Dao‐Bo Li, Jie Li, Dong‐Feng Liu et al.

Biotechnology and Bioengineering • 2019

Abstract Dissimilatory metal reducer Geobacter sulfurreducens can mediate redox processes through extracellular electron transfer and exhibit potential‐dependent electrochemical activity in biofilm. Understanding the microbial acclimation to potential is of critical importance for developing robust electrochemically active biofilms and facilitating their environmental, geochemical, and energy applications. In this study, the metabolism and redox conduction behaviors of G. sulfurreducens biofilms developed at different potentials were explored. We found that electrochemical acclimation occurred at the initial hours of polarizing G. sulfurreducens cells to the potentials. Two mechanisms of acclimation were found, depending on the polarizing potential. In the mature biofilms, a low level of biosynthesis and a high level of catabolism were maintained at +0.2 V versus standard hydrogen electrode (SHE). The opposite results were observed at potentials higher than or equal to +0.4 V versus SHE. The potential also regulated the constitution of the electron transfer network by synthesizing more extracellular cytochrome c such as OmcS at 0.0 and +0.2 V and exhibited a better conductivity. These findings provide reasonable explanations for the mechanism governing the electrochemical respiration and activity in G. sulfurreducens biofilms.

Laura Katherin Chaparro Díaz, Antonio Berná, Karina Boltes

Toxics • 2024

Bioelectrochemical processes are emerging as one of the most efficient and sustainable technologies for wastewater treatment. Their application for industrial wastewater treatment is still low due to the high toxicity and difficulty of biological treatment for industrial effluents. This is especially relevant in pharmaceutical industries, where different solvents, active pharma ingredients (APIs), extreme pH, and salinity usually form a lethal cocktail for the bacterial community in bioreactors. This work evaluates the impact of the anode architecture on the detoxification performance and analyzes, for the first time, the profile of some key bioremediation enzymes (catalase and esterase) and reactive oxygen species (ROS) during the operation of microbial electrochemical cells treating real pharmaceutical wastewater. Our results show the existence of oxidative stress and loss of cell viability in planktonic cells, while the electrogenic bacteria that form the biofilm maintain their biochemical machinery intact, as observed in the bioelectrochemical response. Monitorization of electrical current flowing in the bioelectrochemical system showed how electroactive biofilm, after a short adaptation period, started to degrade the pharma effluent. The electroactive biofilms are responsible for the detoxification of this type of industrial wastewater.

Jaecheul Yu, Hana Park, Younghyun Park et al.

Energies • 2022

This study investigated the effect of initially set anodic potentials (−0.3, −0.2, −0.1 and +0.1 V) on voltage production and microbial community in electroactive biofilm reactors (EBRs) treating synthetic and domestic wastewater (WW). In phase 1, EBRs were acclimated with different anodic potentials for synthetic and domestic WW. EBR (SE4) poised with +0.1 V showed the highest maximum power density (420 mW/m2) for synthetic WW, while EBR (DE3) poised with −0.1 V showed the highest maximum power density (235 mW/m2) for domestic WW. In phase 2, the EBRs were operated with a fixed external resistance (100 Ω for synthetic WW and 500 Ω for domestic WW) after the applied potentials were stopped. The EBRs showed slightly different voltage productions depending on the WW type and the initial anodic potential, but both EBRs applied with +0.1 V for synthetic (SE4) and domestic (DE4) WW showed the highest voltage production. Principal component analysis results based on denaturing gel gradient electrophoresis band profiles showed that the microbial community was completely different depending on the WW type. Nevertheless, it was found that the microbial community of EBRs applied with a negative potential (−0.3, −0.2, and −0.1 V) seemed to shift to those of EBRs applied with a positive potential (+0.1 V) regardless of WW type. Therefore, positive anodic potential is an important operating factor in electroactive biofilm development and voltage generation for rapid start-up.

Yang‐Chun Yong, Yang‐Yang Yu, Xinhai Zhang et al.

Angewandte Chemie • 2014

Abstract Low extracellular electron transfer performance is often a bottleneck in developing high‐performance bioelectrochemical systems. Herein, we show that the self‐assembly of graphene oxide and Shewanella oneidensis MR‐1 formed an electroactive, reduced‐graphene‐oxide‐hybridized, three‐dimensional macroporous biofilm, which enabled highly efficient bidirectional electron transfers between Shewanella and electrodes owing to high biomass incorporation and enhanced direct contact‐based extracellular electron transfer. This 3D electroactive biofilm delivered a 25‐fold increase in the outward current (oxidation current, electron flux from bacteria to electrodes) and 74‐fold increase in the inward current (reduction current, electron flux from electrodes to bacteria) over that of the naturally occurring biofilms.

Baoli Qin, Yu Huang, Tongxu Liu et al.

Carbon Research • 2024

Abstract Dissolved organic matter (DOM) as critical redox active soil carbon plays a crucial role in shuttling electrons between bacteria and solid electron acceptors, such as iron oxides. However, research on DOM as an electron shuttle has traditionally focused on its impact on typical iron-reducing bacteria, namely strong exoelectrogens, like Geobacter . Besides these strong exoelectrogens, there is a significant presence of weak exoelectrogens in the soil, but studies examining how DOM affects their survival and competitiveness are lacking. This study focused on exploring the influence of DOM on weak exoelectrogens like Bacillus in the soil. By utilizing soil-bioelectrochemical systems (s-BESs) to enrich soil electroactive microorganisms, it investigated the relationship between the abundance of strong and weak exoelectrogens under conditions rich in DOM and conditions lacking DOM. The results showed that in the rich DOM treatment, the abundance of Geobacter was relatively lower (12 ± 0.5% vs. 41 ± 3%), and there was a significant negative correlation between the abundance changes of 18 weak exoelectrogens and Geobacter . This suggests that DOM caused a decrease in the population of strong exoelectrogens (e.g., Geobacter ) while simultaneously promoting the growth of weak exoelectrogens (e.g., Bacillus and Sedimentibacter ). Based on this, we propose that DOM, acting as an electron shuttle, creates favorable ecological niches for the thriving and propagation of weak exoelectrogens, enhancing their competitiveness within the microbial community. This new understanding provides deeper insights into the significance of DOM electron shuttling in soil microbial ecology, and raises the question: is the role of weak exoelectrogens in soil iron cycling underestimated due to the existence of DOM? Graphical Abstract

Osamu Ichihashi, Tatiana A. Vishnivetskaya, Abhijeet P. Borole

ChemElectroChem • 2014

Abstract A bioanode was optimized to generate current densities reaching 38.4±4.9 A m −2 , which brings bioelectrochemical systems closer to commercial consideration. Glucose and lactate were fed together in a continuous or fed‐batch mode. The current density increased from 2.3 A m −2 to 38.4 A m −2 over a 33 day period and remained stable thereafter. The Coulombic efficiency ranged from 50 % to 80 %. A change in substrate concentration from 200 mg L −1 to 5 mg L −1 decreased maximum current density from 38.4 A m −2 to 12.3 A m −2 . The anode consortia included Firmicutes (55.0 %), Proteobacteria (41.8 %) and Bacteroidetes (2.1 %) constituting two potentially electrogenic genera: Geobacter (6.8 %) and Aeromonas (31.9 %). The current production was found to be limited by kinetics during the growth period (33 days), and mass transfer, thereafter. The results indicate the necessity of removing spent biomass for efficient long‐term operation and treatment of wastewater streams.

Pierre Belleville, Gerard Merlin, Julien Ramousse et al.

Scientific Reports • 2022

Abstract Activity distribution limitation in electroactive biofilm remains an unclear phenomenon. Some observations using confocal microscopy have shown notable difference between activity close to the anode and activity at the liquid interface. A numerical model is developed in this work to describe biofilm growth and local biomass segregation in electroactive biofilm. Under our model hypothesis, metabolic activity distribution in the biofilm results from the competition between two limiting factors: acetate diffusion and electronic conduction in the biofilm. Influence of inactive biomass fraction (i.e. non-growing biomass fraction) properties (such as conductivity and density) is simulated to show variation in local biomass distribution. Introducing a dependence of effective diffusion to local density leads to a drastic biomass fraction segregation. Increasing density of inactive fraction reduces significantly acetate diffusion in biofilm, enhances biomass activity on the outer layer (liquid/biofilm interface) and maintains inner core largely inactive. High inactive fraction conductivity enhances biomass activity in the outer layer and enhances current production. Hence, investment in extracellular polymer substance (EPS), anchoring redox components, is benefit for biofilm electroactivity. However, under our model hypothesis it means that conductivity should be two order lower than biofilm conductivity reported in order to observe inner core active biomass segregation.

Carlos A. Ramírez-Vargas, Carlos A. Arias, Liang Zhang et al.

• 2018

Abstract. The performance enhancement of constructed wetlands can be achieved through the coupling with microbial electrochemical technologies (MET). MET is a setup designed to mimic metabolic electrons exchange with insoluble donors and acceptors with the aid of electroactive bacteria and external electrical circuits. An alternative MET that dispenses of electrodes and circuits but uses an electro-conductive biofilter is called Microbial Electrochemical-based Constructed Wetland (METland). Previously it has been demonstrated that a METland has higher biodegradation rates than horizontal flow constructed wetlands, however given its novelty there are still uncertainties related to the removal of pollutants, including their microbial activity. The genetic characterization of microbial communities of a METland is desirable, but is time and resource consuming, then a characterization alternative could be based on functional analysis of the microbial communities. Community-level physiological profile (CLPP) is a useful method to evaluate the functional diversity of microbial communities based on the carbon source utilization pattern (CSUP). Therefore, this study was focused on the microbial characterization of laboratory scale METland based on CLPP analysis. The study included the characterization of microbial communities attached to two carbon-based electro-conductive materials (calcined petroleum coke from crushed electrodes – PK-A; calcined petroleum coke with low sulphur and nitrogen content – PK-LSN), in planted and non-planted set-ups. Variations on the metabolic activity of tested systems were identified and it seems to be related to the characteristics of the material, rather than the presence/absence of plants. In general, CSUP show differences along flow pathway, as well as among the tested systems, being carbohydrates and carboxylic/acetic acids the most consumed carbon sources, followed by polymers, amides/amines and amino acids. Also, were established some correlations between the utilization of carbon sources and the removal of pollutants. The obtained results provide useful insight into the spatial dynamics of METland systems.

Valentina Domenici, Blaž Župančič, Maja Remškar et al.

Advances in Science and Technology • 2008

The insertion of inorganic nanoparticles and nanowires in a liquid crystalline elastomeric environment is here investigated. The combination of ferroelectric and conductive properties of the nanomaterials with the thermo-mechanical and shape memory response of liquid single crystal elastomers based on polysiloxane is indeed very promising for new technological applications, such as electroactive actuators. In this work the preparation and physical-chemical properties of new composites are presented and discussed in comparison with those of standard liquid single crystal elastomers (LSCEs). In particular, we are reporting the preliminary results of new composites including either lead titanate nanoparticles or molibdene oxide nanowires, having different electric and conductive properties.

Saniyat Kurbanalieva, Vyacheslav Arlyapov, Anna Kharkova et al.

Sensors • 2022

The possibility of the developing a biochemical oxygen demand (BOD) biosensor based on electroactive biofilms of activated sludge grown on the surface of a graphite-paste electrode modified with carbon nanotubes was studied. A complex of microscopic methods controlled biofilm formation: optical microscopy with phase contrast, scanning electron microscopy, and laser confocal microscopy. The features of charge transfer in the obtained electroactive biofilms were studied using the methods of cyclic voltammetry and electrochemical impedance spectroscopy. The rate constant of the interaction of microorganisms with the extracellular electron carrier (0.79 ± 0.03 dm3(g s)−1) and the heterogeneous rate constant of electron transfer (0.34 ± 0.02 cm s−1) were determined using the cyclic voltammetry method. These results revealed that the modification of the carbon nanotubes’ (CNT) electrode surface makes it possible to create electroactive biofilms. An analysis of the metrological and analytical characteristics of the created biosensors showed that the lower limit of the biosensor based on an electroactive biofilm of activated sludge is 0.41 mgO2/dm3, which makes it possible to analyze almost any water sample. Analysis of 12 surface water samples showed a high correlation (R2 = 0.99) with the results of the standard method for determining biochemical oxygen demand.

Philippe Dubois, Samuel Rosset, Muhamed Niklaus et al.

Advances in Science and Technology • 2008

One of the key factors to obtain large displacements and high efficiency with dielectric electroactive polymer (DEAPs) actuators is to have compliant electrodes. Attempts to scale DEAPs down to the mm or micrometer range have encountered major difficulties, mostly due to the challenge of micropatterning sufficiently compliant electrodes. Simply evaporating or sputtering thin metallic films on elastomer membranes produces DEAPs whose stiffness is dominated by the metallic film. Low energy metal ion implantation for fabricating compliant electrodes in DEAPs presents several advantages: a) it is clean to work with, b) it does not add thick passive layers, and c) it can be easily patterned. We use this technology to fabricate DEAPs micro-actuators whose relative displacement is the same as for macro-scale DEAPs. With transmission electron microscope (TEM) we observed the formation of metallic clusters within the elastomer (PDMS) matrix, forming a nano-composite. We focus our studies on relating the properties of this nano-composite to the implantation parameters. We identified the optimal implantation parameters for which an implanted electrode presents an exceptional combination of high electrical conductivity and low compliance.

Federico Carpi, Carlo Menon, Danilo De Rossi

Advances in Science and Technology • 2008

Technologies for space applications are often considered to be rather conservative, aimed at ensuring reliability and robustness. Nevertheless, novel concepts coming from research activities have been and are always the lymph for the development of successful and competitive new solutions. This paper presents new concepts and ideas inspired by natural systems with distributed actuation embedded in their structure, considered as ideal models for possible uses in space applications. Preliminary concepts for possible technical solutions for long-term future implementations are here proposed and briefly analyzed. Peristaltic-like actuations obtained by the use of dielectric elastomer actuators is proposed as one of the most promising solutions. Experimental performances of a single actuation unit are here presented and directions for future implementations are proposed.

Anna Patrícya Florentino, Ahmed Sharaf, Lei Zhang et al.

Environmental Science: Water Research & Technology • 2019

Methanogenesis and enrichment of microorganisms capable of interspecies electron and/or hydrogen exchange was investigated with addition of granular activated carbon (GAC) to batch anaerobic digesters treating vacuum collected blackwater with high ammonia concentration.

Junqi Zhang, Zixuan You, Dingyuan Liu et al.

Quantitative Biology • 2023

Abstract Electroactive microorganisms (EAMs) could utilize extracellular electron transfer (EET) pathways to exchange electrons and energy with their external surroundings. Conductive cytochrome proteins and nanowires play crucial roles in controlling electron transfer rate from cytosol to extracellular electrode. Many previous studies elucidated how the c ‐type cytochrome proteins and conductive nanowires are synthesized, assembled, and engineered to manipulate the EET rate, and quantified the kinetic processes of electron generation and EET. Here, we firstly overview the electron transfer pathways of EAMs and quantify the kinetic parameters that dictating intracellular electron production and EET. Secondly, we systematically review the structure, conductivity mechanisms, and engineering strategies to manipulate conductive cytochromes and nanowire in EAMs. Lastly, we outlook potential directions for future research in cytochromes and conductive nanowires for enhanced electron transfer. This article reviews the quantitative kinetics of intracellular electron production and EET, and the contribution of engineered c ‐type cytochromes and conductive nanowire in enhancing the EET rate, which lay the foundation for enhancing electron transfer capacity of EAMs.

Huajun Feng, Liyang Xu, Ruya Chen et al.

Frontiers in Microbiology • 2022

Remediation of environmental toxic pollutants has attracted extensive attention in recent years. Microbial bioremediation has been an important technology for removing toxic pollutants. However, microbial activity is also susceptible to toxicity stress in the process of intracellular detoxification, which significantly reduces microbial activity. Electroactive microorganisms (EAMs) can detoxify toxic pollutants extracellularly to a certain extent, which is related to their unique extracellular electron transfer (EET) function. In this review, the extracellular and intracellular aspects of the EAMs’ detoxification mechanisms are explored separately. Additionally, various strategies for enhancing the effect of extracellular detoxification are discussed. Finally, future research directions are proposed based on the bottlenecks encountered in the current studies. This review can contribute to the development of toxic pollutants remediation technologies based on EAMs, and provide theoretical and technical support for future practical engineering applications.

Fei Xing, Liang Duan, Haiya Zhang et al.

Toxics • 2024

A biological treatment is the core process for removing organic pollutants from industrial wastewater. However, industrial wastewater often contains large amounts of toxic and harmful pollutants, which can inhibit the activity of microorganisms in a treatment system, precipitate the deterioration of effluent quality, and threaten water ecological security from time to time. In most of the existing anaerobic biological treatment processes, toxic effects on microorganisms are determined according to the amounts of end-products of the biochemical reactions, and the evaluation results are relatively lacking. When microorganisms contact toxic substances, changes in biological metabolic activity precede the accumulation of reaction products. As sensitive units, electroactive microorganisms can generate electrical signals, a change in which can directly reflect the toxicity level. The applications of electroactive microorganisms for the toxicity monitoring of wastewater are very promising. Further attention needs to be paid to considering the appropriate evaluation index, the influence of the environment on test results, mechanisms, and other aspects. Therefore, we reviewed the literature regarding the above aspects in order to provide a research foundation for the practical application of electroactive microorganisms in toxicant monitoring.

Anne Kuchenbuch, Ronny Frank, José Vazquez Ramos et al.

Frontiers in Bioengineering and Biotechnology • 2022

Microbial resource mining of electroactive microorganism (EAM) is currently methodically hampered due to unavailable electrochemical screening tools. Here, we introduce an electrochemical microwell plate (ec-MP) composed of a 96 electrochemical deepwell plate and a recently developed 96-channel multipotentiostat. Using the ec-MP we investigated the electrochemical and metabolic properties of the EAM models Shewanella oneidensis and Geobacter sulfurreducens with acetate and lactate as electron donor combined with an individual genetic analysis of each well. Electrochemical cultivation of pure cultures achieved maximum current densities ( j max ) and coulombic efficiencies ( CE ) that were well in line with literature data. The co-cultivation of S. oneidensis and G. sulfurreducens led to an increased current density of j max of 88.57 ± 14.04 µA cm −2 (lactate) and j max of 99.36 ± 19.12 µA cm −2 (lactate and acetate). Further, a decreased time period of reaching j max and biphasic current production was revealed and the microbial electrochemical performance could be linked to the shift in the relative abundance.

Zhijin Gong, Rong Xie, Yang Zhang et al.

Microorganisms • 2023

The development of MFC using electroactive industrial microorganisms has seen a surge of interest because of the co-generation for bioproduct and electricity production. Vibrio natriegens as a promising next-generation industrial microorganism chassis and its application for microbial fuel cells (MFC) was first studied. Mediated electron transfer was found in V. natriegens MFC (VMFC), but V. natriegens cannot secrete sufficient electron mediators to transfer electrons to the anode. All seven electron mediators supplemented are capable of improving the electronic transfer efficiency of VMFC. The media and carbon sources switching study reveals that VMFCs have excellent bioelectricity generation performance with feedstock flexibility and high salt-tolerance. Among them, 1% glycerol as the sole carbon source produced the highest power density of 111.9 ± 6.7 mW/cm2. The insight of the endogenous electronic mediators found that phenazine-1-carboxamide, phenazine-1-carboxylic acid, and 1-hydroxyphenazine are synthesized by V. natriegens via the shikimate pathway and the phenazine synthesis and modification pathways. This work provides the first proof for emerging industrial biotechnology chassis V. natriegens as a novel high salt-tolerant and feedstock flexibility electroactive microorganism for MFC, and giving insight into the endogenous electron mediator biosynthesis of VMFC, paving the way for the application of V. natriegens in MFC and even microbial electrofermentation (EF).

Christin Koch, Falk Harnisch

ChemElectroChem • 2016

Abstract The core of primary microbial electrochemical technologies (METs) is the ability of the electroactive microorganisms to interact with electrodes via extracellular electron transfer (EET), allowing wiring of current flow and microbial metabolism. Geobacter sulfurreducens and Shewanella oneidensis are the model organisms for understanding and engineering EET. Many other microorganisms are reported being electroactive but are often sparsely characterized. Based on a literature survey 94 species are ascribed as electroactive. Their apparent diversity raises questions on the natural importance and distribution of the EET capacity, that is, of the ecological niche of microbial electroactivity. To identify this potential niche the environmental preferences and natural habitat characteristics of all electroactive species were combined with their metabolic, growth and EET characteristics and an extensive meta‐analysis performed. The results indicate that there is not a single ecological niche for electroactive microorganisms. Significantly more electroactive species presumably exist in nature as well as already existing strain collections but due to current cultivation techniques their EET potential is not leveraged. Thus, in the light of specific traits required for industrial application, microbial resource mining based on ecological knowledge bears a great potential for broadening the foundation of microbial electrochemistry as well as for future developments of primary METs.

Theresia D. Askitosari, Carola Berger, Till Tiso et al.

Microorganisms • 2020

Sufficient supply of oxygen is a major bottleneck in industrial biotechnological synthesis. One example is the heterologous production of rhamnolipids using Pseudomonas putida KT2440. Typically, the synthesis is accompanied by strong foam formation in the reactor vessel hampering the process. It is caused by the extensive bubbling needed to sustain the high respirative oxygen demand in the presence of the produced surfactants. One way to reduce the oxygen requirement is to enable the cells to use the anode of a bioelectrochemical system (BES) as an alternative sink for their metabolically derived electrons. We here used a P. putida KT2440 strain that interacts with the anode using mediated extracellular electron transfer via intrinsically produced phenazines, to perform heterologous rhamnolipid production under oxygen limitation. The strain P. putida RL-PCA successfully produced 30.4 ± 4.7 mg/L mono-rhamnolipids together with 11.2 ± 0.8 mg/L of phenazine-1-carboxylic acid (PCA) in 500-mL benchtop BES reactors and 30.5 ± 0.5 mg/L rhamnolipids accompanied by 25.7 ± 8.0 mg/L PCA in electrode containing standard 1-L bioreactors. Hence, this study marks a first proof of concept to produce glycolipid surfactants in oxygen-limited BES with an industrially relevant strain.

Lijun Ling, Zibin Li, Caiyun Yang et al.

bioRxiv (Cold Spring Harbor Laboratory) • 2020

Abstract Electroactive microorganisms play a significant role in microbial fuel cells (MFCs). These devices, which are based on a wide microbial diversity, can convert a large array of organic matter components into sustainable and renewable energy. At present, electricity-producing microorganisms are mostly isolated from sewage, anaerobic sediments and soil, however, the sources are very limited. For a more comprehensive understanding of the electron transfer mechanism of the electricity-producing microorganisms and the interaction with the environment, it is necessary to obtain a thorough understanding of their resource distribution and discover potential resources. In this study, plant tissues were selected to isolate endophytic bacteria, and the electrochemical activity potential of those bacteria was evaluated by high-throughput screening with a WO3 nanoprobe. Twenty-six strains of endophytic bacteria were isolated from plant tissues belonging to Angelica and Sweet Potato, of which 17 strains from 6 genera had electrochemical activity, including Bacillus sp., Pleomorphomonas sp., Rahnella sp., Shinella sp., Paenibacillus sp. and Staphylococcus sp.. Moreover, the electricity-producing microorganisms in the plant tissue are enriched. Microbial community analysis by high-throughput sequence indicated that Pseudomonas and Clostridioides are the dominant genera of MFC anode inoculated with angelica tissue.Staphylococcus and Lachnoclostridium 5 are the dominant genera in MFC anode inoculated with sweet potato tissue. And the most representative Gram-positive strain Staphylococcus succinus subsp. succinus H6 and plant tissue-inoculated MFC were further analyzed for electrochemical activity. After nearly 1500 h of voltage monitoring and cyclic voltammetry analysis, the results showed that a strain numbered H6 and plant tissue-inoculated MFC had a good electrogenerating activity. Importance Some biological characteristics of microorganisms are inextricably linked to their living environment. For plant endophytes, some of their biological characteristics have a profound impact on the host. The discovery of the production of electrobacteria in plants helps us to understand the interaction between microorganisms and plants more deeply. For example, there may be intercellular electron transfer between the internally producing bacteria and nitrogen-fixing bacteria to improve the efficiency of nitrogen fixation. In addition, there may be a connection between the weak electrical signal of the plant and the the endophytic electricity-producing microorganismsThe discovery of electricity-producing bacteria in plants also brings a more comprehensive understanding of the distribution of electricity-producing microbial resources and the mechanism of origin.

Esther Balaguer-Arnandis, Beatriz Cuartas-Uribe, M. Amparo Bes-Piá et al.

Chemical Engineering & Technology • 2017

Abstract Tannery wastewater has a high environmental impact due to its low biodegradability. Sequencing batch reactors (SBRs) are an established method for treating highly polluted wastewater. To minimize the hydraulic retention time ( HRT ) of the SBRs, various HRT values were tested and the best value was chosen according to the removal efficiency of the soluble chemical oxygen demand ( COD ). A series of experiments was then carried out with two cationic polyelectrolytes added to the system in two different modes to improve the effluent quality. Both modes were evaluated in terms of the soluble COD , suspended solid concentration, and turbidity of the final effluent. The results showed that reducing the HRT to two days did not diminish the COD removal efficiencies.

Nicolas Baeza, Elena Mercade

Microbial Ecology • 2021

Abstract Biofilms offer a safe environment that favors bacterial survival; for this reason, most pathogenic and environmental bacteria live integrated in biofilm communities. The development of biofilms is complex and involves many factors, which need to be studied in order to understand bacterial behavior and control biofilm formation when necessary. We used a collection of cold-adapted Antarctic Gram-negative bacteria to study whether their ability to form biofilms is associated with a capacity to produce membrane vesicles and secrete extracellular ATP. In most of the studied strains, no correlation was found between biofilm formation and these two factors. Only Shewanella vesiculosa M7 T secreted high levels of extracellular ATP, and its membrane vesicles caused a significant increase in the speed and amount of biofilm formation. In this strain, an important portion of the exogenous ATP was contained in membrane vesicles, where it was protected from apyrase treatment. These results confirm that ATP influences biofilm formation. Although the role of extracellular ATP in prokaryotes is still not well understood, the metabolic cost of its production suggests it has an important function, such as a role in biofilm formation. Thus, the liberation of extracellular ATP through membrane vesicles and its function deserve further study.

Paul Sajda, Andrew Laine, Yehoshua Zeevi

Disease Markers • 2002

Identifying physiological and anatomical signatures of disease in signals and images is one of the fundamental challenges in biomedical engineering. The challenge is most apparent given that such signatures must be identified in spite of tremendous inter and intra‐subject variability and noise. Crucial for uncovering these signatures has been the development of methods that exploit general statistical properties of natural signals. The signal processing and applied mathematics communities have developed, in recent years, signal representations which take advantage of Gabor‐type and wavelet‐type functions that localize signal energy in a joint time‐frequency and/or space‐frequency domain. These techniques can be expressed as multi‐resolution transformations, of which perhaps the best known is the wavelet transform. In this paper we review wavelets, and other related multi‐resolution transforms, within the context of identifying signatures for disease. These transforms construct a general representation of signals which can be used in detection, diagnosis and treatment monitoring. We present several examples where these transforms are applied to biomedical signal and imaging processing. These include computer‐aided diagnosis in mammography, real‐time mosaicking of ophthalmic slit‐lamp imagery, characterization of heart disease via ultrasound, predicting epileptic seizures and signature analysis of the electroencephalogram, and reconstruction of positron emission tomography data.

Aida Mayorgas, Isabella Dotti, Azucena Salas

Molecular Nutrition & Food Research • 2021

Abstract Chronic inflammatory disorders are rising worldwide. The implication of the microbiota in persistent inflammation has been studied for years, but a direct causal relationship has not yet been stablished. Intestinal epithelial cells (IECs) form a protective barrier against detrimental luminal components. Indeed, a decrease in epithelial integrity may trigger a severe inflammatory reaction due to the infiltration of potentially harmful molecules and microorganisms. Bacterial imbalance, more commonly known as dysbiosis, occurs during inflammation and several strategies have been proposed to counteract this condition. Probiotics have been widely used to positively alter the inherited microbial composition and recover a eubiotic status. Nevertheless, probiotics are thought to impair the return of the indigenous microbiome, and to aggravate inflammation in compromised patients. In contrast, postbiotics—bacterial‐free metabolites secreted by probiotic strains—have been proposed as a better and safer strategy. Recent scientific studies that have demonstrated the immunomodulatory properties and epithelial protection of postbiotics are summarized in this review, with an emphasis on the available methods that are currently in use to better understand the role of postbiotics in health and nutrition.

C. H. Nakatsu

Soil Science Society of America Journal • 2007

The most biological diversity on this planet is probably harbored in soils. Understanding the diversity and function of the microbiological component of soil poses great challenges that are being overcome by the application of molecular biological approaches. This review covers one of many approaches being used: separation of polymerase chain reaction (PCR) amplicons using denaturing gradient gel electrophoresis (DGGE). Extraction of nucleic acids directly from soils allows the examination of a community without the limitation posed by cultivation. Polymerase chain reaction provides a means to increase the numbers of a target for its detection on gels. Using the rRNA genes as a target for PCR provides phylogenetic information on populations comprising communities. Fingerprints produced by this method have allowed spatial and temporal comparisons of soil communities within and between locations or among treatments. Numerous samples can be compared because of the rapid high throughput nature of this method. Scientists now have the means to begin addressing complex ecological questions about the spatial, temporal, and nutritional interactions faced by microbes in the soil environment.

Richard S. Berk, James H. Canfield

Applied Microbiology • 1964

The interaction between photosynthetic microorganisms and an inert electrode material was examined. Cathodic polarization values of platinum-bearing marine algae were obtained over a wide current-density range under both illumination and dark conditions. A potential shift of 0.6 v in the cathodic direction occurred upon illumination at a current density of 4.3 μa/cm 2 . Similar photo-induced results, involving anodic polarization, were obtained by use of resting cells of Rhodospirillum rubrum supplemented with malate. Appropriate combinations of such bioelectrodes were used to assemble an electrochemical cell capable of light-dependent production of electrical energy.

Shinsuke Sakai, Tatsuo Yagishita

Biotechnology and Bioengineering • 2007

Abstract H 2 and ethanol production from glycerol‐containing wastes discharged from a biodiesel fuel production plant by Enterobacter aerogenes NBRC 12010 was demonstrated in bioelectrochemical cells. Thionine as an exogenous electron transfer mediator was reduced by E. aerogenes , and was re‐oxidized by a working electrode applied at +0.2 V against a Ag/AgCl reference electrode by a potentiostat (electrode system). At the initial glycerol concentration of 110 mM, 92.9 mM glycerol was consumed in the electrode system with 2 mM thionine after 48 h. On the other hand, the concentration of glycerol consumed was only 50.3 mM under the control conditions without thionine and the electrodes (normal fermentation). There are no differences in the yields of H 2 and ethanol against glycerol consumed between the control conditions and the conditions with the electrode system. A pH of 6.0 was suitable for the H 2 production in the range between pH 6 and pH 7.5 in the electrode system. At pH values of 7.0 and 7.5, H 2 production decreased and formate was remarkably produced in the reaction solution. The rates of both glycerol consumption and the H 2 and ethanol production increased as the thionine concentration and the surface area of the working electrode increased. After 60 h, 154 mM of the initial 161 mM glycerol concentration in the wastes was consumed in the electrode system, which is a 2.6‐fold increase compared to the control experiment. Biotechnol. Bioeng. 2007;98: 340–348. © 2007 Wiley Periodicals, Inc.

Daisuke Sasaki, Kengo Sasaki, Atsushi Watanabe et al.

AMB Express • 2013

Abstract A cylindrical bioelectrochemical reactor (BER) containing carbon fiber textiles (CFT; BER + CFT) has characteristics of bioelectrochemical and packed-bed systems. In this study, utility of a cylindrical BER + CFT for degradation of a garbage slurry and recovery of biogas was investigated by applying 10% dog food slurry. The working electrode potential was electrochemically regulated at −0.8 V (vs. Ag/AgCl). Stable methane production of 9.37 L-CH 4 · L −1 · day −1 and dichromate chemical oxygen demand (CODcr) removal of 62.5% were observed, even at a high organic loading rate (OLR) of 89.3 g-CODcr · L −1 · day −1 . Given energy as methane (372.6 kJ · L −1 · day −1 ) was much higher than input electric energy to the working electrode (0.6 kJ · L −1 · day −1 ) at this OLR. Methanogens were highly retained in CFT by direct attachment to the cathodic working electrodes (52.3%; ratio of methanogens to prokaryotes), compared with the suspended fraction (31.2%), probably contributing to the acceleration of organic material degradation and removal of organic acids. These results provide insight into the application of cylindrical BER + CFT in efficient methane production from garbage waste including a high percentage of solid fraction.

A. Kuznetsov, N. N. Khorina, E. Konovalova et al.

IOP Conference Series: Earth and Environmental Science • 2021

A facultative anaerobic strain was isolated and studied from the activated sludge of the treatment facilities of a petrochemical enterprise. Its morphological and cultural, physiological and biochemical, tinctorial, molecular genetic characteristics have been investigated. Based on the data obtained, strain 1-I was assigned to the species Micrococcus luteus. The electrogenic activity of this bacterium in BFC was shown using dicarboxylic amino acids - glutamic and aspartic. The open-circuit voltage indices in the BFC with M. luteus 1-I increased in 6 days to 511.5 mV with the addition of aspartic acid, and 419 ± 38.5 mV with the addition of glutamic acid. In this case, the short-circuit current increased to 3.17 ± 0.12 and 1.6 ± 0.14 mA, respectively. The specific power of BFCs based on M. luteus 1-I was the highest with the addition of aspartic acid (40-50 mW / m2 at a current density of 0.15 to 0.4 A / m2). The indicated indicator in a similar BFC with glutamic acid was 26-32 mW / m2 (at a current density of 0.08 to 0.28 A / m2). The oxidation of these compounds by the studied bacterial strain was also confirmed by the methods of cyclic voltammetry.

S. Spiess, Amaia Sasiain Conde, J. Kucera et al.

Frontiers in Bioengineering and Biotechnology • 2022

Carbon capture and utilization has been proposed as one strategy to combat global warming. Microbial electrolysis cells (MECs) combine the biological conversion of carbon dioxide (CO2) with the formation of valuable products such as methane. This study was motivated by the surprising gap in current knowledge about the utilization of real exhaust gas as a CO2 source for methane production in a fully biocatalyzed MEC. Therefore, two steel mill off-gases differing in composition were tested in a two-chamber MEC, consisting of an organic substrate-oxidizing bioanode and a methane-producing biocathode, by applying a constant anode potential. The methane production rate in the MEC decreased immediately when steel mill off-gas was tested, which likely inhibited anaerobic methanogens in the presence of oxygen. However, methanogenesis was still ongoing even though at lower methane production rates than with pure CO2. Subsequently, pure CO2 was studied for methanation, and the cathodic biofilm successfully recovered from inhibition reaching a methane production rate of 10.8 L m−2d−1. Metagenomic analysis revealed Geobacter as the dominant genus forming the anodic organic substrate-oxidizing biofilms, whereas Methanobacterium was most abundant at the cathodic methane-producing biofilms.

Xin Zhou, Panpan Gai, Pengbo Zhang et al.

ACS Applied Materials & Interfaces • 2019

A water-oxygen-water photosynthetic bioelectrochemical cell (PBEC) comprised of hybrid poly(fluorene-alt-phenylene) (PFP)/PSII-enriched membranes (BBY) photoanode and bilirubin oxidase (BOD) biocathode has been designed and fabricated. In the PBEC, water is split into oxygen, protons and electrons through light-dependent reaction of PSII at the photoanode, and oxygen is converted into water catalyzed by BOD at the biocathode, forming the electronic circuit and generating current. At photoanode, PFP can simultaneously accelerate the photosynthetic water oxidation and the electron transfer between BBY and electrode. Interestingly, the photocurrent density produced by PBEC after the introduction of PFP reaches 1.05±0.01 μA/cm2, which is 2.5 times more than that of BBY electrode, indicating that conjugated polymer can enhance the photoelectric response of PBEC.

Dina Hassan El Salamony, Mohamed Salah Eldin Hassouna, Taha Ibrahim Zaghloul et al.

Microbial Cell Factories • 2024

Abstract Background Poultry feather waste has a potential for bioenergy production because of its high protein content. This research explored the use of chicken feather hydrolysate for methane and hydrogen production via anaerobic digestion and bioelectrochemical systems, respectively. Solid state fermentation of chicken waste was conducted using a recombinant strain of Bacillus subtilis DB100 (p5.2). Results In the anaerobic digestion, feather hydrolysate produced maximally 0.67 Nm 3 CH 4 /kg feathers and 0.85 mmol H 2 /day.L concomitant to COD removal of 86% and 93%, respectively. The bioelectrochemical systems used were microbial fuel and electrolysis cells. In the first using a microbial fuel cell, feather hydrolysate produced electricity with a maximum cell potential of 375 mV and a current of 0.52 mA. In the microbial electrolysis cell, the hydrolysate enhanced the hydrogen production rate to 7.5 mmol/day.L, with a current density of 11.5 A/m 2 and a power density of 9.26 W/m 2 . Conclusions The data indicated that the sustainable utilization of keratin hydrolysate to produce electricity and biohydrogen via bioelectrical chemical systems is feasible. Keratin hydrolysate can produce electricity and biofuels through an integrated aerobic-anaerobic fermentation system. Graphical Abstract

Jinhwan Lee, Hyejun Cho, Sunghyun Kim

ChemElectroChem • 2020

Abstract There is a growing interest in photosynthetic microorganisms for converting solar energy to electricity aiming at practical application. Despite extensive research, existing methods are suffered from limited photocurrent. Here we report that appreciable photocurrent can be generated in a photo‐bioelectrochemical cell (PBEC) where reduced graphene oxide‐coated ITO electrode is used as an anode and wild type cyanobacterium Anabaena variabilis as photo‐biocatalyst that oxidizes water by solar light. With A. variabilis dispersed in buffer and 1,4‐benzoquinone as a redox mediator, our PBEC produced photocurrent of 223 μA cm −2 at an applied voltage of 0.4 V vs. Ag/AgCl. Incident photon to current efficiencies of 0.50 % and 5.2 % were obtained with white and monochromatic light at 660 nm, respectively. A complete PBEC with Pt/C cathode produced P max of 13 μW cm −2 at 115 μA cm −2 . Methodology in this study can be extended to cover other cyanobacteria, electrode materials, and mediators to further enhance photocurrent and power density. Our results demonstrate the possibility of utilizing cyanobacteria that are ubiquitous in the environment as alternative energy sources.

Mareike Engel, André Gemünde, Dirk Holtmann et al.

ChemElectroChem • 2020

Abstract Bacterial cell appendix formation supports cell‐cell interaction, cell adhesion and cell movement. Additionally, in bioelectrochemical systems (BES), cell appendages have been shown to participate in extracellular electron transfer. In this work, the cell appendix formation of Clostridium acetobutylicum in biofilms of a BES are imaged and compared with conventional biofilms. Under all observed conditions, the cells possess filamentous appendages with a higher number and density in the BES. Differences in the amount of extracellular polymeric substance in the biofilms of the electrodes lead to the conclusion that the cathode can be used as electron donor and the anode as electron acceptor by C. acetobutylicum . When using conductive atomic force microscopy, a current response of about 15 nA is found for the cell appendages from the BES. This is the first report of conductivity for clostridial cell appendices and represents the basis for further studies on their role for biofilm formation and electron transfer.

H. A. Videla, A. J. Arvía

Biotechnology and Bioengineering • 1975

Abstract Working conditions of a biochemical fuel cell formed by an oxygen cathode and a platinum bioanode in a Saccharomyces cerevisiae suspension metabolizing glucose are described. The biocell response in terms of bioanode potential and current drainage under different fermentation conditions is reported. A kinetic equation relating the current, the number of microorganisms, and the substrate concentration is obtained. The bioanode potential corresponds to that of an oxygen concentration polarization cell.

J. Patrick O'Brien, Nikhil S. Malvankar

Current Protocols in Microbiology • 2016

Abstract Anaerobic microorganisms play a central role in several environmental processes and regulate global biogeochemical cycling of nutrients and minerals. Many anaerobic microorganisms are important for the production of bioenergy and biofuels. However, the major hurdle in studying anaerobic microorganisms in the laboratory is the requirement for sophisticated and expensive gassing stations and glove boxes to create and maintain the anaerobic environment. This appendix presents a simple design for a gassing station that can be used readily by an inexperienced investigator for cultivation of anaerobic microorganisms. In addition, this appendix also details the low‐cost assembly of bioelectrochemical systems and outlines a simplified procedure for cultivating and analyzing bacterial cell cultures and biofilms that produce electric current, using Geobacter sulfurreducens as a model organism. © 2016 by John Wiley & Sons, Inc.

Brenda Alvarez Chavez, V. Raghavan, B. Tartakovsky

RSC Advances • 2022

Production of biopolymers from renewable carbon sources provides a path towards a circular economy. This review compares several existing and emerging approaches for polyhydroxyalkanoate (PHA) production from soluble organic and gaseous carbon sources and considers technologies based on pure and mixed microbial cultures. While bioplastics are most often produced from soluble sources of organic carbon, the use of carbon dioxide (CO2) as the carbon source for PHA production is emerging as a sustainable approach that combines CO2 sequestration with the production of a value-added product. Techno-economic analysis suggests that the emerging approach of CO2 conversion to carboxylic acids by microbial electrosynthesis followed by microbial PHA production could lead to a novel cost-efficient technology for production of green biopolymers.

N. K. Singh, A. S. Mathuriya, S. Mehrotra et al.

Environmental Technology • 2023

ABSTRACT Bioelectrochemical systems (BES) have emerged as a sustainable and highly promising technology that has garnered significant attention from researchers worldwide. These systems provide an efficient platform for the removal and recovery of valuable products from wastewater, with minimal or no net energy loss. Among the various types of BES, microbial fuel cells (MFCs) are a notable example, utilizing microbial biocatalytic activities to generate electrical energy through the degradation of organic matter. Other BES variants include microbial desalination cells (MDCs), microbial electrolysis cells (MECs), microbial electrosynthesis cells (MXCs), microbial solar cells (MSCs), and more. BESs have demonstrated remarkable potential in the recovery of diverse products such as hydrogen, methane, volatile fatty acids, precious nutrients, and metals. Recent advancements in scaling up BESs have facilitated a more realistic assessment of their net energy recovery and resource yield in real-world applications. This comprehensive review focuses on the practical applications of BESs, from laboratory-scale developments to their potential for industrial commercialization. Specifically, it highlights successful examples of value-added product recovery achieved through various BES configurations. Additionally, this review critically evaluates the limitations of BESs and provides suggestions to enhance their performance at a larger scale, enabling effective implementation in real-world scenarios. By providing a thorough analysis of the current state of BES technology, this review aims to emphasize the tremendous potential of these systems for sustainable wastewater treatment and resource recovery. It underscores the significance of bridging the gap between laboratory-scale achievements and industrial implementation, paving the way for a more sustainable and resource-efficient future. GRAPHICAL ABSTRACT

J. Mathew, A. Inobeme, Y. Azeh et al.

Confluence University Journal of Science and Technology • 2024

Rapid industrialization and urbanization have led to the widespread occurrence of emerging contaminants and micropollutants in water sources, posing a significant threat to both ecosystems and human health. Traditional water treatment methods often fall short in efficiently removing these complex and persistent pollutants. In recent years, electrochemical and bioelectrochemical techniques have emerged as promising and sustainable alternatives for the removal of emerging contaminants and micropollutants. As the global community strives to address water pollution challenges, the integration of electrochemical and bioelectrochemical techniques presents a promising avenue for the development of efficient, cost-effective, and environmentally friendly solutions for the removal of emerging contaminants and micropollutants from water sources. This review highlights the recent advancements and applications of electrochemical and bioelectrochemical processes in the removal of a diverse range of emerging contaminants, including pharmaceuticals, personal care products, pesticides, and industrial chemicals. Electrochemical methods such as electrocoagulation, electrooxidation, and electrochemical adsorption have demonstrated high efficacy in the degradation and removal of these pollutants. Furthermore, bioelectrochemical systems, harnessing the power of microbial metabolism, have shown great potential in enhancing pollutant removal through processes such as microbial fuel cells, bioelectrochemical reactors, and enzymatic bioelectrodes. The synergistic combination of electrochemical and biological mechanisms offers a versatile and sustainable approach for the remediation of water contaminated with micropollutants. This review explores the underlying mechanisms, key factors influencing performance, and recent developments in electrode materials and microbial consortia for enhanced pollutant removal. Additionally, the economic feasibility and scalability of electrochemical and bioelectrochemical technologies for large-scale water treatment are discussed.