and endogenous decay rate (k(d)) were 1.30 h(-1), 1.42 g/L, 0.1195 and 0.0205 h(-1), respectively. A high correlation (>0.98) was obtained between the experimental data and model predictions for both model validation and cross validation processes. An increase of the lactate production in the range of 40-80% was obtained through CLF pathway compared to the classic dark fermentation model. The proposed kinetic model is the first mechanistically based model for the CLF pathway. This model provides useful information to improve the knowledge about how acetate and CO2 are recycled back by Thermotoga neapolitana to produce lactate without compromising the overall hydrogen yield. (C) 2016 Elsevier Ltd. All rights reserved.

The wetland of focus, Inle Lake, located in central Myanmar, is well known for its unique biodiver- sity and culture, as well as for ingenious floating garden agriculture. During the last decades, the lake area has seen extensive degradation in terms of water quality, erosion, deforestation, and biodiversity concomitant with a major shift to unsustainable land use. The study was conducted, with an emphasis on water quality, to analyze environmental impacts (effects) changing the ecosystem and to comprehensively evaluate the envi- ronmental state of the ecosystem through an innovative Rapid Cumulative Effects Assessment framework tool. The assessment started with a framework-forming Participatory Rural Appraisal (PRA), which quantified and prioritized impacts over space and time. Critically important impacts were assessed for Bintra-inter interactions^ using the loop analysis simulation. Water samples were analyzed while geographic information system (GIS) and remote sensing were used to identify water pollution hotspots. It was concluded that out of a plethora of impacts, pollution from municipal sources, sedimentation, and effects exerted by floating gardens hadthe mostdetrimental impacts, which cumulative- ly affected the entire ecosystem. The framework tool was designed in a broad sense with a refer- ence to highly needed assessments of poorly stud- ied wetlands where degradation is evident, but scarcely quantified, and where long-term field studies are fraught with security issues and resource unavail- ability (post-conflict, poor and remote regions, e.g., Afghanistan, Laos, Sudan, etc.)