Enhancement strategies for the microbial protein production of nitrogen-fixing hydrogen-oxidizing bacterial community

The feasibility and superiority of utilizing nitrogen-fixing hydrogen-oxidizing bacteria (NF-HOB) for microbial protein (MP) production have been proposed. This study simulated air as the source of nitrogen and oxygen and enhanced production efficiency by employing key strategies, including continuous gas supply, selecting a higher hydrogen-to-oxygen ratio, designing initial community structures and domestication, and exploring appropriate hydraulic retention times (HRT) in continuous culture. The results demonstrated that sequencing batch culture achieved an MP titer of 0.98 g/L, with N ₂ fixation efficiency surpassing natural nodules by two orders of magnitude at 1.6 mg N ₂ per g dry biomass per hour. Under an HRT of 48 hours, MP volumetric productivity reached 2.297 mg/(L·h), accompanied by a maximum biomass yield of 0.11 g CDW/g COD-H ₂ . The high abundance of nitrogenase may provide crucial functional support, enabling the NF-HOB community to exhibit potential beyond previous understanding.