Enhancing pigment production with cyanobacteria-rich microbiomes: Effect of light quality and exposure time

Cyanobacteria-rich microbiomes may stand as a cost-effective source of pigments, as they exhibit improved stability in comparison to monocultures and do not require sterile media to grow. However, these bioproduct sources have not been thoroughly optimized for pigment production. The aim of the present study was to evaluate the effects of light quality and exposure time on pigment concentration and population distribution in 6 microbiomes rich in Synechococcus sp. and Synechocystis sp. A multivariable experimental design was implemented for selecting the optimal culture conditions in terms of light quality (white, red, green and blue) and exposure time (4 and 6 days). As a result, differential light quality exposures did not favor the growth of one species over another. Green light had a significantly positive effect on phycobiliprotein content in all microbiomes, with up to a 2.3-fold increase as compared to white light. Indeed, 4 days of exposure induced a change in phycobiliprotein composition in 5 microbiomes. Microbiome M11 was the best phycobiliprotein producer (content up to 145.5 mg gDW⁻¹). Meanwhile, carotenoid contents above 1.8 mg gDW⁻¹ were attained in all the microbiomes under optimized conditions. In conclusion, light quality modulation is a promising approach to stimulate the production of pigments in cyanobacteria-rich microbiomes.