Sustainable Outdoor Cultivation of <i>Cyanobacterium aponinum</i> under Artificial Lighting Using Low-Cost Fertilizer Medium

Outdoor cultivation of cyanobacteria represents a scalable solution for carbon capture and sustainable biomass production.However, natural sunlight presents fluctuating light intensity and spectral quality that limit the growth efficiency.This study developed an innovative cultivation system for Cyanobacterium aponinum under outdoor conditions using low-cost fertilizerbased medium and integrated lighting strategies for the first time.External peripheral light and internal white or red LED strips were applied to investigate their influence on biomass and biochemical composition.The optimal biomass of 1.37 g/L was achieved with 0.5 g/L fertilizer as a medium and increased to 1.73 g/L with 0.02 g/L Na 2 CO 3 supplementation under direct air capture (at 0.04% CO 2 ).Red LED enhanced C-phycocyanin and starch accumulation, while white LED improved cell growth.Extending illumination to 24 h further increased both biomass and starch yields.When the CO 2 enrichment of 1% (v/v) and combined peripheral and red LED light strips, it synergistically increased the biomass to 5.73 g/L and achieved a starch content of 51.6% ultimately.A scalable framework is presented for improving algal culture in outdoor conditions toward the development of scalable carbon-negative bioprocesses.