Conversion of gaseous one carbon substrates (CO, CO₂) and H₂ by acetogenic bacteria is a promising technology to establish sustainable bioproduction scenarios. The thermophilic acetogen Thermoanaerobacter kivui (Topt = 66 °C) grows on H₂/CO₂ in chemically defined mineral medium with growth rates (doubling time: 2 h), exceeding those of mesophilic acetogens. Nevertheless, there is currently no bioprocessing system available for quantitative characterization of T. kivui as a model thermophilic acetogen under well-defined bioreactor conditions. In this study, we established a continuous high-temperature gas fermentation system and characterized T. kivui wildtype as well as a strain adapted to grow on CO (referred to as CO-1). T. kivui CO-1 grew in a 100 % CO gas phase in chemically defined mineral medium with a growth rate of up to 0.25 h⁻¹ (doubling time: 2.8 h) and adaptation occurred in as little as 30 generations, similar to previous work by Weghoff and Müller (2016) using rich medium [1]. Genomic analysis of the clonal strain CO-1 using short and long read sequencing technologies indicated that a handful of SNPs and large-scale genomic rearrangements might be responsible for the successful adaptation of T. kivui to CO. To characterize the physiology of strain CO-1 in more detail, steady state chemostat cultures operated at specific growth rates of 0.10-0.20 h⁻¹ were used to quantify growth, gas consumption, and acetate production on H₂/CO₂, syngas and pure CO. Transcriptomic analysis gave further clues how the physiology of strain CO-1 is adapted to growth on CO. Furthermore, synthesis gas generated from biomass gasification was successfully evaluated as a feedstock for gas fermentation with T. kivui in continuous mode in 200 mL stirred tank bioreactors as well as a 20 L bubble column bioreactor. Collectively, the knowledge gained in this study represents a first step toward establishing high-temperature gas fermentation processes.