Sónia G. Barbosa, L. Peixoto, J. I. Alves et al.

Renewable and Sustainable Energy Reviews • 2020

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.

Luis F. Arenas, Carlos Ponce de León, Frank C. Walsh

Current Opinion in Electrochemistry • 2019

Qian Sun, Zhiling Li, You-Zhao Wang et al.

Bioresource Technology • 2016

Bo Wang, Wenzong Liu, Yifeng Zhang et al.

Chemical Engineering Journal • 2021

Patrick T. Sekoai, Anish Ghimire, Obinna T. Ezeokoli et al.

Renewable and Sustainable Energy Reviews • 2021

Sam Molenaar, Pradip Saha, Annemerel R. Mol et al.

International Journal of Molecular Sciences • 2017

Microbial electrosynthesis is a useful form of technology for the renewable production of organic commodities from biologically catalyzed reduction of CO₂. However, for the technology to become applicable, process selectivity, stability and efficiency need strong improvement. Here we report on the effect of different electrochemical control modes (potentiostatic/galvanostatic) on both the start-up characteristics and steady-state performance of biocathodes using a non-enriched mixed-culture inoculum. Based on our results, it seems that kinetic differences exist between the two dominant functional microbial groups (i.e., homoacetogens and methanogens) and that by applying different current densities, these differences may be exploited to steer product selectivity and reactor performance.

Cinzia Tornatore, Luca Marchitto, Pino Sabia et al.

Frontiers in Mechanical Engineering • 2022

Ammonia (NH 3 ) is among the largest-volume chemicals produced and distributed in the world and is mainly known for its use as a fertilizer in the agricultural sector. In recent years, it has sparked interest in the possibility of working as a high-quality energy carrier and as a carbon-free fuel in internal combustion engines (ICEs). This review aimed to provide an overview of the research on the use of green ammonia as an alternative fuel for ICEs with a look to the future on possible applications and practical solutions to related problems. First of all, the ammonia production process is discussed. Present ammonia production is not a “green” process; the synthesis occurs starting from gaseous hydrogen currently produced from hydrocarbons. Some ways to produce green ammonia are reviewed and discussed. Then, the chemical and physical properties of ammonia as a fuel are described and explained in order to identify the main pros and cons of its use in combustion systems. Then, the most viable solutions for fueling internal combustion engines with ammonia are discussed. When using pure ammonia, high boost pressure and compression ratio are required to compensate for the low ammonia flame speed. In spark-ignition engines, adding hydrogen to ammonia helps in speeding up the flame front propagation and stabilizing the combustion. In compression-ignition engines, ammonia can be successfully used in dual-fuel mode with diesel. On the contrary, an increase in NOx and the unburned NH 3 at the exhaust require the installation of apposite aftertreatment systems. Therefore, the use of ammonia seems to be more practicable for marine or stationary engine application where space constraints are not a problem. In conclusion, this review points out that ammonia has excellent potential to play a significant role as a sustainable fuel for the future in both retrofitted and new engines. However, significant further research and development activities are required before being able to consider large-scale industrial production of green ammonia. Moreover, uncertainties remain about ammonia safe and effective use and some technical issues need to be addressed to overcome poor combustion properties for utilization as a direct substitute for standard fuels.

Gonzalo E. Fenoy, Omar Azzaroni, Wolfgang Knoll et al.

Chemosensors • 2021

Organic bioelectronics involves the connection of organic semiconductors with living organisms, organs, tissues, cells, membranes, proteins, and even small molecules. In recent years, this field has received great interest due to the development of all kinds of devices architectures, enabling the detection of several relevant biomarkers, the stimulation and sensing of cells and tissues, and the recording of electrophysiological signals, among others. In this review, we discuss recent functionalization approaches for PEDOT and PEDOT:PSS films with the aim of integrating biomolecules for the fabrication of bioelectronics platforms. As the choice of the strategy is determined by the conducting polymer synthesis method, initially PEDOT and PEDOT:PSS films preparation methods are presented. Later, a wide variety of PEDOT functionalization approaches are discussed, together with bioconjugation techniques to develop efficient organic-biological interfaces. Finally, and by making use of these approaches, the fabrication of different platforms towards organic bioelectronics devices is reviewed.

Ji‐Dong Gu

Applied Environmental Biotechnology • 2021

Environmental biotechnology (EB) can play positive and an important role in detoxifying and eliminating pollutants, and cleaning up the contaminated sites of ecosystems, but the development of any EB is based largely on the scientific knowledge and results of (micro)biology and chemistry, and then application mainly on engineering and management. Biodegradation and bioremediation by definition are different in meaning and, as a result, they must be treated differently. On the fundamental basis, the biochemical reactions and the biochemical degradation pathway of any targeted toxicant concerned are basic information before the degradability of the selective pollutant by a microorganism can be claimed. Bioremediation becomes feasible for implementation with the knowledge of the biochemical reactions by the biological agent coupling with the engineering and management to achieve a successful attempt at a site. Though the degradability by a microorganism can be achieved in laboratory condition, the cleaning up of the pollutant at any site needs additional information and knowledge of the physical, chemical and ecological characteristics of the site to allow any success to be achieved. The broad EB can include utilization of pure and selective microorganisms, the biochemical reactions by either pure or mixed culture, enzymes, and metabolic products of microorganisms. In addition, microorganisms may also work in the form of biofilm to carry out the function to detoxify the toxic environmental chemicals. In addition to microorganisms, plants can play an important role in phytoremediation. Overall, environmental biotechnology needs at least three steps to prove its effectiveness from concept testing in laboratory, establishment of the mechanisms involved, workability in complex system and ecosystems, and lastly the implementation and practice on site. A laboratory success on degradation cannot be quickly and simply treated as a claim of EB for bioremediation for application.

Meritxell Romans-Casas, Laura Feliu-Paradeda, Michele Tedesco et al.

Environmental Science and Ecotechnology • 2023

Microbial electrosynthesis (MES) is a promising carbon utilization technology, but the low-value products (i.e., acetate or methane) and the high electric power demand hinder its industrial adoption. In this study, electrically efficient MES cells with a low ohmic resistance of 15.7 mΩ m 2 were operated galvanostatically in fed-batch mode, alternating periods of high CO 2 and H 2 availability. This promoted acetic acid and ethanol production, ultimately triggering selective (78% on a carbon basis) butyric acid production via chain elongation. An average production rate of 14.5 g m -2 d -1 was obtained at an applied current of 1.0 or 1.5 mA cm -2 , being Megasphaera sp. the key chain elongating player. Inoculating a second cell with the catholyte containing the enriched community resulted in butyric acid production at the same rate as the previous cell, but the lag phase was reduced by 82%. Furthermore, interrupting the CO 2 feeding and setting a constant pH 2 of 1.7-1.8 atm in the cathode compartment triggered solventogenic butanol production at a pH below 4.8. The efficient cell design resulted in average cell voltages of 2.6-2.8 V and a remarkably low electric energy requirement of 34.6 kWh el kg -1 of butyric acid produced, despite coulombic efficiencies being restricted to 45% due to the cross-over of O 2 and H 2 through the membrane. In conclusion, this study revealed the optimal operating conditions to achieve energy-efficient butyric acid production from CO 2 and suggested a strategy to further upgrade it to valuable butanol.

Xavier Alexis Walter, Iwona Gajda, Samuel Forbes et al.

Biotechnology for Biofuels • 2016

The scaling-up approach, with limited power-density losses, was achieved by maintaining a plurality of microenvironments within the module, and resulted in a simple and robust system fuelled by urine. This scaling-up approach, within the tested range, was successful in converting chemical energy in urine into electricity.

Yanhong Bian, Aaron Leininger, Harold D. May et al.

Environmental Science and Ecotechnology • 2023

Microbial electrosynthesis (MES) converts CO 2 into value-added products such as volatile fatty acids (VFAs) with minimal energy use, but low production titer has limited scale-up and commercialization. Mediated electron transfer via H 2 on the MES cathode has shown a higher conversion rate than the direct biofilm-based approach, as it is tunable via cathode potential control and accelerates electrosynthesis from CO 2 . Here we report high acetate titers can be achieved via improved in situ H 2 supply by nickel foam decorated carbon felt cathode in mixed community MES systems. Acetate concentration of 12.5 g L -1 was observed in 14 days with nickel-carbon cathode at a poised potential of -0.89 V (vs. standard hydrogen electrode, SHE), which was much higher than cathodes using stainless steel (5.2 g L -1 ) or carbon felt alone (1.7 g L -1 ) with the same projected surface area. A higher acetate concentration of 16.0 g L -1 in the cathode was achieved over long-term operation for 32 days, but crossover was observed in batch operation, as additional acetate (5.8 g L -1 ) was also found in the abiotic anode chamber. We observed the low Faradaic efficiencies in acetate production, attributed to partial H 2 utilization for electrosynthesis. The selective acetate production with high titer demonstrated in this study shows the H 2 -mediated electron transfer with common cathode materials carries good promise in MES development.

Connor T. Skennerton, Karuna Chourey, Ramsunder Iyer et al.

mBio • 2017

The anaerobic oxidation of methane by anaerobic methanotrophic (ANME) archaea in syntrophic partnership with deltaproteobacterial sulfate-reducing bacteria (SRB) is the primary mechanism for methane removal in ocean sediments. The mechanism of their syntrophy has been the subject of much research as traditional intermediate compounds, such as hydrogen and formate, failed to decouple the partners. Recent findings have indicated the potential for extracellular electron transfer from ANME archaea to SRB, though it is unclear how extracellular electrons are integrated into the metabolism of the SRB partner. We used metagenomics to reconstruct eight genomes from the globally distributed SEEP-SRB1 clade of ANME partner bacteria to determine what genomic features are required for syntrophy. The SEEP-SRB1 genomes contain large multiheme cytochromes that were not found in previously described free-living SRB and also lack periplasmic hydrogenases that may prevent an independent lifestyle without an extracellular source of electrons from ANME archaea. Metaproteomics revealed the expression of these cytochromes at in situ methane seep sediments from three sites along the Pacific coast of the United States. Phylogenetic analysis showed that these cytochromes appear to have been horizontally transferred from metal-respiring members of the Deltaproteobacteria such as Geobacter and may allow these syntrophic SRB to accept extracellular electrons in place of other chemical/organic electron donors. IMPORTANCE Some archaea, known as anaerobic methanotrophs, are capable of converting methane into carbon dioxide when they are growing syntopically with sulfate-reducing bacteria. This partnership is the primary mechanism for methane removal in ocean sediments; however, there is still much to learn about how this syntrophy works. Previous studies have failed to identify the metabolic intermediate, such as hydrogen or formate, that is passed between partners. However, recent analysis of methanotrophic archaea has suggested that the syntrophy is formed through direct electron transfer. In this research, we analyzed the genomes of multiple partner bacteria and showed that they also contain the genes necessary to perform extracellular electron transfer, which are absent in related bacteria that do not form syntrophic partnerships with anaerobic methanotrophs. This genomic evidence shows a possible mechanism for direct electron transfer from methanotrophic archaea into the metabolism of the partner bacteria.

Jean‐Marie Fontmorin, Paniz Izadi, Da Li et al.

Electrochimica Acta • 2021

Microbial electrosynthesis (MES) is a promising technology to convert CO2 into value-added chemicals. Enhancing the interactions between biofilms and electrodes is the key of bioelectrochemical systems (BES). In this work, we studied the conversion of CO2 by MES in reactors equipped with novel gas diffusion electrodes (GDEs) modified with a polyaniline (PANI) polymer binary doped with H2SO4 and ammonium lauryl sulfate. The enhanced conductive and hydrophilic properties of the polymer increased the biocompatibility of the PANI-modified GDEs compared to the non-modified carbon GDEs. This increased biocompatibility resulted in faster start-up and higher bioproduction of volatile fatty acids (VFAs) such as acetate and butyrate. Up to 4400 ppm acetate was produced in PANI-modified reactors after 24 days of operation, compared to 408 ppm in reactors equipped with non-modified GDEs. A maximum acetate concentration of 7500 ppm (production rate of 554.8 ± 267.5 ppm day−1) was reached in reactors equipped with PANI-GDEs. After 60 days, apart from acetate, 245 ppm butyrate was produced in reactors equipped with the electrodes modified with PANI, while less than 60 ppm was produced with non-modified GDEs. SEM analysis revealed the development of biofilms on both modified and non-modified electrodes, but the images also suggest differences in compositions.

Silvia Bolognesi, Daniele Cecconet, Arianna Callegari et al.

Environmental Research • 2020

Qing Ge, Peng Li, Miao Liu et al.

Bioresources and Bioprocessing • 2023

A series of activated biochar (KBBC-700, KBBC-800 and KBBC-900) which were modified by KOH and pyrolysis at various temperatures from ball-milling bamboo powder were obtained. The physicochemical properties and pore structures of activated biochar were investigated by scanning electron microscopy (SEM), fourier transform infrared spectoscopy (FT-IR), X-ray diffraction (XRD) and N 2 adsorption/desorption. The adsorption performance for the removal of methylene blue (MB) was deeply studied. The results showed that KBBC-900 obtained at activation temperature of 900 °C exhibited a great surface area which reached 562 m 2 /g with 0.460 cm 3 /g of total pore volume. The enhancement of adsorption capacity could be ascribed to the increase of surface oxygen-containing functional groups, aromatization and mesoporous channels. The adsorption capacity was up to 67.46 mg/g under the optimum adsorption parameters with 2 g/L of adsorbent dose, 11 of initial solution pH and 298 K of the reactive temperature. The adsorption capacity was 70.63% of the first time after the material was recycled for three cycles. The kinetics indicated that the adsorption equilibrium time for MB on KBBC-900 was of about 20 min with the data fitted better to the pseudo-second-order kinetics model. The adsorption process was mainly dominated by chemical adsorption. Meanwhile, the adsorption isotherm showed that the Langmuir model fitted the best, and thermodynamic parameters revealed that the adsorption reaction was the endothermic nature and the spontaneous process. Adsorption of MB mainly attributed to electrostatic interactions, cation-π electron interaction and redox reaction. This study suggested that the activated biochar obtained by KOH activation from bamboo biochar has great potentials in the practical application to remove MB from wastewater.

Xiubei Yang, Qizheng An, Xuewen Li et al.

Nature Communications • 2024

Covalent organic frameworks (COFs) are ideal templates for constructing metal-free catalysts for the oxygen reduction reaction due to their highly tuneable skeletons and controllable porous channels. However, the development of highly active sites within COFs remains challenging due to their limited electron-transfer capabilities and weak binding affinities for reaction intermediates. Herein, we constructed highly active catalytic centres by modulating the electronic states of the pyridine nitrogen atoms incorporated into the frameworks of COFs. By incorporating different pyridine units (such as pyridine, ionic pyridine, and ionic imidazole units), we tuned various properties including dipole moments, reductive ability, hydrophilicity, and binding affinities towards reaction intermediates. Notably, the ionic imidazole COF (im-PY-BPY-COF) exhibited greater activity than the neutral COF (PY-BPY-COF) and ionic pyridine COF (ion-PY-BPY-COF). Specifically, im-PY-BPY-COF demonstrated a half-wave potential of 0.80 V in 0.1 M KOH, outperforming other metal-free COFs. Theoretical calculations and in situ synchrotron radiation Fourier transform infrared spectroscopy confirmed that the carbon atoms in the ionic imidazole rings improved the activity by facilitating binding of the intermediate OOH* and promoting the desorption of OH*. This study provides new insights into the design of highly active metal-like COF catalysts.

Korneel Rabaey

Joule • 2020

Muhammad Saghir, Shagufta Zafar, Amiza Tahir et al.

Frontiers in Energy Research • 2019

Being a developing economy, Pakistan is facing a severe energy crisis that limits its economic development. Pakistan relies heavily on energy resources like natural gas, oil, hydropower, nuclear, coal and liquefied petroleum gas (LPG) which contribute as 48.3, 32.1, 11.3, 7.6, and 0.6% of the primary energy supply, respectively. Because of the rapidly growing population and economy, Pakistan's energy needs are huge; to accomplish these energy necessities, Pakistan is continually spending $7-9 billion on the import of fossil fuels. To resolve the serious issues of energy availability, the Alternative Energy Development Board (AEDB) of Pakistan is currently exploring the development of renewable energy technologies in Pakistan that will be beneficial for the developing economy so that Pakistan might be able to minimize the growing energy crisis. Out of all the renewable energy resources, biomass is considered the best and most easily accessible source of energy with its unique environmentally friendly nature, constant supply, wider availability, and ease of integration into existing infrastructure. Despite the presence of an abundance of biomass energy resources, there is still a need for work on the use of these sources to produce energy. This literature review explores the availability of biomass resources in Pakistan and their potential for addressing rapidly growing energy demand in the country, which can assist in the stabilization of a Pakistan's energy demand for challenged economic development.

Amir Hatamie, Shayan Angizi, Saurabh Kumar et al.

Journal of The Electrochemical Society • 2020

The emergence of textile-based wearable sensors as light-weight portable devices to monitor desired parameters, has recently gained much interest and has led to the development of flexible electronics on non-rigid substrates. The flexible biosensors may result in improved sports performance, to monitor the desired bodies for injuries, improved clinical diagnostics and monitor biological molecules and ions in biological fluids such as saliva, sweat. In addition, they could help users with different types of disorders such as blindness. In this context, new composite and nanomaterials have been found to be promising candidates to obtain improved performance of the textile based wearable devices and to optimize the structures for intimate contact with the skin for better functionality. This review aims to provide the most recent cutting-edge information on emergence, fabrication, materials, and applications of chemical and physical flexible and stretchable textile-based (bio)sensors. Besides this, we discusss the recent key innovations and applications of textile-based sensors in healthcare.

Xinxin Xiao

eScience • 2021

Enzymatic biofuel cells (EBFCs) are a subgroup of fuel cells that use enzymes as catalysts. EBFCs that utilize physiological substrates such as glucose or lactate are of great interest as implantable or wearable power sources to activate medical devices. This contribution introduces the working principles of EBFCs and summarizes recent progress in EBFC-enabled biosensors, pulse generators, and therapy. Biosensors with self-powered characteristic enjoy high selectivity, leading to potential “instrument-free” or “expensive-instrument-free” measurement. Autonomous pulse generation is based on the hybrid of EBFC and supercapacitor, which is promising for the application in medical related electrostimulation. By providing the direct electrical stimulation, or controllably releasing drug, EBFCs can also be used for self-powered therapeutic system. The further combination of self-powered sensing and treating enables EBFC as a possible platform of diagnostics and therapeutics. Future efforts can be focused on resolving the limited power density and lifetime of EBFC.

Fong-Lee Ng, Siew‐Moi Phang, Vengadesh Periasamy et al.

Scientific Reports • 2017

We report for the first time a photosynthetically active algae immobilized in alginate gel within a fuel cell design for generation of bioelectricity. The algal-alginate biofilm was utilized within a biophotovoltaics (BPV) device developed for direct bioelectricity generation from photosynthesis. A peak power output of 0.289 mWm -2 with an increase of 18% in power output compared to conventional suspension culture BPV device was observed. The increase in maximum power density was correlated to the maximum relative electron transport rate (rETRm). The semi-dry type of photosynthetically active biofilm proposed in this work may offer significantly improved performances in terms of fuel cell design, bioelectricity generation, oxygen production and CO 2 reduction.

García Hernández, Johann F. Osma

Frontiers in Environmental Science • 2020

Microbial electrochemical systems (MES) can be described as a combination of technologies with the unique ability to use microorganisms to conduct the transformation between chemical- and electric- energy. This property holds the promise to offer an alternative to the use of fossil fuels in the generation of electricity, and hazardous compounds in the production of chemical products. In this review, the fundamental aspects to describe the mechanisms involved in the MES microbe-electrode interaction are presented. Furthermore, a detailed discussion on the current classification strategies is presented including the techniques used at distinctive characterization levels. Also, the implementation of a dual-iterative bibliographic analysis is presented. The first iteration of the bibliographic analysis was considered from a historical perspective, allowing to identify, in a systematic manner, the main research areas related to MES. In the second iteration, the previously identified areas were surveyed in order to obtain a representative sample for the analysis and identification of trends and main research objectives of MES technologies. The MES areas that displayed the highest growth rate value are those related to “wastewater”, “wastewater treatment” and “extracellular electron transfer”; while “system (configuration/application)” and “microbial fuel cell” reported the highest number of related documents.

Ahmed I. Osman, Umair Qasim, Farrukh Jamil et al.

Renewable and Sustainable Energy Reviews • 2021

Sayalee Joshi, Aide Robles, Samuel Aguiar et al.

The ISME Journal • 2021

Chain elongation is a growth-dependent anaerobic metabolism that combines acetate and ethanol into butyrate, hexanoate, and octanoate. While the model microorganism for chain elongation, Clostridium kluyveri, was isolated from a saturated soil sample in the 1940s, chain elongation has remained unexplored in soil environments. During soil fermentative events, simple carboxylates and alcohols can transiently accumulate up to low mM concentrations, suggesting in situ possibility of microbial chain elongation. Here, we examined the occurrence and microbial ecology of chain elongation in four soil types in microcosms and enrichments amended with chain elongation substrates. All soils showed evidence of chain elongation activity with several days of incubation at high (100 mM) and environmentally relevant (2.5 mM) concentrations of acetate and ethanol. Three soils showed substantial activity in soil microcosms with high substrate concentrations, converting 58% or more of the added carbon as acetate and ethanol to butyrate, butanol, and hexanoate. Semi-batch enrichment yielded hexanoate and octanoate as the most elongated products and microbial communities predominated by C. kluyveri and other Firmicutes genera not known to undergo chain elongation. Collectively, these results strongly suggest a niche for chain elongation in anaerobic soils that should not be overlooked in soil microbial ecology studies.

Le Zhang, Agnès Kuroki, Yen Wah Tong

Frontiers in Energy Research • 2020

In the context of accelerating development of renewable and sustainable energy, biogas upgrading has attracted significant attention in order to yield high quality biomethane which can be utilized as an alternative to natural gas. Biogas upgrading techniques have been revolutionized in the past decade with the emergence of new strategies such as enhanced hydrogenotrophic methanogenesis. This review comprehensively summarizes the latest in situ biogas upgrading technologies via enhanced hydrogenotrophic methanogenesis in order to facilitate their development and commercial application: (1) hydrogen injection into anaerobic digesters for in situ enhancement of hydrogenotrophic methanogenic pathways, (2) membrane electrolysis-assisted CO2 extraction and bioelectrochemical removal of CO2, and (3) additives (e.g. ash, zero-valent iron and biochar). The key findings and technical limitations are summarized and critically analyzed for each in situ biogas upgrading technique. Additionally, potential industrial applications of these in situ biogas upgrading strategies in anaerobic digesters are also discussed, before concluding with their future development.

Yeji Lee, Vineeth Kumar Bandari, Zhe Li et al.

Nature Communications • 2021

Today's smallest energy storage devices for in-vivo applications are larger than 3 mm 3 and lack the ability to continuously drive the complex functions of smart dust electronic and microrobotic systems. Here, we create a tubular biosupercapacitor occupying a mere volume of 1/1000 mm 3 (=1 nanoliter), yet delivering up to 1.6 V in blood. The tubular geometry of this nano-biosupercapacitor provides efficient self-protection against external forces from pulsating blood or muscle contraction. Redox enzymes and living cells, naturally present in blood boost the performance of the device by 40% and help to solve the self-discharging problem persistently encountered by miniaturized supercapacitors. At full capacity, the nano-biosupercapacitors drive a complex integrated sensor system to measure the pH-value in blood. This demonstration opens up opportunities for next generation intravascular implants and microrobotic systems operating in hard-to-reach small spaces deep inside the human body.

Mon Oo Yee, Amelia‐Elena Rotaru

Scientific Reports • 2020

The co-occurrence of Geobacter and Methanosarcinales is often used as a proxy for the manifestation of direct interspecies electron transfer (DIET) in the environment. Here we tested eleven new co-culture combinations between methanogens and electrogens. Previously, only the most electrogenic Geobacter paired by DIET with Methanosarcinales methanogens, namely G. metallireducens and G. hydrogenophilus. Here we provide additional support, and show that five additional Methanosarcinales paired with G. metallireducens, while a strict hydrogenotroph could not. We also show that G. hydrogenophilus, which is incapable to grow with a strict hydrogenotrophic methanogen, could pair with a strict non-hydrogenotrophic Methanosarcinales. Likewise, an electrogen outside the Geobacter cluster (Rhodoferrax ferrireducens) paired with Methanosarcinales but not with strict hydrogenotrophic methanogens. The ability to interact with electrogens appears to be conserved among Methanosarcinales, the only methanogens with c-type cytochromes, including multihemes (MHC). Nonetheless, MHC, which are often linked to extracellular electron transfer, were neither unique nor universal to Methanosarcinales and only two of seven Methanosarcinales tested had MHC. Of these two, one strain had an MHC-deletion knockout available, which we hereby show is still capable to retrieve extracellular electrons from G. metallireducens or an electrode suggesting an MHC-independent strategy for extracellular electron uptake.

Salma Elhenawy, Majeda Khraisheh, Fares Almomani et al.

Sustainability • 2022

Due to fossil fuel depletion and the rapid growth of industry, it is critical to develop environmentally friendly and long-term alternative energy technologies. Microbial fuel cells (MFCs) are a powerful platform for extracting energy from various sources and converting it to electricity. As no intermediate steps are required to harness the electricity from the organic substrate’s stored chemical energy, MFC technology offers a sustainable alternative source of energy production. The generation of electricity from the organic substances contained in waste using MFC technology could provide a cost-effective solution to the issue of environmental pollution and energy shortages in the near future. Thus, technical advancements in bioelectricity production from wastewater are becoming commercially viable. Due to practical limitations, and although promising prospects have been reported in recent investigations, MFCs are incapable of upscaling and of high-energy production. In this review paper, intensive research has been conducted on MFCs’ applications in the treatment of wastewater. Several types of waste have been extensively studied, including municipal or domestic waste, industrial waste, brewery wastewater, and urine waste. Furthermore, the applications of MFCs in the removal of nutrients (nitrogen and sulphates) and precious metals from wastewater were also intensively reviewed. As a result, the efficacy of various MFCs in achieving sustainable power generation from wastewater has been critically addressed in this study.

Sudipta Chatterjee, Indranil Dutta, Yanwei Lum et al.

Energy & Environmental Science • 2021

Power to formic acid via CO 2 hydrogenation or electrochemical CO 2 reduction has great potential to enable a complete cycle with formic acid to power for the storage and utilization of low-carbon electricity at a scale of multi-gigatonnes per year.

Ziyu Li, Weiwei Chang, Tianyu Cui et al.

Communications Materials • 2021

Abstract Microbiologically influenced corrosion of metals is prevalent in both natural and industrial environments, causing enormous structural damage and economic loss. Exactly how microbes influence corrosion remains controversial. Here, we show that the pitting corrosion of stainless steel is accelerated in the presence of Shewanella oneidensis MR-1 biofilm by extracellular electron transfer between the bacterial cells and the steel electrode, mediated by a riboflavin electron shuttle. From pitting measurements, X-ray photoelectron spectroscopy and Mott-Schottky analyses, the addition of an increased amount of riboflavin is found to induce a more defective passive film on the stainless steel. Electrochemical impedance spectroscopy reveals that enhanced bioanodic and biocathodic process can both promote the corrosion of the stainless steel. Using in situ scanning electrochemical microscopy, we observe that extracellular electron transfer between the bacterium and the stainless steel is bidirectional in nature and switchable depending on the passive or active state of the steel surface.

N’Dah Joel Koffi, Satoshi Okabe

Scientific Reports • 2020

Although microbial fuel cells (MFCs) can produce renewable energy from wastewater, the generated power is practically unusable. To extract usable power from an MFC fed with wastewater, we newly developed a low voltage booster multiplier (LVBM), which is composed of a self-oscillating LVB and multistage voltage multiplier circuits (VMCs). The low output MFC voltage (ca. 0.4 V) was successfully boosted up to 99 ± 2 V, which was the highest voltage that has been ever reported, without voltage reversal by connecting an LVB with 20-stage VMCs. Moreover, the boosted voltage (81 ± 1 V) was stably maintained for > 40 h even after disconnecting the LVBM from the MFC. The energy harvesting efficiency of LVBM was > 80% when an LVB with 4-stage VMCs was charged to 9.3 V. These results clearly suggest that the proposed LVBM system is an efficient and self-starting energy harvester and storage for low-power generating MFCs.

Huawei Zhu, Hengkai Meng, Wei Zhang et al.

Nature Communications • 2019

Microbial biophotovoltaics (BPV) offers a biological solution for renewable energy production by using photosynthetic microorganisms as light absorbers. Although abiotic engineering approaches, e.g., electrode modification and device optimization, can enhance the electrochemical communication between living cells and electrodes, the power densities of BPV are still low due to the weak exoelectrogenic activity of photosynthetic microorganisms. Here, we develop a BPV based on a D-lactate mediated microbial consortium consisting of photosynthetic cyanobacteria and exoelectrogenic Shewanella. By directing solar energy from photons to D-lactate, then to electricity, this BPV generates a power density of over 150 mW·m -2 in a temporal separation setup. Furthermore, a spatial-temporal separation setup with medium replenishment enables stable operation for over 40 days with an average power density of 135 mW·m -2 . These results demonstrate the electron flow constrained microbial consortium can facilitate electron export from photosynthetic cells and achieve an efficient and durable power output.

A.G. Olabi, Tabbi Wilberforce, Mohammad Ali Abdelkareem et al.

Energies • 2021

This review presents a detailed summary of the latest technologies used in flywheel energy storage systems (FESS). This paper covers the types of technologies and systems employed within FESS, the range of materials used in the production of FESS, and the reasons for the use of these materials. Furthermore, this paper provides an overview of the types of uses of FESS, covering vehicles and the transport industry, grid leveling and power storage for domestic and industrial electricity providers, their use in motorsport, and applications for space, satellites, and spacecraft. Different types of machines for flywheel energy storage systems are also discussed. This serves to analyse which implementations reduce the cost of permanent magnet synchronous machines. As well as this, further investigations need to be carried out to determine the ideal temperature range of operation. Induction machines are currently stoutly designed with lower manufacturing cost, making them unsuitable for high-speed operations. Brushless direct current machines, the Homolar machines, and permanent magnet synchronous machines should also be considered for future research activities to improve their performance in a flywheel energy storage system. An active magnetic bearing can also be used alongside mechanical bearings to reduce the control systems’ complications, thereby making the entire system cost-effective.

Iwona Gajda, Andrew Stinchcombe, John Greenman et al.

International Journal of Hydrogen Energy • 2016

This paper describes the suitability of the Microbial Fuel Cell (MFC) for generation of electrical power with a simultaneous synthesis of active catholyte in the form of caustic solution. The active solution formed inside a terracotta based MFC reactor was a product of self-powered wastewater electrolysis utilizing i) wastewater with added sodium acetate as a carbon source and ii) neat urine. The catholyte solution that has been actively synthesized was harvested and used for precipitation of heavy metals such as: iron, copper and zinc showing its suitability for use in electro-coagulation (electro-flocculation). This proposed alternative approach to self-powered electrocoagulation is based on electrochemically formed caustic catholyte within the inner cathode chamber of the MFC and then used ex situ to form metal hydroxides that precipitate out from heavy metal solutions.

Márk Szuhaj, Norbert Ács, Roland Tengölics et al.

Biotechnology for Biofuels • 2016

Fed-batch reactors significantly improve the efficiency of the biological power-to-gas process. Besides their storage function, biogas fermentation effluent reservoirs can serve as large-scale bio CH4 reactors. On the basis of this recognition, a novel concept is proposed, which merges biogas technology with other means of renewable electricity production for improved efficiency and sustainability.

A.G. Olabi, Tabbi Wilberforce, Enas Taha Sayed et al.

Energies • 2020

Combined heat and power (CHP) in a single and integrated device is concurrent or synchronized production of many sources of usable power, typically electric, as well as thermal. Integrating combined heat and power systems in today’s energy market will address energy scarcity, global warming, as well as energy-saving problems. This review highlights the system design for fuel cell CHP technologies. Key among the components discussed was the type of fuel cell stack capable of generating the maximum performance of the entire system. The type of fuel processor used was also noted to influence the systemic performance coupled with its longevity. Other components equally discussed was the power electronics. The thermal and water management was also noted to have an effect on the overall efficiency of the system. Carbon dioxide emission reduction, reduction of electricity cost and grid independence, were some notable advantages associated with fueling cell combined heat and power systems. Despite these merits, the high initial capital cost is a key factor impeding its commercialization. It is, therefore, imperative that future research activities are geared towards the development of novel, and cheap, materials for the development of the fuel cell, which will transcend into a total reduction of the entire system. Similarly, robust, systemic designs should equally be an active research direction. Other types of fuel aside, hydrogen should equally be explored. Proper risk assessment strategies and documentation will similarly expand and accelerate the commercialization of this novel technology. Finally, public sensitization of the technology will also make its acceptance and possible competition with existing forms of energy generation feasible. The work, in summary, showed that proton exchange membrane fuel cell (PEM fuel cell) operated at a lower temperature-oriented cogeneration has good efficiency, and is very reliable. The critical issue pertaining to these systems has to do with the complication associated with water treatment. This implies that the balance of the plant would be significantly affected; likewise, the purity of the gas is crucial in the performance of the system. An alternative to these systems is the PEM fuel cell systems operated at higher temperatures.

Oliver Hädicke, Axel von Kamp, Timur Aydogan et al.

PLoS Computational Biology • 2018

Constraint-based modeling techniques have become a standard tool for the in silico analysis of metabolic networks. To further improve their accuracy, recent methodological developments focused on integration of thermodynamic information in metabolic models to assess the feasibility of flux distributions by thermodynamic driving forces. Here we present OptMDFpathway, a method that extends the recently proposed framework of Max-min Driving Force (MDF) for thermodynamic pathway analysis. Given a metabolic network model, OptMDFpathway identifies both the optimal MDF for a desired phenotypic behavior as well as the respective pathway itself that supports the optimal driving force. OptMDFpathway is formulated as a mixed-integer linear program and is applicable to genome-scale metabolic networks. As an important theoretical result, we also show that there exists always at least one elementary mode in the network that reaches the maximal MDF. We employed our new approach to systematically identify all substrate-product combinations in Escherichia coli where product synthesis allows for concomitant net CO2 assimilation via thermodynamically feasible pathways. Although biomass synthesis cannot be coupled to net CO2 fixation in E. coli we found that as many as 145 of the 949 cytosolic carbon metabolites contained in the genome-scale model iJO1366 enable net CO2 incorporation along thermodynamically feasible pathways with glycerol as substrate and 34 with glucose. The most promising products in terms of carbon assimilation yield and thermodynamic driving forces are orotate, aspartate and the C4-metabolites of the tricarboxylic acid cycle. We also identified thermodynamic bottlenecks frequently limiting the maximal driving force of the CO2-fixing pathways. Our results indicate that heterotrophic organisms like E. coli hold a possibly underestimated potential for CO2 assimilation which may complement existing biotechnological approaches for capturing CO2. Furthermore, we envision that the developed OptMDFpathway approach can be used for many other applications within the framework of constrained-based modeling and for rational design of metabolic networks.

Isaac Owusu-Agyeman, Elżbieta Płaza, Zeynep Çetecioğlu

Waste Management • 2020

Volatile fatty acids (VFAs) are intermediates of anaerobic digestion with high value and wide range of usage. Co-digestion of sewage sludge and external organic waste (OW) for VFA production can help achieve both resource recovery and ensure sustainable and innovative waste management. In view of this, the effect of substrate proportions on VFA production from co-digestion of primary sewage sludge and OW is studied. Long-term operation in a semi-continuous reactor was performed to assess the resilience of such a system and the VFA-rich effluent was tested for its ability to be used as carbon source for denitrification. Co-digestion was initially carried out in batch reactors with OW proportion of 0%, 25%, 50%, 75%, 100% in terms of COD and scaled up in a semi-continuous reactor operation with 50% OW. In the short-term operation in the batch mode, acetic acid dominated, however, increasing OW fraction resulted in increased valeric and caproic acid production. Moreover, in the long-term semi-continuous operation, caproic acid dominated, accounting for ≈55% of VFAs. The VFA-rich effluent from the semi-continuous reactor achieved the highest denitrification rate as a carbon source when compared with acetic acid and methanol. The results demonstrate that co-fermentation can increase VFA yield and shift products from acetic acid to caproic acid in long-term operation and the VFAs can be used within wastewater treatment plants to close the loop.

Nigel Rambhujun, Muhammad Salman, Ting Wang et al.

MRS Energy & Sustainability • 2020