A Broad Light-Harvesting Conjugated Oligoelectrolyte Enables Photocatalytic Nitrogen Fixation in a Bacterial Biohybrid

We report a rationally designed membrane-intercalating conjugated oligoelectrolyte (COE), namely COE-IC, which endows aerobic N-2-fixing bacteria Azotobacter vinelandii with a light-harvesting ability that enables photosynthetic ammonia production. COE-IC possesses an acceptor-donor-acceptor (A-D-A) type conjugated core, which promotes visible light absorption with a high molar extinction coefficient. Furthermore, COE-IC spontaneously associates with A. vinelandii to form a biohybrid in which the COE is intercalated within the lipid bilayer membrane. In the presence of L-ascorbate as a sacrificial electron donor, the resulting COE-IC/A. vinelandii biohybrid showed a 2.4-fold increase in light-driven ammonia production, as compared to the control. Photoinduced enhancement of bacterial biomass and production of L-amino acids is also observed. Introduction of isotopically enriched N-15(2) atmosphere led to the enrichment of N-15-containing intracellular metabolites, consistent with the products being generated from atmospheric N-2.

Automated summary

We report a membrane-intercalating conjugated oligoelectrolyte (COE) called COE-IC, designed to enable the aerobic N-2-fixing bacteria Azotobacter vinelandii to perform photosynthetic ammonia production through light-harvesting ability. COE-IC has a conjugated core that promotes visible light absorption, and can spontaneously associate with A. vinelandii to form a biohybrid where COE is intercalated within the lipid bilayer membrane. The resulting COE-IC/A. vinelandii biohybrid showed a 2.4-fold increase in light-driven ammonia production compared to the control, along with enhanced bacterial biomass and production of L-amino acids. Introduction of isotopically enriched N-15(2) atmosphere confirmed the generation of products from atmospheric N-2.