Interactive effect of light quality and temperature on Chlamydomonas reinhardtii growth kinetics and lipid synthesis

The efficient operation of an algal photobioreactor (PBR) requires appropriate lighting conditions. Despite recent advantages in PBR design and operation, optimal lighting conditions are still not fully understood. This work focuses on the effect of light quality and culturing temperature on the algal growth kinetics and lipid content. The green alga Chlamydomonas reinhardtii was grown in batch culture in a constant-temperature incubator-shaker under LED light. Three light wavelength regimes were studied: blue light (peaking at 433 nm–447 nm, 458 nm–470 nm), white-yellow light (peaking at 456–458 nm in blue, 545 nm in green and 570 nm in yellow) and red-orange light (peaking at 580 nm–594 nm and 604 nm in yellow-orange, 630 nm and 656 nm in red, and 735 nm in IR). Results show that red-orange light obtained 38% higher biomass productivity than blue light at 24 °C, and blue light obtained 13% higher biomass productivity than red-orange light at 32 °C. Red-orange light or temperatures of 30–32 °C favored lipid accumulation with a lipid mass fraction and lipid concentration of 44% and 80% higher, respectively, compared to blue light at 24 °C. In the late exponential phase, when nutrients in the medium were still sufficient, light quality was the predominant factor controlling the lipid synthesis and accumulation. While in the late stationary phase under nutrient starvation, a strong interactive effect was detected between the light quality and temperature (P = 0.02) for lipid synthesis and accumulation. Under both temperature and nutrient stress, there was a reduced effect of the light quality on the lipid synthesis.