Enhancement of biomass production in Scenedesmus bijuga high-density culture using weakly absorbed green light

To increase microalgae biomass production and support high density cultures in photobioreactors artificial illumination systems have been designed to increase photosynthetic activity. Supplemental lighting systems are commonly composed by a combination of chlorophyll (a + b) strongly absorbed wavelengths, while weakly absorbed wavelengths are not present. At this work we compared the photosynthetic activity and biomass production induced by chlorophyll (a + b) strongly versus weakly absorbed wavelengths in Scenedesmus bijuga microalgae cultures at different biomass densities. Photosynthetic activity and biomass production induced by 4 different wavelengths using LEDs (blue - peak at λ470 nm; green - peak at λ530 nm; red - peak at λ655 nm; and white-4100 K) were measured and analyzed on high-density cultures of S. bijuga. As culture density increased the chlorophyll (a + b) weakly absorbed green light penetrated deeper into the samples inducing higher oxygen evolution at culture concentration of 1.45 g L−1 compared to the chlorophyll (a + b) strongly absorbed red light. High-density culture (2.19 g L−1) cultivated under green light showed higher biomass production rate (30 mg L−1 d−1) with a 8.43% biomass growth in a 6-day period compared to the same quantum flux of red light that induced 4.35% biomass growth on the same period. The integration of green LEDs into photobioreactors lighting apparatus could improve the existing systems composed predominantly by red and blue LEDs increasing biomass productivity of high-density cultures at latter stages of microalgae cultivation.