Lumostatic operation of bubble column photobioreactors for Haematococcus pluvialis cultures using a specific light uptake rate as a control parameter

This study proposes lumostatic operations using a specific light uptake rate (q_e) as a control parameter in order to maintain a desirable light condition. As a model system, bubble column photobioreactors have been operated lumostatically for photoautotrophic cultivations of Haematococcus pluvialis. Lumostatic operations were conducted at three levels of specific light uptake rates (q_e=1.5×10^-8, 3×10 ^-8, and 4.5×10^-8μEcell^-1s ^-1) and compared with constant light energy supply (I₀=40, 90, and 140μEm^-2s^-1). In the case of the lumostatic operation at 4.5×10^-8μEcell^-1s^-1, the cell concentration was enhanced over 250% than that obtained under constant light energy, without inducing astaxanthin accumulation. For the lumostat at q_e of 3.0×10^-8μEcell^-1s^-1, the cell concentration increased almost 200% than that of the control experiments. These results indicate that a specific light uptake rate can be a useful parameter for lumostatic operation of photobioreactors and that the productivity of vegetative stage can be greatly improved by regulating the light condition based on the specific light uptake rates.