Enrichment of nitrogen-fixing hydrogen-oxidizing bacteria community for efficient microbial protein production in airlift reactor.

Autotrophic nitrogen-fixing hydrogen-oxidizing bacteria (NF-HOB) have the capability to directly utilize carbon dioxide and dinitrogen for the sustainable production of microbial protein (MP), offering a promising alternative for food and feed applications. However, the low production rate of MP remains a major bottleneck for the practical implementation of NF-HOB. This study enriched a highly active and stable NF-HOB functional community for enhanced MP production. Utilizing an airlift reactor and implementing a two-stage gas supply strategy achieved a maximum cell dry weight (CDW) of 4.8 g/L and a biomass yield of 0.25 g CDW/L/day, surpassing previously reported values. The produced MP exhibited an essential amino acid profile superior to soybean meal and comparable to fish meal, with a notable accumulation of branched-chain amino acids (BCAAs). These findings provide new insights into NF-HOB enrichment strategies and further highlight their potential as a sustainable platform for MP production.