| 1. |
- Abromaitis, V., et al.
(author)
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Effect of shear stress and carbon surface roughness on bioregeneration and performance of suspended versus attached biomass in metoprolol-loaded biological activated carbon systems
- 2017
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In: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 317, s. 503-511
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Journal article (peer-reviewed)abstract
- The bioregeneration of activated carbon (AC) in biological activated carbon (BAC) systems is limited by sorption-desorption hysteresis and transport between the adsorbent and biomass. In this study, we investigated these limitations and whether a biofilm covering the AC surface is required. Consequently, BAC reactors were operated at different shear stress and AC surface smoothness, since this may affect biofilm formation. The experiments were carried out in BAC and blank reactors treating synthetic wastewater containing the pharmaceutical metoprolol. After start-up, all reactors removed metoprolol completely; however, after 840 h the removal dropped due to saturation of the AC. In the blank reactors, the removal dropped to 0% while in the BAC reactors removal recovered to >99%, due to increased biological activity. During the initial phase, the metoprolol was adsorbed, rather than biodegraded. At the end, the AC from the BAC reactors had higher pore volume and sorption capacity than from the blank reactors, showing that the AC had been bioregenerated. At high shear (G = 25 s(-1)), the rough AC granules (R-a = 13 mu m) were covered with a 50-400 gm thick biofilm and the total protein content of the biofilm was 2.6 mg/gAC, while at lower shear (G = 8.8 s(-1)) the rough AC granules were only partly covered. The biofilm formation at lower shear (G = 8.8 s(-1)) on smooth AC granules (R-a = 1.6 mu m) was negligible. However, due to the presence of suspended biomass the reactor performance or bioregeneration were not reduced. This showed that direct contact between the AC and biomass was not essential in mixed BAC systems. The microbial analyses of the suspended biomass and the biofilm on AC surface indicated that metoprolol was mainly biodegraded in suspension. (C) 2017 Elsevier B.V. All rights reserved.
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| 2. |
- Broman, Elias, 1985-, et al.
(author)
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Low temperature, autotrophic microbial denitrification using thiosulfate or thiocyanate as electron donor
- 2017
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In: Biodegradation. - : Springer. - 0923-9820 .- 1572-9729. ; 28:4, s. 287-301
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Journal article (peer-reviewed)abstract
- Wastewaters generated during mining and processing of metal sulfide ores are often acidic (pH < 3) and can contain significant concentrations of nitrate, nitrite, and ammonium from nitrogen based explosives. In addition, wastewaters from sulfide ore treatment plants and tailings ponds typically contain large amounts of inorganic sulfur compounds, such as thiosulfate and tetrathionate. Release of these wastewaters can lead to environmental acidification as well as an increase in nutrients (eutrophication) and compounds that are potentially toxic to humans and animals. Waters from cyanidation plants for gold extraction will often conjointly include toxic, sulfur containing thiocyanate. More stringent regulatory limits on the release of mining wastes containing compounds such as inorganic sulfur compounds, nitrate, and thiocyanate, along the need to increase production from sulfide mineral mining calls for low cost techniques to remove these pollutants under ambient temperatures (approximately 8 °C). In this study, we used both aerobic and anaerobic continuous cultures to successfully couple inorganic sulfur compound (i.e. thiosulfate and thiocyanate) oxidation for the removal of nitrogenous compounds under neutral to acidic pH at the low temperatures typical for boreal climates. Furthermore, the development of the respective microbial communities was identified over time by DNA sequencing, and found to contain a consortium including populations aligning within Flavobacterium, Thiobacillus, and Comamonadaceae lineages. This is the first study to remediate mining waste waters by coupling autotrophic thiocyanate oxidation to nitrate reduction at low temperatures and acidic pH by means of an identified microbial community.
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| 3. |
- Dopson, Mark, et al.
(author)
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Possibilities for extremophilic microorganisms in microbial electrochemical systems
- 2016
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In: FEMS Microbiology Reviews. - : Oxford University Press (OUP). - 0168-6445 .- 1574-6976. ; 40:2, s. 164-181
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Research review (peer-reviewed)abstract
- Microbial electrochemical systems exploit the metabolism of microorganisms to generate electrical energy or a useful product. In the past couple of decades, the application of microbial electrochemical systems has increased from the use of wastewaters to produce electricity to a versatile technology that can use numerous sources for the extraction of electrons on the one hand, while on the other hand these electrons can be used to serve an ever increasing number of functions. Extremophilic microorganisms grow in environments that are hostile to most forms of life and their utilization in microbial electrochemical systems has opened new possibilities to oxidize substrates in the anode and produce novel products in the cathode. For example, extremophiles can be used to oxidize sulfur compounds in acidic pH to remediate wastewaters, generate electrical energy from marine sediment microbial fuel cells at low temperatures, desalinate wastewaters and act as biosensors of low amounts of organic carbon. In this review, we will discuss the recent advances that have been made in using microbial catalysts under extreme conditions and show possible new routes that extremophilic microorganisms open for microbial electrochemical systems.This review highlights the use of microbial electrochemical systems to catalyze environmental processes coupled to the production of energy or valuable resources and how utilizing extremophilic microorganisms opens up new possibilities such as bioremediation of environmentally hazardous wastes.This review highlights the use of microbial electrochemical systems to catalyze environmental processes coupled to the production of energy or valuable resources and how utilizing extremophilic microorganisms opens up new possibilities such as bioremediation of environmentally hazardous wastes.
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| 4. |
- Ni, Gaofeng, et al.
(author)
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A novel inorganic sulfur compound metabolizing Ferroplasma-like population is suggested to mediate extracellular electron transfer
- 2018
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In: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X.
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Journal article (peer-reviewed)abstract
- Mining and processing of metal sulfide ores produces waters containing metals and inorganic sulfur compounds such as tetrathionate and thiosulfate. If released untreated, these sulfur compounds can be oxidized to generate highly acidic wastewaters [termed 'acid mine drainage (AMD)'] that cause severe environmental pollution. One potential method to remediate mining wastewaters is the maturing biotechnology of 'microbial fuel cells' that offers the sustainable removal of acid generating inorganic sulfur compounds alongside producing an electrical current. Microbial fuel cells exploit the ability of bacterial cells to transfer electrons to a mineral as the terminal electron acceptor during anaerobic respiration by replacing the mineral with a solid anode. In consequence, by substituting natural minerals with electrodes, microbial fuel cells also provide an excellent platform to understand environmental microbemineral interactions that are fundamental to element cycling. Previously, tetrathionate degradation coupled to the generation of an electrical current has been demonstrated and here we report a metagenomic and metatranscriptomic analysis of the microbial community. Reconstruction of inorganic sulfur compound metabolism suggested the substrate tetrathionate was metabolized by the Ferroplasma-like and Acidithiobacillus-like populations via multiple pathways. Characterized Ferroplasma species do not utilize inorganic sulfur compounds, suggesting a novel Ferroplasma-likepopulation had been selected. Oxidation of intermediate sulfide, sulfur, thiosulfate, and adenylylsulfate released electrons and the extracellular electrontransfer to the anode was suggested to be dominated by candidate soluble electron shuttles produced by the Ferroplasma-like population. However, as the soluble electron shuttle compounds also have alternative functions within the cell, it cannot be ruled out that acidophiles use novel, uncharacterized mechanisms to mediate extracellular electron transfer. Several populations within the community were suggested to metabolize intermediate inorganicsulfur compounds by multiple pathways, which highlights the potential for mutualistic or symbiotic relationships. This study provided the genetic base for acidophilic microbial fuel cells utilized for the remediation of inorganic sulfur compounds from AMD.
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| 5. |
- Ni, Gaofeng, et al.
(author)
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Electricity generation from an inorganic sulfur compound containing mining wastewater by acidophilic microorganisms
- 2016
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In: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 167:7, s. 568-575
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Journal article (peer-reviewed)abstract
- Sulfide mineral processing often produces large quantities of wastewaters containing acid-generating inorganic sulfur compounds. If released untreated, these wastewaters can cause catastrophic environmental damage. In this study, microbial fuel cells were inoculated with acidophilic microorganisms to investigate whether inorganic sulfur compound oxidation can generate an electrical current. Cyclic voltammetry suggested that acidophilic microorganisms mediated electron transfer to the anode, and that electricity generation was catalyzed by microorganisms. A cation exchange membrane microbial fuel cell, fed with artificial wastewater containing tetrathionate as electron donor, reached a maximum whole cell voltage of 72 +/- 9 mV. Stepwise replacement of the artificial anolyte with real mining process wastewater had no adverse effect on bioelectrochemical performance and generated a maximum voltage of 105 +/- 42 mV. 16S rRNA gene sequencing of the microbial consortia resulted in sequences that aligned within the genera Thermoplasma, Ferroplasma, Leptospirillum, Sulfobacillus and Acidithiobacillus. This study opens up possibilities to bioremediate mining wastewater using microbial fuel cell technology. (C) 2016 The Authors. Published by Elsevier Masson SAS on behalf of Institut Pasteur.
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| 6. |
- Ni, Gaofeng, et al.
(author)
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Haloalkaliphilic microorganisms assist sulfide removal in a microbial electrolysis cell
- 2019
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In: Journal of Hazardous Materials. - : Elsevier. - 0304-3894 .- 1873-3336. ; 363, s. 197-204
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Journal article (peer-reviewed)abstract
- Several industrial processes produce toxic sulfide containing streams that are often scrubbed using caustic solutions. An alternative, cost effective sulfidetreatment method is bioelectrochemical sulfide removal. For the first time, a haloalkaliphilic sulfide-oxidizing microbial consortium was introduced to the anodic chamber of a microbial electrolysis cell operated at alkaline pH and with 1.0 M sodium ions. Under anode potential control, the highest sulfideremoval rate was 2.16 mM/day and chemical analysis supported that the electrical current generation was from the sulfide oxidation. Biotic operation produced a maximum current density of 3625 mA/m(2) compared to 210 mA/m2 while under abiotic operation. Furthermore, biotic electrical production was maintained for a longer period than for abiotic operation, potentially due to the passivation of the electrode by elemental sulfur during abiotic operation. The use of microorganisms reduced the energy input in this study compared to published electrochemical sulfide removal technologies. Sulfide-oxidizing populations dominated both the planktonic and electrode-attached communities with 16S rRNA gene sequences aligning within the genera Thioctikalivibrio, Thioalkaihnicrobium, and Desulfurivibrio. The dominance of the Desulfurivibrio-like population on the anode surface offered evidence for the first haloalkaliphilic bacterium able to couple electrons from sulfide oxidation to extracellular electron transfer to the anode.
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| 7. |
- Ni, Gaofeng, et al.
(author)
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Microbial Community and Metabolic Activity in Thiocyanate Degrading Low Temperature Microbial Fuel Cells
- 2018
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In: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 9
-
Journal article (peer-reviewed)abstract
- Thiocyanate is a toxic compound produced by the mining and metallurgy industries that needs to be remediated prior to its release into the environment. If the industry is situated at high altitudes or near the poles, economic factors require a low temperature treatment process. Microbial fuel cells are a developing technology that have the benefits of both removing such toxic compounds while recovering electrical energy. In this study, simultaneous thiocyanate degradation and electrical current generation was demonstrated and it was suggested that extracellular electron transfer to the anode occurred. Investigation of the microbial community by 16S rRNA metatranscriptome reads supported that the anode attached and planktonic anolyte consortia were dominated by a Thiobacillus-like population. Metatranscriptomic sequencing also suggested thiocyanate degradation primarily occurred via the 'cyanate' degradation pathway. The generated sulfide was metabolized via sulfite and ultimately to sulfate mediated by reverse dissimilatory sulfite reductase, APS reductase, and sulfate adenylyltransferase and the released electrons were potentially transferred to the anode via soluble electron shuttles. Finally, the ammonium from thiocyanate degradation was assimilated to glutamate as nitrogen source and carbon dioxide was fixed as carbon source. This study is one of the first to demonstrate a low temperature inorganic sulfur utilizing microbial fuel cell and the first to provide evidence for pathways of thiocyanate degradation coupled to electron transfer.
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| 8. |
- Ni, Gaofeng
(author)
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When bioelectrochemical systems meet extremophiles, possibilities and challenges
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- Extremophiles are microorganisms live and thrive in extreme environments that are harsh and hostile to most forms of life on earth (e.g. low pH, low temperature, high pH and high salinity). They have developed strategies to obtain nutrients and conserve energy to sustain life under these adverse conditions. Such metabolic capabilities are valuable to be exploit for industrial applications such as the remediation of environmental pollutions, which typically bring about extreme physicochemical conditions. The advancing technology bioelectrochemical systems can utilize the microbial metabolism to oxidize a substrate while simultaneously recover electrical energy or produce a useful product in an electrochemical set-up. It enables the remediation of pollutions, and its integration with extremophiles has opened up a wide range of possibilities to tackle various industrial waste streams with extreme conditions in an environmentally friendly manner. Inorganic sulfur compounds such as tetrathionate, thiocyanate and sulfide that originate from mining, metal refinery and petroleum industries are toxic and hazardous to the recipient water body and human health if discharged untreated. The remediation of these three compounds with bioelectrochemical systems that incorporates extremophiles was investigated in three separate studies of this thesis. 16S rRNA gene amplicon sequencing, metagenomics and metatranscriptomics are utilized to profile the microbial communities, and to understand their metabolic potential and states. Tetrathionate degradation with acidophilic microorganisms in microbial fuel cells at pH 2 was demonstrated in the first study of this thesis. Electricity was produced from the oxidation of tetrathionate, facilitated by the anodic microbiome. 16S rRNA gene amplicon sequencing showed that this community was dominated by members of the genera Thermoplasma, Ferroplasma, Leptospirillum, Sulfobacillus and Acidithiobacillus. Metagenomic analysis reconstructed genomes that were most similar to the genera Ferroplasma, Acidithiobacillus, Sulfobacillus and Cuniculiplasma. Together with metatranscriptomic analysis, it was indicated that this microbial community was metabolizing tetrathionate and other intermediate sulfur compounds via multiple pathways, the electrons released from oxidation were suggested to be transferred to the electrode via soluble electron shuttles. In addition, the Ferroplasma-like population in this study was suggested to be active in metabolising inorganic sulfur compounds and synthesizing soluble electron shuttles. Since characterized Ferroplasma species do not utilize inorganic sulfur compounds, the anodic compartment might have selected a novel Ferroplasma population. Next, thiocyanate degradation with psychrophilic microorganisms in microbial fuel cells at 8 °C was demonstrated for the first time. Electricity generation alongside with thiocyanate degradation facilitated by the anodic microbiome was observed. 16S rRNA gene amplicon sequencing and metatranscriptomics suggested that Thiobacillus was the predominant and most active population. mRNA analysis revealed that thiocyanate was metabolized primarily via the ‘cyanate’ degradation pathway; the resultant sulfide was oxidized; ammonium was assimilated; carbon dioxide was fixed as carbon source. It was also suggested by mRNA analysis that the consortium used multiple mechanisms to acclimate low temperature such as the synthesis of cold shock proteins, cold inducible proteins and molecular chaperones. Finally, sulfide removal with haloalkaliphilic microorganisms in microbial electrolysis cells operated at pH 8.8 to 9.5 and with 1.0 M sodium ion was investigated. The anodic microbiome was hypothesized to facilitate current generation by the oxidation of sulfide and of intermediate sulfur compounds to sulfate, which was supported by chemical analysis and microbial profiling. Dominant populations from the anode had 16S rRNA gene sequences that aligned within the genera Thioalkalivibrio, Thioalkalimicrobium, and Desulfurivibrio, which are known for sulfide oxidation. Intriguingly, Desulfurivibrio dominated the electrode-attached community, possibly enriched by the electrode as a selecting pressure. This finding suggested a novel role of this organism to carry out sulfide oxidation coupled to electron transfer to the electrode. These three studies demonstrated the possibilities of utilizing extremophilic bioelectrochemical systems to remediate various inorganic sulfur pollution streams. The advancing molecular microbiological tools facilitated the investigation towards the composition and metabolic state of the microbial community. Challenges remain in a more thorough understanding regarding the metabolism of extremophiles (e.g. sulfur metabolism and extracellular electron transfer) and better energy recovery in bioelectrochemical systems.
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