Novel photo-chemoautotrophic system combining microalgae and hydrogen oxidizing bacteria for microbial protein production from carbon dioxide

This study investigated the production of microbial protein (MP) using a novel microbial consortium composed of microalgae and hydrogen-oxidizing bacteria (HOB). This photo-chemoautotrophic consortium was aimed at capturing and valorising carbon dioxide (CO₂) while overcoming typical limitations of each microbial group. Batch tests were run under varying gas mixtures of oxygen (O₂), CO₂ and hydrogen (H₂) to assess process performance in terms of biomass growth, nitrogen assimilation, gas consumption, final biomass and microbial community composition. The consortium was compared to the single microalgae and HOB cultures grown under photo- and chemoautotrophic conditions, respectively. The consortium achieved significant growth (5.5 g VSS/L) under a non-explosive gas mixture, reaching a protein content of 40.3 ± 8.5 %. The consortium achieved up to 1.8- and 10-times higher biomass growth compared to the single microalgae and HOB cultures, respectively, showing a higher CO₂ consumption and stimulating photosynthetic O₂ production.