Technische Universität Wien

High-performance thermoelectric (TE) materials near room temperature are crucial for cooling and energy harvesting applications. This study reports the outstanding thermoelectric performance of p-type Mn-doped Fe₂VAl Heusler alloy thin films, specifically Fe₂V_0.8Mn_0.2Al, prepared using magnetron sputtering. These films were deposited on insulating oxide substrates to eliminate any spurious contributions from the substrate. Large p-type Seebeck coefficients (S) have been observed for all films, revealing a maximum power factor of 4.26 mWK^-2m^-1 at 300 K. This study revealed thickness-dependent thermoelectric properties, with the highest power factor achieved in the 500 nm film. Films with d = 300 nm and 500 nm exhibit weak ferromagnetism. Hall resistivity measurements evidence an anomalous Hall effect (AHE) for the 300 nm and 500 nm samples. The AHE is strongest for the 500 nm film, consistent with a magnetic enhancement of the Seebeck coefficient and power factor. Additionally, we synthesized Al-rich p-type Fe₂V_0.9Mn_0.1Al_1.5 thin films at room temperature, 200°C, 400°C, and 600°C. The film deposited at 600°C exhibits an exceptional figure of merit ZT _appr ~0.8 and a power factor of 6.7 mW·K^-2·m^-1 at room temperature, which are respectively, 4 times and 1.5 times larger than the best values ever reported for any bulk or thin film p-type Fe₂VAl-based material.

The fight against climate change requires consideration of carbon as a critical parameter in production systems, with the ultimate aim of creating a truly sustainable circular carbon economy. In this context, microbial bioproduction systems are a promising route to renewably generate value-added chemicals and fuels. Methanol and formate have recently gained interest as microbial one-carbon feedstocks, which can be produced sustainably from carbon dioxide and renewable energy, are easy to store and transport and readily dissolve in aqueous solutions. Acetogenic bacteria are strictly anaerobic microorganisms that can grow autotrophically on molecular hydrogen or use methanol, formate, and carbon monoxide as their sole carbon and energy sources via the Wood-Ljungdahl pathway, the most energetically efficient carbon fixation pathway known to date. Here, known variants of the Wood-Ljungdahl pathway, the physiology of a selection of methylotrophic and formatotrophic acetogens, and emphasize recent advancements in bioprocessing with respect to quantification of acetogen metabolism of methanol and formate as well as research aiming at establishing novel bioprocesses are reviewed. Additionally, the tools available for physiological and metabolic studies as well as for metabolic and genetic engineering are discussed. Finally, the features and constraints that govern the bioenergetics and stoichiometry of acetogen metabolism during growth on methanol and formate are reviewed, and future perspectives of the field discussed. The high energetic efficiency with which acetogens can convert methanol and formate into products renders them highly attractive platform hosts in the circular carbon economy.

Ever since the potential of inclusion bodies (IBs) has been recognized, substantial advances have been made towards understanding IB processes and enabling efficient and controlled development strategies. Still, the influence of the chosen upstream processing (USP) strategy on the properties of inclusion bodies (IBs) and their refolding performance remains poorly understood. This work aims to target this challenge by investigating the influence of two chosen USP parameters, namely the specific substrate uptake rate and the temperature during induction, on IB titer, IB properties, namely IB purity, size and secondary protein structure of the IBs, as well as refolding yield of single-chain variable fragment M (scFvM) IBs. Contrary to findings in the literature, USP conditions neither had a statistically significant effect on the aforementioned IB properties nor on the refolding yield, but could clearly alter the IB titer. Our results provide detailed analytical insights on the independence of IB properties from USP conditions for this protein, while increasing the volumetric IB productivity proved feasible through variations in USP parameters. Therefore, titer maximization appears to be the sole optimization strategy for scFvM IBs and these findings may also apply to other target proteins with similar structural properties.