Model-based optimisation of microalgae growth under high-intensity and high-frequency pulsed light conditions

High-frequency pulsed light is a promising tool to enhance the performance of microalgae cultivation under artificial illumination. The quantitative comprehension of the effects of pulsed light on cell growth is essential to maximise biomass productivity and to increase the efficiency of artificial light for microalgae growth. In this work, a mathematical model is developed to capture the effect of high-frequency and high-intensity pulsed light in photobioreactors. The model extends the formulation proposed by Zarmi et al. 2020 (https://doi.org/10.1016 /j.isci.2020.101115) in order to account for the role of the dark time on photoproduction, photoinhibition effects, and the impact of mixing on cell growth in real photobioreactors. High-frequency pulsed light data from steady state and respirometry experiments are used to calibrate the model, which is demonstrated to shed light on the key photosynthetic mechanisms occurring in these extreme experimental conditions. Furthermore, it is shown how the model can be used to identify optimal operation conditions for microalgae growth, which are confirmed and validated by two respirometry experiments. In particular, it is shown that, for a fixed ratio of the light and dark times, a maximum of productivity can be achieved by minimising the dissipation of photons linked to high light conditions. The result paves the way towards a model-based approach to boost microalgae growth via optimisation of high-frequency high-intensity conditions in artificial light illumination.