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1.
Water Sci Technol ; 81(4): 744-752, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32460277

RESUMO

Biofouling is unwanted accumulation of microbial population on the membrane surface which limits the use of membrane bioreactor (MBR) in the market. Disruption of the biofilm formation by Quorum Quenching (QQ) by using cell entrapping beads (CEBs) is an approach with great potential to control membrane biofouling as the beads used provide not only mitigating effect on biofilm formation, by interfering Quorum Sensing, but also physical forces to detach the biofilm from the membrane surface. This research aimed to develop QQ-CEB with locally available chemicals in Pakistan and its application to evaluate the QQ effect together with physical and chemical cleaning. Various CEBs were made of different mixtures of sodium alginate and polyvinyl alcohol (PVA) and their quality was tested considering physical and biological aspects. Rhodococcus sp. BH4 and Pseudomonas putida were entrapped in the CEBs and then introduced in MBR as one of biofouling control methods along with standard backwash and chemical backwash. The CEBs made of specific concentration of PVA were proven to be more durable and helpful in mitigating biofouling as compared to that of sodium alginate. An MBR operated with PVA-alginate QQ CEBs together with chemical backwash showed the best performance without deterioration of effluent quality.


Assuntos
Incrustação Biológica , Percepção de Quorum , Reatores Biológicos , Membranas , Membranas Artificiais
2.
Chemosphere ; 255: 126953, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402884

RESUMO

In this study, fouling propensities of loosely bound extracellular polymeric substances (LB-EPSs) and tightly bound EPSs (TB-EPSs) in a membrane bioreactor (MBR) were investigated. It was found that, both the LB-EPSs and TB-EPSs possessed rather high specific filtration resistance (SFR), and LB-EPSs possessed about three times higher SFR but a lower adhesion ability than the TB-EPSs. A series of characterizations demonstrated that LB-EPSs had higher ratio of proteins to polysaccharides (PN/PS ratio), lower CO bonds content, higher hydrophilicity, higher deformation or mixing ability and more abundant high molecular weight (MW) substances than TB-EPSs. Thermodynamic analyzes revealed that the total interaction energy between the TB-EPSs and membrane was always attractive and strengthened, well explaining the higher adhesion ability of the TB-EPSs than the LB-EPSs. Meanwhile, the filtration process was found to be associated with gel layer formation, and the high SFR of EPSs was caused by the chemical potential change in gel layer filtration. According to the Flory-Huggins lattice theory, LB-EPSs tended to form a gel layer with higher cross-linking and/or polymer entanglement level because they contained more abundant high molecular weight (MW) substance, corresponding to higher SFR than that of the TB-EPSs. The proposed thermodynamic mechanisms well interpreted the different fouling propensities of LB-EPSs and TB-EPSs in MBRs.


Assuntos
Reatores Biológicos , Matriz Extracelular de Substâncias Poliméricas , Filtração , Membranas , Membranas Artificiais , Polímeros/química , Polissacarídeos , Esgotos/química , Termodinâmica
3.
Water Res ; 181: 115930, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32470713

RESUMO

Transparent exopolymer particles (TEP) as gel-like particulate acidic polysaccharide have been commonly found in marine, surface water and wastewater. Currently, increasing interest has been devoted to TEP-associated membrane fouling in different membrane systems for water and wastewater treatment, thus this review attempts to provide a holistic view and critical analysis with regard to the definition, formation, detection and properties of TEP, which could ultimately determine its fouling potential. It appears that there is not a common consensus on the actual role of TEP in membrane fouling development due to the subjective definition and highly debatable detection method of TEP. It was clearly demonstrated in this review that the formation of TEP was largely related to cations in water and wastewater which indeed determined the cross-linking degree of precursor materials (e.g. polysaccharides) via intermolecular interactions, and subsequently the quantity of TEP formed. The binding between cations ions (e.g. monovalent, divalent and trivalent cations) and polysaccharide not only depends on the functional groups of polysaccharide, but also its spatial configuration. These in turn suggest that the formation, property and ultimate fouling potential of TEP would be closely related to the type and concentration of cations, while well explaining the controversial reports on TEP-associated fouling in the literature. In addition, the fouling mechanisms of TEP are also elucidated with details in this review, including (i) the formation of TEP-associated gel layer on membrane surface; (ii) carrying microorganisms to membrane surface via protobiofilm and (iii) trapping of deformable TEP in membrane pores. Consequently, it is apparent that TEP is an ignored determinant of membrane fouling, which has not yet been seriously addressed in the design and operation of membrane systems for water and wastewater treatment.


Assuntos
Filtração , Purificação da Água , Matriz Extracelular de Substâncias Poliméricas , Membranas , Membranas Artificiais , Águas Residuárias
4.
Chemosphere ; 256: 127053, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32454351

RESUMO

To meet the increasing worldwide need for freshwater, it has become critical to exploit non-potable saline water. Solar membrane distillation (MD) is a promising desalination technique, which does not require conventional energy and can reduce the cost of water production. We developed a cost-effective and high-efficiency photothermal membrane that employs TiN nanoparticles as an absorber of sunlight and energy converter. Due to a strong photothermal effect, the solar energy efficiency significantly improved. With optimal membrane and MD operating conditions, we obtained an MD flux of 0.940 kg/m2∙h and a solar efficiency of 64.1% under 1.0 kW/m2 solar irradiation. Compared with a bare poly(vinylidene fluoride) (PVDF) membrane, 65.8% more pure water was produced. Furthermore, the temperature polarization encountered in the conventional MD process was relieved on account of the unique interfacial heating of the photothermal coating, which also contributed to the high solar efficiency. In addition, the membrane was quite stable and the permeate water was of a high, potable quality. The as-prepared photothermal membrane demonstrated a good performance and application prospects for solar MD.


Assuntos
Nanopartículas/química , Titânio/química , Purificação da Água/métodos , Destilação/métodos , Membranas , Membranas Artificiais , Energia Solar , Luz Solar , Temperatura , Água
5.
Nat Microbiol ; 5(5): 655-667, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32341569

RESUMO

The discovery of Asgard archaea, phylogenetically closer to eukaryotes than other archaea, together with improved knowledge of microbial ecology, impose new constraints on emerging models for the origin of the eukaryotic cell (eukaryogenesis). Long-held views are metamorphosing in favour of symbiogenetic models based on metabolic interactions between archaea and bacteria. These include the classical Searcy's and Hydrogen hypothesis, and the more recent Reverse Flow and Entangle-Engulf-Endogenize models. Two decades ago, we put forward the Syntrophy hypothesis for the origin of eukaryotes based on a tripartite metabolic symbiosis involving a methanogenic archaeon (future nucleus), a fermentative myxobacterial-like deltaproteobacterium (future eukaryotic cytoplasm) and a metabolically versatile methanotrophic alphaproteobacterium (future mitochondrion). A refined version later proposed the evolution of the endomembrane and nuclear membrane system by invagination of the deltaproteobacterial membrane. Here, we adapt the Syntrophy hypothesis to contemporary knowledge, shifting from the original hydrogen and methane-transfer-based symbiosis (HM Syntrophy) to a tripartite hydrogen and sulfur-transfer-based model (HS Syntrophy). We propose a sensible ecological scenario for eukaryogenesis in which eukaryotes originated in early Proterozoic microbial mats from the endosymbiosis of a hydrogen-producing Asgard archaeon within a complex sulfate-reducing deltaproteobacterium. Mitochondria evolved from versatile, facultatively aerobic, sulfide-oxidizing and, potentially, anoxygenic photosynthesizing alphaproteobacterial endosymbionts that recycled sulfur in the consortium. The HS Syntrophy hypothesis accounts for (endo)membrane, nucleus and metabolic evolution in a realistic ecological context. We compare and contrast the HS Syntrophy hypothesis to other models of eukaryogenesis, notably in terms of the mode and tempo of eukaryotic trait evolution, and discuss several model predictions and how these can be tested.


Assuntos
Archaea/metabolismo , Evolução Biológica , Eucariotos/metabolismo , Células Eucarióticas/metabolismo , Filogenia , Archaea/genética , Bactérias/genética , Núcleo Celular , Eucariotos/genética , Genoma Arqueal , Hidrogênio/metabolismo , Membranas/metabolismo , Mitocôndrias/metabolismo , Oxirredução , Enxofre/metabolismo , Simbiose/fisiologia
6.
Environ Sci Technol ; 54(9): 5832-5842, 2020 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-32289225

RESUMO

Membrane biofouling constitutes a great challenge in anaerobic membrane bioreactor (AnMBR). Here, we studied the initial deposition of anaerobes, the first step in biofilm formation, with a consortium isolated from an AnMBR on membranes with different surface properties and under two shear rate conditions without filtration. We found that the cell transfer coefficient, calculated from the initial deposition experiments, was similar under the two shear rates for the hydrophobic membranes, but much higher under low shear rate and much lower under high shear rate, for the hydrophilic membrane. The cell transfer coefficient measured under filtration mode and at a higher shear rate showed a similar trend. The pioneer bacteria and archaea (without filtration) were identified by next-generation sequencing. The results showed that the selective force for the dissimilarity of the pioneer bacterial and archaeal diversity was the shear rate and the membrane surface properties, respectively. However, statistical analyses revealed minor changes in the pioneer bacteria (class level) and archaea (order level) populations under the various conditions. These results shed light on the first step of biofilm formation on the membranes in AnMBRs and emphasize the importance of hydrodynamic shear and membrane surface properties on the initially deposited anaerobes.


Assuntos
Incrustação Biológica , Reatores Biológicos , Anaerobiose , Bactérias Anaeróbias , Membranas , Membranas Artificiais , Eliminação de Resíduos Líquidos
7.
Chemosphere ; 254: 126810, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32334259

RESUMO

Anaerobic membrane bioreactor (AnMBR) is used for the treatment of organic solid waste. Clogging of filtration membrane pores, called membrane fouling, is one of the most serious issues for the sustainable operation of AnMBR. Although the physical and chemical mechanisms of the membrane fouling have been widely studied, the biological mechanisms are still unclear. The biofilm formation and development on the membrane might cause the membrane fouling. In this study, the prokaryotic and eukaryotic microbiomes of the membrane-attached biofilms in an AnMBR treating a model slurry of organic solid waste were investigated by non-destructive microscopy and high-throughput sequencing of 16S and 18S rRNA genes. The non-destructive visualization indicated that the biofilm was layered with different structures. The lowermost residual fouling layer was mesh-like and composed of filamentous microorganisms, while the upper cake layer was mainly the non-dense and non-cell region. The principal coordinate and phylogenetic analyses of the sequence data showed that the biofilm microbiomes were different from the sludge. The lowermost layer consisted of operational taxonomic units that were related to Leptolinea tardivitalis and Methanosaeta concilii (9.53-10.07% and 1.14-1.64% of the total prokaryotes, respectively) and Geotrichum candidum (30.22-82.31% of the total eukaryotes), all of which exhibited the filamentous morphology. Moreover, the upper layer was inhabited by the presumably cake-degrading bacteria and predatory eukaryotes. The biofilm microbiome features were consistent with the microscope-visualized structure. These results demonstrated that the biofilm structure and microbiome were the layer specific, which provides better understanding of biological mechanisms of membrane fouling in the AnMBR.


Assuntos
Reatores Biológicos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Anaerobiose , Bactérias , Biofilmes/crescimento & desenvolvimento , Eucariotos , Sequenciamento de Nucleotídeos em Larga Escala , Membranas , Membranas Artificiais , Microbiota , Microscopia , Filogenia , Células Procarióticas , Esgotos , Resíduos Sólidos
8.
PLoS One ; 15(4): e0231194, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32271817

RESUMO

Various injuries to the neural tissues can cause irreversible damage to multiple functions of the nervous system ranging from motor control to cognitive function. The limited treatment options available for patients have led to extensive interest in studying the mechanisms of neuronal regeneration and recovery from injury. Since many neurons are terminally differentiated, by increasing cell survival following injury it may be possible to minimize the impact of these injuries and provide translational potential for treatment of neuronal diseases. While several cell types are known to survive injury through plasma membrane repair mechanisms, there has been little investigation of membrane repair in neurons and even fewer efforts to target membrane repair as a therapy in neurons. Studies from our laboratory group and others demonstrated that mitsugumin 53 (MG53), a muscle-enriched tripartite motif (TRIM) family protein also known as TRIM72, is an essential component of the cell membrane repair machinery in skeletal muscle. Interestingly, recombinant human MG53 (rhMG53) can be applied exogenously to increase membrane repair capacity both in vitro and in vivo. Increasing the membrane repair capacity of neurons could potentially minimize the death of these cells and affect the progression of various neuronal diseases. In this study we assess the therapeutic potential of rhMG53 to increase membrane repair in cultured neurons and in an in vivo mouse model of neurotrauma. We found that a robust repair response exists in various neuronal cells and that rhMG53 can increase neuronal membrane repair both in vitro and in vivo. These findings provide direct evidence of conserved membrane repair responses in neurons and that these repair mechanisms can be targeted as a potential therapeutic approach for neuronal injury.


Assuntos
Regeneração Nervosa , Nervo Isquiático/lesões , Nervo Isquiático/fisiopatologia , Cicatrização , Animais , Linhagem Celular , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Lesões por Esmagamento/patologia , Lesões por Esmagamento/fisiopatologia , Modelos Animais de Doenças , Humanos , Proteínas de Membrana/metabolismo , Membranas , Camundongos Endogâmicos C57BL , Regeneração Nervosa/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Proteínas Recombinantes/farmacologia , Nervo Isquiático/efeitos dos fármacos , Nervo Isquiático/patologia , Proteínas com Motivo Tripartido/farmacologia , Cicatrização/efeitos dos fármacos
9.
PLoS One ; 15(3): e0230207, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32208423

RESUMO

We consider the development and fitting of a dynamic model for desalinated water production by a direct-contact membrane distillation (DCMD) unit. Two types of dynamic-model structures, namely, lumped parameter and spatial, were evaluated. Both the models were validated using experimental response data generated by step testing the inlet hot stream temperature of a DCMD pilot plant. Both the model structures failed to follow the dynamic response adequately. However, a modification of the model by adding a heat loss term resulted in enhanced predictions for both model structures. The overall relative error in the model-plant mismatch was approximately 3%. This is reasonable considering the random uncertainties associated with the plant operation. This observation also improves our understanding of the importance of using better correlations for heat-transfer coefficients, to develop a more reliable and accurate predictive model for a wide range of operating conditions.


Assuntos
Águas Residuárias/química , Purificação da Água/métodos , Água/química , Destilação/métodos , Membranas/química , Temperatura
10.
Nat Rev Mol Cell Biol ; 21(3): 151-166, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32034394

RESUMO

During division, eukaryotic cells undergo a dramatic, complex and coordinated remodelling of their cytoskeleton and membranes. For cell division to occur, chromosomes must be segregated and new cellular structures, such as the spindle apparatus, must be assembled. Pre-existing organelles, such as the nuclear envelope, endoplasmic reticulum and Golgi apparatus, must be disassembled or remodelled, distributed and reformed. Smaller organelles such as mitochondria as well as cytoplasmic content must also be properly distributed between daughter cells. This mixture of organelles and cytoplasm is bound by a plasma membrane that is itself subject to remodelling as division progresses. The lipids resident in these different membrane compartments play important roles in facilitating the division process. In recent years, we have begun to understand how membrane remodelling is coordinated during division; however, there is still much to learn. In this Review, we discuss recent insights into how these important cellular events are performed and regulated.


Assuntos
Divisão Celular/fisiologia , Membranas/metabolismo , Organelas/fisiologia , Animais , Membrana Celular/metabolismo , Retículo Endoplasmático/metabolismo , Endossomos/metabolismo , Células Eucarióticas/citologia , Complexo de Golgi/metabolismo , Humanos , Membranas/fisiologia , Microtúbulos/metabolismo , Mitocôndrias/metabolismo , Organelas/metabolismo , Fuso Acromático/metabolismo
11.
Chemosphere ; 244: 125544, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32050341

RESUMO

Bacterial mercury oxidation coupled to denitrification offers great potential for simultaneous removal of elemental mercury (Hg0) and nitric oxide (NO) in a denitrifying membrane biofilm reactor (MBfR). Four potentially contributory mechanisms tested separately, namely, membrane gas separation, medium absorption, biosorption and biotransformation, which contributed 4.9%/7.2%, 8.1%/8.9%, 38.8%/9.5% and 48.2%/84.9% of overall Hg0/NO removal in MBfR. Herein, Hg0 bio-oxidation, oxidative Hg0 biosorption and denitrification played leading roles in simultaneous removal of Hg0 and NO. Living microbes performed simultaneous Hg0 bio-oxidation and denitrification, in which Hg0 as electron donor was biologically oxidized to oxidized mercury (Hg2+), while NO as the terminal electron acceptor was denitrified to N2. The Hg2+ further complexed with humic acids in extracellular polymeric substances via functional groups (-SH, -OH, -NH- and -COO-) and formed humic acids bound mercury (HA-Hg). Non-living microbial matrix performed oxidative Hg0 biosorption, in which Hg0 may be physically adsorbed by cellular matrix, then non-metabolically oxidized to Hg2+ via oxidative complexation with -SH in humic acids and finally cleavage of S-H bond and surface charge transfer led to formation of HA-Hg. Therefore, bioconversion of Hg0 to HA-Hg by Hg0 bio-oxidation and oxidative Hg0 biosorption coupled with NO denitrification to N2 dynamically cooperated to accomplish simultaneous removal of Hg0 and NO in MBfR.


Assuntos
Reatores Biológicos/microbiologia , Mercúrio/metabolismo , Óxido Nítrico/metabolismo , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/metabolismo , Bactérias , Biofilmes , Desnitrificação , Substâncias Húmicas , Membranas , Mercúrio/análise , Oxirredução
12.
PLoS One ; 15(2): e0226123, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32032370

RESUMO

The visual photopigment protein rhodopsin (Rh) is a typical G protein-coupled receptor (GPCR) that initiates the phototransduction cascade in retinal disk membrane of rod-photoreceptor cells. Rh molecule has a tendency to form dimer, and the dimer tends to form rows, which is suggested to heighten phototransduction efficiency in single-photon regime. In addition, the dimerization confers Rh an affinity for lipid raft, i.e. raftophilicity. However, the mechanism by which Rh-dimer raftophilicity contributes to the organization of the higher order structure remains unknown. In this study, we performed coarse-grained molecular dynamics simulations of a disk membrane model containing unsaturated lipids, saturated lipids with cholesterol, and Rh-dimers. We described the Rh-dimers by two-dimensional particle populations where the palmitoyl moieties of each Rh exhibits raftophilicity. We simulated the structuring of Rh in a disk for two types of Rh-dimer, i.e., the most and second most stable Rh dimers, which exposes the raftophilic regions at the dimerization-interface (H1/H8 dimer) and two edges away from the interface (H4/H5 dimer), respectively. Our simulations revealed that only the H1/H8 dimer could form a row structure. A small number of raftophilic lipids recruited to and intercalated in a narrow space between H1/H8 dimers stabilize the side-by-side interaction between dimers in a row. Our results implicate that the nano-sized lipid raft domains act as a "glue" to organize the long row structures of Rh-dimers.


Assuntos
Simulação de Dinâmica Molecular , Multimerização Proteica , Rodopsina/química , Rodopsina/metabolismo , Colesterol/metabolismo , Cristalografia por Raios X , Ácidos Graxos Insaturados/metabolismo , Cinética , Bicamadas Lipídicas/metabolismo , Lipoilação , Microdomínios da Membrana/metabolismo , Membranas/química , Membranas/metabolismo , Modelos Moleculares , Conformação Proteica em alfa-Hélice , Células Fotorreceptoras Retinianas Bastonetes/metabolismo
13.
J Dairy Sci ; 103(4): 3017-3024, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32089302

RESUMO

Xinong Saanen goat milk is a major source of milk in the Chinese dairy industry. Milk fat globule membrane (MFGM) proteomes of goat colostrum and mature milk were analyzed and compared using proteomic technology. A total of 543 and 585 proteins were identified in goat colostrum and mature milk, respectively. Functional category analyses revealed that most of the MFGM proteins in both colostrum and mature milk were related to phosphoprotein and acetylation. The biological process of translation, cellular component of extracellular exosome, and molecular function of poly(A) RNA binding were the main gene ontology annotations of both colostrum and mature milk. Pathways associated with disease and genetic information processing involved large number of proteins in colostrum and mature milk, and more metabolism-related pathways were observed in mature milk. Protein-protein interaction network analyses showed that ribosome was abundant in both colostrum and mature milk. Colostrum showed more functions associated with protein processing in the endoplasmic reticulum, whereas mature milk had more oxidative phosphorylation functions. The results could provide further understanding of the unique biological properties of MFGM proteins of goat colostrum and mature milk.


Assuntos
Colostro/química , Glicolipídeos/química , Glicoproteínas/química , Cabras , Leite/química , Proteoma , Animais , Feminino , Ontologia Genética , Cabras/metabolismo , Membranas , Proteínas do Leite/análise , Gravidez , Espectrometria de Massas em Tandem
14.
J Dairy Sci ; 103(4): 3002-3016, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32037171

RESUMO

Milk fat globule membrane (MFGM) is a glycosylated, protein-embedded, phospholipid fraction that surrounds triglycerides in milk. Commercial bovine sources have recently come to the market as a novel food ingredient and have been added to various products, including infant formula. Considering that MFGM is a heterogeneous mixture of fat, protein, and carbohydrate, it can be expected that variations among MFGM products exist. For this reason, our aim was to characterize the composition of commercial MFGM samples through a combination of proteomic and lipidomic analyses. Six bovine milk fractions, represented as MFGM fractions or phospholipid fractions, were obtained from various commercial sources. Additionally, the MFGM samples were compared with 2 infant formulas, a standard formula as well as a premium formula containing MFGM. For proteomic analysis, bottom-up data-dependent liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed on each MFGM fraction, and nearly a thousand proteins were identified across all samples, with 364 of them having different abundance across the samples tested. One hundred twelve proteins differed by a fold-change of 10 or greater, 14 by a fold-change of 50, and 2 by a fold-change of 100 in at least 1 pair, suggesting large differences in the proteins present in these fractions. Even though the classical MFGM proteins were enriched in the MFGM fractions, the relative protein composition varied considerably, and all contain an abundance of milk (casein and whey) proteins. Lipidomic analysis identified a total of 393 lipid species across both positive and negative ionization modes, with the major classes detected being triglycerides, sphingomyelins, and several phospholipids. Across all samples, triglycerides comprised at least 50% of total lipids, with phosphatidylcholine and sphingomyelin being the second and third most abundant lipid classes, respectively. These findings demonstrate the heterogeneous nature of various bovine commercial MFGM fractions. This variation must be considered when evaluating and describing potential functional benefits of these products shown in clinical trials.


Assuntos
Glicolipídeos , Glicoproteínas , Leite/química , Animais , Caseínas/análise , Bovinos , Cromatografia Líquida , Humanos , Lactente , Fórmulas Infantis/química , Membranas , Proteômica/métodos , Espectrometria de Massas em Tandem , Triglicerídeos/análise , Triglicerídeos/química , Proteínas do Soro do Leite/análise
15.
Water Res ; 172: 115509, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31986399

RESUMO

A MBR treating compost leachate was studied in order to link the operating parameters (solid and hydraulic retention time) to contaminant's specific bacterial catabolic activity. In this context, a lab-scale aerobic membrane bioreactor was operated for 200 days, at solid retention times (SRT) of 30 and 45 days and four different contaminant load rates. Results showed that increasing the food to microorganism ratio (F/M) by increasing the contaminant load rates lessened the selectivity pressure, which allowed the proliferation of subdominant operational taxonomic units (OTU) (relative abundance >3%) that were otherwise inhibited by highly adapted dominant OTUs (relative abundance >10%). Subsequently, increasing the SRT resulted in a lower species richness and the selection of two dominant types of bacteria: 1) genera with low growth rates that feed on non-limiting substrates or substrates with few competitors, and 2) genera with metabolisms that are highly specific to the available substrates and that can outcompete the other genera by using the substrate more efficiently. The bacterial population evolution observed during this study suggests that the mixed liquor population diversity and structure can be modulated with the operating conditions for the bioenhancement of contaminant specific catabolic activity. Identified dominant and subdominant genera were linked to the MBR's NH4+ and COD removal performances. Interestingly, nitrification performances were unaffected by the organic load rate and the Nitrosomonas relative abundance.


Assuntos
Bactérias , Reatores Biológicos , Membranas , Nitrificação , Nitrosomonas
16.
Nat Commun ; 11(1): 541, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992713

RESUMO

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging.


Assuntos
Grafite/química , Microscopia Eletrônica/instrumentação , Microscopia Eletrônica/métodos , Fenômenos Químicos , Microscopia Crioeletrônica/métodos , Elétrons , Desenho de Equipamento , Processamento de Imagem Assistida por Computador , Membranas , Polímeros , Proteínas
17.
Chemosphere ; 244: 125508, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31812042

RESUMO

Two H2-based membrane biofilm reactor (H2-MBfR) systems, differing in membrane type, were tested for sulfate reduction from a real mining-process water having low alkalinity and high concentrations of dissolved sulfate and calcium. Maximum sulfate reductions were 99%, with an optimum pH range between 8 and 8.5, which minimized any toxic effect of unionized hydrogen sulfide (H2S) on sulfate-reducing bacteria (SRB) and calcite scaling on the fibers and in the biofilm. Although several strategies for control of pH and gas back-diffusion were applied, it was not possible to sustain a high degree of sulfate reduction over the long-term. The most likely cause was precipitation of calcite inside the biofilm and on the surface of fibers, which was shown by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) analysis. Another possible cause was a decline in pH, leading to inhibition by H2S. A H2/CO2 mixture in the gas supply was able to temporarily recover the effectiveness of the reactors and stabilize the pH. Biomolecular analysis showed that the biofilm was comprised of 15-20% SRB, but a great variety of autotrophic and heterotrophic genera, including sulfur-oxidizing bacteria, were present. Results also suggest that the MBfR system can be optimized by improving H2 mass transfer using fibers of higher gas permeability and by feeding a H2/CO2 mixture that is automatically adjusted for pH control.


Assuntos
Reatores Biológicos/microbiologia , Mineração , Sulfatos/metabolismo , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/metabolismo , Processos Autotróficos , Bactérias , Biofilmes , Hidrogênio/química , Membranas , Membranas Artificiais , Oxirredução , Sulfatos/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
18.
Bioresour Technol ; 296: 122314, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31671329

RESUMO

Processing complexities associated with different lignocellulosic bioethanol production stages have hindered reaching full commercial capacity. Therefore, in this study efforts were made to remediate some issues associated with hydrolysis and fermentation, by the integration of immersed membrane bioreactors (iMBRs) into lignocellulosic bioethanol production process. In this regards, double-staged continuous saccharification-filtration and co-fermentation-filtration of wheat straw slurry was conducted using iMBRs at filtration fluxes up to 51.0 l.m-2.h-1 (LMH). The results showed a stable long-term (264 h) continuous hydrolysis-filtration and fermentation-filtration with effective separation of lignin-rich solids (up to 70% lignin) from hydrolyzed sugars, and separation of yeast cells from bioethanol stream at an exceptional filtration performance at 21.9 LMH. Moreover, the effect of factors such as filtration flux, medium quality and backwashing on fouling and cake-layer formation was studied. The results confirmed the process intensification potentials of iMBRs in tackling commonly faced technical obstacles in lignocellulosic bioethanol production.


Assuntos
Etanol , Lignina , Reatores Biológicos , Fermentação , Hidrólise , Membranas
19.
Bioresour Technol ; 296: 122301, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31678707

RESUMO

The formation of the dynamic membrane (DM) in an anaerobic dynamic membrane bioreactor (AnDMBR) treating food waste was, previously, found to be beneficial to the stable performance of an anaerobic digestion system. This study examines the effect of shear velocity and feed concentration on the performance and microbial community of an AnDMBR treating food waste. The shear velocity was varied from 0.04 to 1.74 m/h, using three different feed concentrations (50, 80, and 100 g-COD/L). The highest average methane production rate of 2.6 L-CH4/L/d was achieved at a feed concentration and shear velocity of 100-g COD/L and 0.34 m/h, respectively. Increasing shear velocity, within certain limits, is beneficial to AnDMBR systems, promoting better mixing, substrate-biomass interactions, and DM layer formation. Methanosarcina flavescens proliferated (69%) at high shear velocities when acetic acid was the major volatile fatty acid. The abundance ratio between Bacteroidetes and Firmicutes showed a linear relationship to methanogenic performance.


Assuntos
Microbiota , Eliminação de Resíduos , Anaerobiose , Reatores Biológicos , Alimentos , Membranas , Metano
20.
Bioresour Technol ; 296: 122352, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31708385

RESUMO

The aim of this work was to study reverse solute flux (RSF) from osmotic membrane bioreactor (OMBR) and consequent solute buildup in the feed side. A polyelectrolyte (PAA-Na) served as a draw solute (DS) to minimize RSF in OMBRs. In addition, a bioelectrochemical system (BES) was employed to drive accumulated cations from the feed/anode side into the cathode compartment, subsequently achieving PAA-Na DS recovery with the aid of high catholyte pH. Compared to the 1 M NH4HCO3 DS, the 0.48 g mL-1 PAA-Na DS produced consistently stable water flux, enhanced water recovery and increased ammonium removal efficiency. Due to a dynamic balance between PAA removal and continuing RSF, the residual PAA concentration was 72 mg L-1 on the feed side (27.0% of TOC). These results demonstrate the advantages of integrating a PAA-Na DS with a BES to mitigate RSF and to support further development of OMBR technology.


Assuntos
Polieletrólitos , Purificação da Água , Reatores Biológicos , Membranas , Membranas Artificiais , Osmose
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