Operation at thermophilic temperatures: an underestimated asset for gas fermentation processes.

Gas fermentation technology presents great potential for enhancing the transition of our society to a sustainable era and alleviating the climate crisis. Scalability, robustness, and economic viability are decisive factors for successfully bringing emerging technologies on a commercial scale. Compared to traditional liquid phase fermentation, gas fermentation comes with additional challenges that mainly stem from gas-liquid mass transfer limitations. Operation at moderately elevated temperatures (50-60 °C) enhances the mass transfer rate and consequently productivity, thus improving the economic indicators. However, the scarcity of studies at the thermophilic range that could set the foundation for further scaling-up for products other than biomethane is noticeable. This review summarizes progress in the last 10 years regarding thermophilic CO2 and syngas fermentation and discusses a way forward to improving the competitiveness of gas fermentation technology via operation at elevated temperature.