Abstract
Flashing lights are next-generation tools to mitigate light attenuation and increase the photosynthetic efficiency of microalgal cultivation systems illuminated by light-emitting diodes (LEDs). Optimal flashing light conditions depend on the reaction kinetics and properties of the linear electron transfer chain, energy dissipation, and storage mechanisms of a phototroph. In particular, extremely short and intense light flashes potentially mitigate light attenuation in photobioreactors without impairing photosynthesis. Intelligently controlling flashing light units and selecting electronic components can maximize light emission and energy efficiency. We discuss the biological, physical, and technical properties of flashing lights for algal production. We combine recent findings about photosynthetic pathways, self-shading in photobioreactors, and developments in solid-state technology towards the biotechnological application of LEDs to microalgal production.
Highlights
To prevent photo-damage and inhibition of the phototroph under cultivation by too intense light flashes, the repetition rate of the light-dark transition and the relative proportion of the light flash period within the flashing cycle should be adjusted to the biological reaction kinetics of photosynthetic processes and energy dissipation mechanisms
PSII by the water oxidising complex (≈ 1-3 ms). To mitigate such imbalances in the linear electron transfer chain, flashing light may be tailored to a flash period duration of a few hundred picoseconds to reduce efficiently the reaction centre II without triggering excitation dissipation mechanisms, and a dark period of 3-5 ms to allow the timely oxidation of plastoquinol, avoiding the overreduction of the PQ pool
Data beyond these conditions will be of particular interest for artificial light-based microalgal production
Summary
Microalgae are a promising biological resource for the mass production of lipids, sugars, polymers or proteins for the food, feed and chemical industries [1]. To prevent photo-damage and inhibition of the phototroph under cultivation by too intense light flashes, the repetition rate of the light-dark transition (i.e., flashing light frequency, f) and the relative proportion of the light flash period (i.e., the duty cycle, ø) within the flashing cycle should be adjusted to the biological reaction kinetics of photosynthetic processes and energy dissipation mechanisms ( often referred to as non-photochemical quenching or NPQ). Well-engineered luminaries are essential to emit efficiently flashing light regimes that are advantageous for phototrophic cultivation [4, 12]. Balancing these factors, flashing light can result into higher growth performance per input energy as if the same light energy is supplied in a continuous way [4, 12]. The flash intensity and the duty cycle are inversely proportional at a given averaged light intensity
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