Microalgae growth in ultra-thin steady-state continuous photobioreactors: assessing self-shading effects.

To disclose the net effect of light on microalgal growth in photobioreactors, self-shading and mixing-induced light-dark cycles must be minimized and discerned from the transient phenomena of acclimation. In this work, we performed experiments of continuous microalgal cultivation in small-scale photobioreactors with different thicknesses (from 2 to 35 mm): working at a steady state allowed us to describe the effect of light after acclimation, while the geometry of the reactor was adjusted to find the threshold light path that can discriminate different phenomena. Experiments showed an increased inhibition under smaller culture light paths, suggesting a strong shading effect at thicknesses higher than 8 mm where mixing-induced light-dark cycles may occur.