Hydrogen sulfide removal from synthetic biogas using anoxic biofilm reactors

Tämän tutkimuksen tarkoituksena oli kehittää bioreaktoreita sulfidin poistamiseen nestemäisistä jätevirroista anoksisissa olosuhteissa. Lisäksi tavoitteena oli mahdollistaa rikkivetyä sisältävien kaasumaisten ja nitraattia sisältävien nestemäisten jätevirtojen yhtaikainen käsittely. Ensiksi tutkittiin liukoisten epäorgaanisten rikkiyhdisteiden hapetusta rikkiä hapettavia ja nitraattia pelkistäviä (SO-NR) bakteereita sisältävällä mikrobiviljelmällä kahdessa erilaisessa bioreaktorissa, leijupetireaktorissa (FBR) ja kantajakappalereaktorissa (MBBR). Bioreaktoreiden toimintaa syötteen eri typen ja rikin moolisuhteilla vertailtiin käyttäen tiosulfaattia elektronidonorina ja nitraattia elektroniakseptorina. Molemmissa reaktoreissa saavutettiin yli 98 %:n tiosulfaatin poistotehokkuus ja nitraatti saatiin poistettua kokonaan N/S-suhteen ollessa 0,5. Erittäin typpirajoitteisissa olosuhteissa (NS suhde 0,1), MBBR:llä saavutettu tiosulfaatin poistotehokkuus (37,8 %) oli korkeampi kuin FBR:llä saavutettu tiosulfaatin poistotehokkuus (26,1 %). Kun syötteen N/S suhde palautettiin arvoon 0,5, MBBR:llä tiosulfaatin poistotehokkuus palautui yhden päivän aikana arvoon 94 %, kun taas FBR:llä kesti kolme päivää, että tiosulfaatin poistotehokkuus nousi arvoon 80 %. Kummallekin reaktorille kehitettiin oman euroverkko-pohjainen malli, joka ennusti luotettavasti tiosulfaatin ja nitraatin poistotehokkuuksia eri olosuhteissa. MBBR:ään rikastunutta SO-NR-viljelmää hyödynnettiin valutusbiosuodattimessa (BTF) rikkivetyä ja nitraattia sisältävien synteettisten jätevirtojen samanaikaiseen käsittelyyn. Anoksisella BTF:llä suurin saavutettu rikkivedyn poistokapasiteetti oli 19,2 g S m-3 h-1 (99 % poistotehokkuus) rikkivetykuorman ollessa 20,0 g S m-3 h-1 (~500 ppmv) ja N/S suhteen noin 1,7. Koska nitraattia sisältävät jätevedet voivat sisältää myös orgaanisia yhdisteitä toisessa BTF:ssä tutkittiin Paracoccus versutus MAL 1HM19 kannan kykyä poistaa samanaikaisesti rikkivetyä, nitraattia ja orgaanisia yhdisteitä. Tällä BTF:llä saavutettiin nitraatin poistonopeus 16,7 g NO3--N m-3 h-1 ja asetaatin poistonopeus 42,0 g-asetaattia m-3 h-1. Saavutetut poistonopeudet olivat korkeampia kuin autotrofisia SO-NR bakteereja hyödyntävällä BTF:llä saavutetut arvot, jotka olivat 11,1 g NO3--N m-3 h-1 ja 10,2 g-asetaattia m-3 h-1. SO-NR bakteerien hallitseman anoksisen BTF:n toimintaa tutkittiin vaihtuvissa olosuhteissa kuten muuttuva kaasun ja valutusnesteen virtausnopeus, katkonainen nitraatin syöttö ja rikkivedyn shokkikuormitus, sillä tällaiset häiriöt ovat mahdollisia käytännön sovelluksissa. Olosuhteiden ohimenevät muutokset vaikuttivat merkittävästi rikkivedyn poistokapasiteettiin. Esimerkiksi rikkivedyn shokkikuormituksen jälkeen kesti 1,7 päivää ennen kuin rikkivedyn poistotehokkuus palasi yli 99 %:n tasolle. Yhteenvetona voidaan todeta, että MBBR mahdollisti tehokkaamman tiosulfaatin poiston kuin FBR erityisesti typpirajoitteisissa olosuhteissa. MBBR:n ja BTF:n osoitettiin palautuvan nopeasti ohimenevistä kuormitustilanteista ja mahdollistavan siis vakaan epäorgaanisten rikkiyhteisen poiston synteettisistä jätevirroista.The aim of this work was to develop and study anoxic bioreactors for the removal of reduced inorganic sulfur compounds from liquid and gaseous waste streams. In addition, the aim was to enable process integration for the simultaneous treatment of H2S con-taminated gas streams and NO3--containing wastewater. The experiments related to sulfide oxidation in the liquid phase were conducted in two different attached growth bioreactors, i.e. a fluidized-bed reactor (FBR) and a moving bed biofilm reactor (MBBR), inoculated with the same mixed culture of sulfur-oxidizing nitrate-reducing (SO-NR) bacteria. The bioreactors were operated under different nitro-gen-to-sulfur (N/S) molar ratios using S2O32- and NO3- as an energy source and electron acceptor, respectively. Results revealed that both the FBR and MBBR achieved S2O32- removal efficiencies (RE) >98% and completely removed NO3- at an N/S ratio of 0.5. Under severe nitrate limitation (N/S ratio of 0.1), the S2O32- RE in the MBBR (37.8%) was higher than that observed in the FBR (26.1%). In addition, the MBBR showed better resilience to nitrate limitation than the FBR as the S2O32- RE was recovered to 94% within 1 day after restoring the feed N/S ratio to 0.5, while it took 3 days to obtain 80% S2O32- RE in the FBR. Artificial neural network models were successfully used to predict the FBR and MBBR performance, i.e. S2O32- and NO3- RE as well as sulfate production. The SO-NR biomass from the MBBR was used to inoculate an anoxic biotrickling filter (BTF), which was studied for simultaneous treatment of H2S and NO3- containing waste streams. In the anoxic BTF, a maximum H2S elimination capacity (EC) of 19.2 g S m-3 h-1 (99% RE) was obtained at an inlet H2S load of 20.0 g S m-3 h-1 (~500 ppmv) and an N/S ratio of ~1.7. As some NO3--containing wastewaters can also contain organic compounds, the anoxic BTF inoculated with Paracoccus versutus strain MAL 1HM19 was studied for the simultaneous treatment of H2S, NO3- and organic carbon containing waste streams. With this BTF, NO3- and acetate removal rates of 16.7 g NO3--N m-3 h-1 and 42.0 g acetate m-3 h-1, respectively, were achieved, which was higher than the values observed in the BTF inoculated with the mixed culture of autotrophic SO-NR bacteria (11.1 g NO3--N m-3 h-1 and 10.2 g acetate m-3 h-1). Anoxic BTFs were operated under several transient conditions (i.e. varied gas and trickling liquid flow rates, intermittent NO3- supply and H2S shock loads) to evaluate the impacts of sudden changes that usually occur in practical applications. The different transient conditions significantly affected the H2S EC of the anoxic BTF. After applying H2S shock loads, the H2S RE fully recovered to >99% within 1.7 days after resuming normal operation. In summary, the MBBR was more effective for the removal of S2O32- than the FBR, es-pecially under nitrate limited conditions. Based on the short recovery times after expo-sure to transient-state conditions, the anoxic MBBR and BTF were found to be resilient and robust systems for removal of reduced sulfur compounds under autotrophic and mixotrophic conditions

Draft genome sequence data of a psychrophilic tundra soil methanotroph, Methylobacter psychrophilus Z-0021 (DSM 9914).

Psychrophilic methanotrophic bacteria are abundant and play an important role in methane removal in cold methanogenic environments, such as boreal and arctic terrestrial and aquatic ecosystems. They could be also applied in the bioconversion of biogas and natural gas into value-added products (e.g., chemicals and single-cell protein) in cold regions. Hence, isolation and genome sequencing of psychrophilic methanotrophic bacteria are needed to provide important data on their functional capabilities. However, psychrophilic methanotroph isolates and consequently their genome sequences are rare. Fortunately, Leibniz Institute, DSMZ-German Collection of Microorganisms and Cell Cultures GmbH was able to revive the long-extinct pure culture of a psychrophilic methanotrophic tundra soil isolate, Methylobacter psychrophilus Z-0021 (DSM 9914), from their stocks during 2022. Here, we describe the de novo assembled genome sequence of Methylobacter psychrophilus Z-0021 comprising a total of 4691082 bp in 156 contigs with a G+C content of 43.1% and 4074 coding sequences. The preliminary genome annotation analysis of Z-0021 identified genes encoding oxidation of methane, methanol and formaldehyde, assimilation of carbon and nitrate, and N2 fixation. In pairwise genome-to-genome comparisons with closely related methanotrophic strains, the strain Z-0021 had an average nucleotide identity (ANI) of 92.9% and 78.2% and a digital DNA-DNA hybridization (dDDH) value of 50.6% and 22% with a recently described psychrophilic, lake isolate, Methylobacter sp. S3L5C and a psychrotrophic, arctic wetland soil isolate, Methylobacter tundripaludum SV96, respectively. In addition, the respective similarities between genomes of the strains S3L5C and SV96 were 78.1% ANI and 21.8% dDDH. Comparison to widely used ANI and dDDH thresholds to delineate unique species (<95% ANI and <70% dDDH) suggests that Methylobacter psychrophilus Z-0021, Methylobacter tundripaludum SV96 and Methylobacter sp. S3L5C are different species. The draft genome of Z-0021 has been deposited at GenBank under the accession JAOEGU000000000

Organic matter lability modifies the vertical structure of methane-related microbial communities in lake sediments

Eutrophication increases the input of labile, algae-derived, organic matter (OM) into lake sediments. This potentially increases methane (CH4) emissions from sediment to water through increased methane production rates and decreased methane oxidation efficiencyefficiency in sediments. However, the effecteffect of OM lability on the structure of methane oxidizing (methanotrophic) and methane producing (methanogenic) microbial communities in lake sediments is still understudied. We studied the vertical profilesprofiles of the sediment and porewater geochemistry and the microbial communities (16S rRNA gene amplicon sequencing) at fivefive profundal stations of an oligo-mesotrophic, boreal lake (Lake Paajarvi, Finland), varying in surface sediment OM sources (assessed via sediment C:N ratio). Porewater profilesprofiles of methane, dissolved inorganic carbon (DIC), acetate, iron, and sulfur suggested that sites with more autochthonous OM showed higher overall OM lability, which increased remineralization rates, leading to increased electron acceptor (EA) consumption and methane emissions from sediment to water. When OM lability increased, the abundance of anaerobic nitrite-reducing methanotrophs (Candidatus Methylomirabilis) relative to aerobic methanotrophs (Methylococcales) in the methane oxidation layer of sediment surface decreased, suggesting that Methylococcales were more competitive than Ca. Methylomirabilis under decreasing redox conditions and increasing methane availability due to their more diverse metabolism (fermentation and anaerobic respiration) and lower affinityaffinity for methane. Furthermore, when OM lability increased, the abundance of methanotrophic community in the sediment surface layer, especially Ca. Methylomirabilis, relative to the methanogenic community decreased. We conclude that increasing input of labile OM, subsequently affectingaffecting the redox zonation of sediments, significantlysignificantly modifies the methane producing and consuming microbial community of lake sediments

Organic matter lability modifies the vertical structure of methane-related microbial communities in lake sediments

Eutrophication increases the input of labile, algae-derived, organic matter (OM) into lake sediments. This potentially increases methane (CH4) emissions from sediment to water through increased methane production rates and decreased methane oxidation efficiency in sediments. However, the effect of OM lability on the structure of methane oxidizing (methanotrophic) and methane producing (methanogenic) microbial communities in lake sediments is still understudied. We studied the vertical profiles of the sediment and porewater geochemistry and the microbial communities (16S rRNA gene amplicon sequencing) at five profundal stations of an oligo-mesotrophic, boreal lake (Lake Pääjärvi, Finland), varying in surface sediment OM sources (assessed via sediment C:N ratio). Porewater profiles of methane, dissolved inorganic carbon (DIC), acetate, iron, and sulfur suggested that sites with more autochthonous OM showed higher overall OM lability, which increased remineralization rates, leading to increased electron acceptor (EA) consumption and methane emissions from sediment to water. When OM lability increased, the abundance of anaerobic nitrite-reducing methanotrophs (Candidatus Methylomirabilis) relative to aerobic methanotrophs (Methylococcales) in the methane oxidation layer of sediment surface decreased, suggesting that Methylococcales were more competitive than Ca. Methylomirabilis under decreasing redox conditions and increasing methane availability due to their more diverse metabolism (fermentation and anaerobic respiration) and lower affinity for methane. Furthermore, when OM lability increased, the abundance of methanotrophic community in the sediment surface layer, especially Ca. Methylomirabilis, relative to the methanogenic community decreased. We conclude that increasing input of labile OM, subsequently affecting the redox zonation of sediments, significantly modifies the methane producing and consuming microbial community of lake sediments

Hydrogen sulfide removal from synthetic biogas using anoxic biofilm reactors

Tämän tutkimuksen tarkoituksena oli kehittää bioreaktoreita sulfidin poistamiseen nestemäisistä jätevirroista anoksisissa olosuhteissa. Lisäksi tavoitteena oli mahdollistaa rikkivetyä sisältävien kaasumaisten ja nitraattia sisältävien nestemäisten jätevirtojen yhtaikainen käsittely. Ensiksi tutkittiin liukoisten epäorgaanisten rikkiyhdisteiden hapetusta rikkiä hapettavia ja nitraattia pelkistäviä (SO-NR) bakteereita sisältävällä mikrobiviljelmällä kahdessa erilaisessa bioreaktorissa, leijupetireaktorissa (FBR) ja kantajakappalereaktorissa (MBBR). Bioreaktoreiden toimintaa syötteen eri typen ja rikin moolisuhteilla vertailtiin käyttäen tiosulfaattia elektronidonorina ja nitraattia elektroniakseptorina. Molemmissa reaktoreissa saavutettiin yli 98 %:n tiosulfaatin poistotehokkuus ja nitraatti saatiin poistettua kokonaan N/S-suhteen ollessa 0,5. Erittäin typpirajoitteisissa olosuhteissa (NS suhde 0,1), MBBR:llä saavutettu tiosulfaatin poistotehokkuus (37,8 %) oli korkeampi kuin FBR:llä saavutettu tiosulfaatin poistotehokkuus (26,1 %). Kun syötteen N/S suhde palautettiin arvoon 0,5, MBBR:llä tiosulfaatin poistotehokkuus palautui yhden päivän aikana arvoon 94 %, kun taas FBR:llä kesti kolme päivää, että tiosulfaatin poistotehokkuus nousi arvoon 80 %. Kummallekin reaktorille kehitettiin oman euroverkko-pohjainen malli, joka ennusti luotettavasti tiosulfaatin ja nitraatin poistotehokkuuksia eri olosuhteissa. MBBR:ään rikastunutta SO-NR-viljelmää hyödynnettiin valutusbiosuodattimessa (BTF) rikkivetyä ja nitraattia sisältävien synteettisten jätevirtojen samanaikaiseen käsittelyyn. Anoksisella BTF:llä suurin saavutettu rikkivedyn poistokapasiteetti oli 19,2 g S m-3 h-1 (99 % poistotehokkuus) rikkivetykuorman ollessa 20,0 g S m-3 h-1 (~500 ppmv) ja N/S suhteen noin 1,7. Koska nitraattia sisältävät jätevedet voivat sisältää myös orgaanisia yhdisteitä toisessa BTF:ssä tutkittiin Paracoccus versutus MAL 1HM19 kannan kykyä poistaa samanaikaisesti rikkivetyä, nitraattia ja orgaanisia yhdisteitä. Tällä BTF:llä saavutettiin nitraatin poistonopeus 16,7 g NO3--N m-3 h-1 ja asetaatin poistonopeus 42,0 g-asetaattia m-3 h-1. Saavutetut poistonopeudet olivat korkeampia kuin autotrofisia SO-NR bakteereja hyödyntävällä BTF:llä saavutetut arvot, jotka olivat 11,1 g NO3--N m-3 h-1 ja 10,2 g-asetaattia m-3 h-1. SO-NR bakteerien hallitseman anoksisen BTF:n toimintaa tutkittiin vaihtuvissa olosuhteissa kuten muuttuva kaasun ja valutusnesteen virtausnopeus, katkonainen nitraatin syöttö ja rikkivedyn shokkikuormitus, sillä tällaiset häiriöt ovat mahdollisia käytännön sovelluksissa. Olosuhteiden ohimenevät muutokset vaikuttivat merkittävästi rikkivedyn poistokapasiteettiin. Esimerkiksi rikkivedyn shokkikuormituksen jälkeen kesti 1,7 päivää ennen kuin rikkivedyn poistotehokkuus palasi yli 99 %:n tasolle. Yhteenvetona voidaan todeta, että MBBR mahdollisti tehokkaamman tiosulfaatin poiston kuin FBR erityisesti typpirajoitteisissa olosuhteissa. MBBR:n ja BTF:n osoitettiin palautuvan nopeasti ohimenevistä kuormitustilanteista ja mahdollistavan siis vakaan epäorgaanisten rikkiyhteisen poiston synteettisistä jätevirroista.The aim of this work was to develop and study anoxic bioreactors for the removal of reduced inorganic sulfur compounds from liquid and gaseous waste streams. In addition, the aim was to enable process integration for the simultaneous treatment of H2S con-taminated gas streams and NO3--containing wastewater. The experiments related to sulfide oxidation in the liquid phase were conducted in two different attached growth bioreactors, i.e. a fluidized-bed reactor (FBR) and a moving bed biofilm reactor (MBBR), inoculated with the same mixed culture of sulfur-oxidizing nitrate-reducing (SO-NR) bacteria. The bioreactors were operated under different nitro-gen-to-sulfur (N/S) molar ratios using S2O32- and NO3- as an energy source and electron acceptor, respectively. Results revealed that both the FBR and MBBR achieved S2O32- removal efficiencies (RE) >98% and completely removed NO3- at an N/S ratio of 0.5. Under severe nitrate limitation (N/S ratio of 0.1), the S2O32- RE in the MBBR (37.8%) was higher than that observed in the FBR (26.1%). In addition, the MBBR showed better resilience to nitrate limitation than the FBR as the S2O32- RE was recovered to 94% within 1 day after restoring the feed N/S ratio to 0.5, while it took 3 days to obtain 80% S2O32- RE in the FBR. Artificial neural network models were successfully used to predict the FBR and MBBR performance, i.e. S2O32- and NO3- RE as well as sulfate production. The SO-NR biomass from the MBBR was used to inoculate an anoxic biotrickling filter (BTF), which was studied for simultaneous treatment of H2S and NO3- containing waste streams. In the anoxic BTF, a maximum H2S elimination capacity (EC) of 19.2 g S m-3 h-1 (99% RE) was obtained at an inlet H2S load of 20.0 g S m-3 h-1 (~500 ppmv) and an N/S ratio of ~1.7. As some NO3--containing wastewaters can also contain organic compounds, the anoxic BTF inoculated with Paracoccus versutus strain MAL 1HM19 was studied for the simultaneous treatment of H2S, NO3- and organic carbon containing waste streams. With this BTF, NO3- and acetate removal rates of 16.7 g NO3--N m-3 h-1 and 42.0 g acetate m-3 h-1, respectively, were achieved, which was higher than the values observed in the BTF inoculated with the mixed culture of autotrophic SO-NR bacteria (11.1 g NO3--N m-3 h-1 and 10.2 g acetate m-3 h-1). Anoxic BTFs were operated under several transient conditions (i.e. varied gas and trickling liquid flow rates, intermittent NO3- supply and H2S shock loads) to evaluate the impacts of sudden changes that usually occur in practical applications. The different transient conditions significantly affected the H2S EC of the anoxic BTF. After applying H2S shock loads, the H2S RE fully recovered to >99% within 1.7 days after resuming normal operation. In summary, the MBBR was more effective for the removal of S2O32- than the FBR, es-pecially under nitrate limited conditions. Based on the short recovery times after expo-sure to transient-state conditions, the anoxic MBBR and BTF were found to be resilient and robust systems for removal of reduced sulfur compounds under autotrophic and mixotrophic conditions

Élimination de l'hydrogène sulfuré du biogaz synthétique à l'aide de bioréacteurs à biofilm anoxiques

The aim of this work was to develop and study anoxic bioreactors for the removal of re-duced inorganic sulfur compounds from liquid and gaseous waste streams. In addition, the aim was to enable process integration for the simultaneous treatment of H2S con-taminated gas streams and NO3--containing wastewater. The experiments related to sulfide oxidation in the liquid phase were conducted in two different attached growth bioreactors, i.e. a fluidized-bed reactor (FBR) and a moving bed biofilm reactor (MBBR), inoculated with the same mixed culture of sulfur-oxidizing nitrate-reducing (SO-NR) bacteria. The bioreactors were operated under different nitro-gen-to-sulfur (N/S) molar ratios using S2O32- and NO3- as an energy source and electron acceptor, respectively. Results revealed that both the FBR and MBBR achieved S2O32- removal efficiencies (RE) >98% and completely removed NO3- at an N/S ratio of 0.5. Under severe nitrate limitation (N/S ratio of 0.1), the S2O32- RE in the MBBR (37.8%) was higher than that observed in the FBR (26.1%). In addition, the MBBR showed better resilience to nitrate limitation than the FBR as the S2O32- RE was recovered to 94% with-in 1 day after restoring the feed N/S ratio to 0.5, while it took 3 days to obtain 80% S2O32- RE in the FBR. Artificial neural network models were successfully used to predict the FBR and MBBR performance, i.e. S2O32- and NO3- RE as well as sulfate production. The SO-NR biomass from the MBBR was used to inoculate an anoxic biotrickling filter (BTF), which was studied for simultaneous treatment of H2S and NO3- containing waste streams. In the anoxic BTF, a maximum H2S elimination capacity (EC) of 19.2 g S m-3 h-1 (99% RE) was obtained at an inlet H2S load of 20.0 g S m-3 h-1 (~500 ppmv) and an N/S ratio of ~1.7. As some NO3--containing wastewaters can also contain organic com-pounds, the anoxic BTF inoculated with Paracoccus versutus strain MAL 1HM19 was studied for the simultaneous treatment of H2S, NO3- and organic carbon containing waste streams. With this BTF, NO3- and acetate removal rates of 16.7 g NO3--N m-3 h-1 and 42.0 g acetate m-3 h-1, respectively, were achieved, which was higher than the val-ues observed in the BTF inoculated with the mixed culture of autotrophic SO-NR bacte-ria (11.1 g NO3--N m-3 h-1 and 10.2 g acetate m-3 h-1). Anoxic BTFs were operated under several transient conditions (i.e. varied gas and trickling liquid flow rates, intermittent NO3- supply and H2S shock loads) to evaluate the impacts of sudden changes that usu-ally occur in practical applications. The different transient conditions significantly affect-ed the H2S EC of the anoxic BTF. After applying H2S shock loads, the H2S RE fully re-covered to >99% within 1.7 days after resuming normal operation.In summary, the MBBR was more effective for the removal of S2O32- than the FBR, especially under nitrate limited conditions. Based on the short recovery times after expo-sure to transient-state conditions, the anoxic MBBR and BTF were found to be resilient and robust systems for removal of reduced sulfur compounds under autotrophic and mixotrophic conditionsL’objectif de cette étude a été de développer et étudier des bioréacteurs anoxiques pour l’élimination du soufre des flux de déchets liquides, et d’évaluer l’intégration du processus pour le traitement simultané des flux gazeux contaminés au H2S et des eaux usées contenant du NO3-.Les expériences relatives à l’oxydation du soufre dans la phase liquide ont été évaluées dans deux bioréacteurs à croissance fixe différents, à savoir un réacteur à lit fluidisé (RLF) et un réacteur filtrant sur lit mobile (RFLM), inoculés par une bactérie ayant la capacité de réduire les nitrates et d’oxyder le soufre (SO-NR). Les bioréacteurs ont été évalués sous différent ratios molaires azote/soufre (N/S) en utilisant le S2O32- et le NO3- comme source d’énergie et accepteur d’électrons, respectivement. Les résultats ont révélé que le RLF et le RFLM sont parvenus à des capacités d’extraction (CE) du S2O32- supérieures à 98 %, et à extraire complètement le NO3- au ratio N/S de 0,5. En conditions de forte limitation en nitrate (ratio N/S de 0,1), la CEx du S2O32- dans le RFLM (37,8 %) était supérieure à celle observée dans le RLF (26,1 %). En conséquence, le RFLM a montré une meilleure résilience à la limitation en nitrate que le RLF puisque la CEx du S2O32- a été ramenée à 94 % en une journée après restauration du ratio N/S à 0,5, alors que le RLF a pris 3 jours pour obtenir une CEx de 80 % pour le S2O32-. Les modèles de réseau neuronal artificiel ont pu être utilisés pour prédire les performances du RLF et du RFLM, à savoir la CE du S2O32- et du NO3-ainsi que la production de sulfate. La biomasse SO-NR développée dans le RFLM a été utilisée pour traiter simultanément les flux de déchets contenant du H2S et du NO3- dans un biofiltre (BF) anoxique. Le BF anoxique a obtenu une capacité d’élimination (CEl) maximale du H2S de 19,2 g de S m-3 h-1 (CEx) pour un apport de 20,0 g S m-3 h-1 (~500 ppmv) en H2S et un ratio N/S d’environ 1,7, respectivement. Comme certaines eaux usées contenant du NO3-peuvent contenir des produits organiques, le RLF anoxique inoculé avec du Paracoccus versatus souche MAL 1HM19 a été développé pour l’extraction simultanée du H2S, du NO3- et du carbone organique contenus dans les flux de déchets. Les résultats ont montré des taux d’extraction respectifs de 16,7 g NO3--N m-3 h-1 et 42,0 g d’acétate m-3 h-1, ce qui est supérieur aux valeurs observées dans le BF inoculé avec des autotrophes (11,1 g NO3--N m-3 h-1 et 10,2 g d’acétate m-3 h-1). Le BF anoxique a été opéré sous différentes conditions transitoires (i.e. gaz divers et plusieurs vitesses de flux de ruissellement liquides, un apport intermittent en NO3- et apports élevés en H2S) afin d’évaluer l’impact des modifications sur les variables du processus qui se produisent généralement dans les applications pratiques. Les différentes conditions transitoires ont significativement affecté la CEl du H2S dans le BF anoxique. En appliquant des apports élevés en H2S, la CEx du H2S a été presque totalement rétabli à 100 % dans les 40 heures suivant la reprise de l’opération normale. En résumé, le RFLM s’est montré plus efficace que le RLF pour l’extraction du S2O32. D’après un moment de récupération instantanée après tolérance des conditions transitoires, le RFLM anoxique et le RLF anoxique s’avèrent être de résilients et robustes systèmes de biofilms pour le traitement des composés soufrés réduits en conditions autotrophes et mixotrophe

Conversion of methane to organic acids is a widely found trait among gammaproteobacterial methanotrophs of freshwater lake and pond ecosystems

Aerobic gammaproteobacterial methanotrophs (gMOB) are key organisms controlling methane fluxes at the oxic-anoxic interfaces of freshwater ecosystems. Under hypoxic environments, gMOB may shift their aerobic metabolism to fermentation, resulting in the production of extracellular organic acids. We recently isolated a gMOB strain representing the Methylobacter spp. of boreal lake water columns (i.e., Methylobacter sp. S3L5C) and demonstrated that it converts methane to organic acids (acetate, formate, malate, and propionate) under hypoxic conditions. Annotation for putative genes encoding organic acid production within the isolate's genome and in environmental metagenome-assembled genomes (MAGs) representing Methylobacter spp. suggests that the potential for methane conversion into organic acids is widely found among Methylobacter spp. of freshwater ecosystems. However, it is not known yet whether the capability to convert methane to organic acids is restricted to Methylobacter spp. or ubiquitously present among other freshwater gMOB genera. Therefore, we isolated representatives of two additional gMOB genera from the boreal lake water columns, i.e., Methylomonas paludis S2AM and Methylovulum psychrotolerans S1L, and demonstrated similar bioconversion capacities. These genera could convert methane to organic acids, including acetate, formate, succinate, and malate. Additionally, S2AM produced lactate. Furthermore, we detected genes encoding organic acid production within their genomes and in MAGs representing Methylomonas spp. and Methylovulum spp. of lake and pond ecosystems. Altogether, our results demonstrate that methane conversion to various organic acids is a widely found trait among lake and pond gMOB, highlighting their role as pivotal mediators of methane carbon into microbial food webs of freshwater lake and pond ecosystems. IMPORTANCE Aerobic gammaproteobacterial methanotrophic bacteria (gMOB) play an important role in reducing methane emissions from freshwater ecosystems. In hypoxic conditions prevalent near oxic-anoxic interfaces, gMOB potentially shift their metabolism to fermentation, resulting in the conversion of methane to extracellular organic acids, which would serve as substrates for non-methanotrophic microbes. We intended to assess the prevalence of fermentation traits among freshwater gMOB. Therefore, we isolated two strains representing relevant freshwater gMOB genera, i.e., Methylovulum and Methylomonas, from boreal lakes, experimentally showed that they convert methane to organic acids and demonstrated via metagenomics that the fermentation potential is widely dispersed among lake and pond representatives of these genera. Combined with our recent study showing coherent results from another relevant freshwater gMOB genus, i.e., Methylobacter, we conclude that the conversion of methane to organic acids is a widely found trait among freshwater gMOB, highlighting their role as pivotal mediators of methane carbon into microbial food webs.Peer reviewe

Characterization and genome analysis of a psychrophilic methanotroph representing a ubiquitous Methylobacter spp. cluster in boreal lake ecosystems

Lakes and ponds are considered as a major natural source of CH4 emissions, particularly during the ice-free period in boreal ecosystems. Aerobic methane-oxidizing bacteria (MOB), which utilize CH4 using oxygen as an electron acceptor, are one of the dominant microorganisms in the CH4-rich water columns. Metagenome-assembled genomes (MAGs) have revealed the genetic potential of MOB from boreal aquatic ecosystems for various microaerobic/anaerobic metabolic functions. However, experimental proof of these functions, i.e., organic acid production via fermentation, by lake MOB is lacking. In addition, psychrophilic (i.e., cold-loving) MOB and their CH4-oxidizing process have rarely been investigated. In this study, we isolated, provided a taxonomic description, and analyzed the genome of Methylobacter sp. S3L5C, a psychrophilic MOB, from a boreal lake in Finland. Based on phylogenomic comparisons to MAGs, Methylobacter sp. S3L5C represented a ubiquitous cluster of Methylobacter spp. in boreal aquatic ecosystems. At optimal temperatures (3–12 °C) and pH (6.8–8.3), the specific growth rates (µ) and CH4 utilization rate were in the range of 0.018–0.022 h−1 and 0.66–1.52 mmol l−1 d−1, respectively. In batch cultivation, the isolate could produce organic acids, and the concentrations were elevated after replenishing CH4 and air into the headspace. Up to 4.1 mM acetate, 0.02 mM malate, and 0.07 mM propionate were observed at the end of the test under optimal operational conditions. The results herein highlight the key role of Methylobacter spp. in regulating CH4 emissions and their potential to provide CH4-derived organic carbon compounds to surrounding heterotrophic microorganisms in cold ecosystems.publishedVersionPeer reviewe

Draft genome sequence data of a psychrophilic tundra soil methanotroph, Methylobacter psychrophilus Z-0021 (DSM 9914)

Psychrophilic methanotrophic bacteria are abundant and play an important role in methane removal in cold methanogenic environments, such as boreal and arctic terrestrial and aquatic ecosystems. They could be also applied in the bioconversion of biogas and natural gas into value-added products (e.g., chemicals and single-cell protein) in cold regions. Hence, isolation and genome sequencing of psychrophilic methanotrophic bacteria are needed to provide important data on their functional capabilities. However, psychrophilic methanotroph isolates and consequently their genome sequences are rare. Fortunately, Leibniz Institute, DSMZ-German Collection of Microorganisms and Cell Cultures GmbH was able to revive the long-extinct pure culture of a psychrophilic methanotrophic tundra soil isolate, Methylobacter psychrophilus Z-0021 (DSM 9914), from their stocks during 2022. Here, we describe the de novo assembled genome sequence of Methylobacter psychrophilus Z-0021 comprising a total of 4691082 bp in 156 contigs with a G+C content of 43.1% and 4074 coding sequences. The preliminary genome annotation analysis of Z-0021 identified genes encoding oxidation of methane, methanol and formaldehyde, assimilation of carbon and nitrate, and N2 fixation. In pairwise genome-to-genome comparisons with closely related methanotrophic strains, the strain Z-0021 had an average nucleotide identity (ANI) of 92.9% and 78.2% and a digital DNA-DNA hybridization (dDDH) value of 50.6% and 22% with a recently described psychrophilic, lake isolate, Methylobacter sp. S3L5C and a psychrotrophic, arctic wetland soil isolate, Methylobacter tundripaludum SV96, respectively. In addition, the respective similarities between genomes of the strains S3L5C and SV96 were 78.1% ANI and 21.8% dDDH. Comparison to widely used ANI and dDDH thresholds to delineate unique species (publishedVersionPeer reviewe

H2S removal and microbial community composition in an anoxic biotrickling filter under autotrophic and mixotrophic conditions

Removal of H2S from gas streams using NO3--containing synthetic wastewater was investigated in an anoxic biotrickling filter (BTF) at feed N/S ratios of 1.2-1.7 mol mol-1 with an initial nominal empty bed residence time of 3.5 min and a hydraulic retention time of 115 min. During 108 days of operation under autotrophic conditions, the BTF showed a maximum elimination capacity (EC) of 19.2 g S m-3 h-1 and H2S removal efficiency (RE) above 99%. Excess biofilm growth reduced the HRT from 115 to 19 min and decreased the desulfurization efficiency of the BTF. When the BTF was operated under mixotrophic conditions by adding organic carbon (43.2 g acetate m-3 h-1) to the synthetic wastewater, the H2S EC decreased from 16.4 to 13.1 g S m-3 h-1, while the NO3- EC increased from 9.9 to 11.1 g NO3--N m-3 h-1, respectively. Thiobacillus sp. (98-100% similarity) was the only sulfur-oxidizing nitrate-reducing bacterium detected in the BTF biofilm, while the increased abundance of heterotrophic denitrifiers, i.e. Brevundimonas sp. and Rhodocyclales, increased the consumed N/S ratio during BTF operation. Residence time distribution tests showed that biomass accumulation during BTF operation reduced gas and liquid retention times by 17.1% and 83.5%, respectively.submittedVersionacceptedVersionPeer reviewe