| 1. |
- Valk, Laura C., et al.
(författare)
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Galacturonate Metabolism in Anaerobic Chemostat Enrichment Cultures : Combined Fermentation and Acetogenesis by the Dominant sp nov "Candidatus Galacturonibacter soehngenii"
- 2018
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 84:18
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural residues such as sugar beet pulp and citrus peel are rich in pectin, which contains galacturonic acid as a main monomer. Pectin-rich residues are underexploited as feedstocks for production of bulk chemicals or biofuels. The anaerobic, fermentative conversion of D-galacturonate in anaerobic chemostat enrichment cultures provides valuable information toward valorization of these pectin-rich feedstocks. Replicate anaerobic chemostat enrichments, with D-galacturonate as the sole limiting carbon source and inoculum from cow rumen content and rotting orange peels, yielded stable microbial communities, which were dominated by a novel Lachnospiraceae species, for which the name "Candidatus Galacturonibacter soehngenii" was proposed. Acetate was the dominant catabolic product, with formate and H-2 as coproducts. The observed molar ratio of acetate and the combined amounts of H-2 and formate deviated significantly from 1, which suggested that some of the hydrogen and CO2 formed during D-galacturonate fermentation was converted into acetate via the Wood-Ljungdahl acetogenesis pathway. Indeed, metagenomic analysis of the enrichment cultures indicated that the genome of "Candidatus G. soehngenii" encoded enzymes of the adapted Entner-Doudoroff pathway for D-galacturonate metabolism as well as enzymes of the Wood-Ljungdahl pathway. The simultaneous operation of these pathways may provide a selective advantage under D-galacturonate-limited conditions by enabling a higher specific ATP production rate and lower residual D-galacturonate concentration than would be possible with a strictly fermentative metabolism of this carbon and energy source. IMPORTANCE This study on D-galacturonate metabolism by open, mixed-culture enrichments under anaerobic, D-galacturonate-limited chemostat conditions shows a stable and efficient fermentation of D-galacturonate into acetate as the dominant organic fermentation product. This fermentation stoichiometry and population analyses provide a valuable baseline for interpretation of the conversion of pectin-rich agricultural feedstocks by mixed microbial cultures. Moreover, the results of this study provide a reference for studies on the microbial metabolism of D-galacturonate under different cultivation regimes.
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| 2. |
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| 3. |
- Ekholm, Jennifer, et al.
(författare)
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Full-scale aerobic granular sludge for municipal wastewater treatment – granule formation, microbial succession, and process performance
- 2022
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Ingår i: Environmental Science: Water Research & Technology. - 2053-1419. ; :8, s. 3138-3154
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Tidskriftsartikel (refereegranskat)abstract
- Aerobic granular sludge (AGS) plants have gained growing interest and application due to their low energy demand, small footprint, and low operational costs. However, the fulfilment of strict discharge limits for nitrogen and phosphorus, vast seasonal temperature variations, and large peaks in influent flows may pose challenges to the implementation of AGS. Moreover, the knowledge about microbial community assembly and process performance under varying environmental conditions in full-scale reactors is still limited. In this study, the first implementation of the AGS process in the Nordic countries was assessed. In two full-scale AGS reactors with different seeding sludges, the start-up was associated with rapid changes in microbial community composition in both, but only successful granulation in one. As a consequence, the non-granulated reactor was eventually reseeded with biomass from the better granulated reactor. This resulted in a convergence of the microbial communities in the two reactors with the maintenance of stable sludge concentrations (6–8 g L−1) with large granules (50–80% with diameter >2 mm) and fast settling of biomass (SVI30/SVI10 of 0.9–1). Immigration from the influent wastewater was a minor factor affecting the microbial community once the granules had formed, while the seasonal variations in environmental factors were identified as important. Key guilds of AOB (Nitrosomonas), NOB (mainly Ca. Nitrotoga), PAOs (mainly Tetrasphaera), and GAOs (mainly Ca. Competibacter) varied considerably in abundance throughout the study period. After 15 months, stable organic matter, nitrogen, and phosphorus removal were attained with low effluent concentrations. During the start-up, the BOD7/N ratio, influent flow, and temperature were important factors influencing the performance of the AGS.
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| 4. |
- Ekholm, Jennifer, 1992, et al.
(författare)
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Full-scale aerobic granular sludge for municipal wastewater treatment - granule formation, microbial succession, and process performance
- 2022
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Ingår i: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 8:12, s. 3138-3154
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Tidskriftsartikel (refereegranskat)abstract
- Aerobic granular sludge (AGS) plants have gained growing interest and application due to their low energy demand, small footprint, and low operational costs. However, the fulfilment of strict discharge limits for nitrogen and phosphorus, vast seasonal temperature variations, and large peaks in influent flows may pose challenges to the implementation of AGS. Moreover, the knowledge about microbial community assembly and process performance under varying environmental conditions in full-scale reactors is still limited. In this study, the first implementation of the AGS process in the Nordic countries was assessed. In two full-scale AGS reactors with different seeding sludges, the start-up was associated with rapid changes in microbial community composition in both, but only successful granulation in one. As a consequence, the non-granulated reactor was eventually reseeded with biomass from the better granulated reactor. This resulted in a convergence of the microbial communities in the two reactors with the maintenance of stable sludge concentrations (6-8 g L-1) with large granules (50-80% with diameter >2 mm) and fast settling of biomass (SVI30/SVI10 of 0.9-1). Immigration from the influent wastewater was a minor factor affecting the microbial community once the granules had formed, while the seasonal variations in environmental factors were identified as important. Key guilds of AOB (Nitrosomonas), NOB (mainly Ca. Nitrotoga), PAOs (mainly Tetrasphaera), and GAOs (mainly Ca. Competibacter) varied considerably in abundance throughout the study period. After 15 months, stable organic matter, nitrogen, and phosphorus removal were attained with low effluent concentrations. During the start-up, the BOD7/N ratio, influent flow, and temperature were important factors influencing the performance of the AGS.
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| 5. |
- Ekholm, Jennifer, 1992, et al.
(författare)
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Microbiome structure and function in parallel full-scale aerobic granular sludge and activated sludge processes
- 2024
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Ingår i: Applied Microbiology and Biotechnology. - 1432-0614 .- 0175-7598. ; 108:1
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Aerobic granular sludge (AGS) and conventional activated sludge (CAS) are two different biological wastewater treatment processes. AGS consists of self-immobilised microorganisms that are transformed into spherical biofilms, whereas CAS has floccular sludge of lower density. In this study, we investigated the treatment performance and microbiome dynamics of two full-scale AGS reactors and a parallel CAS system at a municipal WWTP in Sweden. Both systems produced low effluent concentrations, with some fluctuations in phosphate and nitrate mainly due to variations in organic substrate availability. The microbial diversity was slightly higher in the AGS, with different dynamics in the microbiome over time. Seasonal periodicity was observed in both sludge types, with a larger shift in the CAS microbiome compared to the AGS. Groups important for reactor function, such as ammonia-oxidising bacteria (AOB), nitrite-oxidising bacteria (NOB), polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs), followed similar trends in both systems, with higher relative abundances of PAOs and GAOs in the AGS. However, microbial composition and dynamics differed between the two systems at the genus level. For instance, among PAOs, Tetrasphaera was more prevalent in the AGS, while Dechloromonas was more common in the CAS. Among NOB, Ca. Nitrotoga had a higher relative abundance in the AGS, while Nitrospira was the main nitrifier in the CAS. Furthermore, network analysis revealed the clustering of the various genera within the guilds to modules with different temporal patterns, suggesting functional redundancy in both AGS and CAS. Key points: • Microbial community succession in parallel full-scale aerobic granular sludge (AGS) and conventional activated sludge (CAS) processes. • Higher periodicity in microbial community structure in CAS compared to in AGS. • Similar functional groups between AGS and CAS but different composition and dynamics at genus level. Graphical abstract: (Figure presented.).
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| 6. |
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| 7. |
- Olsson, Gustaf, et al.
(författare)
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Process Control
- 2008
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Ingår i: Biological Wastewater Treatment - Principles, Modelling and Design. - 9781843391883 ; , s. 393-414
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Bokkapitel (refereegranskat)
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| 8. |
- Pérez, Julio, et al.
(författare)
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The role of the external mass transfer resistance in nitrite oxidizing bacteria repression in biofilm-based partial nitritation/anammox reactors
- 2020
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 186
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Tidskriftsartikel (refereegranskat)abstract
- A model-based study was developed to analyse the behaviour of Moving Bed Biofilm Reactor (MBBR) and Integrated Fixed-Film Activated Sludge (IFAS) reactor configurations for the removal of nitrogen in the main water line of municipal wastewater treatment plants via partial nitritation/anammox (PN/AMX). The basic principles and underlying mechanisms linking operating conditions to process performance were investigated, with particular focus on nitrite oxidizing bacteria (NOB) repression and resulting volumetric conversion rates. The external mass transfer resistance is a major factor differentiating granular sludge PN/AMX processes from MBBR or IFAS systems. The external mass transfer resistance was found to promote the metabolic coupling between anammox (AMX) and ammonia oxidizing bacteria (AOB), crucial for NOB repression in the biofilm. Operation at low bulk DO prevents NOB proliferation in the flocs of IFAS systems as AMX activity limits nitrite availability (the so-called AMX nitrite sink). Importantly, the effectiveness of the AMX nitrite sink strongly depends on the AMX sensitivity to oxygen. Also, over a broad range of operational conditions, the seeding of AOB from the biofilm played a crucial role in maintaining their activity in the flocs. From a practical perspective, while low DO promotes NOB repression, lower nitrogen loads have to be applied to maintain the same effluent quality. Thus, a trade-off between NOB repression and volumetric conversion capacity needs to be defined. To this end, IFAS allow for higher volumetric rates, but the window of operating conditions with effective NOB repression is smaller than that for MBBR. Ultimately, this study identified the principles controlling NOB in MBBR and IFAS systems and the key differences with granular reactors, allowing for the interpretation of (seemingly contradictory) published experimental results.
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