Mono- and dichromatic LED illumination leads to enhanced growth and energy conversion for high-efficiency cultivation of microalgae for application in space

• Published in: Biotechnology journal 2016-08, Vol.11 (8), p.1060-1071
• Main Authors: Wagner, Ines, Steinweg, Christian, Posten, Clemens
• Format: Article
• Language: English
• Subjects: Biomass; Biotechnology - instrumentation; Biotechnology - methods; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - growth & development; Chlamydomonas reinhardtii - radiation effects; Extraterrestrial Environment; Green gap; Illumination; Light; Microalgae - growth & development; Microalgae - radiation effects; Photo conversion efficiency; Photobioreactor; Photobioreactors; Sensory pigments
• ISSN: 1860-6768; 1860-7314
• DOI: 10.1002/biot.201500357

Illumination with red and blue photons is known to be efficient for cultivation of higher plants. For microalgae cultivation, illumination with specific wavelengths rather than full spectrum illumination can be an alternative where there is a lack of knowledge about achievable biomass yields. This study deals with the usage of color LED illumination to cultivate microalgae integrated into closed life support systems for outer space. The goal is to quantify biomass yields using color illumination (red, blue, green and mixtures) compared to white light. Chlamydomonas reinhardtii was cultivated in plate reactors with color compared to white illumination regarding PCE, specific pigment concentration and cell size. Highest PCE values were achieved under low PFDs with a red/blue illumination (680 nm/447 nm) at a 90 to 10% molar ratio. At higher PFDs saturation effects can be observed resulting from light absorption characteristics and the linear part of PI curve. Cell size and aggregation are also influenced by the applied light color. Red/blue color illumination is a promising option applicable for microalgae‐based modules of life support systems under low to saturating light intensities and double‐sided illumination. Results of higher PCE with addition of blue photons to red light indicate an influence of sensory pigments. Quality of light influences growth and physiology of microalgae via accessory and sensory pigments. Experimental results from this study indicate that for dichromatic red/blue LED illumination within the range of low to saturating light intensities highest photo conversion efficiency was achieved for the green alga Chlamydomonas reinhardtii. Furthermore size of the cells as well as aggregation and pigment content were dependent on the applied light color or color mixture.