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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 , Production of acetoin from renewable resources under heterotrophic and mixotrophic conditionsThis study aimed to reveal whether Cupriavidus necator H16 is suited for the production of acetoin based on the carboxylic acids acetate, butyrate and propionate under heterotrophic and mixotrophic conditions. The chosen production strain, lacking the polyhydroxybutyrate synthases phaC1 and phaC2, was revealed to be beneficiary for autotrophic acetoin production. Proteomic analysis of the strain determined that the deletions do indeed have a significant impact on pyruvate formation and its subsequent direction towards the introduced acetoin-synthesis pathway. Moreover, the strain was tested for its ability to use typical dark fermentation products under hetero- and mixotrophic conditions. Growth with butyrate and acetate led to low efficiencies, while 46.54% ±0.78 of the added propionate was converted into acetoin. Interestingly, mixotrophic conditions led to simultaneous consumption of acetate and butyrate with the gaseous substrates and lowered efficiency. In contrast, mixotrophic propionate consumption led to diauxic behavior and high carbon efficiency of 71.2% ±0.64.Publicationtype: Journal ArticleScopus© Citations 8 74 - 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