Ishita Chanana, Parneet Kaur, Lokender Kumar et al.

Fermentation • 2023

In the energy sector, bioenergy has been utilized as a replacement for non-renewable resources. Due to the depletion of resources, mankind may face adversities in the future. To overcome these challenges, sustainable and reliable bioenergy-based alternatives are to be used. Bioenergy sources are bio-based alternatives that have become acceptable in society for their renewability, sustainability, and environmentally friendly characteristics, but they still lag in the energy market due to their less cost-effective output of upstream and downstream processing in comparison with age-old fossil fuels. This review provides a detailed overview of their techno-economic and life cycle assessment, their positioning and competition in the energy market, and the strategies that might assist them in overcoming the market challenges. Microalgal bioenergy products have been lifting their market positioning at a slower rate that is almost unnoticeable, but their assistance in becoming a better solution against adversities of energy resource depletion in the future makes them quite promising. The new research alternatives for microalgal biomass conversion in biorefinery products for bioenergy production, which are based on combating pollution and reuse of waste products, along with the strategic application for combating the energy market competition, have also been highlighted.

Hai Tang, Wen‐Cheng Pu, Cai Chang-feng et al.

Polish Journal of Environmental Studies • 2016

In this study, a coupled membrane-free microbial fuel cell (MFC) with permeable reactive barrier (PRB) was reported and its treatment performance and electricity generation for acid mine drainage (AMD) were examined. The pilot-scale continuous flow MFC-PRB was operated for five periods at a hydraulic retention time of 48.0 h, and the average sulphate removal percentages of 51.2%, 39.8%, and 33.1% were obtained in effluent of 1,000, 2,000, 3,000 mg/l, respectively. More than 99.5% of the initial concentrations of Cu 2+ , Zn 2+ , and Pb 2+ were removed, resulting in concentrations of those elements of 0.01-0.05 mg/l in the effluent. The results demonstrated that the MFC-PRB holds a potential capacity for remediation of AMD.

Andi Kurniawan, Tatsuya Yamamoto

International Journal of Microbiology • 2019

Microbial biofilms are ubiquitous in aquatic ecosystems. Inside the biofilm is the nutrient-rich microenvironment promoted by the accumulation of the nutrient ions such as NH 4 + and NO 3 - from surrounding water. The present study investigated the characteristics of NH 4 + and NO 3 - accumulation into the biofilm of natural microbial consortia collected from Lake Biwa, Japan. The results showed the following: (1) the concentrations of NH 4 + and NO 3 - inside the biofilm were much higher than those in the surrounding water; (2) the nutrient ion concentration inside the biofilm changed in synchrony with those in the surrounding water; (3) biofilm polymers have both positively and negatively charged sites; (4) electrostatic attractive interactions between the charged sites on biofilm polymers and oppositely charged ions outside the biofilm seem to play important roles in the accumulation of nutrient ions into the biofilm from the surrounding water; (5) the bacterial community structure differs between the biofilm and surrounding water. The present study revealed that the accumulation of nutrient ions into the biofilm indicates the removal of these ions from water outside the biofilm. According to the result of this study, accumulation of ions such as NH 4 + and NO 3 - into the biofilm of natural microbial consortia may have implications on nutrients seasonal dynamic in aquatic ecosystems.

Chun Kiat Ng, Jiabao Xu, Zhao Cai et al.

Microbial Biotechnology • 2020

Electrochemically active biofilms are capable of exchanging electrons with solid electron acceptors and have many energy and environmental applications such as bioelectricity generation and environmental remediation. The performance of electrochemically active biofilms is usually dependent on c-type cytochromes, while biofilm development is controlled by a signal cascade mediated by the intracellular secondary messenger bis-(3'-5') cyclic dimeric guanosine monophosphate (c-di-GMP). However, it is unclear whether there are any links between the c-di-GMP regulatory system and the expression of c-type cytochromes. In this study, we constructed a S. oneidensis MR-1 strain with a higher cytoplasmic c-di-GMP level by constitutively expressing a c-di-GMP synthase and it exhibited expected c-di-GMP-influenced traits, such as lowered motility and increased biofilm formation. Compared to MR-1 wild-type strain, the high c-di-GMP strain had a higher Fe(III) reduction rate (21.58 vs 11.88 pM of Fe(III)/h cell) and greater expression of genes that code for the proteins involved in the Mtr pathway, including CymA, MtrA, MtrB, MtrC and OmcA. Furthermore, single-cell Raman microspectroscopy (SCRM) revealed a great increase of c-type cytochromes in the high c-di-GMP strain as compared to MR-1 wild-type strain. Our results reveal for the first time that the c-di-GMP regulation system indirectly or directly positively regulates the expression of cytochromes involved in the extracellular electron transport (EET) in S. oneidensis, which would help to understand the regulatory mechanism of c-di-GMP on electricity production in bacteria.

Irena Kostova

Inorganics • 2023

Biogenic metals and their various inorganic, organometallic, and coordination compounds are comprehensively studied and extensively used in medical practice. Since the biogenic metals have various chemical properties corresponding to their position in the periodic table, their biological functions are different. Almost all of the discussed biogenic elements have an ability to form coordination complexes. Furthermore, the different accessible oxidation states occupied by most of these elements enables the body to catalyze oxy-reduction interactions, depending on the biological conditions. As they are biogenic in nature, their deficiency or their excess in the body leads to numerous pathological obstructions. The application of metal-based compounds as medications is connected with the oxy-reduction properties and the capability to form coordination complexes, which are involved in many bioreactions. The usefulness of these metals as therapeutic and diagnostic agents is also pointed out.

Ibtihaj Albalawi, Anna Hogan, Hanan Alatawi et al.

Sensors and Actuators B Chemical • 2023

A novel and effective method for immobilization of active ruthenium (II) bipyridine complex on screen printed gold electrode surface was developed for simultaneous determination of Cd (II) and Pb (II) in an environmental water sample. The electrostatic interaction between negatively charged graphene oxide (GO) or citrate-capped gold nanoparticles (AuNPs) and positively charged ruthenium (II) bipyridine complex ([Ru(bpy)3]2+) was studied with the incorporation of cation exchanging Nafion polymer, which enhanced electron transfer rate, reduced the interference caused by active compounds and results in long term stability. The comparison between the hybrid Ru-GO/Nafion and Ru-Au/Nafion nanocomposites’ behavior was electrochemically investigated in this paper through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave anodic stripping voltammetry (SWASV). Additionally, the surface morphologies of the screen-printed electrode were evaluated using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The proposed Ru-GO/Nafion sensor exhibited a higher sensitivity towards cadmium ion with a detection limit of 4.2 ppb compared to the Ru-Au/Nafion assay, which reveals low sensitivity with a limit of detection of 12.01 ppb. The developed assays show excellent electrochemical performance towards lead ions with a detection limit of 5.3 ppb and 2.5 ppb for Ru-GO/Nafion and Ru-Au/Nafion, respectively, indicating that the lead ions can be accumulated more on the surface of Ru-Au/Nafion SPGE. The hybrid nanocomposite assays were successfully employed in river and tap water samples and validated using Atomic Absorption Spectroscopy (AAS).

Yu. G. Maksimova, Yana Bykova, A. I. Maksimov

Microorganisms • 2022

Releasing multi-walled carbon nanotubes (MWCNTs) into ecosystems affects the biofilm formation and metabolic activity of bacteria in aquatic and soil environments. Pristine (pMWCNTs), oleophilic (oMWCNTs), hydrophilic (hMWCNTs), and carboxylated (cMWCNTs) carbon nanotubes were used to investigate their effects on bacterial biofilm. A pronounced probiofilm effect of modified MWCNTs was observed on the Gram-negative bacteria of Pseudomonas fluorescens C2, Acinetobacter guillouiae 11 h, and Alcaligenes faecalis 2. None of the studied nanomaterials resulted in the complete inhibition of biofilm formation. The complete eradication of biofilms exposed to MWCNTs was not observed. The functionalization of carbon nanotubes was shown to change their probiofilm and antibiofilm effects. Gram-negative bacteria were the most susceptible to destruction, and among the modified MWCNTs, oMWCNTs had the greatest effect on biofilm destruction. The number of living cells in the biofilms was assessed by the reduction of XTT, and metabolic activity was assessed by the reduction of resazurin to fluorescent resorufin. The biofilms formed in the presence of MWCNTs reduced tetrozolium to formazan more actively than the control biofilms. When mature biofilms were exposed to MWCNTs, dehydrogenase activity decreased in Rhodococcus erythropolis 4-1, A. guillouiae 11 h, and A. faecalis 2 in the presence of pMWCNTs and hMWCNTs, as well as in A. guillouiae 11 h exposed to cMWCNTs. When mature biofilms were exposed to pMWCNTs, hMWCNTs, and cMWCNTs, the metabolism of cells decreased in most strains, and oMWCNTs did not have a pronounced inhibitory effect. The antibiofilm and probiofilm effects of MWCNTs were strain-dependent.

Edoardo Dell’Armi, Marco Zeppilli, Maria Letizia Di Franca et al.

Journal of Water Process Engineering • 2022

In the present study, the sequential reductive/oxidative bioelectrochemical process has been tested with real groundwater from a contaminated site in Northern Italy for chlorinated aliphatic hydrocarbons (CAHs) removal. The sequential system was developed by connecting in series two membrane-less microbial electrolysis cells (MECs) equipped with an internal graphite counter electrode. The first MEC aimed at the CAHs reductive dechlorination (RD) and was constituted of a granular graphite working electrode. In the second MEC, a mixed metal oxide working electrode stimulated the oxidative dechlorination of the low chlorinated RD's by-products through oxygen production. The sequential process allowed complete mineralization of the CAHs contained in the real groundwater. A complete reduction of the perchloroethylene into vinyl chloride (VC) was observed in the first MEC polarized at −450 mV vs SHE, while the resulting VC was oxidized with a 92 ± 2 % efficiency in the second MEC due to the HRT increment from 0.7 to 1.7 days. Biomarkers of the reductive (Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes) and oxidative (etnE, etnC genes) dechlorination have been monitored in the two MECs along with the ecotoxicity tests. Overall, they provide information on the efficiency of the applied technology and allow to assess the potential adverse effects. According to the Tetrahymena pyriformis reproduction inhibition test and Panagrellus redivivus mortality tests, showed a significant ecotoxicity reduction with respect its initial inhibitory effect at the tested concentrations.

Liping Huang, Zijing Xu, Ying‐Hong Shi et al.

Chemical Engineering Journal • 2021

Jose Rodrigo Quejigo, Ulrike Dörfler, Reiner Schroll et al.

Microbial Biotechnology • 2016

The absence of suitable terminal electron acceptors (TEA) in soil might limit the oxidative metabolism of environmental microbial populations. Microbial electroremediating cells (MERCs) consist in a variety of bioelectrochemical devices that aim to overcome electron acceptor limitation and maximize metabolic oxidation with the purpose of enhancing the biodegradation of a pollutant in the environment. The objective of this work was to use MERCs principles for stimulating soil bacteria to achieve the complete biodegradation of the herbicide (14) C-isoproturon (IPU) to (14) CO(2) in soils. Our study concludes that using electrodes at a positive potential [+600 mV (versus Ag/AgCl)] enhanced the mineralization by 20-fold respect the electrode-free control. We also report an overall profile of the (14) C-IPU metabolites and a (14) C mass balance in response to the different treatments. The remarkable impact of electrodes on the microbial activity of natural communities suggests a promising future for this emerging environmental technology that we propose to name bioelectroventing.

Shusheel Kumar, Aneela Tahira, Adeel Liaquat Bhatti et al.

Journal of Energy Storage • 2023

Ana V. Silva, Miriam Edel, Johannes Gescher et al.

Frontiers in Microbiology • 2020

Microbial electrochemical technologies (METs) have emerged in recent years as a promising alternative green source of energy, with microbes consuming organic matter to produce energy or valuable byproducts. It is the ability of performing extracellular electron transfer that allows these microbes to exchange electrons with an electrode in these systems. The low levels of current achieved have been the limiting factor for the large-scale application of METs. Shewanella oneidensis MR-1 is one of the most studied electroactive organisms regarding extracellular electron transfer, and it has been shown that biofilm formation is a key factor for current generation. The transcription factor bolA has been identified as a central player in biofilm formation in other organisms, with its overexpression leading to increased biofilm. In this work we explore the effect of this gene in biofilm formation and current production by S. oneidensis MR-1. Our results demonstrate that an increased biofilm formation and consequent current generation was achieved by the overexpression of this gene. This information is crucial to optimize electroactive organisms toward their practical application in METs.

Mohammad Fahimizadeh, Pooria Pasbakhsh, Lee Sui Mae et al.

Engineering • 2022

Microbially induced calcium carbonate (CaCO3) precipitation (MICP) has been investigated as a sustainable alternative to conventional concrete remediation methods for improving the mechanical properties and durability of concrete structures. To date, urea-dependent MICP is the most widely employed MICP pathway in biological self-healing concrete research as its use has resulted in efficient CaCO3 precipitation rates. NH3 is a byproduct of ureolysis, and can be hazardous to cementitious structures and the health of various species. Accordingly, non-ureolytic bacterial concrete self-healing systems have been developed as eco-friendly alternatives to urea-dependent self-healing systems. Non-ureolytic pathways can improve the physical properties of concrete samples and incorporate the use of waste materials; they have the potential to be cost-effective and sustainable. Moreover, they can be applied in terrestrial and marine environments. To date, research on non-ureolytic concrete self-healing systems has been scarce compared to that on ureolytic systems. This article discusses the advances and challenges in non-ureolytic bacterial concrete self-healing studies and highlights the directions for future research.

Nada Alfryyan, Mohamed G. M. Kordy, Mohammed Abdel‐Gabbar et al.

Scientific Reports • 2022

The biosynthesis of silver nanoparticles (Ag NPs) has been studied in detail using two different approaches. For the first time, Bacillus cereus is used for one-pot biosynthesis of capsulated Ag NPs, using both intracellular and extracellular approaches. To discriminate between the produced nanostructures by these two approaches, their structures, nanomorphologies, optical properties, hydrodynamic sizes and zeta potentials are studied using different techniques. Fourier-transform infrared spectroscopy was used to identify the bioactive components responsible for the reduction of Ag + ions into Ag and the growth of stable Ag NPs. Scanning and transmission electron microscopy images displayed spherical and polygon nanomorphology for the intracellular and extracellular biosynthesized Ag NPs. For intracellular and extracellular biosynthesized Ag NPs, a face-centred cubic structure was observed, with average crystallite sizes of 45.4 and 90.8 nm, respectively. In comparison to the noncatalytic reduction test, the catalytic activities of intracellular and extracellular biosynthesized Ag NPs were explored for the reduction of highly concentrated MB dye solution. Extracellular Ag NPs achieved 100% MB reduction efficacy after around 80 min, compared to 50.6% and 24.1% in the presence and absence of intracellular Ag NPs, respectively. The rate of MB reduction was boosted by 22 times with the extracellular catalyst, and by 3 times with the intracellular catalyst. Therefore, the extracellular production process of Ag NPs utilizing Bacillus cereus bacteria might be applied in the industry as a cost-effective way for eliminating the toxic MB dye.

Sourav Manna, Sampurna Roy, Avishek Dolai et al.

Frontiers in Nanotechnology • 2023

Christina Engel, David Vorländer, Rebekka Biedendieck et al.

PLoS ONE • 2020

Geobacter sulfurreducens was originally considered a strict anaerobe. However, this bacterium was later shown to not only tolerate exposure to oxygen but also to use it as terminal electron acceptor. Research performed has so far only revealed the general ability of G. sulfurreducens to reduce oxygen, but the oxygen uptake rate has not been quantified yet, nor has evidence been provided as to how the bacterium achieves oxygen reduction. Therefore, microaerobic growth of G. sulfurreducens was investigated here with better defined operating conditions as previously performed and a transcriptome analysis was performed to elucidate possible metabolic mechanisms important for oxygen reduction in G. sulfurreducens. The investigations revealed that cell growth with oxygen is possible to the same extent as with fumarate if the maximum specific oxygen uptake rate (sOUR) of 95 mgO2 gCDW-1 h-1 is not surpassed. Hereby, the entire amount of introduced oxygen is reduced. When oxygen concentrations are too high, cell growth is completely inhibited and there is no partial oxygen consumption. Transcriptome analysis suggests a menaquinol oxidase to be the enzyme responsible for oxygen reduction. Transcriptome analysis has further revealed three different survival strategies, depending on the oxygen concentration present. When prompted with small amounts of oxygen, G. sulfurreducens will try to escape the microaerobic area; if oxygen concentrations are higher, cells will focus on rapid and complete oxygen reduction coupled to cell growth; and ultimately cells will form protective layers if a complete reduction becomes impossible. The results presented here have important implications for understanding how G. sulfurreducens survives exposure to oxygen.

Till Tiso, Nina Ihling, Sonja Kubicki et al.

Frontiers in Bioengineering and Biotechnology • 2020

Rhamnolipids are biosurfactants produced by microorganisms with the potential to replace synthetic compounds with petrochemical origin. To promote industrial use of rhamnolipids, recombinant rhamnolipid production from sugars needs to be intensified. Since this remains challenging, the aim of the presented research is to utilize a multidisciplinary approach to take a step toward developing a sustainable rhamnolipid production process. Here, we developed expression cassettes for stable integration of the rhamnolipid biosynthesis genes into the genome outperformed plasmid-based expression systems. Furthermore, the genetic stability of the production strain was improved by using an inducible promoter. To enhance rhamnolipid synthesis, energy- and/or carbon-consuming traits were removed: mutants negative for the synthesis of the flagellar machinery or the storage polymer PHA showed increased production by 50%. Variation of time of induction resulted in an 18% increase in titers. A scale-up from shake flasks was carried out using a 1-L bioreactor. By recycling of the foam, biomass loss could be minimized and a rhamnolipid titer of up to 1.5 g/L was achieved without using mechanical foam destroyers or antifoaming agents. Subsequent liquid-liquid extraction was optimized by using a suitable minimal medium during fermentation to reduce undesired interphase formation. A technical-scale production process was designed and evaluated by a life-cycle assessment (LCA). Different process chains and their specific environmental impact were examined. It was found that next to biomass supply, the fermentation had the biggest environmental impact. The present work underlines the need for multidisciplinary approaches to address the challenges associated with achieving sustainable production of microbial secondary metabolites. The results are discussed in the context of the challenges of microbial biosurfactant production using hydrophilic substrates on an industrial scale.

Anabela S. Lorenzetti, Tania Sierra, Claudia E. Domini et al.

Sensors • 2019

Disposable electrochemically reduced graphene oxide-based (ERGO) screen-printed electrodes (SPE) were developed for the determination of total tetracyclines as a sample screening approach. To this end, a selective adsorption-detection approach relied on adsorptive transfer stripping differential pulse voltammetry (AdTDPV) was devised, where the high adsorption capacity and the electrochemical properties of ERGO were simultaneously exploited. The approach was very simple, fast (6 min.), highly selective by combining the adsorptive and the electrochemical features of tetracyclines, and it used just 10 μL of the sample. The electrochemical sensor applicability was demonstrated in the analysis of environmental and food samples. The not-fully explored AdTDPV analytical possibilities on disposable nanostructured transducers become a new tool in food and environmental fields; drawing new horizons for "in-situ" analysis.

Naroa Uría, Erika Fiset, Miguel Aller Pellitero et al.

Environmental Science and Ecotechnology • 2020

Microbial biosensors can be an excellent alternative to classical methods for toxicity monitoring, which are time-consuming and not sensitive enough. However, bacteria typically connect to electrodes through biofilm formation, leading to problems due to lack of uniformity or long device production times. A suitable immobilisation technique can overcome these challenges. Still, they may respond more slowly than biofilm-based electrodes because bacteria gradually adapt to electron transfer during biofilm formation. In this study, we propose a controlled and reproducible way to fabricate bacteria-modified electrodes. The method consists of an immobilisation step using a cellulose matrix, followed by an electrode polarization in the presence of ferricyanide and glucose. Our process is short, reproducible and led us to obtain ready-to-use electrodes featuring a high-current response. An excellent shelf-life of the immobilised electrochemically active bacteria was demonstrated for up to one year. After an initial 50% activity loss in the first month, no further declines have been observed over the following 11 months. We implemented our bacteria-modified electrodes to fabricate a lateral flow platform for toxicity monitoring using formaldehyde (3%). Its addition led to a 59% current decrease approximately 20 min after the toxic input. The methods presented here offer the ability to develop a high sensitivity, easy to produce, and long shelf life bacteria-based toxicity detectors.

Mahmoud M. Berekaa

International Journal of Current Microbiology and Applied Sciences • 2016

During the last few decades there is growing interest for the use of nanoparticles in water and wastewater treatment technology, due to their distinctive physiochemical characteristics.This review outlines the conceivable opportunities regarding the interaction of nanoparticles with the biological systems during water and wastewater treatment processes.An overview on the recent advances in application of nanoparticles in biofouling prevention and disinfection is provided.Recent advances in nanoscience allow for development of nanosensors for biomonitoring and diagnostic purposes.Due to remarkable use of nanoparticles, wastewater treatment plants received considerable amount of NPs such as TiO 2 , ZnO, N 2 O, AgO, CuO, SiO 2 , Al 2 O 3 and CeO 2 .Toxic effects of nanoparticles on structural and physiological activity of various microbial communities including; nitrification, denitrification and phosphorus removal processes are critically reviewed.

Sara Monasterio Martinez, Mirella Di Lorenzo

Chemical Engineering Science • 2019

Ginevra Giangeri, Panagiotis Tsapekos, Maria Gaspari et al.

Environmental Science & Technology • 2023

It is known that the presence of sulfate decreases the methane yield in the anaerobic digestion systems. Sulfate-reducing bacteria can convert sulfate to hydrogen sulfide competing with methanogens for substrates such as H 2 and acetate. The present work aims to elucidate the microbial interactions in biogas production and assess the effectiveness of electron-conductive materials in restoring methane production after exposure to high sulfate concentrations. The addition of magnetite led to a higher methane content in the biogas and a sharp decrease in the level of hydrogen sulfide, indicating its beneficial effects. Furthermore, the rate of volatile fatty acid consumption increased, especially for butyrate, propionate, and acetate. Genome-centric metagenomics was performed to explore the main microbial interactions. The interaction between methanogens and sulfate-reducing bacteria was found to be both competitive and cooperative, depending on the methanogenic class. Microbial species assigned to the Methanosarcina genus increased in relative abundance after magnetite addition together with the butyrate oxidizing syntrophic partners, in particular belonging to the Syntrophomonas genus. Additionally, Ruminococcus sp. DTU98 and other species assigned to the Chloroflexi phylum were positively correlated to the presence of sulfate-reducing bacteria, suggesting DIET-based interactions. In conclusion, this study provides new insights into the application of magnetite to enhance the anaerobic digestion performance by removing hydrogen sulfide, fostering DIET-based syntrophic microbial interactions, and unraveling the intricate interplay of competitive and cooperative interactions between methanogens and sulfate-reducing bacteria, influenced by the specific methanogenic group.

Xu Zhang, Hongjie Shi, Ningjie Tan et al.

Bioresources and Bioprocessing • 2023

In modern societies, the accumulation of vast amounts of waste Li-ion batteries (WLIBs) is a grave concern. Bioleaching has great potential for the economic recovery of valuable metals from various electronic wastes. It has been successfully applied in mining on commercial scales. Bioleaching of WLIBs can not only recover valuable metals but also prevent environmental pollution. Many acidophilic microorganisms (APM) have been used in bioleaching of natural ores and urban mines. However, the activities of the growth and metabolism of APM are seriously inhibited by the high concentrations of heavy metal ions released by the bio-solubilization process, which slows down bioleaching over time. Only when the response mechanism of APM to harsh conditions is well understood, effective strategies to address this critical operational hurdle can be obtained. In this review, a multi-scale approach is used to summarize studies on the characteristics of bioleaching processes under metal ion stress. The response mechanisms of bacteria, including the mRNA expression levels of intracellular genes related to heavy metal ion resistance, are also reviewed. Alleviation of metal ion stress via addition of chemicals, such as spermine and glutathione is discussed. Monitoring using electrochemical characteristics of APM biofilms under metal ion stress is explored. In conclusion, effective engineering strategies can be proposed based on a deep understanding of the response mechanisms of APM to metal ion stress, which have been used to improve bioleaching efficiency effectively in lab tests. It is very important to engineer new bioleaching strains with high resistance to metal ions using gene editing and synthetic biotechnology in the near future.

Narcís Pous, Lluı́s Bañeras, Philippe F.-X. Corvini et al.

Environmental Science and Ecotechnology • 2023

It has been recently suggested that Alcaligenes use a previously unknown pathway to convert ammonium into dinitrogen gas (Dirammox) via hydroxylamine (NH 2 OH). This fact alone already implies a significant decrease in the aeration requirements for the process, but the process would still be dependent on external aeration. This work studied the potential use of a polarised electrode as an electron acceptor for ammonium oxidation using the recently described Alcaligenes strain HO-1 as a model heterotrophic nitrifier. Results indicated that Alcaligenes strain HO-1 requires aeration for metabolism, a requirement that cannot be replaced for a polarised electrode alone. However, concomitant elimination of succinate and ammonium was observed when operating a previously grown Alcaligenes strain HO-1 culture in the presence of a polarised electrode and without aeration. The usage of a polarised electrode together with aeration did not increase the succinate nor the nitrogen removal rates observed with aeration alone. However, current density generation was observed along a feeding batch test representing an electron share of 3% of the ammonium removed in the presence of aeration and 16% without aeration. Additional tests suggested that hydroxylamine oxidation to dinitrogen gas could have a relevant role in the electron discharge onto the anode. Therefore, the presence of a polarised electrode supported the metabolic functions of Alcaligenes strain HO-1 on the simultaneous oxidation of succinate and ammonium.

Dawn E. Holmes, Jinjie Zhou, Jessica A. Smith et al.

mLife • 2022

Direct interspecies electron transfer (DIET) may be most important in methanogenic environments, but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor. To better understand DIET with methanogens, the transcriptome of Geobacter metallireducens during DIET-based growth with G. sulfurreducens reducing fumarate was compared with G. metallireducens grown in coculture with diverse Methanosarcina . The transcriptome of G. metallireducens cocultured with G. sulfurreducens was significantly different from those with Methanosarcina . Furthermore, the transcriptome of G. metallireducens grown with Methanosarcina barkeri , which lacks outer-surface c -type cytochromes, differed from those of G. metallireducens cocultured with M. acetivorans or M. subterranea , which have an outer-surface c -type cytochrome that serves as an electrical connect for DIET. Differences in G. metallireducens expression patterns for genes involved in extracellular electron transfer were particularly notable. Cocultures with c -type cytochrome deletion mutant strains, ∆Gmet_0930, ∆Gmet_0557 and ∆Gmet_2896, never became established with G. sulfurreducens but adapted to grow with all three Methanosarcina . Two porin-cytochrome complexes, PccF and PccG, were important for DIET; however, PccG was more important for growth with Methanosarcina . Unlike cocultures with G. sulfurreducens and M. acetivorans , electrically conductive pili were not needed for growth with M. barkeri . Shewanella oneidensis , another electroactive microbe with abundant outer-surface c -type cytochromes, did not grow via DIET. The results demonstrate that the presence of outer-surface c -type cytochromes does not necessarily confer the capacity for DIET and emphasize the impact of the electron-accepting partner on the physiology of the electron-donating DIET partner.

Gary S. Caldwell, Pichaya In-na, Rachel Hart et al.

Energies • 2021

There is a groundswell of interest in applying phototrophic microorganisms, specifically microalgae and cyanobacteria, for biotechnology and ecosystem service applications. However, there are inherent challenges associated with conventional routes to their deployment (using ponds, raceways and photobioreactors) which are synonymous with suspension cultivation techniques. Cultivation as biofilms partly ameliorates these issues; however, based on the principles of process intensification, by taking a step beyond biofilms and exploiting nature inspired artificial cell immobilisation, new opportunities become available, particularly for applications requiring extensive deployment periods (e.g., carbon capture and wastewater bioremediation). We explore the rationale for, and approaches to immobilised cultivation, in particular the application of latex-based polymer immobilisation as living biocomposites. We discuss how biocomposites can be optimised at the design stage based on mass transfer limitations. Finally, we predict that biocomposites will have a defining role in realising the deployment of metabolically engineered organisms for real world applications that may tip the balance of risk towards their environmental deployment.

Murat Kuşcu, Ergin Dinc, Bilgesu A. Bilgin et al.

Proceedings of the IEEE • 2019

Inspired by nature, molecular communications (MC), i.e., the use of molecules to encode, transmit, and receive information, stands as the most promising communication paradigm to realize the nanonetworks. Even though there has been extensive theoretical research toward nanoscale MC, there are no examples of implemented nanoscale MC networks. The main reason for this lies in the peculiarities of nanoscale physics, challenges in nanoscale fabrication, and highly stochastic nature of the biochemical domain of envisioned nanonetwork applications. This mandates developing novel device architectures and communication methods compatible with MC constraints. To that end, various transmitter and receiver designs for MC have been proposed in the literature together with numerable modulation, coding, and detection techniques. However, these works fall into domains of a very wide spectrum of disciplines, including, but not limited to, information and communication theory, quantum physics, materials science, nanofabrication, physiology, and synthetic biology. Therefore, we believe it is imperative for the progress of the field that an organized exposition of cumulative knowledge on the subject matter can be compiled. Thus, to fill this gap, in this comprehensive survey, we review the existing literature on transmitter and receiver architectures toward realizing MC among nanomaterial-based nanomachines and/or biological entities and provide a complete overview of modulation, coding, and detection techniques employed for MC. Moreover, we identify the most significant shortcomings and challenges in all these research areas and propose potential solutions to overcome some of them.

Kensuke Igarashi, Eijiro Miyako, Souichiro Kato

Frontiers in Microbiology • 2020

Conductive materials are known to promote direct interspecies electron transfer (DIET) by electrically bridging microbial cells. Previous studies have suggested that supplementation of graphene oxide (GO) based materials, including GO, and reduced GO (rGO), to anaerobic microbial communities, can promote DIET. This promotion mechanism is thought to be involved in electron transfer via rGO or biologically formed rGO. However, concrete evidence that rGO directly promotes DIET is still lacking. Furthermore, the effects of the physicochemical properties of GO-based materials on DIET efficiency have not been elucidated. In the current work, we investigated whether chemically and biologically reduced GO compounds can promote DIET in a defined model coculture system, and also examined the effects of surface properties on DIET-promoting efficiency. Supplementation of GO to a defined DIET coculture composed of an ethanol-oxidizing electron producer Geobacter metallireducens and a methane-producing electron consumer Methanosarcina barkeri promoted methane production from ethanol. X-ray photoelectron spectroscopy revealed that GO was reduced to rGO during cultivation by G. metallireducens activity. The stoichiometry of methane production from ethanol and the isotope labeling experiments clearly showed that biologically reduced GO induced DIET-mediated syntrophic methanogenesis. We also assessed the DIET-promoting efficiency of chemically reduced GO and its derivatives, including hydrophilic amine-functionalized rGO (rGO-NH 2 ) and hydrophobic octadecylamine-functionalized rGO (rGO-ODA). While all tested rGO derivatives induced DIET, the rGO derivatives with higher hydrophilicity showed higher DIET-promoting efficiency. Optical microscope observation revealed that microbial cells, in particular, G. metallireducens , more quickly adhered to more hydrophilic GO-based materials. The superior ability to recruit microbial cells is a critical feature of the higher DIET-promoting efficiency of the hydrophilic materials. This study demonstrates that biologically and chemically reduced GO can promote DIET-mediated syntrophic methanogenesis. Our results also suggested that the surface hydrophilicity (i.e., affinity toward microbial cells) is one of the important determinants of the DIET-promoting efficiencies. These observations will provide useful guidance for the selection of conductive particles for the improvement of methanogenesis in anaerobic digesters.

Boyu Jia, Siyu Zhang, Lijuan Zhang et al.

ACS ES&T Engineering • 2025

Intermittent electrostimulation plays a crucial role in the microbial processing of toxic vanadate [V(V)], influencing microbial metabolism, extracellular polymeric substances (EPS) secretion, and population dynamics. However, its influence on these aspects, particularly regarding microbial metabolism pathways and electron transfer mechanisms mediated by microbial metabolic activities, remains inadequately elucidated. Herein, electric-stimulated reactors incorporating different electrostimulation modes (continuous, intermittent, and none) were constructed and operated for over 150 days, with or without electroactive bacteria (EAB), to evaluate the V(V) reduction and immobilization. The bioreactor employing intermittent electrostimulation with an EAB-enriched inoculum (IP/AS-EB) showed rapid and efficient startup, achieving stable performance with significantly higher V(V) reduction efficiency (RE: 95.8%) and immobilization efficiency (IE: 93.1%) compared to those with continuous electrostimulation (CP/AS-EB: RE, 89.4%; IE, 68.9%) and control groups (AS-EB Ctrl: RE, 65.1%; IE, 52.5%). The reduction product included amorphous VO(OH)2 and CaV2(PO4)2(OH)4·3H2O, both occurring either intracellularly or extracellularly. Increased activity in the IP/AS-EB reactor results from enhanced targeted microbial and EPS, significantly enriching species like Geobacter, Petrimonas, Rhodococcus, Sedimentibacter, and Christensenellaceae_R-7_group. Total EPS, particularly humic-like substances and proteins, was significantly higher in IP/AS and IP/AS-EB reactors than in CP/AS, CP/AS-EB, and control groups. Besides, proteomic analysis further indicated that intermittent electrostimulation enriched bacteria capable of producing significant amounts of humic substances, redox-active proteins, and electron transfer proteins. These components, along with endogenous electron mediators identified via metabolomic analyses, effectively facilitated electron transfer within respiratory chains and interspecies. This study elucidates how intermittent electrostimulation boosts specific microbial communities and their metabolic pathways, offering insights into optimizing V(V) reduction processes and broadening their potential applications in heavy metal bioremediation.

Alexandre Augusto P. Selva Filho, Attílio Converti, Rita de Cássia F. Soares da Silva et al.

Energies • 2023

Fuel and oil spills during the exploration, refining, and distribution of oil and petrochemicals are primarily responsible for the accumulation of organic pollutants in the environment. The reduction in contamination caused by hydrocarbons, heavy metals, oily effluents, and particulate matter generated by industrial activities and the efficient recovery of oil at great depths in an environmentally friendly way pose a challenge, as recovery and cleaning processes require the direct application of surface-active agents, detergents, degreasers, or solvents, often generating other environmental problems due to the toxicity and accumulation of these substances. Thus, the application of natural surface-active agents is an attractive solution. Due to their amphipathic structures, microbial surfactants solubilize oil through the formation of small aggregates (micelles) that disperse in water, with numerous applications in the petroleum industry. Biosurfactants have proven their usefulness in solubilizing oil trapped in rock, which is a prerequisite for enhanced oil recovery (EOR). Biosurfactants are also important biotechnological agents in anti-corrosion processes, preventing incrustations and the formation of biofilms on metallic surfaces, and are used in formulations of emulsifiers/demulsifiers, facilitate the transport of heavy oil through pipelines, and have other innovative applications in the oil industry. The use of natural surfactants can reduce the generation of pollutants from the use of synthetic detergents or chemical solvents without sacrificing economic gains for the oil industry. Therefore, investments in biotechnological processes are essential. It is predicted that, in the not-too-distant future, natural surfactants will become viable from an economic standpoint and dominate the world market. The application of biosurfactants in these settings would lead to industrial growth and environmental sustainability. The main goal of this paper is to provide an overview of diverse applications of biosurfactants on environmental remediation, petroleum biotechnology, and the oil industry through a scientific literature review.

Pei Sean Goh, Woei Jye Lau, Ahmad Fauzi Ismail et al.

Water • 2022

Pesticides have been identified as major contaminants of various waterways. Being classified as potential endocrine disrupting compounds, pesticides in aqueous system are highly hazardous to aquatic organisms and the ecosystem. The treatment of pesticide-containing wastewater can be performed through several means, but a wastewater treatment strategy which emphasizes both treatment efficiency and sustainability is a necessity of current time. In this context, bioremediation has been increasingly promoted as an alternative technique for the remediation of diverse pollutants. Particularly, bioremediation which involves the utilization of microalgae for the removal or conversion of pesticides to the harmless or less harmful compounds is becoming a trend. Exploiting microalgae as a tool for wastewater treatment presents multiple advantages over conventional treatment technologies, which include an opportunity to simultaneously treat pesticide-containing wastewater and nutrient recovery for microalgae cultivation as well as less formation of toxic sludge. This review discusses the roles of microalgae in mitigating pesticide pollution issue, while offering an opportunity for nutrient recovery from various wastewater sources. Based on the current laboratory studies, the use of microalgae bioremediation as a promising strategy for pesticide treatment has been rationalized. The establishment of more pilot scale studies is highly encouraged to further facilitate the implementation of this treatment approach for practical application.

Jing Xu, Bo Wang, Wenhui Zhang et al.

AMB Express • 2021

p-Nitrophenol (PNP) is an important environmental pollutant and can causes significant environmental and health risks. Compared with the traditional methods, biodegradation is a useful one to completely remove the harmful pollutants from the environment. Here, an engineered strain was first constructed by introducing PNP biodegradation pathway via the hydroquinone (HQ) pathway into Escherichia coli. In the engineered strain BL-PNP, PNP was completely degraded to β-ketoadipate and subsequently enter the metabolites of multiple anabolic pathways. The high tolerance and rapid degradation ability to PNP enable the engineered strain to have the potential to degrade toxic substances. The engineered strain created in this study can be used as a functional strain for bioremediation of PNP and potential toxic intermediates, and the method of assembling aromatic hydrocarbons metabolic pathway can be used to eradicate nitroaromatic pollutants in the environment.

Ahmed Barhoum, Selma Hamimed, Hamda Slimi et al.

Trends in Environmental Analytical Chemistry • 2023

In recent decades, much attention has been paid to using nanomaterials in the development of highly-sensitive sensors for environmental monitoring. This review describes how nanomaterials are being used to develop electrochemical sensing platforms for environmental analysis (air pollution, water quality, soil nutrients, and soil pathogens). In particular, we discuss the use of nanofabrication techniques (e.g., monolayer self-assembly, drop-casting, molecular imprinting, electrodeposition, in situ polymerization, hydrogenation, and 3D printing) in the fabrication of high-sensitive electrodes is addressed. The potential use of carbon, organic, inorganic, and hybrid nanomaterials in electrochemical sensing platforms and to enable automation, real-time detection, and multiplexed test development are also addressed. Recent applications of mobile, disposable, wearable, implantable, and self-powered electrochemical sensors for monitoring ions, particles, compounds, nutrients, microorganisms, and contaminants in real environmental samples are covered. Finally, the opportunities and challenges in nanofabrication high-performance electrochemical sensors and optimizing their performance in testing real samples are highlighted. All data used are only avilable in this article

Meshack Imologie Simeon, Felix Uzochukwu Asoiro, Mohamad Aliyu et al.

International Journal of Energy Research • 2020

Microbial fuel cells (MFCs) are bio-electrochemical devices that use microbial metabolic processes to convert organic substances into electricity with high efficiency. In this study, the performance of a soil-based MFC using urine as a substrate was assessed using polarization and power density curves. A single-chamber, membrane-less MFC with a carbon-felt air cathode and a carbon-felt anode fully buried in biologically active soil was constructed to examine the impact of urine treatment on the performance of the MFC. The peak power of the urine-treated MFC was 124.16 mW/m2 and was obtained 24 hours after the first urine addition; a control MFC showed a value of 65.40 mW/m2 in the same period. The treated MFC produced an average power of 70.75 mW/m2 up to 21 days after the initial urine addition; the control MFC gave an average value of 4.508 mW/m2 over the same period. The average internal resistances of the treated MFC and the control MFC obtained after the initial treatment were 269.94 and 1627.89 Ω, respectively. This study demonstrates the potential of human urine to reduce internal losses in soil MFCs and to provide stable power densities across various external resistors. These results are propitious for future advancements in soil MFCs for power generation utilizing human urine (a readily available source of nutrients) as a substrate.

Peng Ouyang, Mathiyazhagan Narayanan, Xiaojun Shi et al.

Biochar • 2023

Abstract Due to anthropogenic activities, heavy metal (HM) pollution in soils has increased, resulting in severe ecological problems and posing a constant threat to human health. Among various remediation methods, bacterial remediation is a relatively clean, efficient, and minimally negative approach. However, bacterial agents face multiple environmental stresses, making them challenging to achieve long-lasting and stable restoration effects. To address this issue, supportive organic substances such as biochar can be added to the soil with bacteria. According to bibliometric studies, integrating biochar and bacteria is extensively researched and widely used for HM-contaminated soil remediation. By integrating biochar and bacteria, heavy metals in the soil can be remediated, and soil conditions can be improved over time. Bacteria can also better promote plant growth or contribute effectively to phytoremediation processes when assisted by biochar. However, the remediation agents integrating biochar and bacteria are still some distance away from large-scale use because of their high cost and possible environmental problems. Therefore, further discussion on the interaction between biochar and bacteria and the integration approach, along with their remediation efficiency and environmental friendliness, is needed to achieve sustainable remediation of HM-contaminated soils by integrating biochar and bacteria. This paper discusses the potential mechanisms of biochar-bacteria-metal interactions, current advancements in biochar-bacteria combinations for HM-contaminated soil treatment, and their application in sustainable remediation, analyzes the interaction between biochar and bacteria and compares the remediation effect of different ways and feedstocks to integrate biochar and bacteria. Finally, future directions of biochar-bacteria combinations are presented, along with evidence and strategies for improving their commercialization and implementation. Graphical Abstract

Tazien Rashid, Danish Iqbal, Abu Hazafa et al.

Journal of environmental chemical engineering • 2020

Marco Resitano, Matteo Tucci, Ghada Sellami et al.

Chemical Engineering Journal Advances • 2025

• MNPs enhanced electrogenic acetate oxidation in sand packed BES up to 2.2-fold • Current generation increased up to 2.6 fold in presence of MNPs • MNPs enabled formation of conductive network composed of electroactive bacteria • The conductive network spanned over 1.8 cm away from the anodic surface • Higher abundance of electroactive microorganisms in the packing material with MNPs Electroactive biofilms (EABs) play a pivotal role in bioelectrochemical systems (BESs), enabling microbial respiration on solid electrodes. However, the spatial limitations of electron transfer often constrain biofilm development and performance, particularly in porous, heterogeneous environments. In this study, we investigated the effect of magnetite nanoparticles on the formation and electrochemical behavior of EABs in continuous-flow reactors packed with sand or a sand–magnetite mixture. Chronoamperometry revealed that the magnetite-amended reactor produced significantly higher electric currents (up to 2.6-fold) alongside increased acetate removal rates (up to 2.2-fold) and prolonged electron discharge following substrate depletion, indicative of enhanced electron storage and release. Cyclic voltammetry confirmed greater bioelectrocatalytic activity and revealed an over fourfold increase in anode capacitance, suggesting the development of a more extensive and electrochemically active biofilm. Spatial profiling with a titanium probe demonstrated that electrocatalytic activity extended up to 1.8 centimeters from the anode only in the presence of magnetite, consistent with the formation of a biologically mediated conductive network beyond the electrode surface. In line with these evidences, a higher abundance of electroactive microorganisms was detected within the packing material surrounding the anode. These findings provide the first experimental support for the concept of Diffuse Electro-Conductive Zones (DECZs) and suggest a viable strategy to extend the radius of electrode influence in soil BESs. This approach may enhance the effectiveness of in situ bioremediation technologies by enabling mesoscale redox connectivity in complex subsurface environments.

Lean Zhou, Yuting Zeng, Chong‐Yu Xu et al.

The Science of The Total Environment • 2024

Bin Wang, Ketong Li, Jingmei Sun

Journal of Water Process Engineering • 2025

Fengbin Wang, Khawla Mustafa, Victor Suciu et al.

Nature Microbiology • 2022