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1.
Curr Biol ; 2024 Apr 16.
Article in English | MEDLINE | ID: mdl-38663397

ABSTRACT

Fungal biomineralization plays an important role in the biogeochemical cycling of metals in the environment and has been extensively explored for bioremediation and element biorecovery. However, the cellular and metabolic responses of fungi in the presence of toxic metals during biomineralization and their impact on organic matter transformations are unclear. This is an important question because co-contamination by toxic metals and organic pollutants is a common phenomenon in the natural environment. In this research, the biomineralization process and oxidative stress response of the geoactive soil fungus Aspergillus niger were investigated in the presence of toxic metals (Co, Cu, Mn, and Fe) and the azo dye orange II (AO II). We have found that the co-existence of toxic metals and AO II not only enhanced the fungal biomineralization of toxic metals but also accelerated the removal of AO II. We hypothesize that the fungus and in situ mycogenic biominerals (toxic metal oxalates) constituted a quasi-bioreactor, where the biominerals removed organic pollutants by catalyzing reactive oxygen species (ROS) generation resulting from oxidative stress. We have therefore demonstrated that a fungal/biomineral system can successfully achieve the goal of toxic metal immobilization and organic pollutant decomposition. Such findings inform the potential development of fungal-biomineral hybrid systems for mixed pollutant bioremediation as well as provide further understanding of fungal organic-inorganic pollutant transformations in the environment and their importance in biogeochemical cycles.

2.
Small ; 20(10): e2306522, 2024 Mar.
Article in English | MEDLINE | ID: mdl-37884468

ABSTRACT

Mimicking efficient biocatalytic cascades using nanozymes has gained enormous attention in catalytic chemistry, but it remains challenging to develop a nanozyme-based cascade system to sequentially perform the desired reactions. Particularly, the integration of sequential hydrolysis and oxidation reactions into nanozyme-based cascade systems has not yet been achieved, despite their significant roles in various domains. Herein, a self-cascade Ce-MOF-818 nanozyme for sequential hydrolysis and oxidation reactions is developed. Ce-MOF-818 is the first Ce(IV)-based heterometallic metal-organic framework constructed through the coordination of Ce and Cu to distinct groups. It is successfully synthesized using an improved solvothermal method, overcoming the challenge posed by the significant difference in the binding speeds of Ce and Cu to ligands. With excellent organophosphate hydrolase-like (Km = 42.3 µM, Kcat = 0.0208 min-1 ) and catechol oxidase-like (Km = 2589 µM, Kcat = 1.25 s-1 ) activities attributed to its bimetallic active centers, Ce-MOF-818 serves as a promising self-cascade platform for sequential hydrolysis and oxidation. Notably, its catalytic efficiency surpasses that of physically mixed nanozymes by approximately fourfold, owning to the close integration of active sites. The developed hydrolysis-oxidation self-cascade nanozyme has promising potential applications in catalytic chemistry and provides valuable insights into the rational design of nanozyme-based cascade systems.


Subject(s)
Metal-Organic Frameworks , Hydrolysis , Oxidation-Reduction , Metal-Organic Frameworks/chemistry , Catalysis , Biocatalysis
3.
Water Res ; 235: 119925, 2023 May 15.
Article in English | MEDLINE | ID: mdl-37028213

ABSTRACT

Singlet oxygen (1O2) attracts much attention in persulfate-based advanced oxidation processes (PS-AOPs), because of its wide pH tolerance and high selectivity toward electron-rich organics. However, there are conflicts about the 1O2 role in PS-AOPs on several aspects, including the formation of different key reactive oxygen species (ROS) at similar active sites, pH dependence, broad-spectrum activity, and selectivity in the elimination of organic pollutants. To a large degree, these conflicts root in the drawbacks of the methods to identify and evaluate the role of 1O2. For example, the quenchers of 1O2 have high reactivity to other ROS and persulfate as well. In addition, electron transfer process (ETP) also selectively oxidizes organics, having a misleading effect on the identification of 1O2. Therefore, in this review, we summarized and discussed some basic properties of 1O2, the debatable role of 1O2 in PS-AOPs on multiple aspects, and the methods and their drawbacks to identify and evaluate the role of 1O2. On the whole, this review aims to better understand the role of 1O2 in PS-AOPs and further help with its reasonable utilization.


Subject(s)
Singlet Oxygen , Water Pollutants, Chemical , Singlet Oxygen/chemistry , Reactive Oxygen Species , Oxidation-Reduction , Electron Transport , Peroxides/chemistry , Water Pollutants, Chemical/chemistry
4.
Environ Sci Technol ; 56(22): 16240-16248, 2022 Nov 15.
Article in English | MEDLINE | ID: mdl-36322385

ABSTRACT

Fabricating two-dimensional transition-metal dichalcogenide (TMD)-based unique composites is an effective way to boost the overall physical and chemical properties, which will be helpful for the efficient and fast capture of elemental mercury (Hg0) over a wide temperature range. Herein, we constructed a defect-rich Cu2WS4 nano-homojunction decorated on covalent organic frameworks (COFs) with abundant S vacancies. Highly well-dispersed and uniform Cu2WS4 nanoparticles were immobilized on COFs strongly via an ion pre-anchored strategy, consequently exhibiting enhanced Hg0 removal performance. The saturation adsorption capacity of Cu2WS4@COF composites (21.60 mg·g-1) was 9 times larger than that of Cu2WS4 crystals, which may be ascribed to more active S sites exposed in hybrid interfaces formed in the Cu2WS4 nano-homojunction and between Cu2WS4 nanoparticles and COFs. More importantly, such hybrid materials reduced adsorption deactivation at high temperatures, having a wide operating temperature range (from 40 to 200 °C) owing to the thermostability of active S species immobilized by both physical confined and chemical interactions in COFs. Accordingly, this work not only provides an effective method to construct uniform TMD-based sorbents for mercury capture but also opens a new realm of advanced COF hybrid materials with designed functionalities.

5.
Carbohydr Polym ; 296: 119944, 2022 Nov 15.
Article in English | MEDLINE | ID: mdl-36087992

ABSTRACT

Poly/oligosaccharides are renewable natural resources with abundant chirality. Herein, we develop a general route to prepare optically active particles by using poly/oligosaccharides as both chiral inducers and growth templates. By complexing with Cu(NH3)42+ ions, OH groups on C2 and C3 in poly/oligosaccharides can transfer the chirality to Cu(II) and retain it in CuO. At the same time, poly/oligosaccharides direct growth of CuO by in situ transformation of Cu(NH3)42+ ions. Cellulose nanocrystal (CNC) and starch (ST) are used as representative polysaccharides, and ß-cyclodextrin (ß-CD) as a representative oligosaccharide, thus dandelion, duchesnea, and chrysanthemum-like composite particles with chiroptical activity are obtained. Besides, chiral CuO/poly(oligo)saccharide particles (CSP) demonstrate enantioselective ability by differentiating coordination with tryptophan (Trp) enantiomers and form Cu-Trp metal organic framework architectures with different morphologies. The study provides an easily accessible approach to prepare novel functional materials by poly/oligosaccharide-based chiral induction and hold great promise in chiral applications.


Subject(s)
Cellulose , beta-Cyclodextrins , Cellulose/chemistry , Oligosaccharides , Starch , Stereoisomerism , Tryptophan , beta-Cyclodextrins/chemistry
6.
Chemosphere ; 307(Pt 3): 135863, 2022 Nov.
Article in English | MEDLINE | ID: mdl-35961451

ABSTRACT

Covalently-bound organic silicate-aluminum hybrid coagulants (CBHyC) have been shown to efficiently remove low molecular weight organic contaminants from wastewater. However, the interaction dynamics and motivations during the coagulation of contaminant molecules by CBHyC are limited. In this study, a molecular dynamics (MD) simulation showed that CBHyC forms core-shell structure with the aliphatic carbon chains gather inside as a core and the hydrophilic quaternary ammonium-Si-Al complexes disperse outside as a shell. This wrapped structure allowed the coagulant to diffuse into solutions easily and capture target contaminants. The adsorption of anionic organic contaminants (e.g., diclofenac) onto the CBHyC aggregates was driven equally by van der Waals forces and electrostatic interactions. Cationic organic contaminants (e.g., tetracycline) were seldom bound to CBHyC because of substantial repulsive forces between cationic molecules and CBHyC. Neutrally-charged organic molecules were generally bound through hydrophobic interactions. For adenine and thymine deoxynucleotide, representatives of antibiotic resistance genes, van der Waals forces and electrostatic interaction became the dominant driving force with further movement for adenine and thymine, respectively. Driving forces between target contaminant and coagulant directly affect the size and stability of formed aggregate, following the coagulation efficiency of wastewater treatment. The findings of this study enrich the database of aggregation behavior between low molecular weight contaminants and CBHyC and contribute to further and efficient application of CBHyC in wastewater treatment.


Subject(s)
Ammonium Compounds , Wastewater , Adenine , Aluminum , Carbon , Diclofenac , Molecular Dynamics Simulation , Molecular Structure , Silicates , Tetracyclines , Thymine
7.
Water Res ; 222: 118945, 2022 Aug 15.
Article in English | MEDLINE | ID: mdl-35963137

ABSTRACT

Sulfate scaling, as insoluble inorganic sulfate deposits, can cause serious operational problems in various industries, such as blockage of membrane pores and subsurface media and impairment of equipment functionality. There is limited article to bridge sulfate formation mechanisms with field scaling control practice. This article reviews the molecular-level interfacial reactions and thermodynamic basis controlling homogeneous and heterogeneous sulfate mineral nucleation and growth through classical and non-classical pathways. Common sulfate scaling control strategies were also reviewed, including pretreatment, chemical inhibition and surface modification. Furthermore, efforts were made to link the fundamental theories with industrial scale control practices. Effects of common inhibitors on different steps of sulfate formation pathways (i.e., ion pair and cluster formation, nucleation, and growth) were thoroughly discussed. Surface modifications to industrial facilities and membrane units were clarified as controlling either the deposition of homogeneous precipitates or the heterogeneous nucleation. Future research directions in terms of optimizing sulfate chemical inhibitor design and improving surface modifications are also discussed. This article aims to keep the readers abreast of the latest development in mechanistic understanding and control strategies of sulfate scale formation and to bridge knowledge developed in interfacial chemistry with engineering practice.


Subject(s)
Minerals , Sulfates , Thermodynamics
8.
Water Res ; 212: 118091, 2022 Apr 01.
Article in English | MEDLINE | ID: mdl-35093603

ABSTRACT

Graphene oxide (GO) coating has recently been reported as a novel approach to increase membrane flux of membrane distillation (MD), yet the phenomena underlying the process are still not fully understood. In this study, a mathematical model based on capillary-film assumption was developed and validated with the results (R2>0.99) from a series of MD experiments. According to the model, when GO layer was placed at the evaporation interface, the temperature difference across the membrane surface increases significantly (44.2%∼92.0%) and the temperature polarization coefficient is increased greatly from 0.29∼0.38 to around 0.55. This leads to a big increase of driving force for higher heat flow and subsequently mass flux (17.8∼45.5%). However, the vapor pressure on membrane surface was decreased due to Kelvin effect of GO capillary pores, which has a negative influence on the driving force, accounting for about 26.9% to 52.6% drop in the achieved flux. In comparison, when GO layer was placed at the condensation interface, the temperature difference across the membrane surface decreases slightly (7.2∼12.2%), but the reduced vapor pressure on GO capillary pores due to Kelvin effect become the dominant factor affecting membrane flux, resulting in an increase mass flux of 12.4∼16.4%. The model developed in this study provides a theoretical foundation for understanding the role of GO coating on flux improvement, and can be used for further development of high flux membranes.


Subject(s)
Graphite , Water Purification , Distillation , Membranes, Artificial
9.
Water Res ; 203: 117541, 2021 Sep 15.
Article in English | MEDLINE | ID: mdl-34416650

ABSTRACT

Efficient removal of low-concentration refractory pollutants is a crucial problem to ensuring water safety. The use of heterogeneous catalysis of molecular imprinting technology combined with traditional catalysts is a promising method to improve removal efficiency. Presently, the research into molecular imprinting targeting catalysts focuses mainly on material preparation and performance optimization. However, more researchers are investigating other applications of imprinting materials. This review provides recent progress in photocatalyst preparation, electrocatalyst, and Fenton-like catalysts synthesized by molecular imprinting. The principle and control points of target catalysts prepared by precipitation polymerization (PP) and surface molecular imprinting (S-MIP) are introduced. Also, the application of imprinted catalysts in targeted degradation of drugs, pesticides, environmental hormones, and other refractory pollutants is summarized. In addition, the reusability and stability of imprinted catalyst in water treatment are discussed, and the possible ecotoxicity risk is analyzed. Finally, we appraised the prospects, challenges, and opportunities of imprinted catalysts in the advanced oxidation process. This paper provides a reference for the targeted degradation of refractory pollutants and the preparation of targeted catalysts.


Subject(s)
Molecular Imprinting , Water Pollutants, Chemical , Water Purification , Catalysis , Wastewater , Water Pollutants, Chemical/analysis
10.
Water Res ; 195: 116976, 2021 May 01.
Article in English | MEDLINE | ID: mdl-33706215

ABSTRACT

Membrane technology has been widely used in the wastewater treatment and seawater desalination. In recent years, the reverse osmosis (RO) membrane represented by polyamide (PA) has made great progress because of its excellent properties. However, the conventional PA RO membranes still have some scientific problems, such as membrane fouling, easy degradation after chlorination, and unclear mechanisms of salt retention and water flux, which seriously impede the widespread use of RO membrane technology. This paper reviews the progress in the research and development of the RO membrane, with key focus on the mechanisms and strategies of the contemporary separation, anti-fouling and chlorine resistance of the PA RO membrane. This review seeks to provide state-of-the-art insights into the mitigation strategies and basic mechanisms for some of the key challenges. Under the guidance of the fundamental understanding of each mechanism, operation and modification strategies are discussed, and reasonable analysis is carried out, which can address some key technical challenges. The last section of the review focuses on the technical issues, challenges, and future perspective of these mechanisms and strategies. Advances in synergistic mechanisms and strategies of the PA RO membranes have been rarely reviewed; thus, this review can serve as a guide for new entrants to the field of membrane water treatment and established researchers.


Subject(s)
Chlorine , Water Purification , Filtration , Membranes, Artificial , Nylons , Osmosis
11.
Water Res ; 191: 116802, 2021 Mar 01.
Article in English | MEDLINE | ID: mdl-33433336

ABSTRACT

Both the benefits of bacterial quorum sensing (QS) and cross-feeding for bio-reactor performance in wastewater treatment have been recently reported. As the social traits of microbial communities, how bacterial QS regulating bacterial trade-off by cross-feeding remains unclear. Here, we find diffusion signal factor (DSF), a kind of QS molecules, can bridge bacterial interactions through regulating public goods (extracellular polymeric substances (EPS), amino acids) for metabolic cross-feedings. It showed that exogenous DSF-addition leads to change of public goods level and community structure dynamics in the anammox consortia. Approaches involving meta-omics clarified that anammox and a Lautropia-affiliated species in the phylum Proteobacteria can supply costly public goods for DSF-Secretor species via secondary messenger c-di-GMP regulator (Clp) after sensing DSF. Meanwhile, DSF-Secretor species help anammox bacteria scavenge extracellular detritus, which creates a more suitable environment for the anammox species, enhances the anammox activity, and improves the nitrogen removal rate of anammox reactor. The trade-off induces discrepant metabolic loads of different microbial clusters, which were responsible for the community succession. It illustrated the potential to artificially alleviate metabolic loads for certain bacteria. Deciphering microbial interactions via QS not only provides insights for understanding the social behavior of microbial community, but also creates new thought for enhancing treatment performance through regulating bacterial social traits via quorum sensing-mediated public goods.


Subject(s)
Bacteria , Microbiota , Bacteria/genetics , Bioreactors , Nitrogen , Quorum Sensing , Sociological Factors
12.
RSC Adv ; 11(51): 31865-31876, 2021 Sep 27.
Article in English | MEDLINE | ID: mdl-35495518

ABSTRACT

Poly(vinylidene fluoride) (PVDF) membranes are a commonly used cheap material and have been widely used in wastewater treatment. In this study, a simple strategy was proposed to construct PVDF-g-PEG membranes with an interpenetrating network structure by simulating plant roots for the treatment of oil/water emulsion. Meanwhile, the hydrophilicity, antifouling, and mechanical properties of the membrane were improved. A series of chemical and physical characterization methods were used to verify the successful formation of a PVDF-g-PEG layer on the membrane surface. The effects of graft modifier content on the crystallization behavior, microstructure, and membrane permeability were studied. When the optimized membrane (m-PVDF-2) was applied to the treatment of oily wastewater, its separation performance was significantly better than that of the blank PVDF membrane, and the oil removal rate was over 99.3%. BSA and oil contamination were nearly reversible, and excellent oil resistance to high-viscosity oil was also observed. The method reported in this article is a one-step, simple method for constructing hydrophilic and oil-resistant PVDF membranes without any intermediate additives and harmful or costly catalysts. They can be used as an ideal material for preparing efficient oil-water separation membranes.

13.
Environ Sci Ecotechnol ; 8: 100129, 2021 Oct.
Article in English | MEDLINE | ID: mdl-36156994

ABSTRACT

Recycling waste tires through pyrolysis technology generates refractory wastewater, which is harmful to the environment if not disposed properly. In this study, a combined process of coagulation detoxification and biodegradation was used to treat tire pyrolysis wastewater. Organics removal characteristics at the molecular level were investigated using electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that nearly 90% of the organic matter from the wastewater was removed through the process. Preference of the two coagulants for different classes of organics in tire pyrolysis wastewater was observed. The covalently bound inorganic-organic hybrid coagulant (CBHyC) used in this work had a complementary relationship with biodegradation for the organics removal: this coagulant reduced toxicity and enhanced the biodegradation by preferentially removing refractory substances such as lignin with a high degree of oxidation (O/C > 0.3). This study provides molecular insight into the organics of tire pyrolysis wastewater removed by a combined treatment process, supporting the advancement and application of waste rubber recycling technology. It also contributes to the possible development of an effective treatment process for refractory wastewater.

14.
Chemosphere ; 270: 128614, 2021 May.
Article in English | MEDLINE | ID: mdl-33092826

ABSTRACT

Inspired by the self-purification process and a low nitrogen content of the ocean, and the fact that the driving-force behind ecological cycle is solar irradiation, a novel photochemical strategy was designed to spontaneously remove inorganic ammonia nitrogen from wastewater with solar irradiation. This strategy is based on the principles of green chemistry and energy efficiency, and meanwhile the prevention from the introduction of accompanying pollution. In our strategy, a photo-Fe (or Mn)-O2 system was built to remove ammonia-nitrogen from its aqueous solution. The results show that with full band solar irradiation at a range of 10-30 mW cm-2, in weak alkaline condition, more than 90% of ammonia-nitrogen can be effectively removed from NH4Cl aqueous solution by the new strategy, with a residual concentration as low as 2 mg L-1. Mn(III) was proved to be a better catalyst than Fe(III). The catalytic mechanism of N-removal is the generation of •OH during the process of the photoreduction of transition metal hydroxides. DFT theory had been applied to help explaining the mechanism. Different from general knowledge, in our strategy, an alkaline environment, where the generation rate of radicals was relatively slow and comparable to oxidation rate of transition metal ions, can guarantee the stability and persistency of the catalytic reaction. No NOx was produced in this strategy. This new strategy provides a new possibility of cost-efficient and environmental-friendly wastewater treatment, and has certain meaning of understanding how self-purification works in nature.


Subject(s)
Wastewater , Water Purification , Ammonia , Catalysis , Ferric Compounds , Nitrogen
15.
Chemosphere ; 268: 128800, 2021 Apr.
Article in English | MEDLINE | ID: mdl-33143885

ABSTRACT

Modifying the electrodes of microbial fuel cells (MFCs) with iron oxides can improve the bacterial attachment performances and electrocatalytic activities for energy conversion, which is of significance in the fabrication of MFCs. However, the conventional modification methods usually result in the aggregation of iron sites, producing the electrodes of poor qualities. Herein, we report a novel method for the modification of electrochemical electrodes to boost the anode performance of MFC. The Shewanella precursor adhered on carbon felt electrode was directly carbonized to form a bacteria-derived biological iron oxide/carbon (Bio-FeOx/C) nanocomposite catalyst. The large spatial separation between the bacteria, as well as those between the iron containing proteins in the bacteria, deliver a highly dispersed Bio-FeOx/C nanocomposite with good electrocatalytic activities. The excellent microbial attachment performance and electron transfer rate of the Bio-FeOx/C modified electrode significantly promote the transfer of produced electrons between bacteria and electrode. Accordingly, the MFC with the Bio-FeOx/C electrode exhibits the maximum power density of 797.0 mW m-2, much higher than that obtained with the conventional carbon felt anode (226.1 mW m-2). Our works have paved a new avenue to the conversion of the natural bacterial precursors into active iron oxide nanoparticles as the anode catalyst of MFCs. The high catalytic activity of the prepared Bio-FeOx endows it great application potentials in the construction of high-performance electrodes.


Subject(s)
Bioelectric Energy Sources , Nanocomposites , Carbon , Electrodes , Ferric Compounds
16.
Environ Sci Technol ; 54(20): 12929-12937, 2020 10 20.
Article in English | MEDLINE | ID: mdl-33040523

ABSTRACT

Dissolved organic matter (DOM) composition in salt lakes is critical for water quality and aquatic ecology, and the salinization of salt lakes affects the DOM composition. To the best of our knowledge, no study has explored the effects of salinity on salt lake DOM composition at the molecular level. In this work, we selected Qinghai Lake (QHL) and Daihai Lake (DHL) as typical saline lakes. The two lakes have similar geographical and climatic conditions, and the salinity of QHL is higher than that of DHL. Fourier transform ion cyclotron resonance mass spectrometry coupled with electrospray ionization was applied to compare the DOM molecular composition in the two lakes. At higher salinity, the DOM showed larger average molecular weight, higher oxidation degree, and lower aromaticity. Moreover, the proportion of DOM that is vulnerable to microbial degradation (e.g., lipids), photo-degradation (e.g., aromatic structures), or both processes (e.g., carbohydrates and unsaturated hydrocarbons) reduced at higher salinity. On the contrary, compounds that are refractory to microbial degradation (e.g., lignins/CRAM-like structures and tannins) or photo-degradation (e.g., aliphatic compounds) accumulated. Our study provides a useful and unique method to study DOM molecular composition in salt lakes with different salinity and is helpful to understand DOM transformation during the salinization of salt lakes.


Subject(s)
Lakes , Salinity , Mass Spectrometry , Molecular Weight
17.
Environ Int ; 143: 105915, 2020 10.
Article in English | MEDLINE | ID: mdl-32652345

ABSTRACT

Widespread application of anammox process has been primarily limited to the high sensitivity of anammox consortia to fluctuations of temperature. However, the metabolic acclimation of anammox consortia to decreased temperature remains unclear, which is the core of developing potential strategies for improving their low-temperature resistance. Here, we operated anammox reactors at 25 °C and 35 °C to explore the acclimation mechanism of anammox consortia in terms of metabolic responses and cross-feedings. Accordingly, we found that the adaptation of anammox consortia to ambient temperature (25 °C) was significantly linked to energy conservation strategy, resulting in decreased extracellular polymeric substance secretion, accumulation of ATP and amino acids. The expression patterns of cold shock proteins and core enzymes caused the apparent metabolic advantage of Candidatus Brocadia fulgida for acclimation to ambient temperature compared to other anammox species. Importantly, strengthened cross-feedings of amino acids, nitrite and glycine betaine benefited adaptation of anammox consortia to ambient temperature. Our work not only uncovers the temperature-adaptive mechanisms of anammox consortia, but also emphasizes the important role of metabolic cross-feeding in the temperature adaptation of microbial community.


Subject(s)
Bioreactors , Extracellular Polymeric Substance Matrix , Acclimatization , Anaerobiosis , Nitrogen , Oxidation-Reduction , Temperature , Wastewater
18.
Chemosphere ; 258: 127289, 2020 Nov.
Article in English | MEDLINE | ID: mdl-32535447

ABSTRACT

Anammox-based processes and microbial consortia have drawn extensive attention for their use in high-efficiency wastewater treatment technologies. Metals substantially affect the activity of anammox consortia and the quality of wastewater treatment plant effluent. Here, we explored the role of anammox consortia in terms of metals complexation in both single and multi-metal systems. Adsorption edges of single metal cations indicate that the adsorption preference was in the order: Pb(II) > Cd(II) > Cr(VI). A competitive effect was observed in multi-metal cations systems, with Pb(II) being preferably adsorbed and the degree of adsorption somewhat reduced in the presence of either Cd(II) or Cr(VI), while Cd(II) and Cr(VI) were easily exchanged and substituted by other metals. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) further suggest that the adsorption of Pb(II) and Cd(II) are as inner-sphere ion-exchange mechanisms, while Cr(VI) adsorption is mainly by outer-sphere complexation. Density functional theory (DFT) calculations highlight that Cd(II) and Pb(II) have different binding sites compared to Cr(VI), and the order of binding energy (Ebd) of three metal cations were Pb(II) > Cd(II) > Cr(VI). These calculations support the adsorption data in that Pb forms more stable complexes with anammox bacterial surface ligands. Surface complexation modelling (SCM) further predicted both the sorption of single metal cations and competitive adsorption of the three metals to anammox consortia, the exception being Cd at higher loadings. The results of this study highlight the potential role of anammox consortia in removing metal cations from wastewater in treatment systems.


Subject(s)
Ammonia/metabolism , Bioreactors/microbiology , Metals, Heavy/chemistry , Microbial Consortia/physiology , Adsorption , Anaerobiosis , Cations , Density Functional Theory , Metals, Heavy/metabolism , Oxidation-Reduction , Photoelectron Spectroscopy , Spectroscopy, Fourier Transform Infrared , Waste Disposal, Fluid/methods , Wastewater/chemistry , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/metabolism
19.
Environ Res ; 185: 109463, 2020 06.
Article in English | MEDLINE | ID: mdl-32247147

ABSTRACT

The power generation performance of a microbial fuel cell (MFC) greatly depends on the relative amount of electricigens in the anodic microbial community. Running the MFC multiple times can practically enrich the electricigens, and thus improve its power generation efficiency. However, Gram-positive electricigens cannot be enriched well because of their thick non-conductive peptidoglycan layer. Herein, we report a new Gram-positive electricigen enrichment method by regulating the peptidoglycan layer of the bacteria using lysozyme. Lysozyme can partially hydrolyze the peptidoglycans layer of Gram-positive Firmicutes to improve the permeability of cell wall, and thus enhance its electricity generation activity. The stimulation of Gram-positive electricigen endows MFCs a high power generation community structure, which results in the power density 42% higher than that of the control sample. Our work has provided a new and simple method for optimizing the anode community structure by regulating weak electricigens in the community with lysozyme.


Subject(s)
Bioelectric Energy Sources , Peptidoglycan , Cell Wall , Electricity , Muramidase
20.
Water Res ; 165: 114974, 2019 Nov 15.
Article in English | MEDLINE | ID: mdl-31450220

ABSTRACT

Although the enhancement of anammox performance for wastewater treatment due to the addition of small amount of acetate has been reported, discrepant metabolic responses of different anammox species have not been experimentally evaluated. Based on metagenomics and metatranscriptomic data, we investigated the competitiveness between two typical anammox species, Candidatus Jettenia caeni (J. caeni) and Candidatus Brocadia sinica (B. sinica), in anammox consortia under mixotrophic condition, where complex metabolic interactions among anammox bacteria and heterotrophs also changed with acetate addition. Contrary to J. caeni, the dissimilatory nitrate reduction to ammonium pathway of B. sinica was markedly stimulated for improving nitrogen removal. More acetate metabolic pathways and up-regulated AMP-acs expression for acetyl-CoA synthesis in B. sinica contributed to its superiority in acetate utilization. Interestingly, cross-feedings, including the nitrogen cycle, amino acid cross-feeding and B-vitamin metabolic exchange between B. sinica and other heterotrophs seemed to be enhanced with acetate addition, contributing to a reduction in metabolic energy cost to the whole community. Our work not only clarified the mechanism underlying discrepant responses of different anammox species to acetate, but also suggests a possible strategy for obtaining higher nitrogen removal rates in wastewater treatment under low C/N ratio.


Subject(s)
Ammonium Compounds , Bacteria , Acetates , Anaerobiosis , Bioreactors , Nitrogen , Oxidation-Reduction , Wastewater
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