A novel electrolytic gas lift reactor for efficient microbial electrosynthesis of hydrogen-oxidizing bacterial single-cell protein from CO₂

Coupling water electrolysis with hydrogen-oxidizing bacteria (HOB) fermentation is a promising approach for single-cell protein (SCP) production. However, this inorganic-biological hybrid system is hindered by low efficiency, primarily due to the inhibition of electrochemical reactions on microbial activities and low hydrogen utilization. Here, we report an electrolytic gas lift reactor designed to improve the efficiency of this hybrid system for HOB-SCP production. By integrating the cathode of the electrolyzer with a gas lift reactor, the setup mitigated the inhibition of anodic reactive oxygen species on HOB and enhanced hydrogen utilization efficiency. By gradually increasing the current (1-2-4-6 A), the reactor achieved a maximum biomass yield of 0.20 g cell dry weight/L/d, a protein content of 58.3%, and a hydrogen utilization efficiency of 100%. The microbial community was dominated by HOB such as Ancylobacter (74.4%) and Xanthobacter (8.2%). These results indicated that the innovative reactor design effectively improved the performance of HOB-SCP production by inorganic-biological hybrid systems. The electrolytic gas lift reactor demonstrates substantial potential for scaling up and practical applications.