Light regime optimization in photobioreactors using a dynamic photosynthesis model

The real light pattern in photobioreactors - a gradual variation of irradiance - differs from the widely accepted simplification of considering it a succession of square, light and dark periods. In this work we will demonstrate that the dynamic model of photosynthesis proposed by Camacho Rubio et al. accurately predicts photosynthetic responses elicited from microalgae in varying light, regardless of the shape of the variation. We characterized the microalgae Scenedesmus almeriensis by obtaining its photosynthetic parameters from square-wave light experiments, and then we used those parameters to obtain the responses of the model to real light regimes and we compared them with experimental data obtained under the actual conditions. Further analysis showed that the predictions of the model fell within a 10% error, of which the major contribution is probably the experimental error of the measurements. We also used the model to optimize the design and operation of photobioreactors for productivity maximization, developing strategies to manage the biomass concentration and the mixing frequency. Our results indicate that the use of square-wave light regimes may severely skew the optimization process, rendering inefficient light use in the photobioreactor and over-estimated power inputs.