Surfactants promote microbial CO2 fixation by enhancing nutrient utilization.

Surfactants, essential chemicals in daily life, are widely utilized across industries, from pharmaceuticals to agriculture, leading to their extensive presence in soils and aquatic environments. Meanwhile, as microbial metabolites, surfactants play a crucial role in enhancing nutrient utilization and promoting the rapid growth of microorganisms. This study aimed to use anionic, nonionic, and cationic surfactants to promote the growth of autotrophic microorganisms and break through the bottleneck of low microbial CO2 fixation efficiency. Among them, only anionic surfactants exhibited significant and universal promoting effects, with a maximum enhancement of 59 %-95 % on autotrophic strains utilizing the Calvin cycle. Furthermore, anionic surfactants, in combination with autotrophic microorganisms, were applied as amendments to improve soil, effectively increasing soil organic carbon content by 27 %-54 %. The long-term effects of these amendments depend on several mechanisms: promoting the Calvin cycle, enhancing soil organic carbon metabolism, facilitating nutrient transport, and reducing the abundance of genes associated with surfactant-degrading enzymes. This study contributes to a deeper understanding of the impacts of surfactants on the environmental CO2 fixation capacity and introduces a novel approach for enhancing soil carbon sink capacity.