Light-emitting diodes (LEDs) for culturing microalgae and cyanobacteria

This review is focused on the use of light-emitting diodes (LEDs) as an artificial light source for photoautotrophic culture of microalgae and cyanobacteria. Photoautotrophic culture requires light. Natural sunlight is often used in large-scale culture, but artificial light is potentially useful for producing some high-value products. Compared to natural light, artificial lighting allows better control of light wavelength and intensity, and the duration of the photoperiod. Artificial lighting eliminates the inevitable diurnal and seasonal variations of natural light. The culture productivity and biochemical composition can be substantially influenced by manipulating the light regimen and the wavelength. Advantages of LEDs over other artificial light sources include a higher energy efficiency, a longer lifespan of the light source, a reduced heat emission, and a more precise spectral control, that is, narrowly defined illumination wavelengths. Compared to natural light, LEDs can be better integrated with various types of photobioreactors to obtain a more uniform light distribution on the surface of the photobioreactor and an improved light penetration in the culture. Wavelength of light (photons) impacts photosynthesis at the molecular level, as discussed in this review. The other light-associated factors affecting the production of biomass and metabolites are discussed.