Aerobic bacteria that oxidise hydrogen, commonly referred to as Knallgas bacteria, are chemoautotrophic microorganisms that oxidise molecular hydrogen while fixing carbon dioxide into cellular material. Historically studied as model systems for lithoautotrophic metabolism, these organisms have regained attention because of their potential for the use of renewable hydrogen, for the production of biomass independent of agricultural land, and for the conversion of carbon dioxide coupled with electrochemistry.
Among them, Cupriavidus necator has emerged as a promising industrial platform, while thermophilic hydrogen oxidisers with a high affinity for hydrogen, such as Kyrpidia spormannii, are increasingly explored in bioelectrochemical systems. Despite the growing interest, substantial gaps remain between laboratory demonstrations and scalable industrial performance.
This review analyses the physiological characteristics of Knallgas bacteria, including their growth kinetics and the parameters of hydrogen oxidation, and evaluates how these translate into gas fermentation and into oxic microbial electrosynthesis.
Particular emphasis is placed on the key engineering limitations: the mass transfer of hydrogen, the partitioning of electrons during aerobic metabolism, the safety constraints of the reactors and the scaling of electrochemical surfaces.
Vivien Jesenofsky, Johannes Gescher, Miriam Edel (2026). Limits of Knallgas bacteria for autotrophic CO₂ conversion: physiology, H₂ kinetics and reactor constraints. Current Opinion in Chemical Engineering 54, 101302.
