Comparative study on light attenuation models of Galdieria sulphuraria for efficient production of phycocyanin

The thermo-acidophilic red microalga Galdieria sulphuraria is valuable especially for the intracellular thermostable phycocyanin with broad application prospects. Heterotrophy or photoinduction had been studied to enhance the production of phycocyanin at small-scale indoors. The aim of this study was to scale up the photoinduction process. The Cornet model could well describe and predict the light attenuation in G. sulphuraria suspension compared with the Lambert-Beer and hyperbolic models. Volume-averaged light intensity was the key parameter for photoinduction by testing respectively in 1-L column bioreactor, 3-L and 15-L flat plate photobioreactors indoors and outdoors, and supposed to be 600 μmol photons m −2 s −1 . Accordingly, amplifying photoinduction in 1.35-m 2 raceway pond outdoors was successfully carried out with the final cell dry weight of 2.37 g L −1 and phycocyanin up to 10.32%, which was comparable with that from Spirulina/Arthrospira and 3.82 times higher than that of heterotrophic cells of G. sulphuraria .