| 1. |
- Abadikhah, Marie, 1992, et al.
(författare)
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Effect of anode material and dispersal limitation on the performance and biofilm community in microbial electrolysis cells
- 2023
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Ingår i: Biofilm. - 2590-2075. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54–80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10–16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61–98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0–20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64–89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.
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| 2. |
- Abadikhah, Marie, 1992, et al.
(författare)
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Evidence of competition between electrogens shaping electroactive microbial communities in microbial electrolysis cells
- 2022
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by hydrogen-utilizing taxa such as Methanobacterium and had a much lower proportion of negative correlations than the anodes. This could be explained by the diffusion of hydrogen throughout the cathode biofilms, reducing the need to compete for space.
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| 3. |
- Burzio, Cecilia, 1991, et al.
(författare)
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Sorption of pharmaceuticals to foam and aerobic granular sludge with different morphologies
- 2024
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Ingår i: Resources, Environment and Sustainability. - : Elsevier BV. - 2666-9161. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- In biological wastewater treatment, the sorption process is an important removal pathway of organic micropollutants from the aqueous phase. Beyond the conventional sorption to biomass and particulate matter, organic molecules can also partition to gas bubbles commonly present in aerated biological processes. This study investigated the partitioning behavior of 21 selected pharmaceuticals to two types of aerobic granular sludge, and the foam generated by aeration. Batch sorption experiments were performed with biologically inactive granules of controlled diameters (0.5–1, 1–2, and >2 mm). Removal during sorption tests was observed for four positively charged micropollutants (sertraline, citalopram, clarithromycin, and erythromycin), four neutral compounds (levonorgestrel, estradiol, ethinylestradiol, and ketoconazole), and one negatively charged pharmaceutical (losartan). This highlights the importance of electrostatic interactions and lipophilic affinity with the solids. For some compounds, the removal increased with time, suggesting that sorption in thick biofilm is limited by molecular diffusion into the biofilm matrix. Furthermore, partitioning of pharmaceuticals to aeration-induced foam was confirmed in separate batch tests. Clarithromycin, erythromycin, ketoconazole, losartan, levonorgestrel, and ethinylestradiol exhibited concentrations in the foam 1.0–5.3 times higher than the initial test values, indicating potential adsorption at the liquid/gas interface for these compounds.
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| 4. |
- Modin, Oskar, 1980, et al.
(författare)
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A relationship between phages and organic carbon in wastewater treatment plant effluents
- 2022
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Ingår i: Water Research X. - : Elsevier BV. - 2589-9147. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- With stringent effluent requirements and the implementation of new processes for micropollutant removal, it is increasingly important for wastewater treatment plants (WWTPs) to understand the factors affecting effluent quality. Phages (viruses infecting prokaryotes) are abundant in the biological treatment processes. They can contribute to organic carbon in the treated effluent both because they are organic in nature and occur in the effluent and because they cause lysis of microorganisms. Today very little is known about the effects of phages on effluent quality. The goal of this study was, therefore, to determine the relationship between phages and organic carbon in WWTP effluents. We also examined the diversity, taxonomy, and host-association of DNA phages using metagenomics. Effluent samples were collected from four WWTPs treating municipal wastewater. Significant differences in both organic carbon and virus-like particle concentrations were observed between the plants and there was a linear relationship between the two parameters. The phage communities were diverse with many members being taxonomically unclassified. Putative hosts were dominated by bacteria known to be abundant in activated sludge systems such as Comamonadaceae. The composition of phages differed between the WWTPs, suggesting that local conditions shape the communities. Overall, our findings suggest that the abundance and composition of phages are related to effluent quality. Thus, there is a need for further research clarifying the association between phage dynamics and WWTP function.
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| 5. |
- Abadikhah, Marie, 1992
(författare)
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Influence of electrode material and stochastic factors on the performance and microbial community assembly in microbial electrochemical systems
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microbial electrolysis cells (MECs) are systems with microbial communities in the form of biofilms on electrode surfaces. The electrogenic bacteria in the anode biofilm act as catalysts for the oxidization of organic compounds, leading to release of electrons, generation of electrical current, and production of hydrogen and methane at the cathode. In addition to production of energy carriers, MECs can be used for other applications as well; for example, as biosensors to monitor biochemical oxygen demand or toxicity. The performance of MECs is determined by both deterministic and stochastic factors influencing the microbial communities on the electrode surfaces, most of which as still poorly understood. In this thesis, the effects of electrode materials on microbial community assembly and MEC performance was investigated. Two experiments were carried out. In the first, three cathode materials (carbon nanoparticles, titanium, and steel) were compared. In the second, three anode materials (carbon cloth, graphene, and nickel) were compared. The cathode materials had no significant effect on the performance of the MECs, as opposed to the anode materials where carbon cloth MECs had the highest current density and the shortest lag time during startup. The differences seen in lag time of replicate systems at the start of the experiment indicated a stochastic initial attachment of the electrogenic bacteria on the anode. Different microbial communities develop in the biofilms on the anodes and cathodes. Electrogens from the Desulfobacterota phylum dominated the anode, while various hydrogenotrophic methanogens, e.g., Methanobacterium, were found to dominate on the cathodes. Diversity and null model analysis of the electrode communities highlighted stochasticity and not electrode material as the important factor in the community assembly. Network analysis showed that the cathode communities had fewer negative interactions between taxa in comparison to the anode. Since hydrogen gas generated at the cathode surface can diffuse through the biofilm, all microorganisms on the cathode have access to the substrate, reducing the need for competition between species. In contrast, electrogens require a short distance to the anode to be able to use it as electron acceptor. Limited space on the anode and competition between electrogens shaped the anode communities and explain the higher number of negative interactions observed. Based on the findings in this thesis, it is suggested that stochastic factors have more influence than electrode material on the anode community even though there is a selective pressure for electrogenic bacteria.
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| 6. |
- Abadikhah, Marie, 1992
(författare)
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Microbial communities in biological electrochemical systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological electrochemical systems (BES) can be used as biosensors and for recovery of resources from waste streams. BES utilizes microbial communities that grow on the surface of electrodes in the form of biofilms. Electrogenic bacteria residing in the anode biofilm initiate oxidation reactions, resulting in the release of electrons and subsequent electrical current generation. The electrons flow to the cathode where reduction reactions take place. Microbial biofilms may also be involved in the catalysis of cathode reactions. Many factors are involved in shaping the composition and performance of the microbial communities in BES, most of which remain poorly understood. In this thesis, the impact of electrode material and biotic interactions on performance and microbial community assembly was investigated in microbial electrolysis cells (MECs) oxidizing volatile fatty acids at the anode. MECs are a type of BES that require an applied electric potential to generate products such as H2, CH4, and acetate at the cathode. MECs with mixed-culture biofilms on both the anode and the cathode were studied. Two experiments were conducted. The first was a comparison of MECs with three different cathode materials: carbon nanoparticles, titanium, and steel. The second was a comparison of MECs with three different anode materials: carbon cloth, graphene, and nickel. Furthermore, the effect of dispersal limitation as well as the presence of viruses and their associations with microorganisms was investigated. MECs with carbon cloth anodes had the highest current density and shortest lag time during startup. In contrast, no significant impact of cathode material on MEC performance was seen. The anode communities were dominated by electrogens from the Desulfobacterota phylum, while the cathodes were dominated by methanogens from the Methanobacteriaceae family. Stochastic initial attachment by competing electrogens on the anode explained variations in the startup time between replicate MECs. In each experiment at least two different Desulfobacterota species competed for dominance on the anode. MECs that enabled dispersal between the system tended to have the same dominating taxa. Biotic interactions also affected the microbial communities in the system. Network analysis showed that the anode communities had a greater number of negative interactions between taxa compared to the cathode. Due to the need for direct contact by electrogens to transfer electrons to the anode, there is a higher competitive element to the colonization of the anode biofilm. Viral infection is another type of biotic interaction. Analysis of the prokaryotic and viral communities resulted in the identification of CRISPR-based and prophage virus-host associations, indicating previous infections and prophage inductions of electrochemically active microorganisms. These findings suggest that while there is selective pressure for electrogenic bacteria on the anode, stochastic factors, and biotic interactions play a larger role compared to electrode material in shaping the anode community.
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