Maxime Blatter, Clément Furrer, Christian Pierre Cachelin et al.

Chemical Engineering Journal • 2020

Phosphate rock is a depleting resource and wastewater a sustainable long-term alternative for phosphorous mining. In modern wastewater treatment phosphate is concentrated 7500 times from wastewater into sludge as iron phosphate (FeP). Recently developed bioelectrochemical reactors enabled phosphate recovery from sewage sludge containing FeP. The integrated bioelectric process was found of much broader utility than initially elaborated. It refines all principle components of wastewater. The implementation is confronted to a number of challenges. Three pilot microbial electrolysis cells (MECs) of 168 L each were constructed and installed in different municipal wastewater treatment plants (WWTPs). The scale-up MECs generated renewable chemical base and co-extracted abundant species such as Na+, K+, Ca2+, Mg2+ and NH4+ from wastewater. The chemical base remobilized phosphate quantitatively from iron phosphates contained in digested sewage sludge. Phosphate extracts contained ammonia and upon magnesium (Mg2+) addition struvite crystalized. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) on heavy metals, Direct Mercury Analysis (DMA), Liquid Chromatography Mass Spectroscopy (LC-MS/MS) on organic micropollutants, metagenomics sequencing, Scanning Electron Microscopy (SEM-EDS), and X-Ray Diffraction (XRD) indicated that a highly pure struvite-fertilizer was produced. Microbial electricity co-generation was verified by electrochemical characterisation and microbiome analysis using 16S rRNA V4-V5 methodology. Geobacter, Dechloromonas, Desulfobulbus and cyanobacteria were the principal electrogens found. All in all, renewable chemical base as well as phosphate were obtained in high quantities and other renewables became accessible such as the critical material magnesium and other compounds of importance like ammonia, potassium, calcium, solid P-free sludge useful as biofuel and purified water. In general, the process recycles important compounds from waste, in a close to traceless manner while purifying wastewater.

Tahereh Jafary, Wan Ramli Wan Daud, Mostafa Ghasemi et al.

Journal of Cleaner Production • 2016

Xiaoxiang Li, Hongrui Cao, Qing Feng et al.

Energy • 2024

Matteo Tucci, Cruz Viggi Carolina, Marco Resitano et al.

Electrochimica Acta • 2021

Tianjie Ao, Xin‐Qing Zhao, Muhammad Aamer Mehmood et al.

Chemical Engineering Journal • 2023

Marc Sugnaux, Manuel Happe, Christian Pierre Cachelin et al.

Bioresource Technology • 2016

Wilgince Apollon, Sathish‐Kumar Kamaraj, Héctor Silos‐Espino et al.

Applied Energy • 2020

Yeray Asensio, María Victoria Llorente, Patricia Fernández et al.

Chemical Engineering Journal • 2020

Hongrui Cao, Jin Sun, Keqiang Wang et al.

The Science of The Total Environment • 2022

Sarah Cotterill, Jan Dolfing, Thomas P. Curtis et al.

Frontiers in Energy Research • 2018

The formation of an electrochemically active biofilm is critical to the function of a Microbial Electrolysis Cell (MEC). We used Illumina 16S rDNA sequencing to analyse the formation and composition of anodic biofilms of two pilot-scale MECs, operated in continuous flow mode on domestic wastewater for over six months, and inoculated with that same wastewater. We observe: (i) a clear correlation between the frequency of detection of taxa in the MECs and their abundance in the metacommunity, (ii) the existence of a “core community” that was present across sites and (iii) the percentage of Geobacter tended to increase with longevity of retention time of the wastewater in the reactor. This suggests that: (i) community composition was largely governed by stochastic processes, (ii) that the technology should work on most if not all domestic wastewaters, as long as the anodes are seeded with the target wastewater and (iii) that deterministic factors may also play a role in establishing the anodic community. Geobacter, the archetypical electrogen in bioelectrochemical systems, comprised only 1.0 ± 0.7 % of the sequences recovered from a functioning pilot-scale MEC anode. Our results imply that influent flow rate may need to be optimised separately for start-up and for operating conditions for maximal performance.

Alba Ceballos‐Escalera, Narcís Pous, Lluı́s Bañeras et al.

Water Research • 2024

The potential of nitrate electro-bioremediation has been fully demonstrated at the laboratory scale, although it has not yet been fully implemented due to the challenges associated with scaling-up bioelectrochemical reactors and their on-site operation. This study describes the initial start-up and subsequent stable operation of an electro-bioremediation pilot plant for the treatment of nitrate-contaminated groundwater on-site (Navata site, Spain). The pilot plant was operated under continuous flow mode for 3 months, producing an effluent suitable for drinking water in terms of nitrates and nitrites (<50 mg NO 3 - L -1 ; 0 mg NO 2 - L -1 ). A maximum nitrate removal rate of 0.9 ± 0.1 kg NO 3 - m -3 d -1 (efficiency 82 ± 18 %) was achieved at a cathodic hydraulic retention time (HRT cat ) of 2.0 h with a competitive energy consumption of 4.3 ± 0.4 kWh kg -1 NO 3 - . Under these conditions, the techno-economic analysis estimated an operational cost of 0.40 € m -3 . Simultaneously, microbiological analyses revealed structural heterogeneity in the reactor, with denitrification functionality concentrated predominantly from the centre to the upper section of the reactor. The most abundant groups were Pseudomonadaceae, Rhizobiaceae, Gallionellaceae, and Xanthomonadaceae. In conclusion, this pilot plant represents a significant advancement in implementing this technology on a larger scale, validating its effectiveness in terms of nitrate removal and cost-effectiveness. Moreover, the results validate the electro-bioremediation in a real environment and encourage further investigation of its potential as a water treatment.

Valentin Larzillière, Florence de Fouchécour, Chrystelle Bureau et al.

Bioelectrochemistry • 2023

Pirjo Isosaari, Mika Sillanpää

Separation and Purification Reviews • 2016

The cleaning of large volumes of metal-loaded water formed at closed and active mine sites can be a valuable resource of metals. Active treatment processes are needed to recover these metals for reuse and for better environmental protection of recipient waters. This review evaluates the mechanisms of metal removal and recovery and practical feasibility of mine water treatment in two bioreactor systems: sulfate-reducing bioreactors and bioelectrochemical reactors. The influence of treatment conditions and reactor designs on metal recovery, as well as limitations to intensify the treatment processes, are discussed. High metal removal efficiencies are reported with sulfate-reducing bioreactors, whereas metal recovery, in particular, requires reactor designs and process conditions that differ from those that are primarily applied for sulfate removal. Bioelectrochemical systems offer another route for utilizing synergistic microbial processes for metal recovery, but the performance data is still limited to laboratory- and pilot-scale experiments.

Teklit Gebregiorgis Ambaye, Mentore Vaccari, Andrea Franzetti et al.

Chemical Engineering Journal • 2022

Md Tabish Noori, Mung Thi Vu, Rana Basit Ali et al.

Chemical Engineering Journal • 2019

Franziska Enzmann

Repository KITopen (Karlsruhe Institute of Technology) • 2020

Als relativ junges Forschungsfeld der Biotechnologie erlaubt es die Bioelektrotechnologie, elektrische Energie und biologische Katalyse zu koppeln. Verschiedene Studien konnten bereits mehrere mögliche Anwendungen demonstrieren, wobei die dazu konstruierten bioelektrochemischen Systeme sich noch auf den Labormaßstab beschränkten. Diese Systeme wurden nur in seltenen Fällen einheitlich charakterisiert und eine universelle Angabe der Leistungsparameter konnte sich noch nicht durchsetzen, was dazu führt dass derzeit Vergleiche der unterschiedlichen Reaktoren und Prozesse nur schwer möglich sind. Dieser Umstand ist ein generelles Hindernis auf dem Weg zur industriellen Anwendung der Bioelektrotechnologie, da durch die fehlende Vergleichbarkeit auch eine rationale Optimierung erschwert wird. Nur wenige Prozesse wurden bisher in größere Maßstäbe übertragen und unter industrienahen Bedingungen über längere Zeit hinweg betrieben. Ziel dieser Doktorarbeit ist die Konzipierung, Charakterisierung und Maßstabsübertragung eines bioelektrochemischen Systems. Die hauptsächliche Anwendung des Reaktors soll die Bioelektromethanogenese sein. Dieser Prozess soll während der Arbeit optimiert werden. Anaerobe Mikroorganismen wandeln dabei Elektronen von einer Kathode und CO2 zu Methan um. Methan könnte einen Ersatz für Erdöl darstellen, da es sowohl als Brennstoff, zur chemischen Synthese wie auch in biologischen Prozessen als Ausgangsstoff eingesetzte werden kann. Es wurde ein bioelektrochemisches System konstruiert, dessen Arbeitskammer als Blasensäule gestaltet ist. Das Arbeitsvolumen in dieser Kammer betrug einen Liter, während die Gegenkammer, die die Arbeitskammer umgab, zehn Liter fasste. Die Arbeitselektrode wurde in der Mitte der Arbeitskammer platziert, die Gegenelektrode um die Arbeitskammer gewickelt. Der Reaktor wurde durch verschiedene Methoden abiotisch charakterisiert. Diese umfassten unter anderem Cyclovoltammetrie, Chronoamperometrie und kLa-Messung, wodurch es ermöglicht werden sollte, verschiedene Reaktortypen miteinander zu vergleichen. Die Berechnung der Wagnerzahl konnte beispielsweise zeigen, dass das elektrische Feld im Reaktor gleichmäßig verteilt war, während die resultierenden Reynolds-, Bond- und Weberzahlen belegten, dass sich in der Arbeitskammer eine laminare, homogene Blasenströmung entwickelte. Anaerobe Methanogene wurden in der Arbeitskammer mit CO2 aus dem sauerstofffreien Eingangsgasstrom und Elektronen von der Arbeitselektrode versorgt, um Methan produzieren zu können. Methanococcus maripaludis wurde als Reinkultur verwendet, da dieser Organismus bereits in der Literatur als elektroaktiv beschrieben wurde und somit Vergleichsdaten vorlagen. In den ersten Versuchen konnte bereits eine absolute Methanproduktionsrate von 0,23 mmol*d-1 erzielt werden, was einer spezifischen Methanproduktionsrate von 33,8 mmol*d-1*m-² entsprach. Dabei wurde eine Coulombeffizienz von 51,0 % erreicht. Die gemessene Produktionsrate lag damit höher als bislang für Bioelektromethanogenese mit M. mariplauds beschrieben. Die Raum-Zeit-Ausbeute im neu entwickelten Reaktor war vergleichbar mit der, die in den üblicherweise im Labor genutzten H-Zellen ermittelt wurde. Die Bioelektromethanogenese wurde im Anschluss weiter optimiert, was eine Verbesserung der absoluten Methanproduktionsrate um den Faktor 9,8 auf 2,3 mmol*d-1 (spezifische Methanproduktionsrate: 81,4 mmol*d-1*m-²) einbrachte. Die Coulombeffizienz lag dabei bei 56,4 %. Die erzielte spezifische Methanproduktion lag damit im Bereich von beschriebenen Produktionsraten, die mit Mischkulturen erreicht wurden, welche üblicherweise höhere Ausbeuten erlauben. Die Ergebnisse aus der bioelektrochemischen Blasensäule sind vergleichbar mit Ergebnissen, die in einem bioelektrochemischen Rührkesselreaktor erzielt wurden und höher als in einer H-Zelle unter vergleichbaren Bedingungen (Elektroden- und Membranmaterial, Arbeitspotential, Eingangsgaszusammensetzung). Die höchste Verbesserung von 14

Carlos Gallardo-Bustos, Natalia Tapia, Ignacio T. Vargas

Bioelectrochemistry • 2024

Max Hackbarth, Johannes Gescher, Harald Horn et al.

Bioresource Technology Reports • 2023

Franziska Enzmann, Dirk Holtmann

Chemical Engineering Science • 2019

Franziska Enzmann, Florian Mayer, Markus Stöckl et al.

Chemical Engineering Science • 2018

Fatemeh Parnianchi, Maryam Nazari, Jila Maleki et al.

International nano letters. • 2018

At present, graphene has been widely utilized in electronics, electric devices, and biosensors. As its unparalleled properties including high surface area, excellent conductivity, ease of functionalization, and production, graphene provides an ideal platform to make useful nanomaterials, and motivates researchers to synthesize metallic nanoparticles–graphene nanocomposites for fabricating of sensors and biosensors. Fabrication of metallic nanoparticle–graphene nanohybrids and their application in sensing systems allows greatly sensitive, selective, stable, and fast electrochemical sensing of analytes. This review presents the recent studies in the construction of metallic nanoparticles graphene or graphene oxide composite-based electrochemical biosensors. It discusses the application of metallic nanomaterials to the assembly of graphene- and graphene oxide-based electrochemical enzymatic biosensors and its analytical performance.

Hengduo Xu, Xiangchun Quan, Chen Liang

Chemosphere • 2018

Míriam Cerrillo, Marc Viñas, August Bonmatí Blasi

Bioresource Technology • 2016

Xin Fang, Shafeer Kalathil, Giorgio Divitini et al.

Proceedings of the National Academy of Sciences • 2020

Integration of electroactive bacteria into electrodes combines strengths of intracellular biochemistry with electrochemistry for energy conversion and chemical synthesis. However, such biohybrid systems are often plagued with suboptimal electrodes, which limits the incorporation and productivity of the bacterial colony. Here, we show that an inverse opal-indium tin oxide electrode hosts a large population of current-producing Geobacter and attains a current density of 3 mA cm -2 stemming from bacterial respiration. Differential gene expression analysis revealed Geobacter 's transcriptional regulations to express more electron-relaying proteins when interfaced with electrodes. The electrode also allows coculturing with Shewanella for syntrophic electrogenesis, which grants the system additional flexibility in converting electron donors. The biohybrid electrode containing Geobacter can also catalyze the reduction of soluble fumarate and heterogenous graphene oxide, with electrons from an external power source or an irradiated photoanode. This biohybrid electrode represents a platform to employ live cells for sustainable power generation and biosynthesis.

Yahan Meng, Mingming Wang, Jiazhi Wang et al.

Nature Communications • 2024

Construction of a solid electrolyte interphase (SEI) of zinc (Zn) electrode is an effective strategy to stabilize Zn electrode/electrolyte interface. However, single-layer SEIs of Zn electrodes undergo rupture and consequent failure during repeated Zn plating/stripping. Here, we propose the construction of a robust bilayer SEI that simultaneously achieves homogeneous Zn 2+ transport and durable mechanical stability for high Zn utilization rate (ZUR) and Coulombic efficiency (CE) of Zn electrode by adding 1,3-Dimethyl-2-imidazolidinone as a representative electrolyte additive. This bilayer SEI on Zn surface consists of a crystalline ZnCO 3 -rich outer layer and an amorphous ZnS-rich inner layer. The ordered outer layer improves the mechanical stability during cycling, and the amorphous inner layer homogenizes Zn 2+ transport for homogeneous, dense Zn deposition. As a result, the bilayer SEI enables reversible Zn plating/stripping for 4800 cycles with an average CE of 99.95% (± 0.06%). Meanwhile, Zn | |Zn symmetric cells show durable lifetime for over 550 h with a high ZUR of 98% under an areal capacity of 28.4 mAh cm -2 . Furthermore, the Zn full cells based on the bilayer SEI functionalized Zn negative electrodes coupled with different positive electrodes all exhibit stable cycling performance under high ZUR.

Nguyan Hoàng Ly, Michaël Badawi, Mallikarjuna N. Nadagouda et al.

Chemical Engineering Journal • 2024

Yun Wu, Qing Yang, Qingnan Zeng et al.

Chemical Engineering Journal • 2016

Samay Garg, Zhenhua Xie, Jingguang G. Chen

Nature Chemical Engineering • 2024

Weifeng Kong, Liping Huang, Xie Quan et al.

Applied Catalysis B: Environmental • 2022

Huanhuan Wei, Rongchao Shi, Lin Sun et al.

Nature Communications • 2021

A graphdiyne-based artificial synapse (GAS), exhibiting intrinsic short-term plasticity, has been proposed to mimic biological signal transmission behavior. The impulse response of the GAS has been reduced to several millivolts with competitive femtowatt-level consumption, exceeding the biological level by orders of magnitude. Most importantly, the GAS is capable of parallelly processing signals transmitted from multiple pre-neurons and therefore realizing dynamic logic and spatiotemporal rules. It is also found that the GAS is thermally stable (at 353 K) and environmentally stable (in a relative humidity up to 35%). Our artificial efferent nerve, connecting the GAS with artificial muscles, has been demonstrated to complete the information integration of pre-neurons and the information output of motor neurons, which is advantageous for coalescing multiple sensory feedbacks and reacting to events. Our synaptic element has potential applications in bioinspired peripheral nervous systems of soft electronics, neurorobotics, and biohybrid systems of brain-computer interfaces.

Yuanyao Ye, Huu Hao Ngo, Wenshan Guo et al.

Bioresource Technology • 2016

Rohit Kumar, Protima Rauwel, Erwan Rauwel

Processes • 2021

Heavy metal pollution of aquatic media has grown significantly over the past few decades. Therefore, a number of physical, chemical, biological, and electrochemical technologies are being employed to tackle this problem. However, they possess various inescapable shortcomings curbing their utilization at a commercial scale. In this regard, nanotechnology has provided efficient and cost-effective solutions for the extraction of heavy metals from water. This review will provide a detailed overview on the efficiency and applicability of various adsorbents, i.e., carbon nanotubes, graphene, silica, zero-valent iron, and magnetic nanoparticles for scavenging metallic ions. These nanoparticles exhibit potential to be used in extracting a variety of toxic metals. Recently, nanomaterial-assisted bioelectrochemical removal of heavy metals has also emerged. To that end, various nanoparticle-based electrodes are being developed, offering more efficient, cost-effective, ecofriendly, and sustainable options. In addition, the promising perspectives of nanomaterials in environmental applications are also discussed in this paper and potential directions for future works are suggested.

Jens Neu, Catharine Shipps, Matthew J. Guberman‐Pfeffer et al.

Nature Communications • 2022

Light-induced microbial electron transfer has potential for efficient production of value-added chemicals, biofuels and biodegradable materials owing to diversified metabolic pathways. However, most microbes lack photoactive proteins and require synthetic photosensitizers that suffer from photocorrosion, photodegradation, cytotoxicity, and generation of photoexcited radicals that are harmful to cells, thus severely limiting the catalytic performance. Therefore, there is a pressing need for biocompatible photoconductive materials for efficient electronic interface between microbes and electrodes. Here we show that living biofilms of Geobacter sulfurreducens use nanowires of cytochrome OmcS as intrinsic photoconductors. Photoconductive atomic force microscopy shows up to 100-fold increase in photocurrent in purified individual nanowires. Photocurrents respond rapidly (<100 ms) to the excitation and persist reversibly for hours. Femtosecond transient absorption spectroscopy and quantum dynamics simulations reveal ultrafast (~200 fs) electron transfer between nanowire hemes upon photoexcitation, enhancing carrier density and mobility. Our work reveals a new class of natural photoconductors for whole-cell catalysis.

Jayeeta Sarkar, Sufia K. Kazy, Abhishek Gupta et al.

Frontiers in Microbiology • 2016

Nutrient deficiency severely impairs the catabolic activity of indigenous microorganisms in hydrocarbon rich environments (HREs) and limits the rate of intrinsic bioremediation. The present study aimed to characterize the microbial community in refinery waste and evaluate the scope for biostimulation based in situ bioremediation. Samples recovered from the wastewater lagoon of Guwahati refinery revealed a hydrocarbon enriched [high total petroleum hydrocarbon (TPH)], oxygen-, moisture-limited, reducing environment. Intrinsic biodegradation ability of the indigenous microorganisms was enhanced significantly (>80% reduction in TPH by 90 days) with nitrate amendment. Preferred utilization of both higher- (>C30) and middle- chain (C20-30) length hydrocarbons were evident from GC-MS analysis. Denaturing gradient gel electrophoresis and community level physiological profiling analyses indicated distinct shift in community's composition and metabolic abilities following nitrogen (N) amendment. High throughput deep sequencing of 16S rRNA gene showed that the native community was mainly composed of hydrocarbon degrading, syntrophic, methanogenic, nitrate/iron/sulfur reducing facultative anaerobic bacteria and archaebacteria, affiliated to γ- and δ- Proteobacteria and Euryarchaeota respectively. Genes for aerobic and anaerobic alkane metabolism ( alk B and bss A), methanogenesis ( mcr A), denitrification ( nir S and nar G) and N 2 fixation ( nif H) were detected. Concomitant to hydrocarbon degradation, lowering of dissolve O 2 and increase in oxidation-reduction potential (ORP) marked with an enrichment of N 2 fixing, nitrate reducing aerobic/facultative anaerobic members [e.g ., Azovibrio , Pseudoxanthomonas and Comamonadaceae members] was evident in N amended microcosm. This study highlighted that indigenous community of refinery sludge was intrinsically diverse, yet appreciable rate of in situ bioremediation could be achieved by supplying adequate N sources.

Siwei Huang, Ling Zhou, Mei‐Chun Li et al.

Materials • 2016

Poly (vinyl pyrrolidone) (PVP)/cellulose nanocrystal (CNC)/silver nanoparticle composite fibers were prepared via electrospinning using N , N '-dimethylformamide (DMF) as a solvent. Rheology, morphology, thermal properties, mechanical properties, and antimicrobial activity of nanocomposites were characterized as a function of material composition. The PVP/CNC/Ag electrospun suspensions exhibited higher conductivity and better rheological properties compared with those of the pure PVP solution. The average diameter of the PVP electrospun fibers decreased with the increase in the amount of CNCs and Ag nanoparticles. Thermal stability of electrospun composite fibers was decreased with the addition of CNCs. The CNCs help increase the composite tensile strength, while the elongation at break decreased. The composite fibers included Ag nanoparticles showed improved antimicrobial activity against both the Gram-negative bacterium Escherichia coli ( E. coli ) and the Gram-positive bacterium Staphylococcus aureus ( S. aureus ). The enhanced strength and antimicrobial performances of PVP/CNC/Ag electrospun composite fibers make the mat material an attractive candidate for application in the biomedical field.

Guiyeoul Lim, Donato Calabrese, Allison E. Wolder et al.

Communications Chemistry • 2024

Despite the increasing demand for efficient and sustainable chemical processes, the development of scalable systems using biocatalysis for fine chemical production remains a significant challenge. We have developed a scalable flow system using immobilized enzymes to facilitate flavin-dependent biocatalysis, targeting as a proof-of-concept asymmetric alkene reduction. The system integrates a flavin-dependent Old Yellow Enzyme (OYE) and a soluble hydrogenase to enable H 2 -driven regeneration of the OYE cofactor FMNH 2 . Molecular hydrogen was produced by water electrolysis using a proton exchange membrane (PEM) electrolyzer and introduced into the flow system via a designed gas membrane addition module at a high diffusion rate. The flow system shows remarkable stability and reusability, consistently achieving >99% conversion of ketoisophorone to levodione. It also demonstrates versatility and selectivity in reducing various cyclic enones and can be extended to further flavin-based biocatalytic approaches and gas-dependent reactions. This electro-driven continuous flow system, therefore, has significant potential for advancing sustainable processes in fine chemical synthesis.

Genping Yi, Difan Fang, Liming Yang et al.

International Journal of Electrochemical Science • 2020

Bioelectrochemical system (BES) exhibits great potential for the wastewater treatment, which can achieve the energy storage simultaneously. However, the application of BES is limited due to the interior structure and composition of electrode materials. Here, a hybrid nano-structure reduced graphene oxide-Mn3O4 (rGO@Mn3O4) electrode was obtained through one-step electrodeposition method, and utilized to enhance the performance of Geobacter sulfurreducens inoculated BES. The hierarchical rGO@Mn3O4 is equipped with open porous and higher surface roughness, which are favorable for the microbial colonization. And the electron transport from exoelectrogens to the electrode facilitated by the three-dimensional interconnecting conductive scaffold. Further, the rGO@Mn3O4 electrode realized the maximum current density in a three-electrode setup reached 0.0376 mA cm−2 with high loading, which is 3.03-fold higher than that of a bare rGO (0.0124 mA cm−2). The great performance is attributed to the proper pore size distribution and the “rose”-like porous structure Mn3O4 particles coating on the surface of the rGO sheets network. This work reveals a synergistic effect in pore structure and surface chemistry design to promote bioelectrocatalysis in BESs.

Zhijun Xu, Shengliang Wang, Chunyu Zhao et al.

Nature Communications • 2020

The spontaneous self-assembly of multicellular ensembles into living materials with synergistic structure and function remains a considerable challenge in biotechnology and synthetic biology. Here, we exploit the aqueous two-phase separation of dextran-in-PEG emulsion micro-droplets for the capture, spatial organization and immobilization of algal cells or algal/bacterial cell communities to produce discrete multicellular spheroids capable of both aerobic (oxygen producing) and hypoxic (hydrogen producing) photosynthesis in daylight under air. We show that localized oxygen depletion results in hydrogen production from the core of the algal microscale reactor, and demonstrate that enhanced levels of hydrogen evolution can be achieved synergistically by spontaneously enclosing the photosynthetic cells within a shell of bacterial cells undergoing aerobic respiration. Our results highlight a promising droplet-based environmentally benign approach to dispersible photosynthetic microbial micro-reactors comprising segregated cellular micro-niches with dual functionality, and provide a step towards photobiological hydrogen production under aerobic conditions.

Zhuang Ma, Lihong Zhou, Sen Wang et al.

Journal of Water Process Engineering • 2025

Basem S. Zakaria, Bipro Ranjan Dhar

Scientific Reports • 2021

The microbial electrolysis cell assisted anaerobic digestion holds great promises over conventional anaerobic digestion. This article reports an experimental investigation of extracellular polymeric substances (EPS), reactive oxygen species (ROS), and the expression of genes associated with extracellular electron transfer (EET) in methanogenic biocathodes. The MEC-AD systems were examined using two cathode materials: carbon fibers and stainless-steel mesh. A higher abundance of hydrogenotrophic Methanobacterium sp. and homoacetogenic Acetobacterium sp. appeared to play a major role in superior methanogenesis from stainless steel biocathode than carbon fibers. Moreover, the higher secretion of EPS accompanied by the lower ROS level in stainless steel biocathode indicated that higher EPS perhaps protected cells from harsh metabolic conditions (possibly unfavorable local pH) induced by faster catalysis of hydrogen evolution reaction. In contrast, EET-associated gene expression patterns were comparable in both biocathodes. Thus, these results indicated hydrogenotrophic methanogenesis is the key mechanism, while cathodic EET has a trivial role in distinguishing performances between two cathode electrodes. These results provide new insights into the efficient methanogenic biocathode development.