Photosynthesis and growth kinetics of Chlorella vulgaris R-117 cultured in an internally LED‑illuminated photobioreactor

The aim of this work was to correlate changes of photosynthesis activity vs. growth in Chlorella vulgaris R-117 (CCALA 1107), fast-growing and robust microalga cultured in an internally illuminated 10-L photobioreactor (PBR). The cultures were grown at high output irradiance provided by four LED light sources submerged in the culture when the light path was short, between 25-30 mm. The culture of Chlorella R-117 grown under 2,500 µmol(photon) m-2 s-1 attained a doubling time of 3.5 d and biomass density of 3.5 g(DM) L-1 after about 10-d period. When grown under 3,500 µmol(photon) m-2 s-1, the culture reached a doubling time of 1.7 d, and biomass density of ~5.5 g L-1 before entering the stationary phase. Electron transport rate changes correlated well with the culture growth demonstrating the usefulness of chlorophyll fluorescence for photosynthesis monitoring. This can be crucial for potential scale-up to large indoor PBRs to optimise culture growth.