Photosynthetic efficiency and oxygen evolution of Chlamydomonas reinhardtii under continuous and flashing light

• Published in: Applied microbiology and biotechnology Vol. 97; no. 4; pp. 1523 - 1532
• Main Authors: Vejrazka, Carsten, Janssen, Marcel, Benvenuti, Giulia, Streefland, Mathieu, Wijffels, René H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-02-2013; Springer Nature B.V
• Subjects: Algae; Biological Evolution; Biomass; Biomedical and Life Sciences; Biotechnological Products and Process Engineering; Biotechnology; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - chemistry; Chlamydomonas reinhardtii - genetics; Chlamydomonas reinhardtii - metabolism; Chlamydomonas reinhardtii - radiation effects; Chlorophyll; cyanobacteria; Efficiency; Evolution; growth; Influence; irradiance; Kinetics; Life Sciences; Light; microalgae; Microalgae - chemistry; Microalgae - genetics; Microalgae - metabolism; Microalgae - radiation effects; Microbial Genetics and Genomics; Microbiology; Oxygen; Oxygen - chemistry; Oxygen - metabolism; photobioreactors; Photosynthesis; phytoplankton; Productivity; Respiration; Studies; Netherlands; Photosynthetic efficiency; Flashing light; PI curve; Microalgae; Quantum yield
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-012-4390-8

As a result of mixing and light attenuation in a photobioreactor (PBR), microalgae experience light/dark (L/D) cycles that can enhance PBR efficiency. One parameter which characterizes L/D cycles is the duty cycle; it determines the time fraction algae spend in the light. The objective of this study was to determine the influence of different duty cycles on oxygen yield on absorbed light energy and photosynthetic oxygen evolution. Net oxygen evolution of
Chlamydomonas reinhardtii
was measured for four duty cycles (0.05, 0.1, 0.2, and 0.5) in a biological oxygen monitor (BOM). Oversaturating light flashes were applied in a square-wave fashion with four flash frequencies (5, 10, 50, and 100 Hz). Algae were precultivated in a turbidostat and acclimated to a low photon flux density (PFD). A photosynthesis–irradiance (PI) curve was measured under continuous illumination and used to calculate the net oxygen yield, which was maximal between a PFD of 100 and 200 μmol m
−2
 s
−1
. Net oxygen yield under flashing light was duty cycle-dependent: the highest yield was observed at a duty cycle of 0.1 (i.e., time-averaged PFD of 115 μmol m
−2
 s
−1
). At lower duty cycles, maintenance respiration reduced net oxygen yield. At higher duty cycles, photon absorption rate exceeded the maximal photon utilization rate, and, as a result, surplus light energy was dissipated which led to a reduction in net oxygen yield. This behavior was identical with the observation under continuous light. Based on these data, the optimal balance between oxygen yield and production rate can be determined to maximize PBR productivity.