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

Environmental Science: Water Research & Technology • 0

<p>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.</p>

Junqi Zhang, Zixuan You, Dingyuan Liu et al.

Quantitative Biology • 2023

<jats:title>Abstract</jats:title><jats:p>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 <jats:italic>c</jats:italic>‐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 <jats:italic>c</jats:italic>‐type cytochromes and conductive nanowire in enhancing the EET rate, which lay the foundation for enhancing electron transfer capacity of EAMs.</jats:p>

Huajun Feng, Liyang Xu, Ruya Chen et al.

Frontiers in Microbiology • 0

<jats:p>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.</jats:p>

Fei Xing, Liang Duan, Haiya Zhang et al.

Toxics • 0

<jats:p>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.</jats:p>

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

Frontiers in Bioengineering and Biotechnology • 0

<jats:p>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 <jats:italic>Shewanella oneidensis</jats:italic> and <jats:italic>Geobacter sulfurreducens</jats:italic> 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 (<jats:italic>j</jats:italic><jats:sub>max</jats:sub>) and coulombic efficiencies (<jats:italic>CE</jats:italic>) that were well in line with literature data. The co-cultivation of <jats:italic>S. oneidensis</jats:italic> and <jats:italic>G. sulfurreducens</jats:italic> led to an increased current density of <jats:italic>j</jats:italic><jats:sub>max</jats:sub> of 88.57 ± 14.04 µA cm<jats:sup>−2</jats:sup> (lactate) and <jats:italic>j</jats:italic><jats:sub>max</jats:sub> of 99.36 ± 19.12 µA cm<jats:sup>−2</jats:sup> (lactate and acetate). Further, a decreased time period of reaching <jats:italic>j</jats:italic><jats:sub>max</jats:sub> and biphasic current production was revealed and the microbial electrochemical performance could be linked to the shift in the relative abundance.</jats:p>

Zhijin Gong, Rong Xie, Yang Zhang et al.

Microorganisms • 0

<jats:p>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).</jats:p>

Christin Koch, Falk Harnisch

ChemElectroChem • 2016

<jats:title>Abstract</jats:title><jats:p>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. <jats:italic>Geobacter sulfurreducens</jats:italic> and <jats:italic>Shewanella oneidensis</jats:italic> 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.</jats:p>

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

Microorganisms • 0

<jats:p>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.</jats:p>

Lijun Ling, Zibin Li, Caiyun Yang et al.

• 0

<jats:title>Abstract</jats:title><jats:p>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.</jats:p><jats:sec><jats:title>Importance</jats:title><jats:p>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.</jats:p></jats:sec>

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

Chemical Engineering &amp; Technology • 2017

<jats:title>Abstract</jats:title><jats:p>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 (<jats:italic>HRT</jats:italic>) of the SBRs, various <jats:italic>HRT</jats:italic> values were tested and the best value was chosen according to the removal efficiency of the soluble chemical oxygen demand (<jats:italic>COD</jats:italic>). 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 <jats:italic>COD</jats:italic>, suspended solid concentration, and turbidity of the final effluent. The results showed that reducing the <jats:italic>HRT</jats:italic> to two days did not diminish the <jats:italic>COD</jats:italic> removal efficiencies.</jats:p>

Nicolas Baeza, Elena Mercade

Microbial Ecology • 2021

<jats:title>Abstract</jats:title><jats:p>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 <jats:italic>Shewanella vesiculosa</jats:italic> M7<jats:sup>T</jats:sup> 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.</jats:p>

Paul Sajda, Andrew Laine, Yehoshua Zeevi

Disease Markers • 2002

<jats:p>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.</jats:p>

Aida Mayorgas, Isabella Dotti, Azucena Salas

Molecular Nutrition &amp; Food Research • 2021

<jats:title>Abstract</jats:title><jats:p>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.</jats:p>

C. H. Nakatsu

Soil Science Society of America Journal • 2007

<jats:p>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.</jats:p>

Richard S. Berk, James H. Canfield

Applied Microbiology • 1964

<jats:p> 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 <jats:sup>2</jats:sup> . Similar photo-induced results, involving anodic polarization, were obtained by use of resting cells of <jats:italic>Rhodospirillum rubrum</jats:italic> supplemented with malate. Appropriate combinations of such bioelectrodes were used to assemble an electrochemical cell capable of light-dependent production of electrical energy. </jats:p>

Shinsuke Sakai, Tatsuo Yagishita

Biotechnology and Bioengineering • 2007

<jats:title>Abstract</jats:title><jats:p>H<jats:sub>2</jats:sub> and ethanol production from glycerol‐containing wastes discharged from a biodiesel fuel production plant by <jats:italic>Enterobacter aerogenes</jats:italic> NBRC 12010 was demonstrated in bioelectrochemical cells. Thionine as an exogenous electron transfer mediator was reduced by <jats:italic>E. aerogenes</jats:italic>, 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<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub> production decreased and formate was remarkably produced in the reaction solution. The rates of both glycerol consumption and the H<jats:sub>2</jats:sub> 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.</jats:p>

Daisuke Sasaki, Kengo Sasaki, Atsushi Watanabe et al.

AMB Express • 2013

<jats:title>Abstract</jats:title> <jats:p>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<jats:sub>4</jats:sub> · L<jats:sup>−1</jats:sup> · day<jats:sup>−1</jats:sup> 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<jats:sup>−1</jats:sup> · day<jats:sup>−1</jats:sup>. Given energy as methane (372.6 kJ · L<jats:sup>−1</jats:sup> · day<jats:sup>−1</jats:sup>) was much higher than input electric energy to the working electrode (0.6 kJ · L<jats:sup>−1</jats:sup> · day<jats:sup>−1</jats:sup>) 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.</jats:p>

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 &amp; 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 • 0

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>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 <jats:italic>Bacillus subtilis</jats:italic> DB100 (p5.2).</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>In the anaerobic digestion, feather hydrolysate produced maximally 0.67 Nm<jats:sup>3</jats:sup> CH<jats:sub>4</jats:sub>/kg feathers and 0.85 mmol H<jats:sub>2</jats:sub>/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<jats:sup>2</jats:sup> and a power density of 9.26 W/m<jats:sup>2</jats:sup>.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>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.</jats:p> </jats:sec><jats:sec> <jats:title>Graphical Abstract</jats:title> </jats:sec>

Jinhwan Lee, Hyejun Cho, Sunghyun Kim

ChemElectroChem • 2020

<jats:title>Abstract</jats:title><jats:p>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 <jats:italic>Anabaena variabilis</jats:italic> as photo‐biocatalyst that oxidizes water by solar light. With <jats:italic>A. variabilis</jats:italic> dispersed in buffer and 1,4‐benzoquinone as a redox mediator, our PBEC produced photocurrent of 223 μA cm<jats:sup>−2</jats:sup> 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 <jats:italic>P</jats:italic><jats:sub>max</jats:sub> of 13 μW cm<jats:sup>−2</jats:sup> at 115 μA cm<jats:sup>−2</jats:sup>. 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.</jats:p>

Mareike Engel, André Gemünde, Dirk Holtmann et al.

ChemElectroChem • 2020

<jats:title>Abstract</jats:title><jats:p>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 <jats:italic>Clostridium acetobutylicum</jats:italic> 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 <jats:italic>C. acetobutylicum</jats:italic>. 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.</jats:p>

H. A. Videla, A. J. Arvía

Biotechnology and Bioengineering • 1975

<jats:title>Abstract</jats:title><jats:p>Working conditions of a biochemical fuel cell formed by an oxygen cathode and a platinum bioanode in a <jats:italic>Saccharomyces cerevisiae</jats:italic> 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.</jats:p>

J. Patrick O'Brien, Nikhil S. Malvankar

Current Protocols in Microbiology • 2016

<jats:title>Abstract</jats:title><jats:p>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 <jats:italic>Geobacter sulfurreducens</jats:italic> as a model organism. © 2016 by John Wiley &amp; Sons, Inc.</jats:p>

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.

Motakatla Venkateswar Reddy, Ahmed ElMekawy, Deepak Pant

Biofuels, Bioproducts and Biorefining • 2018

<jats:title>Abstract</jats:title><jats:p>Chain elongation is one of the common anaerobic fermentation processes in which bacteria convert ethanol and short chain fatty acids (SCFA) into medium chain fatty acids (MCFA). These are single carboxylic acids having six to twelve carbon atoms, with several applications, such as biofuels. Caproate is a promising MCFA, and several technologies were proposed for the valorization of waste to obtain it. Bioelectrochemical systems (BESs) are technologies that are capable of converting the chemical energy of organic/inorganic wastes into value‐added products, using <jats:italic>in situ</jats:italic> generated H<jats:sub>2</jats:sub> or electricity as energy sources. To convert waste biomass into caproate, an electron donor in the form of hydrogen or ethanol should be supplemented within the anaerobic fermentation, which can be used as the electron donor in the cathodic compartment for the conversion of acetate into caproate. This review highlights recent anaerobic and bioelectrochemical processes for the production of caproate. The discussion will also cover the potential applications of this technology, together with obstacles to its use, compared with the conventional anaerobic digestion (AD) process, and considers whether it could be a standalone technology or a complementary one for AD. © 2018 Society of Chemical Industry and John Wiley &amp; Sons, Ltd</jats:p>

Mariana Rodríguez Arredondo, Philipp Kuntke, Annemiek ter Heijne et al.

Journal of Chemical Technology &amp; Biotechnology • 2019

<jats:title>Abstract</jats:title><jats:sec><jats:title>BACKGROUND</jats:title><jats:p>The load ratio is a crucial parameter to optimize the current driven recovery of total ammonia nitrogen (TAN) from urine. The load ratio is the ratio between the current density and the TAN loading rate. It is currently not known if the load ratio concept applies to a bioelectrochemical system (BES) because the current density and TAN loading rate cannot be controlled independently.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>We found a clear increasing trend in TAN removal efficiency with respect to load ratio in the BES for both human and synthetic urine. The maximum TAN removal efficiency was 60.9% at a load ratio of 0.7, corresponding to a TAN transport rate of 119 gN m<jats:sup>−2</jats:sup> day<jats:sup>−1</jats:sup> at an electrical energy input of 1.9 kWh kgN<jats:sup>−1</jats:sup> (synthetic urine). Low load ratios (&lt;1) were obtained, indicating that the current was not enough to transport all the TAN across the membrane.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>BES and ES show the same general relationship between TAN removal efficiency and load ratio. Therefore, given a stable current density, the concept of load ratio can also predict the TAN removal efficiency in BES. Higher current densities, and insights into the factors limiting current, are needed to increase the load ratio and therefore the TAN removal efficiency. © 2019 The Authors. <jats:italic>Journal of Chemical Technology &amp; Biotechnology</jats:italic> published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry.</jats:p></jats:sec>

Luis Fernando Leon‐Fernandez, Hassay Lizeth Medina‐Díaz, Omar González Pérez et al.

Journal of Chemical Technology &amp; Biotechnology • 2021

<jats:title>Abstract</jats:title><jats:sec><jats:title>BACKGROUND</jats:title><jats:p>This work studied the treatment of and metal recovery from a synthetic acid mine drainage (AMD) containing 500 mg L<jats:sup>−1</jats:sup> copper (Cu<jats:sup>2+</jats:sup>) and iron (Fe<jats:sup>+3</jats:sup>), and 50 mg L<jats:sup>−1</jats:sup> nickel (Ni<jats:sup>2+</jats:sup>) and tin (Sn<jats:sup>2+</jats:sup>) by using a bioelectrochemical system (BES). The presence of electroactive bacteria improved the performance of such reactor configuration, by contrast with systems with abiotic anodes.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>Operating as a microbial fuel cell (MFC), all of the Fe<jats:sup>3+</jats:sup> was reduced to Fe<jats:sup>2+</jats:sup> in about 24 h and Cu<jats:sup>2+</jats:sup> was electrodeposited onto the cathodic surface, a Cu electrode, obtaining pure Cu<jats:sup>0</jats:sup>. Almost all of the Cu in the catholyte was recovered after four days. The maximum current density and power attained in this stage were 0.136 mA cm<jats:sup>−2</jats:sup> and 0.0134 mW cm<jats:sup>−2</jats:sup>, respectively. Subsequent operation as a microbial electrolysis cell (MEC) allowed simultaneous recovery of the Fe<jats:sup>2+</jats:sup>, Ni<jats:sup>2+</jats:sup> and Sn<jats:sup>2+</jats:sup> by fixing the cathode potential at −0.7 V <jats:italic>versus</jats:italic> Ag/AgCl. The electrode material in this stage was titanium. The tin was completely deposited onto the cathodic surface after one day of electrolysis. After three days, 77% and 60% of Ni and Fe, respectively, was recovered.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSION</jats:title><jats:p>It was possible to recover Cu<jats:sup>0</jats:sup> while generating electricity at the same time using a BES. The cell voltage required for the metal electrodeposition of Fe<jats:sup>2+</jats:sup>, Ni<jats:sup>2+</jats:sup> and Sn<jats:sup>2+</jats:sup> was low in the case of the BES because of the contribution of the electroactive bacteria. Sequential metal deposition is possible by adjusting the operating parameters of the BES reactors. © 2021 Society of Chemical Industry</jats:p></jats:sec>

Jian Li, Zheng Ge, Zhen He

Journal of Chemical Technology &amp; Biotechnology • 2014

<jats:title>Abstract</jats:title><jats:sec><jats:title>BACKGROUND</jats:title><jats:p><jats:bold>Synergistic cooperation between membrane technology and microbial fuel cells (<jats:styled-content style="fixed-case">MFCs</jats:styled-content>) creates a membrane bioelectrochemical reactor (<jats:styled-content style="fixed-case">MBER</jats:styled-content>) that can produce electricity directly from organics while maintaining a high‐quality effluent. This study aims to advance the <jats:styled-content style="fixed-case">MBER</jats:styled-content> concept with hollow‐fiber membranes installed in a cathode compartment for alleviating membrane fouling</jats:bold>.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p><jats:bold>The <jats:styled-content style="fixed-case">MBER</jats:styled-content> achieved 90% removal of the chemical oxygen demand (<jats:styled-content style="fixed-case">COD</jats:styled-content>), and 69% removal of the total inorganic nitrogen; the turbidity of the membrane permeate was mostly below 2 <jats:styled-content style="fixed-case">NTU</jats:styled-content>. The operation of this <jats:styled-content style="fixed-case">MBER</jats:styled-content> theoretically consumed 0.09 <jats:styled-content style="fixed-case">kWh</jats:styled-content> m<jats:sup>‐3</jats:sup>, significantly lower than the energy consumption in membrane bioreactors (<jats:styled-content style="fixed-case">MBRs</jats:styled-content>). The energy production in the <jats:styled-content style="fixed-case">MBER</jats:styled-content> was 0.011–0.039 <jats:styled-content style="fixed-case">kWh</jats:styled-content> m<jats:sup>‐3</jats:sup> from the synthetic solution, or 0.032–0.064 <jats:styled-content style="fixed-case">kWh</jats:styled-content> m<jats:sup>‐3</jats:sup> from the cheese wastewater. The Coulombic efficiency varied between 10 and 30%, affected by the substrate type and loading rates</jats:bold>.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p><jats:bold>The <jats:styled-content style="fixed-case">MBER</jats:styled-content> with ultrafiltration membranes installed in the cathode greatly improved membrane performance with a constant low trans‐membrane pressure (which drives water through the membrane) during the testing period, when treating either a synthetic solution or real wastewater from a cheese plant. The <jats:styled-content style="fixed-case">MBER</jats:styled-content> technology has potential advantages in energy consumption/production compared with <jats:styled-content style="fixed-case">MBRs</jats:styled-content>, and may offer better handling of operating conditions than <jats:styled-content style="fixed-case">AnMBRs</jats:styled-content>. © 2013 Society of Chemical Industry</jats:bold></jats:p></jats:sec>

Hend M. M. Selim, Ahmed M. Kamal, Dina M. M. Ali et al.

Electroanalysis • 2017

<jats:title>Abstract</jats:title><jats:p>In bioelectrochemical systems (BESs), living microorganisms are capable of converting the chemical energy of degradable organic matters into bioelectricity. The electrical current outputs are dependent on the microbial cell viability and the biodegradation rates. Therefore, monitoring the current generative through the BES is promising for the microbial activity assessments. As compared to conventional microbiological methods, BESs are considered as non‐invasive techniques that offer rapid and sensitive detection of cellular functions (extra‐ and/or intracellular). Therefore, several progressions were made in the last 100 years in order to develop effective BESs. In this review, the involvements of materials sciences, microbiology, and electrochemistry in the effective designing and developments of BESs were intensively discussed. Due to the nanotechnology revolutions, manipulation of electrode materials led to the creation of different BES generations. Therefore, the impact of nanomaterials on the developments of the second and third generations of BESs is still the outlook of this promising research area.</jats:p>

Haiying Guo, Shanfa Tang, S. Xie et al.

Scientific Reports • 2020

Microbial fuel cell (MFC) technology is a simple way to accelerate the treatment of the oily sludge which is a major problem affecting the quality of oil fields and surrounding environment while generating electricity. To investigate the oil removal and the characteristics of changes in the composition of bacteria, sediment microbial fuel cells (SMFCs) supplemented with oily sludge was constructed. The results showed that the degradation efficiency of total petroleum hydrocarbon (TPH) of SMFC treatment was 10.1 times higher than the common anaerobic degradation. In addition, the degradation rate of n-alkanes followed the order of high carbon number > low carbon number > medium carbon number. The odd–even alkane predominance (OEP) increased, indicating that a high contribution of even alkanes whose degradation predominates. The OUT number, Shannon index, AEC index, and Chao1 index of the sludge treated with SMFC (YN2) are greater than those of the original sludge (YN1), showing that the microbial diversity of sludge increased after SMFC treatment. After SMFC treatment the relative abundance of Chloroflexi, Bacteroidia and Pseudomonadales which are essential for the degradation of the organic matter and electricity production increased significantly in YN2. These results will play a crucial role in improving the performance of oily sludge MFC.

Shuwei Li, Y. Song, Jiyun Baek et al.

Energies • 2020

Microbial electrosynthesis (MES) systems can convert CO2 to acetate and other value-added chemicals using electricity as the reducing power. Several electrochemically active redox mediators can enhance interfacial electron transport between bacteria and the electrode in MES systems. In this study, different redox mediators, such as neutral red (NR), 2-hydroxy-1,4-naphthoquinone (HNQ), and hydroquinone (HQ), were compared to facilitate an MES-based CO2 reduction reaction on the cathode. The mediators, NR and HNQ, improved acetate production from CO2 (165 mM and 161 mM, respectively) compared to the control (without a mediator = 149 mM), whereas HQ showed lower acetate production (115 mM). On the other hand, when mediators were used, the electron and carbon recovery efficiency decreased because of the presence of bioelectrochemical reduction pathways other than acetate production. Cyclic voltammetry of an MES with such mediators revealed CO2 reduction to acetate on the cathode surface. These results suggest that the addition of mediators to MES can improve CO2 conversion to acetate with further optimization in an operating strategy of electrosynthesis processes.

A. More, S. Gupta

Journal of Hazardous, Toxic, and Radioactive Waste • 2021

Abstract The hybrid bioelectrochemical systems (BES), a self-sustaining novel technology, was tested for evaluating its efficiency for removal of hexavalent chromium from electroplating industry wa...

Rui Tang, H. Prommer, Shoujun Yuan et al.

Environmental Science &amp; Technology • 2020

Roxarsone (ROX) is widely used in animal farms, thereby producing organoarsenic-bearing manure/wastewater. ROX cannot be completely degraded and nor can its arsenical metabolites be effectively immobilized during anaerobic digestion, potentially causing arsenic contamination upon discharge to the environment. Herein, we designed and tested a sulfate-mediated bioelectrochemical system (BES) to enhance ROX degradation and in situ immobilization of the released inorganic arsenic. Using our BES (0.5 V voltage and 350 μM sulfate), ROX and its metabolite, 4-hydroxy-3-amino-phenylarsonic acid (HAPA), were completely degraded within 13-22 days. In contrast, the degradation efficiency of ROX and HAPA was <85% during 32-day anaerobic digestion. In a sulfate-mediated BES, 75.0-83.2% of the total arsenic was immobilized in the sludge, significantly more compared to the anaerobic digestion (34.1-57.3%). Our results demonstrate that the combination of sulfate amendment and voltage application exerted a synergetic effect on enhancing HAPA degradation and sulfide-driven arsenic precipitation. This finding was further verified using real swine wastewater. A double-cell BES experiment indicated that As(V) and sulfate were transported from the anode to the cathode chamber and coprecipitated as crystalline alacranite in the cathode chamber. These findings suggest that the sulfate-mediated BES is a promising technique for enhanced arsenic decontamination of organoarsenic-bearing manure/wastewater.

M. L. Di Franca, B. Matturro, S. Crognale et al.

Frontiers in Microbiology • 2022

Chlorinated solvents still represent an environmental concern that requires sustainable and innovative bioremediation strategies. This study describes the microbiome composition of a novel bioelectrochemical system (BES) based on sequential reductive/oxidative dechlorination for complete perchloroethylene (PCE) removal occurring in two separate but sequential chambers. The BES has been tested under various feeding compositions [i.e., anaerobic mineral medium (MM), synthetic groundwater (SG), and real groundwater (RG)] differing in presence of sulfate, nitrate, and iron (III). In addition, the main biomarkers of the dechlorination process have been monitored in the system under various conditions. Among them, Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes (tceA, bvcA, and vcrA) involved in anaerobic dechlorination have been quantified. The etnE and etnC genes involved in aerobic dechlorination have also been quantified. The feeding composition affected the microbiome, in particular when the BES was fed with RG. Sulfuricurvum, enriched in the reductive compartment, operated with MM and SG, suggesting complex interactions in the sulfur cycle mostly including sulfur oxidation occurring at the anodic counter electrode (MM) or coupled to nitrate reduction (SG). Moreover, the known Mycobacterium responsible for natural attenuation of VC by aerobic degradation was found abundant in the oxidative compartment fed with RG, which was in line with the high VC removal observed (92 ± 2%). D. mccartyi was observed in all the tested conditions ranging from 8.78E + 06 (with RG) to 2.35E + 07 (with MM) 16S rRNA gene copies/L. tceA was found as the most abundant reductive dehalogenase gene in all the conditions explored (up to 2.46 E + 07 gene copies/L in MM). The microbiome dynamics and the occurrence of biomarkers of dechlorination, along with the kinetic performance of the system under various feeding conditions, suggested promising implications for the scale-up of the BES, which couples reductive with oxidative dechlorination to ensure the complete removal of highly chlorinated ethylene and mobile low-chlorinated by-products.

Julia Pereira Narcizo, Lucca Bonjy Kikuti Mancilio, Matheus Pedrino et al.

• 0

<jats:p>The ability of some bacteria to perform Extracellular Electron Transfer (EET) has been explored in bioelectrochemical systems (BES) to obtain energy or chemicals from pure substances or residual substrates. Here, a new pyoverdine-producing Pseudomonas aeruginosa strain was isolated from a MFC biofilm oxidizing glycerol, a by-product of biodiesel production. Strain EL14 was investigated to assess its electrogenic ability and products. In an open circuit system (fermentation system) EL14 was able to consume glycerol and produce 1,3-propanediol, an unusual product from glycerol oxidation in P. aeruginosa. The microbial fuel cell (MFC), EL14 reached a current density of 82.4 mA m-2, during the first feeding cycle, then drops sharply as the biofilm falls off. Cyclic voltammetry suggests electron transfer to the anode occurrs indirectly, i.e., through a redox substance, with redox peaks at 0.22 and -0.45 V (vs Ag/AgCl) and directly probably by membrane redox-proteins with redox peak at 0.05 V (vs Ag/AgCl). EL14 produced added-value bioproducts, acetic and butyric acids, as well as 1,3 propanediol, in both fermentative and anodic conditions. However, the yield of 1,3-PDO from glycerol was enhanced from 0.57 to 0.89 (mol of 1,3-PDO mol-1 of glycerol) under MFC conditions compared with the fermentation. This result was unexpected since successful 1,3-PDO production is not usually associated with the P. aeruginosa glycerol metabolism. By comparing EL14 genomic sequences related to the 1,3-PDO biosynthesis with reference P. aeruginosa strains, we observed that strain EL14 has three copies of dhaT gene (1,3-propanediol dehydrogenase a different arrangement compared to other Pseudomonas isolates). Thus, this work functionally characterizes a bacterium never before associated to 1,3-PDO biosynthesis, indicating its potential for converting a by-product of the biodiesel industry into an emerging chemical product.</jats:p>

Mi Zhou, Stefano Freguia, Paul G. Dennis et al.

Microbial Biotechnology • 2015

<jats:title>Summary</jats:title><jats:p>In a microbial bioelectrochemical system (<jats:styled-content style="fixed-case">BES</jats:styled-content>), organic substrate such as glycerol can be reductively converted to 1,3‐propanediol (1,3‐<jats:styled-content style="fixed-case">PDO</jats:styled-content>) by a mixed population biofilm growing on the cathode. Here, we show that 1,3‐<jats:styled-content style="fixed-case">PDO</jats:styled-content> yields positively correlated to the electrons supplied, increasing from 0.27 ± 0.13 to 0.57 ± 0.09 mol <jats:styled-content style="fixed-case">PDO</jats:styled-content> mol<jats:sup>−1</jats:sup> glycerol when the cathodic current switched from 1 <jats:styled-content style="fixed-case">A</jats:styled-content> m<jats:sup>−2</jats:sup> to 10 <jats:styled-content style="fixed-case">A</jats:styled-content> m<jats:sup>−2</jats:sup>. Electrochemical measurements with linear sweep voltammetry (<jats:styled-content style="fixed-case">LSV</jats:styled-content>) demonstrated that the biofilm was bioelectrocatalytically active and that the cathodic current was greatly enhanced only in the presence of both biofilm and glycerol, with an onset potential of −0.46 <jats:styled-content style="fixed-case">V</jats:styled-content>. This indicates that glycerol or its degradation products effectively served as cathodic electron acceptor. During long‐term operation (&gt; 150 days), however, the yield decreased gradually to 0.13 ± 0.02 mol <jats:styled-content style="fixed-case">PDO</jats:styled-content> mol<jats:sup>−1</jats:sup> glycerol, and the current–product correlation disappeared. The onset potentials for cathodic current decreased to −0.58 <jats:styled-content style="fixed-case">V</jats:styled-content> in the <jats:styled-content style="fixed-case">LSV</jats:styled-content> tests at this stage, irrespective of the presence or absence of glycerol, with electrons from the cathode almost exclusively used for hydrogen evolution (accounted for 99.9% and 89.5% of the electrons transferred at glycerol and glycerol‐free conditions respectively). Community analysis evidenced a decreasing relative abundance of <jats:styled-content style="fixed-case"><jats:italic>C</jats:italic></jats:styled-content><jats:italic>itrobacter</jats:italic> in the biofilm, indicating a community succession leading to cathode independent processes relative to the glycerol. It is thus shown here that in processes where substrate conversion can occur independently of the electrode, electroactive microorganisms can be outcompeted and effectively disconnected from the substrate.</jats:p>