Long‐term adaptive response to high‐frequency light signals in the unicellular photosynthetic eukaryote Dunaliella salina

Abstract

Productivity of microalgal cultivation processes is tightly related to photosynthetic efficiency, and therefore to light availability at the cell scale. In an agitated, highly turbid suspension,the light signal received by a single phytoplankton cell moving in a dense culture is a succession of flashes. The growth characteristics of microalgae under such dynamic light conditions are thus fundamental information to understand nonlinear properties of the photosynthetic process and to improve cultivation process design and operation. Studies of the long term consequences of dynamic illumination regime on photosynthesis require a very specific experimental set-up where fast varying signals are applied on the long term. In order to investigate the growth response of the unicellular photosynthetic eukaryote Dunaliella salina (Chlorophyceae) to intermittent light exposure, different light regimes using LEDs with the same average total light dose were applied in continuous cultures. Flashing light with different durations of light flashes (△t of 30 s, 15 s, 2 s and 0.1 s) followed by dark periods of variable length (0.67 ≤ L:D ≤ 2) yielding flash frequencies in the range 0.017-5 Hz, were compared to continuous illumination. Specific growth rate, photosynthetic pigments, lipid productivity and elemental composition were measured on two duplicates for each irradiance condition. The different treatments of intermittent light led to specific growth rates ranging from 0.25 to 0.93 day(-1) . While photosynthetic efficiency was enhanced with increased flash frequency, no significant differences were observed in the particular carbon and chlorophyll content. Pigment analysis showed that within this range of flash frequency, cells progressively photoacclimated to the average light intensity.

How Mixing and Light Heterogeneity Impact the Overall Growth Rate in Photobioreactors

“…5 of the Supporting Information. The transition between asymptotic kinetics for various light efficiencies are correctly described by our model with a unique time constant τ = 0.3 s. Similar behaviors and time constants can be found in the literature for other photosynthetic biomass with the same orders of magnitude and frequencies , , , , resp. for Dunaliella, Phaeodactylum, Nanochloropsis, Chlamydomonas , and Chlorella .…”

“…This effect is usually called flashing light effect (FLE) , . Its experimental quantification has been investigated , either by controlling the culture medium flow rate from enlightened to dark zones or directly by temporally managing the light energy transmitted to the microalgae , , . These results prove that some inertia exists in the response of algae to light variation: it cannot be assumed that the growth rate is a function of the local light intensity only.…”

The influence of photoperiod and light intensity on the growth and photosynthesis of Dunaliella salina (chlorophyta) CCAP 19/30

“…The actual pool size of glycerol however could be a reflection of multiple survival strategies under high light intensity since glycerol can also be used for membrane (triglyceride) regeneration, or stored in the form of starch. In some lipid-storing green algae (Combe et al., 2015, Yilancioglu et al., 2014) oxidative stress either caused by nitrogen depletion or by exposure to excess light or by application of exogenous H 2 O 2 is correlated with an increase in triglycerides content (but also see (Ben-Amotz et al., 1985)). Glycerol can also serve as a biocompatible solute or chemical chaperone to assist in refolding damaged proteins (Lamitina et al., 2006).…”

Productie van zoutwateralgen voor toepassingen in food (en feed) deelrapport I : Werkpakketten 1&2 van project Foodgrade productie van zoutwateralgen: deelrapport I: Achtergrondinformatie zoutwateralgen: selectie van soorten en omgevingsomstandigheden

“…Microalgen foto-acclimatiseren aan het beschikbare licht om hun lichtverzamelende efficiëntie aan te passen (Combe et al, 2015). Dit gebeurt door fysieke aanpassingen van het fotosynthese systeem binnen 1 celgroeicyclus.…”