Lorena Janssen - Academia.edu (original) (raw)

Papers by Lorena Janssen

Journal of Applied Phycology

The growth rate and CO2 biofixation rate of a photosynthetic organism depend basically on the ava... more The growth rate and CO2 biofixation rate of a photosynthetic organism depend basically on the availability of light, all other factors being optimum. In dense cultures of cyanobacteria or micro-algae intended for biomass production, incident irradiance on the reactor surface is not the same as the intensity which is received by cells, as irradiance is attenuated by cell absorption and the self-shading effect. In a well-mixed, dense culture, only the average irradiance, I av, can be considered responsible for the photosynthetic response. In this study, the photosynthetic response of Synechocystis sp., estimated from its specific growth rate, was measured for each I av in batch cultures irradiated with different levels of external irradiance, I ext. The specific growth rate of Synechocystis sp. depends on I av, in accordance with the model proposed by Muller-Feuga (J Exp Mar Biol Ecol 236:1–13, 1999). A non-linear regression analysis estimated a maximum specific growth rate of 0.108 h−1, at an I av of 930 μmol photons·m−2·s−1. This reveals that Synechocystis sp. is a highly light-tolerant strain, suitable for outdoor cultures. Higher I av levels caused photoinhibition in batch cultures. Parameters obtained from the Muller-Feuga model show that the minimum irradiance needed to start growth mechanisms becomes less as light availability decreases, i.e. cells become more efficient in the use of light when it is scarce. This observation suggests that choosing for low-light adaptation may be a good strategy to improve productivity in dense cultures, where light is a limiting factor.

Journal of Applied Phycology

The growth rate and CO2 biofixation rate of a photosynthetic organism depend basically on the ava... more The growth rate and CO2 biofixation rate of a photosynthetic organism depend basically on the availability of light, all other factors being optimum. In dense cultures of cyanobacteria or micro-algae intended for biomass production, incident irradiance on the reactor surface is not the same as the intensity which is received by cells, as irradiance is attenuated by cell absorption and the self-shading effect. In a well-mixed, dense culture, only the average irradiance, I av, can be considered responsible for the photosynthetic response. In this study, the photosynthetic response of Synechocystis sp., estimated from its specific growth rate, was measured for each I av in batch cultures irradiated with different levels of external irradiance, I ext. The specific growth rate of Synechocystis sp. depends on I av, in accordance with the model proposed by Muller-Feuga (J Exp Mar Biol Ecol 236:1–13, 1999). A non-linear regression analysis estimated a maximum specific growth rate of 0.108 h−1, at an I av of 930 μmol photons·m−2·s−1. This reveals that Synechocystis sp. is a highly light-tolerant strain, suitable for outdoor cultures. Higher I av levels caused photoinhibition in batch cultures. Parameters obtained from the Muller-Feuga model show that the minimum irradiance needed to start growth mechanisms becomes less as light availability decreases, i.e. cells become more efficient in the use of light when it is scarce. This observation suggests that choosing for low-light adaptation may be a good strategy to improve productivity in dense cultures, where light is a limiting factor.