Plasma-Enhanced Cyanobacterial Biofertilizers for Sustainable Nitrogen Fixation in Rice Cultivation

We developed an atmospheric-pressure nonequilibrium plasma array jets device (N-APPJs) for sustainable cyanobacterial bioengineering, addressing key challenges in green agricultural biotechnology. This portable system combines operational safety with precise control of reactive oxygen and nitrogen species (RONS) to enhance the microbial biofertilizer performance. When applied to nitrogen-fixing Nostoc sp. FACHB-1042 for 30 s, the N-APPJs treatment increased nitrogenase activity by 258%. This enhancement was driven by key long-lived RONS in the liquid phase, primarily H2O2, NO2–, and NO3–, where the synergistic action of H2O2 and NO2– at optimal concentrations crucially stimulated metabolism without oxidative damage. In rice coculture systems, plasma-treated cyanobacteria demonstrated significant sustainability benefits: 78.8% higher shoot biomass, 20.4% greater total nitrogen content, and 61.4% more available phosphorus compared to controls. The system enhanced nitrate reductase activity by 23.9% and optimized the nitrate/ammonium ratios (54.8% improvement), suggesting more efficient nitrogen metabolism. This plasma-assisted approach exemplifies green engineering principles by (1) utilizing atmospheric-pressure operation for energy efficiency, (2) enabling precise microbial control without genetic modification, and (3) demonstrating scalable integration with agricultural systems to minimize chemical inputs. The technology bridges precision bioengineering with sustainable crop production, offering a practical solution aligned with circular economy principles in agriculture.