Mixed gas nanobubbles promote microbial CO₂ fixation: Universal verification, mechanism, and application

Low carbon fixation efficiency of chemoautotrophic microorganisms significantly hinders the advancement of non-photosynthetic microbial CO₂ fixation technology. In this study, the autotrophic metabolism was improved using the special properties of nanobubbles. For autotrophic strains containing form I or Ⅱ RuBisCO, nanobubbles significantly promoted their CO₂ fixation efficiency. Specifically, the promotion rates of CO₂ or O₂ nanobubbles were generally up to 582 %-1544 % or 394 %-1464 %, respectively. Moreover, nanobubbles with a mixture of CO₂ and O₂ as gas source demonstrated 16 %-140 % higher promotion efficiency than nanobubbles with only O₂ or CO₂. Mixed gas nanobubbles enhanced energy metabolism by promoting electron donor consumption and carbon metabolism by stimulating the activity of key carbon fixation enzymes. Additionally, mixed gas nanobubbles were applied to the soil to verify its effect on improving carbon sink. The results showed that nanobubbles could adsorb onto the soil and persist for extended periods, not only altering the soil's porous structure but also increasing the soil's organic carbon content by 24 %-33 %. This study presents a novel technology for improving microbial CO₂ fixation efficiency and soil carbon sink capacity.