Bill Yen, Laura Jaliff, Louis Alberto Gutierrez et al.

Proceedings of the ACM on Interactive Mobile Wearable and Ubiquitous Technologies • 2023

Human-caused climate degradation and the explosion of electronic waste have pushed the computing community to explore fundamental alternatives to the current battery-powered, over-provisioned ubiquitous computing devices that need constant replacement and recharging. Soil Microbial Fuel Cells (SMFCs) offer promise as a renewable energy source that is biocompatible and viable in difficult environments where traditional batteries and solar panels fall short. However, SMFC development is in its infancy, and challenges like robustness to environmental factors and low power output stymie efforts to implement real-world applications in terrestrial environments. This work details a 2-year iterative process that uncovers barriers to practical SMFC design for powering electronics, which we address through a mechanistic understanding of SMFC theory from the literature. We present nine months of deployment data gathered from four SMFC experiments exploring cell geometries, resulting in an improved SMFC that generates power across a wider soil moisture range. From these experiments, we extracted key lessons and a testing framework, assessed SMFC's field performance, contextualized improvements with emerging and existing computing systems, and demonstrated the improved SMFC powering a wireless sensor for soil moisture and touch sensing. We contribute our data, methodology, and designs to establish the foundation for a sustainable, soil-powered future.

О. М. Мороз, S. О. Hnatush, O. Maslovska et al.

Biosystems Diversity • 2020

Technogenic reservoirs mainly contain several possible electron acceptors of anaerobic respiration, many of which are dangerous to the environment. The succession of their reduction (and thus detoxification) by sulfur reducing bacteria is not yet sufficiently studied. We investigated the influence of ferrum (III) citrate, present in the cultivation medium, on the reduction of sulfur, nitrate and nitrite ions by sulfur reducing bacteria Desulfuromonas acetoxidans IMV B-7384, Desulfuromonas sp. Yavor-5 and Desulfuromonas sp. Yavor-7, isolated from Yavorivske Lake. It was established that ferrum (III) citrate inhibits the biomass accumulation and hydrogen sulfide production by bacteria of Desulfuromonas sp. after simultaneous addition to the medium of 3.47 mM S0 and 1.74–10.41 mM ferrum (III) citrate, as compared with growth and hydrogen sulfide production by bacteria in the medium with only sulfur. In the medium with the same initial content (3.47 mM) S0 and ferrum (III) citrate bacteria produced ferrum (II) ions at concentrations 3.5–3.9 times higher than that of hydrogen sulfide. Ferrum (III) citrate inhibits the biomass accumulation, the nitrate or nitrite ions reduction and the ammonium ions production by bacteria of Desulfuromonas sp. after simultaneous addition to the medium of 3.47 mM NaNO3 or NaNO2 and 1.74–10.41 mM ferrum (III) citrate. In the medium with the same initial content (3.47 mM) NaNO3 and ferrum (III) citrate, bacteria produced ammonium ions at concentrations in 1.1 times higher than that of ferrum (II) ions. In the medium with the same initial content (3.47 mM) NaNO2 and ferrum (III) citrate, bacteria reduced 1.5–1.6 times more ferrum (III) than nitrite ions with production of ferrum (II) ions at concentrations 1.7 times higher than that of ammonium ions. The process of nitrate reduction carried out by bacteria of Desulfuromonas genus was less sensitive to the negative influence of ferrum (III) citrate, compared to the process of nitrite ions reduction. When the reduction of nitrate ions by bacteria in the presence of 1.74–10.41 mM ferrum (III) citrate decreased by 1.4–2.2 times, then the reduction of nitrite ions decreased by 1.8–3.2 times compared to their reduction in media with only NaNO3 or NaNO2, respectively. Although the reduction of ferrum (III) by cells in media with 3.47 mM S0, NaNO3 or NaNO2 and 1.74–10.41 mM ferrum (III) citrate decreased by 1.6–2.7, 1.6–2.7 and 1.1–2.2 times, respectively, compared to the reduction in medium with only ferrum (III) citrate, the investigated strains of bacteria were resistant to high concentrations of trivalent ferrum compounds and can therefore can be used in technologies of complex purification of environments polluted by heavy metal and nitrogen compounds.

Li Xie, Naoko Yoshida, Lingyu Meng

Microorganisms • 2023

Graphene oxide (GO), a chemically oxidized sheet of graphite, has been used as a conductive carbon carrier of microbes to boost various bioelectrochemical reactions. However, the types of microbes that can reduce GO have rarely been investigated. In this study, a strain of GO-reducing bacteria, named NIT-SL11, which was obtained from a hydrogel of microbially reduced GO and anaerobic sludge that converts sewage to electricity, was phylogenically identified as a novel strain of Geotalea uraniireducens . Considering the current lack of information on the electrogenic ability of the bacterium and its physicochemical and chemotaxonomic characteristics, the polyphasic characterization of the Geotalea uraniireducens strain NIT-SL11 was performed. NIT-SL11 utilized various organic acids, such as lactate, benzoate, and formate, as electron donors and exhibited respiration using GO, electrodes, fumarate, and malate. The strain contained C16:1ω7c and C16:0 as the major fatty acids and MK-8 and 9 as the major respiratory quinones. The complete genome of NIT-SL11 was 4.7 Mbp in size with a G+C content of 60.9%, and it encoded 80 putative c-type cytochromes and 23 type IV pili-related proteins. The possible extracellular electron transfer (EET) pathways of the strain were the porin-cytochrome (Pcc) EET pathway and type IV pili-based pathway.

Ginevra Giangeri, Panagiotis Tsapekos, Maria Gaspari et al.

Applied Energy • 2024

Bioaugmentation has been recognized as a key strategy to improve the anaerobic digestion efficiency in organic waste treatment. Methanosarcina barkeri possesses direct interspecies electron transfer capability, a characteristic that allows it to outcompete other unwanted species such as sulfate-reducing bacteria. This study investigated the effects of bioaugmentation with Methanosarcina barkeri DSM800 on two continuous-stirred tank reactors fed with a sulfate-rich feedstock. One of the two reactors was supplemented with magnetite to facilitate direct interspecies electron transfer. Time series quantitative polymerase chain reactions were performed to evaluate the absolute abundance of crucial species, including the augmented Methanosarcina. Results showed increased and stabilized methane production of 22% and 21% in the reactor amended with magnetite and in the control reactor, respectively. Moreover, volatile fatty acids were almost completely consumed in the magnetite-supplemented reactor. The quantitative polymerase chain reaction was used to analyze the abundance of targeted species in response to bioaugmentation. Specifically, Methanosarcina barkeri was not retained in either reactor after one hydraulic retention time. Direct interspecies electron transfer-associated microorganisms showed opposite trends in the two reactors, highlighting the different interactions with Methanosarcina barkeri in the presence and absence of magnetite. Sulfate-reducing bacteria following the dissimilatory sulfate reduction pathway exhibited an opposite behavior in the reactor amended with magnetite, in contrast to those employing the assimilatory sulfate reduction pathway. Overall, the study demonstrated that bioaugmentation with exogenous archaea can considerably alter the microbial community, but the introduced species is not able to establish itself in a stable microbiome. In addition, the strategy could be further tested to control H2S production in real-world waste treatment scenarios. Quantitative polymerase chain reaction proved to be a useful tool for monitoring changes in the absolute abundance of microorganisms in bioreactors, implementing effective monitoring and control strategies to improve overall system performance.

Wenbing Tan, Lei Wang, Hanxia Yu et al.

Materials • 2019

Biochar is widely used in the environmental-protection field. This study presents the first investigation of the mechanism of biochar prepared using iron (Fe)-rich biomass and its impact on the reductive removals of Orange G dye by Shewanella oneidensis MR-1. The results show that biochars significantly accelerated electron transfer from cells to Orange G and thus stimulated reductive removal rate to 72-97%. Both the conductive domains and the charging and discharging of surface functional groups in biochars played crucial roles in the microbial reduction of Orange G to aniline. A high Fe content of the precursor significantly enhanced the conductor performance of the produced biochar and thus enabled the biochar to have a higher reductive removal rate of Orange G (97%) compared to the biochar prepared using low-Fe precursor (75%), but did not promote the charging and discharging capacity of the produced biochar. This study can prompt the search for natural biomass with high Fe content to confer the produced biochar with wide-ranging applications in stimulating the microbial reduction of redox-active pollutants.

Stéfano Mocali, Eiko E. Kuramae, George A. Kowalchuk et al.

Frontiers in Environmental Science • 2020

The quality of the vineyard soils has a direct impact on grapes and wine quality and represents a key component of the “Terroir concept”. However, information on the impact of soil microbiota on grapevine plants and wine quality are generally lacking. In fact, over the last few years most of the attempts made to correlate soil microbial communities and wine quality were limited by overlooking both the functional traits of soil microbiota and the spatial variability of vineyards soils. In this work, we used a functional gene microarray approach (GeoChip) and soil enzymatic analyses to assess the soil microbial community functional potential related to the different wine quality. In order to minimize the soil variability, this work was conducted at a “within-vineyard” scale, comparing two similar soils (BRO11 and BRO12) previously identified with respect to pedological and hydrological properties within a single vineyard in Central Tuscany and that yielded highly contrasting wine quality upon cultivation of the same Sangiovese cultivar (BRO12 exhibited the higher quality). Our results showed an enrichment of Actinobacteria in BRO12, whereas Alfa- and Gamma-Proteobacteria were more abundant in BRO11, where an enrichment of bacteria involved in N fixation and denitrification occurred. Overall, the GeoChip output revealed a greater biological activity in BRO11 but a significant enrichment of sulfur-oxidation genes in BRO12 compared to BRO11 soil, where a higher level of arylsulfatase activity was also detected. Moreover, the low content of sulfates and available nitrogen found in BRO12 suggested that the reduced availability of sulfates for vine plants might limit the reduced glutathione (GSH) synthesis, which plays an important role in aroma protection in musts and wines. In conclusion, in addition to nitrogen availability, we propose that soil microbial sulfur metabolism may also play a key role in shaping plant physiology, grapes and wine quality. Overall, these results support the existence of a “microbial functional terroir” effect as a determining factor in vineyard-scale variation among wine grapes.

Diyana S. Sokolova, Ekaterina M. Semenova, Denis S. Grouzdev et al.

Microorganisms • 2021

Application of seawater for secondary oil recovery stimulates the development of sulfidogenic bacteria in the oil field leading to microbially influenced corrosion of steel equipment, oil souring, and environmental issues. The aim of this work was to investigate potential sulfide producers in the high-temperature Uzen oil field (Republic of Kazakhstan) exploited with seawater flooding and the possibility of suppressing growth of sulfidogens in both planktonic and biofilm forms. Approaches used in the study included 16S rRNA and dsrAB gene sequencing, scanning electron microscopy, and culture-based techniques. Thermophilic hydrogenotrophic methanogens of the genus Methanothermococcus (phylum Euryarchaeota) predominated in water from the zone not affected by seawater flooding. Methanogens were accompanied by fermentative bacteria of the genera Thermovirga , Defliviitoga , Geotoga , and Thermosipho (phylum Thermotogae), which are potential thiosulfate- or/and sulfur-reducers. In the sulfate- and sulfide-rich formation water, the share of Desulfonauticus sulfate-reducing bacteria (SRB) increased. Thermodesulforhabdus , Thermodesulfobacterium , Desulfotomaculum , Desulfovibrio , and Desulfoglaeba were also detected. Mesophilic denitrifying bacteria of the genera Marinobacter , Halomonas , and Pelobacter inhabited the near-bottom zone of injection wells. Nitrate did not suppress sulfidogenesis in mesophilic enrichments because denitrifiers reduced nitrate to dinitrogen; however, thermophilic denitrifiers produced nitrite, an inhibitor of SRB. Enrichments and a pure culture Desulfovibrio alaskensis Kaz19 formed biofilms highly resistant to biocides. Our results suggest that seawater injection and temperature of the environment determine the composition and functional activity of prokaryotes in the Uzen oil field.

O. Maslovska, S. Komplikevych, S. О. Hnatush

Studia Biologica • 2023

Microorganisms are exposed to reactive oxygen species (ROS) that are formed in various ways, in particular, as a result of respiration or other intracellular processes, during metal-catalyzed Fenton reactions, as a result of the action of UV- and X-radiation, under the influence of some antimicrobial drugs, or during the host immune oxidative-burst response against infection agents. In this review, we take a look at the mechanisms of microbial cell damage, including damage of lipids and proteins. Lipid peroxidation (LPO) is one of the main molecular mechanisms involved in oxidative damage to cellular structures. A variety of products are formed during LPO reactions: alkoxyl radicals, peroxyl radicals, hydroperoxides, diene conjugates, carbonyl compounds, aldehyde adducts with biopolymers, alcohols, esters, etc. These products include cytotoxic and highly reactive compounds. Free radical reactions of protein damage occur via hydrogen atom abstraction from α-carbon or SH-, NH2-groups of aminoacids and electron abstraction from nucleophile centers of proteins resulting in the fragmentation of proteins, their denaturation and the formation of amino acid radicals. Bacteria show a significant adaptive potential to the influence of stress agents, including ROS. We summarized the data on bacterial antioxidant protection, ROS redox sensors, and regulators of bacterial cell response to ROS exposure, focusing on the features of anaerobic microorganisms, as their responses to the oxidative damage are the least studied, and many problems remain unsolved. This review contains information about changes in fatty acid composition of lipids of the plasma membrane to maintain the necessary fluidity, and, thus, counteract the effects of various stressing agents, including ROS. The main modifications of the fatty acid composition of lipids important for the regulation of membrane fluidity are described, in particular, via changes in the degree of lipid saturation, cis/trans isomerization, and synthesis of cyclopropane fatty acids.

Laura T. Wey, Evan Indigo Wroe, Viktor Sadilek et al.

Electrochimica Acta • 2024

Photosynthetic microorganisms, including algae and cyanobacteria, export electrons in a light-stimulated phenomenon called ‘exoelectrogenesis’. However, the route(s) by which electrons reach an external electrode from the cell remain(s) unclear. For the model cyanobacterium Synechocystis sp. PCC 6803, it has been established that electron transfer does not depend on direct extracellular electron transfer by type IV pili. However, the role of the exopolysaccharide matrix in which cells are embedded has not been investigated. We show that a Synechocystis mutant with substantially reduced exopolysaccharide production has a four-fold greater photocurrent than wild-type cells. This increase is due in part to increased adhesion of exopolysaccharide-deficient cells to electrodes. Stirred system experiments reveal that a substantial portion of the photocurrent depends on an endogenous diffusible electron mediator, supporting indirect extracellular electron transfer as the bioelectrochemical mechanism of exoelectrogenesis. These findings will be important in harnessing exoelectrogenesis for sustainable electricity generation in biophotovoltaic devices.

D.G. Jacobs, Leonard Owino Kachienga, Mpumelelo Casper Rikhotso et al.

Frontiers in Energy Research • 2024

Developing countries facing population growth and increased energy demand present simultaneous challenges regarding wastewater treatment and electricity supply. Constructed wetland-microbial fuel cells (CW-MFCs) offer a dual solution to the challenges of insufficient electricity and wastewater treatment by integrating indigenous plant species. CW-MFCs provide sustainable power generation and wastewater treatment. This approach can enhance sustainability and foster a circular economy by utilising plant-derived byproducts as an added product. Current research indicates various novel designs for effective wastewater treatment and potential power generation. Future studies focusing on rural settings and upscaling operations can apply advanced techniques like mass spectrophotometry and metagenomics to refine the technology for grid use. Developing CW-MFC technology will catapult the idea of developing a robust strategy for addressing power supply and sanitation issues in developing regions. This will also aid in continuous research into system optimisation and microbial communities, aiding long-term viability.

Yidan Zhang, Edward J. O’Loughlin, S Park et al.

The Science of The Total Environment • 2023

Praveena Gangadharan, Indumathi M. Nambi

Sustainable Environment Research • 2020

Abstract The study investigates the performance of Cu 2+ as dissolved cathodic electron-shuttle mediator (dcESM) for simultaneous Cr 6+ reduction and electricity generation in a microbial fuel cell (MFC) at pH 2 and 4 conditions. The dcESM behavior of Cu 2+ on carbon cloth (CC) catalyzes the reduction of Cr 6+ into Cr 3+ at pH 2 by undergoing redox reactions. However, at pH 4, a simultaneous reduction of Cu 2+ and Cr 6+ was observed. Cyclic voltammetry studies were performed at pH 2 and 4 to probe the dcESM behavior of Cu 2+ for Cr 6+ reduction on CC electrode. Also, at pH 2, increasing the concentration of Cu 2+ from 50 to 500 mg L − 1 favors the Cr 6+ reduction by reducing the reaction time from 108 to 48 h and improving the current production from 3.9 to 6.2 mA m − 2 , respectively. Nevertheless, at pH 4, the efficacy of Cr 6+ reduction and electricity generation from MFC is decreased from 63 to 18% and 4.4 to 1.1 mA m − 2 , respectively, by increasing the Cu 2+ concentration from 50 to 500 mg L − 1 . Furthermore, the performance of dcESM behavior of Cu 2+ was explored on carbon felt (CF) and platinum (Pt) electrodes, and compare the results with CC. In MFC, at pH 2, with an initial concentration of 100 mg L − 1 , the reduction of Cr 6+ in 60 h is 9.6 mg L − 1 for CC, 0.2 mg L − 1 for CF, and 51.3 mg L − 1 for Pt cathodes. The reduction of Cr 6+ (initial concentration of 100 mg L − 1 ) at pH 4 in 120 h is 44.7 mg L − 1 for CC, 32.1 mg L − 1 for CF, and 70.9 mg L − 1 for Pt cathodes. Maximum power densities of 1659, 1509, and 1284 mW m − 2 were achieved when CF, CC, and Pt, respectively were employed as cathodes in the MFC.

Duaa R. Saad, Ziad T. Alismaeel, Ali H. Abbar

Journal of Engineering • 2020

In this research, the removal of cadmium (Cd) from simulated wastewater was investigated by using a fixed bed bio-electrochemical reactor. The effects of the main controlling factors on the performance of the removal process such as applied cell voltage, initial Cd concentration, pH of the catholyte, and the mesh number of the cathode were investigated. The results showed that the applied cell voltage had the main impact on the removal efficiency of cadmium where increasing the applied voltage led to higher removal efficiency. Meanwhile increasing the applied voltage was found to be given lower current efficiency and higher energy consumption. No significant effect of initial Cd concentration on the removal efficiency of cadmium but increasing the initial concentration would be given higher current efficiency and lower energy consumption. The results established that using a pH value lower than three results in a sharp decrease in the removal efficiency as well as using a pH value higher than seven results in decreasing the removal efficiency. Using a mesh number higher than 30 gave a lower removal efficiency. The best operating conditions were found to be an applied potential of 1.8 V, an initial Cd concentration of 125 ppm, and a pH of 7. Under these operating conditions with the using a stack of stainless with mesh number 30 as a packed bed cathode, a complete removal efficiency of Cd(100%) was obtained at a current efficiency of 83.57% and energy consumption of 0.57 kWh/kg Cd.

Naoufel Haddour, Yamina Mounia Azri

Electroanalysis • 2022

Abstract In recent years, there have been advancements in the development of bacterial electrochemical sensors for toxicity monitoring, especially through utilization of electroactive bacteria. Accordingly, this mini review summarizes the recent advances in the design of bacterial‐based electrochemical sensors with a specific discussion of main methodologies used for preparation of bioelectrodes based on electroactive bacteria. Additionally, current trends in the design of efficient and high performing bacterial electrochemical sensors for toxicity monitoring are presented. An overview of the most relevant findings and challenges of this technology for practical are provided and might serve as a general outlook for planning further research.

Ghada Mohamed Aleid, Anoud Saud Alshammari, Asma D. Alomari et al.

International Journal of Chemical Engineering • 2023

A potential and developing green technology for producing renewable energy and treating wastewater is the microbial fuel cell (MFC). Despite several advancements, there are still several serious problems with this approach. In the present work, we addressed the problem of the organic substrate in MFC, which is necessary for the degradation of metal ions in conjunction with the production of energy. The utilization of fruit waste as a carbon source was strongly suggested in earlier research. Hence, the mango peel was used as a substrate in the current study. Within 25 days of operation, a 102-mV voltage was achieved in 13 days, while the degradation efficiency of Cr3+ was 69.21%, Co2+ was 72%, and Ni2+ was 70.11%. The procedure is carried out in the batch mode, and there is no continuous feeding of the organic substrate. In addition, a detailed explanation of the hypothesized mechanism for this investigation is provided, which focuses on the process of metal ion degradation. Lastly, future and concluding remarks are also enclosed.

Syaifullah Muhammad, Esam Bashir Yahya, H. P. S. Abdul Khalil et al.

Agriculture • 2023

The global demand for clean water has become increasingly important in the past decade as a result of the growing world population, civilization, and the increase in sources of contaminations. Aerogels are an exceptional form of porous materials with extraordinary unique properties. The aerogel has been fabricated from different inorganic and organic materials and incorporated with a variety of novel compounds for specific applications and to enhance its performance in the desired application. Activated carbon is well known for its water-pollutant adsorption, it has been prepared from several organic materials including agricultural wastes and used to treat water from organic dyes, heavy metals, oils, and toxic chemicals. However, as a powder form, activated carbon must be incorporated either into a filter or undergo a post-treatment step to remove the adsorbent from treated water. This review highlighted the development of agricultural waste-based carbon and activated carbon loaded nano-structured aerogels. A review of the types of aerogels and the properties based on the precursor materials was conducted to extensively discuss the potential use of agricultural waste-based carbon and activated carbon loaded nano-structured aerogels in wastewater treatment applications. We also discussed the challenges and future prospects of carbon and activated carbon nano-structured aerogels for wastewater treatment applications.

Yaci Liu, Mengtuo Wen, Lin Wu et al.

Applied Sciences • 2022

Roxarsone (ROX) is used extensively in the broiler chicken industry, and most is excreted in poultry litter. ROX degradation produces inorganic arsenic, which causes arsenic contamination of soil and aquatic environment. Furthermore, elevated arsenic concentrations are found in livers of chickens fed ROX. Microorganisms, light, and ions are the main factors that promote ROX degradation in the environment. The adsorption of ROX on different substances and its influencing factors have also been studied extensively. Additionally, the remediation method, combining adsorption and degradation, can effectively restore ROX contamination. Based on this, the review reports the ecological hazards, discussed the transformation and adsorption of ROX in environmental systems, documents the biological response to ROX, and summarizes the remediation methods of ROX contamination. Most previous studies of ROX have been focused on identifying the mechanisms involved under theoretical conditions, but more attention should be paid to the behavior of ROX under real environmental conditions, including the fate and transport of ROX in the real environment. ROX remediation methods at real contaminated sites should also be assessed and verified. The summary of previous studies on the environmental behavior and remediation methods of ROX is helpful for further research in the future.

Nga Phuong Dang, Chris Petrich, Dorina Pásztor et al.

Analytical Letters • 2024

Geobacter and Shewanella are the most characterized electroactive bacteria genera. Unlike genus Geobacter that is strictly anaerobic, Shewanella can grow under both oxic and anoxic environments and is capable of metabolizing a wider substrate range. In the present study, the use of strain Shewanella baltica 20 in MFC-based biosensor for BOD monitoring is reported. The S. baltica strain 20 was isolated from river sediment in Hungary. The bacterium could form a biofilm, oxidized glucose, and transferred electrons to produce current when they were enriched on the anode in an air cathode microbial fuel cell (MFC). The tested MFC system demonstrated linearity in the current response to glucose from 50 to 300 mg/L. The electrical efficiency was determined from the polarization curve using the method of Varying Circuit Resistance (VCR) with an external load probed from 10 X to 220 kX. The maximum power production was 1.2 mW/m 2 at an external load of 40 kX. Studying the effect of external resistors on the MFC performance showed that the MFC reached higher saturation for 500 mg/L of glucose at lower resistances of 100 and 470 X, in comparison to 300 mg/L at 1000 X. The results show that the response of the MFC can potentially be tuned by adjusting the external load. Our preliminary study suggests that Shewanella baltica strain 20 may be used for online monitoring of BOD (biological oxygen demand) in wastewater.

Musfique Ahmed, Rifat Anwar, Dongyang Deng et al.

Microorganisms • 2021

This study explicated the functional activities of microorganisms and their interrelationships under four previously reported iron reducing conditions to identify critical factors that governed the performance of these novel iron-dosed anaerobic biological wastewater treatment processes. Various iron-reducing bacteria (FeRB) and sulfate reducing bacteria (SRB) were identified as the predominant species that concurrently facilitated organics oxidation and the main contributors to removal of organics. The high organic contents of wastewater provided sufficient electron donors for active growth of both FeRB and SRB. In addition to the organic content, Fe (III) and sulfate concentrations (expressed by Fe/S ratio) were found to play a significant role in regulating the microbial abundance and functional activities. Various fermentative bacteria contributed to this FeRB-SRB synergy by fermenting larger organic compounds to smaller compounds, which were subsequently used by FeRB and SRB. Feammox (ferric reduction coupled to ammonium oxidation) bacterium was identified in the bioreactor fed with wastewater containing ammonium. Organic substrate level was a critical factor that regulated the competitive relationship between heterotrophic FeRB and Feammox bacteria. There were evidences that suggested a synergistic relationship between FeRB and nitrogen-fixing bacteria (NFB), where ferric iron and organics concentrations both promoted microbial activities of FeRB and NFB. A concept model was developed to illustrate the identified functional interrelationships and their governing factors for further development of the iron-based wastewater treatment systems.

Haipeng Wang, Teng Teeh Lim, Cuong Manh Duong et al.

Microorganisms • 2020

Long-term anaerobic co-digestion of swine manure (SM) and corn stover (CS) was conducted using semi-continuously loaded digesters under mesophilic conditions. A preliminary test was first conducted to test the effects of loading rates, and results indicated the 3 g-VS L -1 d -1 was the optimal loading rate. Based on the preliminary results, a verification replicated test was conducted with 3 g-VS L -1 d -1 loading rate and different SM/CS ratios (1:1, 2:1 and 1:2). Results showed that a SM/CS ratio of 2/1 was optimal, based on maximum observed methane-VS des generation and carbon conversion efficiency (72.56 ± 3.40 mL g -1 and 40.59%, respectively). Amplicon sequencing analysis suggested that microbial diversity was increased with CS loading. Amino-acid-degrading bacteria were abundant in the treatment groups. Archaea Methanoculleus could enhance biogas and methane productions.

Liping Huang, Weifeng Kong, Shiping Song et al.

Applied Catalysis B: Environmental • 2023

Cost-effective, semiconductor ZnFe2O4/g-C3N4 heterojunction cathodes were investigated to achieve efficient treatment of industrial etching terminal wastewater in photo-assisted, single-chamber, microbial electrolysis cells (PS-MECs). The PS-MECs performance progressively increased over time, reaching significant Ni(II) removal (4.4 mg/L/h), recalcitrant organics mineralization (11.3 mg/L/h), hydrogen production (0.55 m3/m3/d) and solar-to-hydrogen conversion efficiency (6.7%) after 12 days fed-batch operation. The progressive deposition of Ni over the cathodes and the physiological release of extracellular polymeric substances (EPS) dynamically influenced the proportions of reactive oxidative species. Triplet 3EPS* (78%) on both electrodes and cathodic holes (22%) contributed to recalcitrant organics mineralization during the 12th fed-batch operational cycle, while cathodic holes (65%) exceeded anodic 3EPS* (35%) during the 1st-cycle. Significantly different bacterial communities were observed over the cathodes (Acinetobacter (17.7%) and Staphylococcus (16.8%) and anodes (Novosphingobium (42.9%)) after the 12th-cycle, as confirmed by KEGG PICRUSt analysis. This study broadens the application of cost-effective PS-MECs for industrial wastewater treatment.

Hongmao Jiang, Youchao Chen, Yang Hu et al.

Frontiers in Ecology and Evolution • 2021

The Tibetan Plateau, widely known as the world’s “Third Pole,” has gained extensive attention due to its susceptibility to climate change. Alpine grasslands are the dominant ecosystem on the Tibetan Plateau, albeit little is known about the microbial community and diversity among different alpine grassland types. Here, soil bacterial composition and diversity in the upper soils of five alpine grassland ecosystems, alpine meadow (AM), alpine steppe (AS), alpine meadow steppe (AMS), alpine desert (AD), and alpine desert steppe (ADS), were investigated based on the 16S rRNA gene sequencing technology. Actinobacteria (46.12%) and Proteobacteria (29.67%) were the two dominant soil bacteria at the phylum level in alpine grasslands. There were significant differences in the relative abundance at the genus level among the five different grassland types, especially for the Rubrobacter , Solirubrobacter , Pseudonocardia , Gaiella , Haliangium , and Geodermatophilus . Six alpha diversity indices were calculated based on the operational taxonomic units (OTUs), including Good’s coverage index, phylogenetic diversity (PD) whole tree index, Chao1 index, observed species index, Shannon index, and Simpson index. The Good’s coverage index value was around 0.97 for all the grassland types in the study area, meaning the soil bacteria samplings sequenced sufficiently. No statistically significant difference was shown in other diversity indices’ value, indicating the similar richness and evenness of soil bacteria in these alpine grasslands. The beta diversity, represented by Bray–Curtis dissimilarity and the non-metric multidimensional scaling (NMDS), showed that OTUs were clustered within alpine grasslands, indicating a clear separation of soil bacterial communities. In addition, soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), pH, and soil water content (SWC) were closely related to the variations in soil bacterial compositions. These results indicated that soil bacterial taxonomic compositions were similar, while soil bacterial community structures were different among the five alpine grassland types. The environmental conditions, including SOM, TN, TP, pH, and SWC, might influence the soil bacterial communities on the Tibetan Plateau.

Rajat Giri, Rakesh Kumar Sharma

Bioresources and Bioprocessing • 2020

Abstract The study was designed to evaluate the production of auxin by eukaryotic unicellular organism Pichia fermentans . Different media formulations were used for the production of indole-3-acetic acid (IAA) under broth and submerged conditions. Wheat straw-based production medium was formulated and optimized using statistical approach. The IAA production was significantly enhanced by nine folds, when the wheat straw was pretreated with Phanerochaete chrysosporium (150 µg/ml) as compared to untreated wheat straw (16.44 µg/ml). Partial purification of IAA was carried out by silica gel column chromatography and further confirmed by high-performance liquid chromatography. Exogenous application of crude and partially purified IAA positively influenced the Vigna radiata seedling growth. The number of lateral roots in the growing seedlings was significantly higher as compared to the control seeds. Thus, the present findings point towards an efficient production of plant hormone by yeast and white rot fungus using abundantly available wheat straw, which may lead to the development of cost-effective production of such metabolites and their further use in agricultural field to reduce the negative impact of chemical fertilizers.

Subed Chandra Dev Sharma, Cuijie Feng, Jiangwei Li et al.

Microbes and Environments • 2016

A facultative anaerobic bacterium, designated as strain SCS5, was isolated from the anodic biofilm of a mediator-less microbial fuel cell using acetate as the electron donor and α-FeOOH as the electron acceptor. The isolate was Gram-negative, motile, and shaped as short rods (0.9-1.3 μm in length and 0.4-0.5 μm in width). A phylogenetic analysis of the 16S rRNA, gyrB, and rpoD genes suggested that strain SCS5 belonged to the Aeromonas genus in the Aeromonadaceae family and exhibited the highest 16S rRNA gene sequence similarity (99.45%) with Aeromonas jandaei ATCC 49568. However, phenotypic, cellular fatty acid profile, and DNA G+C content analyses revealed that there were some distinctions between strain SCS5 and the type strain A. jandaei ATCC 49568. The optimum growth temperature, pH, and NaCl (%) for strain SCS5 were 35°C, 7.0, and 0.5% respectively. The DNA G+C content of strain SCS5 was 59.18%. The isolate SCS5 was capable of reducing insoluble iron oxide (α-FeOOH) and transferring electrons to extracellular material (the carbon electrode). The electrochemical activity of strain SCS5 was corroborated by cyclic voltammetry and a Raman spectroscopic analysis. The cyclic voltammogram of strain SCS5 revealed two pairs of oxidation-reduction peaks under anaerobic and aerobic conditions. In contrast, no redox pair was observed for A. jandaei ATCC 49568. Thus, isolated strain SCS5 is a novel exoelectrogenic bacterium phylogenetically related to A. jandaei, but shows distinct electrochemical activity from its close relative A. jandaei ATCC 49568.

Macarena Mellado, Jeannette Vera

Canadian Journal of Microbiology • 2021

Several biochemical cycles are performed in natural wetlands (NWs) and constructed wetlands (CWs). Knowledge of microorganisms can be used to monitor the restoration of wetlands and the performance of wastewater treatment. The phylum Proteobacteria is the most abundant in NWs and CWs, which plays a role in nitrogen (N), phosphorus (P), and sulfur (S) cycles, and in the degradation of organic matter. Other phyla were present at lower abundance. Archaea participate in methanogenesis, methane oxidation, and methanogenic N 2 fixation. S and P cycles are also performed by other microorganisms, such as Chloroflexi and Nitrospirae . In general, there is more information about the N cycle, especially nitrification and denitrification. Processes where archaea participate (e.g., methane oxidation and methanogenic N 2 fixation) remain unclear, and several of these microorganisms have not been isolated so far. In this study, we used 16S rDNA or functional genes. The use of functional genes provides information to monitor specific microbial populations, and 16S rDNA is more suitable for taxonomic classification. In addition, several Candidatus microorganisms have not been isolated to date. However, their metabolic roles in the biochemical cycle of wetlands have been described.

Jianqiang Zhao, Jinna Wu, Xiaoling Li et al.

Frontiers in Microbiology • 2017

Microbial fuel cells (MFCs) have attracted much attention due to their ability to generate electricity while treating wastewater. The performance of a double-chamber MFC with simultaneous nitrification and denitrification (SND) in the cathode for treating synthetic high concentration ammonia wastewater was investigated at different dissolved oxygen (DO) concentrations and high temperatures. The results showed that electrode denitrification and traditional heterotrophic denitrification co-existed in the cathode chamber. Electrode denitrification by aerobic denitrification bacterium (ADB) is beneficial for achieving a higher voltage of the MFC at high DO concentrations (3.0-4.2 mg/L), while traditional heterotrophic denitrification is conducive to higher total nitrogen (TN) removal at low DO (0.5-1.0 mg/L) concentrations. Under high DO conditions, the nitrous oxide production and TN removal efficiency were higher with a 50 Ω external resistance than with a 100 Ω resistance, which demonstrated that electrode denitrification by ADB occurred in the cathode of the MFC. Sufficient electrons were inferred to be provided by the electrode to allow ADB survival at low carbon:nitrogen ratios (≤0.3). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) results showed that increasing the DO resulted in a change of the predominant species from thermophilic autotrophic nitrifiers and facultative heterotrophic denitrifiers at low DO concentrations to thermophilic ADB at high DO concentrations. The predominant phylum changed from Firmicutes to Proteobacteria , and the predominant class changed from Bacilli to Alpha, Beta , and Gamma Proteobacteria .

Michael P. Coryell, Barbara A. Roggenbeck, Seth T. Walk

Current Pharmacology Reports • 2019

The human gut microbiome can metabolize arsenic and influence arsenical oxidation state, methylation status, thiolation status, bioavailability, and excretion. We discuss the strength of current evidence and propose that the microbiome be considered in future epidemiologic and toxicologic studies of human arsenic exposure.

Zizhang Guo, Yan Kang, Zhen Hu et al.

Bioresource Technology • 2020

Wei Wei, Wenshan Guo, Huu Hao Ngo et al.

Bioresource Technology • 2020

Jong-Hyun Baik, Jae-Hoon Hwang, Keugtae Kim et al.

2024 IEEE SENSORS • 2024

As the electricity is produced by exoelectrogenic bacteria in an microbial fuel cell (MFC), monitoring electrical signals from MFCs can provide a novel way of real-time health monitoring of many engineered systems and processes such as anaerobic digester systems. The purpose of this study was to investigate the potential of the MFC process as a water toxicity sensor for detecting toxins such as heavy metals and BTEX in the water. Cu 2+ , Hg 2+ , benzene, and xylene were selected as the representative toxicants and the toxicity response of the MFC biosensor was evaluated based on the inhibition ratio, indicative of the voltage changes when the toxicants were exposed to the anodic biofilm. It was found that the inhibition ratios were proportional to the concentrations of spiked toxicants. The toxicity responses toward heavy metals demonstrated an excellent linear relationship between the inhibition ratio and the toxicant concentration. Overall, this study demonstrated the potential of MFC technology as a water toxicity biosensor for real-time health monitoring.

Yanghui Xu, Qin Ou, Jan Peter van der Hoek et al.

Environmental Science & Technology • 2024

Micro- and nanoplastics (MNPs) are attracting increasing attention due to their persistence and potential ecological risks. This review critically summarizes the effects of photo-oxidation on the physical, chemical, and biological behaviors of MNPs in aquatic and terrestrial environments. The core of this paper explores how photo-oxidation-induced surface property changes in MNPs affect their adsorption toward contaminants, the stability and mobility of MNPs in water and porous media, as well as the transport of pollutants such as organic pollutants (OPs) and heavy metals (HMs). It then reviews the photochemical processes of MNPs with coexisting constituents, highlighting critical factors affecting the photo-oxidation of MNPs, and the contribution of MNPs to the phototransformation of other contaminants. The distinct biological effects and mechanism of aged MNPs are pointed out, in terms of the toxicity to aquatic organisms, biofilm formation, planktonic microbial growth, and soil and sediment microbial community and function. Furthermore, the research gaps and perspectives are put forward, regarding the underlying interaction mechanisms of MNPs with coexisting natural constituents and pollutants under photo-oxidation conditions, the combined effects of photo-oxidation and natural constituents on the fate of MNPs, and the microbiological effect of photoaged MNPs, especially the biotransformation of pollutants.

Cheng Li, Keaton Larson Lesnik, Yanzhen Fan et al.

FEMS Microbiology Letters • 2016

The functioning of many natural and engineered environments is dependent on long distance electron transfer mediated through electrical currents. These currents have been observed in exoelectrogenic biofilms and it has been proposed that microbial biofilms can mediate electron transfer via electrical currents on the centimeter scale. However, direct evidence to confirm this hypothesis has not been demonstrated and the longest known electrical transfer distance for single species exoelectrogenic biofilms is limited to 100 μm. In the present study, biofilms were developed on electrodes with electrically non-conductive gaps from 50 μm to 1 mm and the in situ conductance of biofilms was evaluated over time. Results demonstrated that the exoelectrogenic mixed species biofilms in the present study possess the ability to transfer electrons through electrical currents over a distance of up to 1 mm, 10 times further than previously observed. Results indicate the possibility of interspecies interactions playing an important role in the spatial development of exoelectrogenic biofilms, suggesting that these biological networks might remain conductive even at longer distance. These findings have significant implications in regards to future optimization of microbial electrochemical systems.

Hakima Kebaili, Antonia Pérez de los Ríos, M.J. Salar-García et al.

Frontiers in Materials • 2020

Ionic liquids (ILs) are widely used as reaction and separation media in many technologies due to their unique and advantageous physicochemical properties. Thus, further studies approaching the study of the toxicity of these materials are required. Moreover, they are utilized in devices in which microorganisms such as Shewanella sp . act as biocatalysts. Thus, in this work, the toxicity of 69 ILs on the marine bacterium Shewanella sp . was tested. Specifically, the ILs analyzed were based on the cations imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, oxazolinium, phosphonium, ammonium, and sulfonium, in combination with different anions. The toxicities of this wide group of ILs on Shewanella sp. were determined using two methods: 1) the agar disk-diffusion test and 2) the growth inhibition test in liquid media. The relationship between toxicity and IL chemical structure was elucidated. A decrease in the hydrophobicity of the alkyl chain length was found to be a key factor to reduce IL toxicity. On the other hand, phosphonium-based ILs containing long alkyl chains were shown to be largely incompatible with Shewanella sp .

Mingzhi Wei, Jinwei Liu, Qinzheng Yang et al.

npj Clean Water • 2022

Abstract The lack of electron donors in oxygen-rich aquatic environments limits the ability of natural denitrification to remove excess nitrate, leading to eutrophication of aquatic ecosystems. Herein, we demonstrate that electron-rich substances in river or lake sediments could participate in long-distance electron rebalancing to reduce nitrate in the overlying water. A microstructure containing Dechloromonas and consisting of an inner layer of green rust and an outer layer of lepidocrocite forms in the sediment-water system through synergetic evolution and self-assembly. The microstructure enables long-distance electron transfer from the sediment to dilute nitrate in the overlying water. Specifically, the inner green rust adsorbs nitrate and reduces the kinetic barrier for denitrification via an Fe(II)/Fe(III) redox mediator. Our study reveals the mechanism of spontaneous electron transfer between distant and dilute electron donors and acceptors to achieve denitrification in electron-deficient aquatic systems.

Rossella Labarile, Danilo Vona, Maria Varsalona et al.

Nano Research • 2024

Recent advances in coupling light-harvesting microorganisms with electronic components have led to a new generation of biohybrid devices based on microbial photocatalysts. These devices are limited by the poorly conductive interface between phototrophs and synthetic materials that inhibit charge transfer. This study focuses on overcoming this bottleneck through the metabolically-driven encapsulation of photosynthetic cells with a bio-inspired conductive polymer. Cells of the purple non sulfur bacterium Rhodobacter sphaeroides were coated with a polydopamine (PDA) nanoparticle layer via the self-polymerization of dopamine under anaerobic conditions. The treated cells show preserved light absorption of the photosynthetic pigments in the presence of dopamine concentrations ranging between 0.05–3.5 mM. The thickness and nanoparticle formation of the membrane-associated PDA matrix were further shown to vary with the dopamine concentrations in this range. Compared to uncoated cells, the encapsulated cells show up to a 20-fold enhancement in transient photocurrent measurements under mediatorless conditions. The biologically synthesized PDA can thus act as a matrix for electronically coupling the light-harvesting metabolisms of cells with conductive surfaces.

Panagiota G. Fragouli, Maria Roulia, Alexandros A. Vassiliadis

Agronomy • 2023

Humic substances are naturally occurring materials composed of complex biogenic mixtures of substituted aromatic and aliphatic hydrocarbon core materials derived from the degradation and decomposition of dead plant and animal matter. They are ubiquitous in both terrestrial and aquatic systems constituting biotic pools and are characterized by unique properties; they are amphiphilic redox compounds with exceptional chelating features. Humic substances play a crucial role in both agriculture and the environment as carbon sequestrators, soil improvers, plant health promoters, as well as stabilizers of soil aggregates and regulators of organic/inorganic nutrients bioavailability. This review article attempts to summarize current knowledge about the molecular nature and characterization techniques employed for the study of humic substances worldwide as the chemistry of their components differs markedly and depends on natural processes, several abiotic and biotic factors, the origin of the organic matter, and their complexation with inorganic, e.g., metal-ion, compounds. This work is equally concerned with the association of humic substances with dyes, a notorious pollutant, responsible for various environmental issues generally arising from the discharge of untreated effluents into soils and water bodies. Azo dyes, in particular, negatively affect soil microbial communities, as well as plant germination and growth. The aim is to feature the potential contribution of humic substances as novel materials for environment-friendly and sustainable processes.

Kamil G. Gareev

Magnetochemistry • 2023

Iron oxide compounds have naturally formed during the whole of Earth’s history. Synthetic compositions with iron oxides are produced with the use of various techniques and widely used for scientific and applied purposes. This review considers an attempt to classify all the information on different iron oxide compound formation mechanisms and intended applications in biomedicine, catalysis, waste remediation, geochemistry, etc. All the literature references analyzed were divided into several groups by their number of included iron oxide compounds: compositions containing only one compound (e.g., magnetite or wüstite), including various polymorphs of iron(III) oxide (α-, β-, γ-, ε-, ζ-, δ-Fe2O3); compositions with two different distinguishable iron oxide phases (e.g., maghemite and hematite); compositions containing non-crystalline phases (amorphous iron oxide or atomic clusters); and compositions with mixed iron oxide phases (indistinguishable separate iron oxide phases). Diagrams on the distribution of the literature references between various iron oxide compounds and between various applications were built. Finally, the outlook on the perspectives of further iron oxide studies is provided.

M. Isabel San-Martín, Adrián Escapa, Raúl M. Alonso et al.

The Science of The Total Environment • 2020

Derek R. Lovley

Frontiers in Microbiology • 2022

OPINION article Front. Microbiol., 06 June 2022Sec. Microbiological Chemistry and Geomicrobiology Volume 13 - 2022 | https://doi.org/10.3389/fmicb.2022.872610

Yulia Plekhanova, Sergei Tarasov, А. Н. Решетилов

Biosensors • 2021

Immobilization of the biocomponent is one of the most important stages in the development of microbial biosensors. In this study, we examined the electrochemical properties of a novel PEDOT:PSS/graphene/Nafion composite used to immobilize Gluconobacter oxydans bacterial cells on the surface of a graphite screen-printed electrode. Bioelectrode responses to glucose in the presence of a redox mediator 2,6-dichlorophenolindophenol were studied. The presence of graphene in the composite reduced the negative effect of PEDOT:PSS on cells and improved its conductivity. The use of Nafion enabled maintaining the activity of acetic acid bacteria at the original level for 120 days. The sensitivity of the bioelectrode based on G. oxydans /PEDOT:PSS/graphene/Nafion composite was shown to be 22 μA × mM -1 × cm -2 within the linear range of glucose concentrations. The developed composite can be used both in designing bioelectrochemical microbial devices and in biotechnology productions for long-term immobilization of microorganisms.