Effects of different light spectra on the growth, productivity and photosynthesis of two acclimated strains of Nannochloropsis sp.

Light (quantity and quality) is the main growth-limiting factor of photoautotrophic microalgae. The integration of selective permeable photovoltaic filters above microalgae cultivation systems has been proposed previously to improve both production efficiencies and economics. In order to optimize such system, we evaluated the growth and photosynthesis of two spectrally acclimated strains of Nannochloropsis sp. (MUR 266 and MUR 267) grown semi-continuously under different light spectra in this study. No significant differences in biomass productivity were observed between cultures acclimated under full blue (BL, 400-525 nm) and narrow blue (LEDB, 430-490 nm) light when compared to the positive control of white light (WL, 400-700 nm), while lower values were recorded under red (RL, 600-700 nm) and pink light (PL, 400-525, 600-700 nm) for both species. When compared to WL, the photosynthetic performance (F-q'/F-m', alpha ETR, ETRmax) of both species was higher under both BL and LEDB except for the F-q'/F-m' of MUR 267 under LEDB. Chlorophyll a content was highest in cultures acclimated to RL while values tended higher under LEDB, RL and PL for MUR 267. Total lipid yield of both MUR 266 and MUR 267 was higher under BL and PL than WL. Based on the results of this study, theoretical modelling of the proposed photovoltaic-microalgae system indicate approximately 150-210 W m(-2) of electricity could be potentially generated if only blue wavelengths (BL and LEDB) are selectively filtered from sunlight while converting the remaining unused spectrum of sunlight into electricity.