@misc{BarthWernerOttoetal., author = {Barth, Maximilian and Werner, Magdalena and Otto, Pascal and Richwien, Benjamin and Bahramsari, Samira and Krause, Maximilian and Schwan, Benjamin and Abendroth, Christian}, title = {Microwave-assisted organic acids and green hydrogen production during mixed culture fermentation}, series = {Biotechnology for Biofuels and Bioproducts}, volume = {17}, journal = {Biotechnology for Biofuels and Bioproducts}, number = {1}, publisher = {Springer Science and Business Media LLC}, issn = {2731-3654}, doi = {10.1186/s13068-024-02573-7}, pages = {18}, abstract = {Background: The integration of anaerobic digestion into bio-based industries can create synergies that help render anaerobic digestion self-sustaining. Two-stage digesters with separate acidification stages allow for the production of green hydrogen and short-chain fatty acids, which are promising industrial products. Heat shocks can be used to foster the production of these products, the practical applicability of this treatment is often not addressed sufficiently, and the presented work therefore aims to close this gap. Methods: Batch experiments were conducted in 5 L double-walled tank reactors incubated at 37 °C. Short microwave heat shocks of 25 min duration and exposure times of 5-10 min at 80 °C were performed and compared to oven heat shocks. Pairwise experimental group differences for gas production and chemical parameters were determined using ANOVA and post-hoc tests. High-throughput 16S rRNA gene amplicon sequencing was performed to analyse taxonomic profiles. Results: After heat-shocking the entire seed sludge, the highest hydrogen productivity was observed at a substrate load of 50 g/l with 1.09 mol H2/mol hexose. With 1.01 mol H2/mol hexose, microwave-assisted treatment was not significantly different from oven-based treatments. This study emphasised the better repeatability of heat shocks with microwave-assisted experiments, revealing low variation coefficients averaging 29\%. The pre-treatment with microwaves results in a high predictability and a stronger microbial community shift to Clostridia compared to the treatment with the oven. The pre-treatment of heat shocks supported the formation of butyric acid up to 10.8 g/l on average, with a peak of 24.01 g/l at a butyric/acetic acid ratio of 2.0. Conclusion: The results support the suitability of using heat shock for the entire seed sludge rather than just a small inoculum, making the process more relevant for industrial applications. The performed microwave-based treatment has proven to be a promising alternative to oven-based treatments, which ultimately may facilitate their implementation into industrial systems. This approach becomes economically sustainable with high-temperature heat pumps with a coefficient of performance (COP) of 4.3.}, language = {en} } @misc{OttoWitkabelBarthetal., author = {Otto, Pascal and Witkabel, Philipp and Barth, Maximilian and Ammar, Aziz Ben and Rocktaeschel, Benjamin and Torrent, Daniel and Latorre-Per{\´e}z, Adriel and Krause, Maximilian and Abendroth, Christian}, title = {Adaptation of the anaerobic microbiome for in-situ power-to-CH4 processes through fuzzy logic control of H2 input}, series = {Bioresource technology reports}, volume = {31}, journal = {Bioresource technology reports}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2589-014X}, doi = {10.1016/j.biteb.2025.102194}, pages = {1 -- 11}, abstract = {This study presents the first application of fuzzy logic control (FLC) for regulating in-situ biological methanation via H2 injection in a fixed-bed reactor. Given the role of CH4 as a storable and infrastructure-compatible energy carrier, the aim was to improve CH4 production by dynamically adapting the H2 supply to the metabolic capacity of the microbiome. This will pave the way for the biological utilisation and storage of renewable H2. Over a 226- day operational period, H2 input was gradually increased based on real-time headspace gas measurements. Coupling the gradual increase in H2 supply with real-time gas composition data allowed the microbiome to adapt dynamically to changing process conditions. This approach led to a 49 \% increase in CH4 concentration, from 58.4 \% to 87.0 \%, and improved H2 conversion rates from 98.2 \% to 99.0 \%. Chemical analyses of COD, organic acids and nitrogen were performed, as well as taxonomic analyses using 16S rRNA sequencing, and multivariate methods were applied to confirm the adaptation of the microbiome to the FLC H2 injection. The adopted microbial community was dominated by strictly hydrogenotrophic methanogens, Methanoculleus and Methanobacterium, while increased abundances of Petrimonas, Rectinema, Syntrophomonas, and Geobacter indicate interspecies H2 transfer and syntrophic cooperation enhancing methanogenesis. These findings demonstrate that FLC-based H2 control enables dynamic adjustment of in-situ methanation, optimising the interaction between hydrogenogenic, fermentative, syntrophic acetate-oxidising, and hydrogenotrophic microorganisms. This work introduces an adaptive control strategy that supports stable and efficient bio-CH4 production and represents a significant advance in the field of power-to-gas technologies.}, language = {en} }