Electricity-powered artificial root nodule

Root nodules are agricultural-important symbiotic plant-microbe composites in which microorganisms receive energy from plants and reduce dinitrogen (N(2)) into fertilizers. Mimicking root nodules using artificial devices can enable renewable energy-driven fertilizer production. This task is challenging due to the necessity of a microscopic dioxygen (O(2)) concentration gradient, which reconciles anaerobic N(2) fixation with O(2)-rich atmosphere. Here we report our designed electricity-powered biological|inorganic hybrid system that possesses the function of root nodules. We construct silicon-based microwire array electrodes and replicate the O(2) gradient of root nodules in the array. The wire array compatibly accommodates N(2)-fixing symbiotic bacteria, which receive energy and reducing equivalents from inorganic catalysts on microwires, and fix N(2) in the air into biomass and free ammonia. A N(2) reduction rate up to 6.5 mg N(2) per gram dry biomass per hour is observed in the device, about two orders of magnitude higher than the natural counterparts.