A novel photobioreactor creating fluctuating light from solar energy for a higher light-to-biomass conversion efficiency

Microalgae represent an exciting resource for biomass, biofuel, valuable chemicals, and they contribute to CO₂ sequestration, thereby mitigating the increase in global warming. Similar to the other solar energy harvesting techniques for commercial purposes, the productivity of algal photosynthesis depends on the absorption and utilization efficiency of the solar irradiance by algae. Here we demonstrate a novel tubular photobioreactor that generates fluctuating light of controlled successive high and low intensities from sunlight, resembling light behavior in aquatic ecosystems, which favors the microalgae growth. The developed photobioreactor significantly increased the photosynthetic rate and growth of microalgae, with a higher light-to-biomass conversion efficiency than conventional photobioreactors, as cell doubling rate and biomass productivity increased >55% when the fluctuating frequency was set at 60 Hz providing ∼100% and ∼30% of total intensity, successively. The proposed photobioreactor enables an efficient mechanism that introduces a sufficient light-dose to the photosynthesizing organisms without fronting moments of photoinhibition or limiting photosynthesis by dark intervals, which can be a feasible and promising technology for large-scale production of microalgae.