Effects of different combination of red, green and blue LED light spectrums on the growth of green algae chlamydomonas reinhardtii (chlorophyta)

The positive effects of LED light source recently used in algae biotechnology on growth and metabolite biosynthesis in microalgae are reported in scientific literature. In this study, the effect of white, monochromatic and combinations of red and blue lights in different ratios on the growth of green algae species Chlamydomonas reinhardtii (Chlorophyta), which is a model organism with high economic value in biotechnology field, were investigated. Additionally, the effect of green light gradual supplementation into red:blue light combination (1:2) percental increase of 0, 7.5, 15, 22.5, 30, and 37.5% in expense of red and blue lights was studied to evaluate the effect of green light supplementation on the growth and chlorophyll concentration in C. reinhardtii. The results showed that both growth rate and chlorophyll concentration were statistically higher under dichromatic red and blue light combinations of the ratios 1:2 and 2:1 with no statistical difference between the combinations. the order of growth rate was Red: Blue (1:2) < Red: Blue (2:1) < Red: Blue (1:1) < White < Red < Blue. Green light supplementation has not shown statistical differences from control group (red1: blue2). However, none of the green-supplemented cultures showed lower growth rate than control group despite having lower red: blue levels that reached 37.5%. Also, chlorophyll concentrations showed significantly higher levels in almost all green light supplemented groups than control. The results support the high adaptation mechanism by C reinhardtii under different light illumination and the additive effect of combining blue and red light through their differential enhancement of growth. Moreover, green light compensation mechanism is indicated in case of low blue and red light.