Philipp Hartmann’s PhD defense- 14/04/14

PhD defense “Effect of hydrodynamics on light utilization in large scale cultures of microalgae” by Philipp HARTMANN, Wednesday May 14th @ 14H00 in Salle Trégouboff, OBSERVATOIRE OCEANOGRAPHIQUE, STATION ZOOLOGIQUE, Villefranche sur mer

“Microalgae are often seen as a promising candidate to contribute to energy generation in the future. However, the link between the energy contained in the biomass and the required energy to grow the microalgae, especially to mix the culture, is complex. Mixing has a direct effect on photosynthesis since it affects the way cells are successively transported between light and dark zones, especially the hydrodynamics modulates the frequency at which light is percept by the cells. In this thesis the question of nonlinear response of the photosynthesis process to varying light signals at different time scales has been investigated. Firstly, the effect of light-dark cycle frequency on the response of a mechanistic model for photosynthesis and growth has been studied. It is shown that increasing the light supply frequency enhances photosynthetic efficiency. A model for photoacclimation has been developed assuming both a change in the number and the cross section of the photosystems. The proposed concepts have been experimentally validated using a self-developed LED device to expose the green algae Dunaliella Salina to light-dark cycles at different frequencies. The results support model hypotheses, i.e. mid-term photoacclimation depends on the average light intensity. Finally, a 3D hydrodynamic model for a raceway type culturing device has been used to compute Lagrangian trajectories numerically. Based on the trajectories, time-dependent light signals for individual cells have been calculated. Using these light signals, a photosynthesis model was integrated in order to investigate the dependency of photosynthetic efficiency on hydrodynamic regime.”

Jury members:

Olivier Bernard, LOV/INRIA
Antoine Sciandra, LOV/INRIA
Clemens Posten, KIT (Karlsruhe)
Jérémy Pruvost, GEPEA (Nantes)
Alain Wande Wouver, University de Bruxelles
Jérome Morchain, INSA Toulouse