Study of carotenoids in cyanobacteria by Raman spectroscopy

• The colours of the cyanobacteria are due to the carotenoids compounds.
• Different protective dyes are synthesized according to the strain necessity.
• Thereby, our proposition is the peridinin pigment as the polyene majority.
• We use the Raman spectroscopy (RS) as a tool for the dye assignment.
• The RS is a preliminary tool for discussion about dyes and the synthetic priority.

Cyanobacteria have established dominant aquatic populations around the world, generally in aggressive environments and under severe stress conditions, e.g., intense solar radiation. Several marine strains make use of compounds such as the polyenic molecules for their damage protection justifying the range of colours observed for these species. The peridinin/chlorophyll-a/protein complex is an excellent example of essential structures used for self-prevention; their systems allow to them surviving under aggressive environments. In our simulations, few protective dyes are required to the initial specimen defense; this is an important data concern the synthetic priority in order to supply adequate damage protection. Raman measurements obtained with 1064 and 514.5 nm excitations for Cylindrospermopsis raciborskii and Microcystis aeruginosa strains shows bands assignable to the carotenoid peridinin. It was characterized by bands at 1940, 1650, 1515, 1449, 1185, 1155 and 1000 cm−1 assigned to ν(CCC) (allenic vibration), ν(CC/CO), ν(CC), δ(CH, C-18/19), δ(CH), ν(CC), and ρ(CCH3), respectively. Recognition by Raman spectroscopy proved to be an important tool for preliminaries detections and characterization of polyene molecules in several algae, besides initiate an interesting discussion about their synthetic priority.

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