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Item type:Publication, Access status: with files , Selective bioelectrochemical purification of propionate from food waste hydrolysate(Elsevier, 2026-12-21); ; Dark fermentation enables hydrogen production while generating propionate-rich streams from food waste. However, efficient separation of propionate from short-chain fatty acid (SCFA) mixtures remains challenging and costly in the downstream processes. Therefore, strategies enabling selective purification of propionate prior to separation from the fermentation broth are highly desirable. In this study, a bioelectrochemically assisted bench-scale process was developed as a proof-of-concept pretreatment to enhance selective purification of propionate prior to downstream processing. A single-chamber rotating disc bioelectrochemical reactor (RDBER) was used to selectively purify the hydrolysate via enhancing the consumption of butyrate by an electroactive biofilm of a recently published butyrate-oxidizing microbial consortium. In the RDBER, different hydraulic retention times (HRTs) without and with pH control were evaluated to investigate their effects on propionate fraction among SCFAs and process stability. The results show that with a pH of 7.0–7.3 and an HRT of 8 days, a propionate fraction of up to 95.5% can be achieved, with its concentration doubling compared to the feed. These results demonstrate the potential of this process as a pretreatment step prior to downstream separation, with the aim of reducing separation complexity and enhancing propionate recovery.Publicationtype: Journal Article15 7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Oxygen in the mix: is oxic microbial electrosynthesis a potential alternative for biomass production?Oxic microbial electrosynthesis (oMES) allows the utilization of renewable electricity and industrial gas streams containing CO2 and O2 for biomass production by cultivating aerobic, autotrophic, hydrogen-oxidizing bacteria, commonly known as Knallgas bacteria. oMES is likely not a direct competitor to conventional anoxic microbial electrosynthesis as harnessing aerobic hydrogen-oxidizing bacteria depends on energetically inefficient assimilatory CO2 reduction pathways. However, it might be a complementary approach to classical biomass production from the perspective of limited land use and the availability of cheap renewable energy. The best characterized Knallgas bacterium is Cupriavidus necator. Extensively studied as lithoautotrophic production host, C. necator already offers a broad arsenal of genetic tools. In contrast, mechanistical knowledge about the recently discovered Kyrpidia spormannii is limited, but this species shows remarkable growth when cultivated as cathodic biofilm in bioelectrochemical systems. In addition, first experiments indicate a low energy demand for biomass production, which is in the order of magnitude of gas fermentation with C. necator or heterotrophic and methanotrophic technologies. Still, many aspects of the electrochemical cultivation of K. spormannii need to be better understood and rigorously improved to be a competitive technology in the making, including electron transfer and microbial kinetics, cultivation conditions, mass and energy balances, and reactor design.Publicationtype: Review Article41 62 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Gastropods as a source for fecal indicator bacteria in drinking waterMicrobial water quality is routinely examined using the fecal indicator bacteria Escherichia coli, coliform bacteria and enterococci. Several practical cases in German drinking water distribution systems indicated invertebrates such as insects or gastropods as a source for the microbiological deterioration. Therefore, we examined three genera of Gastropoda (Arion, Helix and Cepaea) for the presence of fecal indictor bacteria in excreta using standard methods. Enterococci and coliform bacteria were detected in high concentrations (mean values of 1.5 × 106 and 6.3 × 106 per gram feces, respectively). E. coli was also detected, still specification revealed that what was assigned by standard ISO-methods to be E. coli was indeed a novel species of Buttiauxella, exhibiting β-D-glucuronidase activity, thus, explaining the false-positive results. Microbiome analyses confirmed the cultural results. Enterobacteriaceae were dominant in the samples, yet only very few sequences could be assigned to Escherichia. Our study suggests, that enterococci and coliform bacteria are an integral component in the gastropod microbiome, whereas E. coli might be derived from other sources with gastropods being a vector. The results further indicate, that the current concept of fecal indicator bacteria needs to be extended, as not only humans and homeothermic animals could be a source for fecal indictor bacteria, but also gastropods need to be taken into consideration.Publicationtype: Journal ArticleScopus© Citations 1 42 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A scalable, rotating disc bioelectrochemical reactor (RDBER) suitable for the cultivation of both cathodic and anodic biofilmsThis study discusses the construction and operation of a membrane-less bioelectrochemical reactor that employs rotating working electrodes with a surface area of up to 1 m2. As a proof-of-principle for an aerobic microbial electrosynthesis process, Kyrpidia spormannii was cultivated in the reactor. Optical coherence tomography was used to examine the spatial distribution of the cathodic biofilm. After 24 days 87 % of the cathode surface was covered with biofilm that was characterized by a radial increase in its biovolume towards the circumcenter of the electrodes reaching up to 92.13 μm3 μm−2. To demonstrate the versatility of the system, we further operated the reactor as a microbial electrolysis cell employing a co-culture of Shewanella oneidensis and Geobacter sulfurreducens. Anodic current densities of up to 130 μA cm−2 were measured during these batch experiments. This resulted in a maximum production rate of 0.43 L of pure hydrogen per liter reactor volume and day.Publicationtype: Journal Article33 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electron transfer of extremophiles in bioelectrochemical systems(Springer, 2022-10-12); ; ; ; The interaction of bacteria and archaea with electrodes is a relatively new research field which spans from fundamental to applied research and influences interdisciplinary research in the fields of microbiology, biochemistry, biotechnology as well as process engineering. Although a substantial understanding of electron transfer processes between microbes and anodes and between microbes and cathodes has been achieved in mesophilic organisms, the mechanisms used by microbes under extremophilic conditions are still in the early stages of discovery. Here, we review our current knowledge on the biochemical solutions that evolved for the interaction of extremophilic organisms with electrodes. To this end, the available knowledge on pure cultures of extremophilic microorganisms has been compiled and the study has been extended with the help of bioinformatic analyses on the potential distribution of different electron transfer mechanisms in extremophilic microorganisms.Publicationtype: Review ArticleScopus© Citations 5 60 339 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Monitoring and quantification of bioelectrochemical Kyrpidia spormannii biofilm development in a novel flow cell setup(2020-06-15); ; ; ; Spatially resolved data for biofilm structure can often not be assessed easily in bioelectrochemical setups due to the orientation and placement of anode and cathode. However, understanding the interplay of biofilm (structure) development and electrochemical parameters is crucial for optimizing bioelectrochemical biofilm systems. For example, to produce value added products. This study thus, presents a versatile flow cell setup allowing for control of hydrodynamic, substrate (liquid and gaseous), and nutritional conditions as well as physical parameters. Here, a versatile lab-scale flow cell system equipped with a cathode and an anode is presented to monitor the growth of Kyrpidia spormannii biofilm. The monitoring was conducted non-invasively by means of optical coherence tomography. 3D OCT data set analysis revealed that the biofilm accumulation rate is influenced by the distance of Kyrpidia spormannii cells from the cathode surface: the overall accumulation rate of the biofilm decreases when the biovolume exceeds 75 µm3 µm−2. Moreover, a correlation between substratum coverage and measured current density was determined. The increase of substratum coverage led to a decrease of abiotic redox processes at the electrode surface and thereby to a decrease of measured current density with an equilibrium of approx. 13 µA cm−2. The results further show that a well characterized cultivation system was developed for the investigation of any kind of bioelectrochemical biofilm systems. Moreover, this midi-fluidic setup enables the quantitative analysis of representative biofilm volume units, which in turn allow for drawing reliable process parameters.Publicationtype: Journal Article38 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , From an extremophilic community to an electroautotrophic production strain: identifying a novel Knallgas bacterium as cathodic biofilm biocatalystCoupling microbial electrosynthesis to renewable energy sources can provide a promising future technology for carbon dioxide conversion. However, this technology suffers from a limited number of suitable biocatalysts, resulting in a narrow product range. Here, we present the characterization of the first thermoacidophilic electroautotrophic community using chronoamperometric, metagenomic, and 13C-labeling analyses. The cathodic biofilm showed current consumption of up to −80 µA cm−2 over a period of 90 days (−350 mV vs. SHE). Metagenomic analyses identified members of the genera Moorella, Desulfofundulus, Thermodesulfitimonas, Sulfolobus, and Acidianus as potential primary producers of the biofilm, potentially thriving via an interspecies sulfur cycle. Hydrogenases seem to be key for cathodic electron uptake. An isolation campaign led to a pure culture of a Knallgas bacterium from this community. Growth of this organism on cathodes led to increasing reductive currents over time. Transcriptomic analyses revealed a distinct gene expression profile of cells grown at a cathode. Moreover, pressurizable flow cells combined with optical coherence tomography allowed an in situ observation of cathodic biofilm growth. Autotrophic growth was confirmed via isotope analysis. As a natural polyhydroxybutyrate (PHB) producer, this novel species, Kyrpidia spormannii, coupled the production of PHB to CO2 fixation on cathode surfaces.Publicationtype: Journal ArticleScopus© Citations 27 34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Chromate resistance mechanisms in Leucobacter chromiiresistensChromate is one of the major anthropogenic contaminants on Earth. Leucobacter chromiiresistens is a highly chromate-resistant strain, tolerating chromate concentrations in LB medium of up to 400 mM. In response to chromate stress, L. chromiiresistens forms biofilms, which are held together via extracellular DNA. Inhibition of biofilm formation leads to drastically decreased chromate tolerance. Moreover, chromate is reduced intracellularly to the less-toxic Cr(III). The oxidation status and localization of chromium in cell aggregates were analyzed by energy-dispersive X-ray spectroscopy coupled to scanning transmission electron microscopy and X-ray absorption spectroscopy measurements. Most of the heavy metal is localized as Cr(III) at the cytoplasmic membrane. As a new cellular response to chromate stress, we observed an increased production of the carotenoid lutein. Carotenoid production could increase membrane stability and reduce the concentration of reactive oxygen species. Bioinformatic analysis of the L. chromiiresistens genome revealed several gene clusters that could enable heavy-metal resistance. The extreme chromate tolerance and the unique set of resistance factors suggest the use of L. chromiiresistens as a new model organism to study microbial chromate resistance.Publicationtype: Journal ArticleScopus© Citations 30 45 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Kyrpidia spormannii sp. nov., a thermophilic, hydrogenoxidizing, facultative autotroph, isolated from hydrothermal systems at São Miguel Island, and emended description of the genus KyrpidiaA Gram-stain-positive, rod-shaped, non-motile, spore-forming bacterium, strain EA-1 T , was isolated from hydrothermal sediment samples from the Azores (S~ao Miguel, Portugal). 16S rRNA gene sequence analysis of the isolated bacterium revealed a phylogenetic affiliation with the genus Kyrpidia. The sequence similarity of the five 16S rRNA gene copies to its closest relative, Kyrpidia tusciae, ranged from 97.79 to 97.85 %. The in silico estimate of DNA-DNA hybridization was 56.0 %. The dominant fatty acids of the novel isolate were anteiso-C17: 0 (49.9 %), iso-C17: 0 (23.0 %) and iso-C16: 0 (13.3 %), while the quinone detected was menaquinone MK-7. Analysis of polar lipids identified phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and additional unidentified compounds comprising two glycolipids, two phospholipids and two lipids. The presence of meso-diaminopimelic acid in the peptidoglycan and mannose, arabinose and ribose in the cell wall of strain EA-1 T were detected. The strain was able to grow heterotrophically as well as autotrophically with carbon dioxide as the sole carbon source and with hydrogen and oxygen as electron donor and acceptor, respectively. Based on its chemotaxonomic, physiological and genomic characteristics, the new strain is considered to represent a novel species within the genus Kyrpidia, for which the name Kyrpidia spormannii sp. nov. is proposed. The type strain is strain EA-1 T (=DSM 106492 T =CCOS1194 T ).Publicationtype: Journal ArticleScopus© Citations 19 36 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Complete genome sequence of Kyrpidia sp. strain EA-1, a thermophilic knallgas bacterium, isolated from the Azores(American Society for Microbiology, 2018-01-18); ; ; ; Kyrpidia sp. strain EA-1 is a thermophilic hydrogen-oxidizing bacterium isolated from hydrothermal systems at São Miguel Island, Portugal. Here, we present the complete genome sequence of the strain assembled to a single circular chromosome. The genome spans 3,352,175 bp, with a GC content of 58.7%.Publicationtype: Journal ArticleScopus© Citations 5 97 302