Review of the structures and functions of algal photoreceptors to optimize bioproduct production with novel bioreactor designs for strain improvement

Microalgae are important renewable feedstock to produce biodiesel and high‐value chemicals. Different wavelengths of light influence the growth and metabolic activities of algae. Recent research has identified the light‐sensing proteins called photoreceptors that respond to blue or red light. Structural elucidations of algal photoreceptors have gained momentum over recent years. These include channelrhodopsins, PHOT proteins, animal‐like cryptochromes, and blue‐light sensors utilizing flavin‐adenine dinucleotide proteins. Pulsing light has also been investigated as a means to optimize energy inputs into bioreactors. This study summarizes the current structural and functional basis of photoreceptor modulation to optimize the growth, production of carotenoids and other high‐value metabolites from microalgae. The review also encompasses novel photobioreactor designs that implement different light regimes including light wavelengths and time to optimize algal growth and desired metabolite profiles for high‐value products. Microalgae consist of a plethora of photoreceptors receptive to different wavelengths of light. Shankar et al explained the importance of combining flashing light technology to map to the timescales of the photoreceptors which will lead to higher growth and metabolite productivity. These photoreceptors have been found to have an impact on the metabolites (especially carotenoids) at the molecular level. Novel photobioreactor designs with flashing light would help achieve this leading to improved microalgal strains.