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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 , Design approach and performance of a scalable granular packed bed biofilter for electro-fermentationBioelectrochemical systems (BES) represent a promising technology for the production of energy, energy carriers, and chemicals; however, their implementation in industrial applications faces significant challenges related to scalability. In this study, we introduce a novel, scalable, single-chamber BES in which the working electrode is realised as a packed bed of electrically conductive equal-sized spheres made from a graphite-polymer composite. The reactor has a total volume of 3.56 L and a packed bed volume of 1.66 L with an electrode surface area of 1.06 m². A model microbial electrolysis / electro-fermentation of lactate to acetate was catalysed by the exoelectrogenic bacterium Shewanella oneidensis , achieving a maximum current density of 430 mA m<sup>-2</sup> at an anode potential of 300 mV relative to the standard hydrogen electrode.Publicationtype: Journal Article19 6 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Tuning membraneless microbial electrolysis cells operation alters efficiency and anodic microbiome toward scalable hydrogen production from sludge-hydrolysate(Elsevier, 2026-01-21); ; ; ; The practical implementation of microbial electrolysis cells (MECs) is hindered by challenges in optimizing system performance with complex substrates. This study addresses that gap by evaluating MECs fed with hydrolysate, an appealing substrate rich in organic-acids. Through systematic variation of substrate concentration (20–60 %), pH (5–8), and applied anodic potential ( 0.2 to +0.4 V vs standard hydrogen electrode [SHE]), the optimal operational conditions were defined as 40 %-hydrolysate, pH 8, and +0.4 V vs SHE, yielding a mean current density of 3.4 A/m2 and coulombic efficiencies (CE) of 38 % and 96 % based on total organic carbon (TOC) and total volatile fatty acids (VFAs), respectively. Scalability was demonstrated using a 10 L rotating disk bioelectrochemical reactor (RDBER) at 0 and 0.4 V vs SHE, achieving a maximum hydrogen production rate of 30.57 L/m2/d and minimal methane formation at 0.4 V. These findings offer a framework for optimizing MECs under real-feedstock conditions.Publicationtype: Journal Article33 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Efficacious enrichment of butyrate-oxidizing exoelectrogens upgrades energy recovery in relevant bioelectrochemical systems(Elsevier, 2024-11-01); ; ; ; Energy recovery via bioelectrochemical systems (BESs) while treating organic wastes has proven to be a promising technology. Organic waste hydrolysates are appealing feedstocks for BESs due to their richness in short-chain fatty acids rather than complex organics. However, butyrate, among the abundant acids in hydrolysates, has been found to particularly hinder the efficiency of BESs. The lack of efficient anodic butyrate-oxidizers appears to be critical; therefore, this study targeted the enrichment of an anodic community to enhance butyrate oxidation efficiency in BESs. We initially tested three different inoculum sources using butyrate as the sole electron donor. Then, through successive transfers of a bioanode piece to fresh anodes, significant improvement in coulombic efficiency (CE) from 9.4 % to 78.6 % was achieved over six transfers. The enriched bioanode was dominated by the bacterial genera Geobacter (72 %) and Sporomusa (16 %), which correlated positively with CE development over transfers. The metagenomic/transcriptomic analyses confirmed the key role of Geobacter in the anodic oxidation of butyrate, while Sporomusa likely displayed a syntrophic interaction, assimilating acetate from CO2 and excess H2. The enriched culture was further bioaugmented with Geobacter sulfurreducens and tested with real butyrate-containing hydrolysate, in which CE and maximum current density of 86.9 % and ∼3.5 A/m2 were achieved, respectively. Overall, the enriched butyrate-oxidizing culture, bioaugmented with G. sulfurreducens, proves efficient for BESs treating butyrate-rich waste-streams.Publicationtype: Journal Article13 22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Probing the robustness of Geobacter sulfurreducens against fermentation hydrolysate for uses in bioelectrochemical systemsIn this study, impacts of toxic ions/acids found in real fermentation-hydrolysate on the model exoelectrogenic G. sulfurreducens were investigated. Initially, different concentrations of acetate, butyrate, propionate, Na+, and K+ were tested, individually and in combination, for effects on the planktonic growth, followed by validation with diluted-hydrolysate. Meanwhile, it could be shown that (1) excess Na+ (≥100 mM) causes inhibition that can be reduced by K+ replacement, (2) butyrate (≥10 mM) induces higher toxicity than propionate, and (3) hydrolysate induces synergistic inhibition to G. sulfurreducens where organic constituents contributed more than Na+. Afterwards, compared with impacts on planktonic cells, the pre-enriched anodic biofilm of G. sulfurreducens in BESs showed higher robustness against diluted-hydrolysate, achieving current densities of 1.4–1.7 A/m2 (at up to ∼30 mM butyrate and propionate as well as ∼240 mM Na+). As a conclusion, using G. sulfurreducens in BESs dealing with fermentation-hydrolysate can be regulated for efficacious energy recovery.Publicationtype: Journal ArticleScopus© Citations 3 38 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Biological biogas upgrading in a membrane biofilm reactor with and without organic carbon sourceBiogas upgrading is a necessary step to minimize the CO2 of raw biogas and to make it suitable for gas liquefaction or introduction into the national gas grid. Biomethanation is a promising approach since it converts the CO2 to more methane on site, while taking advantage of the organisms responsible for biogas production in the first place. This study investigates the suitability of a pseudo-dead-end membrane biofilm reactor (MBfR) for ex-situ biogas upgrading using biogas as sole carbon source as well as for additional acetoclastic methanation when an organic carbon source is provided. Results prove that the concept of MBfR is especially advantageous for ex-situ hydrogenotrophic methanation of biogas CO2, yielding high product gas qualities of up to 99% methane. It is discussed that cross-flow membrane operation could reduce mass flux of inert methane through membranes, attached biofilms, and reactor liquid, and, thus, improve methanation space time yields.Publicationtype: Journal ArticleScopus© Citations 12 49 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Propionic acid production from food waste in batch reactors: Effect of pH, types of inoculum, and thermal pre-treatmentIn this study, lab-scale batch fermentation tests were carried out at mesophilic temperature (30 °C) to examine the influence of inoculum type, pH-value, and thermal pretreatment of substrate on propionic acid (PA) production from dog food. The selected inocula comprised a mixed bacterial culture, milk, and soft goat cheese. The batch tests were performed at pH 4, pH 6, and pH 8 for both, untreated and thermally pretreated food. Results show that the production of PA and volatile fatty acids (VFAs) in general were significantly dependent on the chosen inoculum and adjusted pH value. The maximum PA production rates and yields were determined for the cheese inoculum at pH 6 using untreated and pretreated dog food. PA concentration reached 10 g L−1 and 26.5 g L−1, respectively. Our findings show that by selecting optimal process parameters, an efficient PA production from model food waste can be achieved.Publicationtype: Journal ArticleScopus© Citations 32 43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Enhanced production of propionic acid through acidic hydrolysis by choice of inoculumBACKGROUND: In this study, the enhancement of propionic acid production from a model feedstock mimicking kitchen waste was investigated. For that purpose, two operational runs of a semicontinuous anaerobic hydrolysis reactor were carried out at pH 6.0 ± 0.1 and mesophilic (30 °C) temperature. Two different types of inocula, a mixed microbial culture selected over 24 months for growth on cellulose and a culture contained in goat cheese were compared. RESULTS: The results show that the goat cheese inoculum was significantly more efficient for propionic acid (PA) production. The highest propionic acid concentration achieved amounted to 139 mmol L−1 at a yield of 23.3 mg g−1 volatile solids (VS), which was 55% greater than what was achieved with the mixed culture. Furthermore, it was observed that propionic acid production was enhanced by a combination of high hydraulic retention time (HRT) with low organic loading rate (OLR), ensuring sufficient time for complete processing of the complex organic substrates. The fermentation could be kept in a stable process of propionic acid production at HRT of 20 days and a rather low OLR of 11.1 g L−1 day−1 VS. CONCLUSION: Our results give a better understanding of PA production in semicontinuous mode, applying optimized process parameters and selecting the adequate microbial community for inoculation. This study provides important information for the improvement of PA production from complex substrates for future industrial application. © 2020 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).Publicationtype: Journal Article35 - 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