Evaluation of potent cyanobacteria species for UV-protecting compound synthesis using bicarbonate-based culture system.

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 (NaHCO3; 0.5, 1 and 2gL- 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 1gL-1, productivity (i.e. 0.92 ± 0.06g day-1L-1) and chlorophyll content (i.e. 0.09gL-1) at 2g day-1L-1. Synechococcus cells were also has the 0.48gdw-1 carbon content with highest CO2 fixation rate (i.e. 0.653g.CO2mL-1day-1) at 2gL-1. Though, they were not able to produce MAAs after long UV-B exposure (i.e. 24 and 48h). 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 ± 2nm) along with carbon fixation (i.e. 0.49gCO2mL-1day-1) at 2gL-1 NaHCO3. 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.