Step experiments enable efficient exploration of microbial microaerobic steady states

Microbial processes are widely considered an alternative to classical chemical processes. However, the need for expensive nutrients often increases the costs of those processes. Microaerobic conditions increase the productivity of microbial processes without requiring expensive feeds. The literature describes several techniques to perform microaerobic experiments, but they are often limited to a single condition per experiment. We introduce step experiments to explore the microaerobic range of two different organisms. For this, we present two different strategies to adjust microaerobic conditions and validate them for two experimental setups: the microaerobic ethanol production using Escherichia coli grown on glycerol and the oxygen-limited polyhydroxybutyrate production of Cupriavidus necator using fructose. This work shows, for the first time, that Cupriavidus necator can produce polyhydroxybutyrate under heterotrophic, oxygen-limited conditions. We consider the proposed step-wise exploration a useful tool to perform microaerobic experiments in a more cost-and time-efficient way.