Dear Mr. Zarmi,

Our research investigate the impact of a design dark fraction. The latter is an unlit part of the photobioreactor. It can be a pump for a recirculation purposes or a degassor. So the dark fraction is not the dark zone that is present inside the photobioreactor because of the high concentration of the biomass or the high light. Joliot et al 2008 have studied the light pulses (light dark cycles) if I understood well. In their case, microalgae cells will experience light zone than dark zone in the same PBR for a very short time (in the order of ms). Marcell 2002 studied also the impact of light dark cycles and he found that it is beneficial for a time in the order of 100ms.

In our case, we built our pilot to make the microalgae cells pass into the dark fraction (so the unlit part) for a duration of 45s and 300s. We have varieted also the design dark fraction volume. We found that the impact is negative, we have a productivity loss.

We are working now on the photosynthetis response regarding this to understand what's happening.

I hope my anwer is helpfull, it's not an answer for your question because the context of the study is not the light dark cycle.

thank you and best regards,

Antoinette

Thank you very much. Your answer is very much to the point. I now understand that your dark times are much longer, so that transition to respiration is important.

Thanks again,

Yair