Designing a hybrid integrated bottled photobioreactor system for enhanced biomass yield and CO2 fixation during Limnospira fusiformis cultivation

This study introduces a novel approach to optimizing the cultivation of Limnospira fusiformis through a hybrid Integrated Bottled Photobioreactor (ITB-PBR). By combining this ITB-PBR with an open raceway pond, the system achieved substantial improvements in biomass yield around 38 % and 55 % higher than hybrid traditional PBR and open raceway pond, respectively, and a 42 % higher areal productivity relative to the hybrid traditional PBR. The hybrid ITB-PBR enhanced CO₂ fixation and photosynthetic efficiency, due to its efficient mixing and mass transfer capabilities. The integration of bottles within the column PBR reduced mixing time by 13 % and increased the mass transfer coefficient by 16 %. Additionally, the optimized design of the hybrid ITB-PBR, through generation of vortices within its sections, facilitated efficient movement of microalgae between light and dark regions, leading to a 9 % boost in photochemical efficiency (Fv/Fm) and a 5 % increase in chlorophyll content. The hybrid ITB-PBR also showed a remarkable 79 % increase in CO₂ fixation compared to conventional reactor. The hybrid ITB-PBR ensured continuous access to both light and carbon sources, resulting in higher biomass yields and enhanced growth by overcoming the common challenges of hybrid traditional PBR, such as poor light penetration and insufficient CO₂ dissolution.