Assessment of various colored lights on the growth pattern and secondary metabolites synthesis in Spirulina platensis

Cyanobacteria are photosynthetic aquatic microorganisms with light and dark photosynthesis reactions. In the present study, the effect of various light spectrums on light and dark reactions in Spirulina platensis was investigated. Chlorophyll a and phycocyanin as light reaction pigments and vitamin B₁₂ as a product of dark reaction were examined. S. platensis was exposed to four different color LEDs (white, red, blue, and yellow) at a fixed intensity. In light reaction, chlorophyll-a has the highest amount in blue, red, white, and yellow by 61.23, 45.46, 34.85, and 22.55 mg·g^-1, respectively. Those microalgae cultured in the blue color produced the highest amount of Chlorophyll a and c-phycocyanin. For C-phycocyanin, the highest to the lowest amount belong to blue, red, yellow, and white light by 168.6, 102.4, 85.77, and 53.81 mg·g^-1. The amount of vitamin B₁₂, from high to low is related to blue, red, white, and yellow light by 68.91, 59.73, 52.56, and 10.2 µg·g^-1. The trend of vitamin B₁₂'s production was similar to the chlorophyll a. In conclusion, blue color can increase the production of vitamin B₁₂ while keeping light reaction products at their highest level.