Dissolved oxygen concentration is a critical point for microalgae in large scale cultivation systems. Highly productive cultures inevitably generate a build-up of oxygen gradients along the reactor which can affect photosynthetic performance. In this study, a fast-growing strain of Chlorella vulgaris R117 was cultured outdoors in a thin-layer cascade during a one-week trial reaching a biomass productivity of 4 g DW L−1 d−1 (27 g DW m−2 d−1). High photosynthetic activity led to oxygen oversaturation of up to 400% in some parts along the culture units at midday. The aim was to examine the effect of high dissolved oxygen concentration on diurnal changes in the photosynthetic performance and growth of the Chlorella culture using multi-technique approach. Photosynthetic activity of Chlorella R117 culture was estimated in situ and ex situ using oxygen production and in vivo Chl a fluorescence measurements, which showed good correlation. The rates of electron transport and of oxygen production were related, but the values of the μmolelectrons/μmolO2 ratio was higher than predicted, suggesting the probable involvement of electron and oxygen consuming processes such as photorespiration and Mehler reaction. These processes probably function as photoprotective mechanisms, since no photodamage was observed in the Chlorella R-117 cultures. Depression (down-regulation) of photosynthetic activity due to the exposition to high dissolved oxygen concentration along the cascade area over time was observed. The usefulness of on-line measurements was demonstrated to obtain immediate and in-situ information on the physiological status of the culture. This data can be used in models of operation control for large-scale microalgae production units.
Bibliographical noteFunding Information:
This work was funded by National Sustainability Programme I of The Ministry of Education, Youth and Sports of the Czech Republic (project Algatech Plus LO1416 ) and in part by the EU programme Horizon 2020 (project SABANA, grant no. 727874 ) and Interreg Czech Republic-Austria programme (project Algenetics ATCZ15 ). TAR was supported by the Universidad de Buenos Aires , Argentina. FLF thanks Junta de Andalucía for financial support of the research group “Photobiology and biotechnology of aquatic organisms” ( FYBOA-RNM295 ). PCP was supported by the Santander scholarship to young research and project FONDECYT No 11180197 . AN thanks BARD Research Grant Award No. US – 4599-13R (The United States – Israel Binational Agricultural Research and Development Fund) and additional funds from the Israeli Ministry for Science and Technology and the Dead Sea-Arava Science Center (DSASC) to AN.
© 2020 Elsevier B.V.
- Chlorophyll fluorescence monitoring
- Outdoor mass cultivation
- Oxygen production
- PSII down-regulation
ASJC Scopus subject areas
- Agronomy and Crop Science