Cyanobacteria, especially the Nostoc and Spirulina genera, have been used for centuries as food, and currently their biotechnological potential is notable for the presence of several compounds relevant to the market, such as pigments and antioxidants. Cyanobacteria are appealing because of the increasing demand for natural pigments and antioxidants over the synthetic ones. Because cyanobacteria are photosynthetic organisms, one of the factors that most influences their metabolism is the level of incident light. However, the relationship between light intensity and the synthesis of bioactive compounds is not well understood in all species. Therefore, the present study aimed to determine the influence of different light intensities on the yield of biomass and pigments present in Nostoc spp. isolates. Lower intensities were more advantageous in terms of the yield of phycobiliproteins and chlorophyll a. For the isolates examined in the present study, the content of light-absorbing pigments, such as chlorophyll a and phycobiliproteins, was higher when the light availability was low. When the light availability increased, the content of these pigments decreased as a strategy for prevention of photo-oxidative damage caused by the production of free radicals. However, with respect to carotenoids, after the content of light-absorbing pigments decreased, it increased again at higher irradiances, which reflects the function of these pigments as dissipaters of excess absorbed light energy and as antioxidants in the photosynthetic apparatus.
Keywords: Carotenoids, Cyanobacteria, chlorophyll., phycobiliproteins, pigments