Abstract
The present investigation evaluates the potential of three cyanobacteria species Anabaena cylindrica, Nostoc commune and Synechococcus BDUSM-13 for photo-protecting mycosporine-like amino acids (MAAs) synthesis using bicarbonate-based culture system. Current investigations witnessed noteworthy bicarbonate tolerance of all species (NaHCO(3); 0.5, 1 and 2 g L(- 1)) in terms of their growth rate, chlorophyll content, biomass productivity and carbon fixation ability. Among all strains, Synechococcus BDUSM-13 showed maximum surge in specific growth rate (i.e. 0.72 day(-1)) at 1 g L(-1), productivity (i.e. 0.92 ± 0.06 g day(-1) L(-1)) and chlorophyll content (i.e. 0.09 g L(-1)) at 2 g day(-1) L(-1). Synechococcus cells were also has the 0.48 g dw(-1) carbon content with highest CO(2) fixation rate (i.e. 0.653 g.CO(2) mL(-1) day(-1)) at 2 g L(-1). Though, they were not able to produce MAAs after long UV-B exposure (i.e. 24 and 48 h). A. cylindrica strain was the most competent species for the bicarbonate-based approach, produced UV-protecting iminomycosporine compound (i.e. shinorine, λ (max) at 334 ± 2 nm) along with carbon fixation (i.e. 0.49 g CO(2) mL(-1) day(-1)) at 2 g L(-1) NaHCO(3). This suggests the bicarbonate supplementation during cultivation is a promising strategy to increase cellular abundance, biomass productivity and carbon fixation in cyanobacteria. However, UV-B irradiation may cause species-specific differences in the MAAs synthesis to produce UV-protecting compounds.