Cyanobacteria are key primary producers in the global biosphere. Morphologically and
metabolically, they have prokaryotic and plant features. They harvest solar energy with
chlorophyll and phycobiliproteins and convert it into chemical energy via Photosystems
I and II. Phycobiliproteins assemble into phycobilisomes that absorb solar energy of
wavelengths that chlorophyll is not capable of absorbing. Structurally, phycobiliproteins
are globins and mostly polymerise into dodecameres that contain different amounts of
chromophores – phycobilins. The interactions between phycobiliproteins and phycobilins
dictate the specificity and functionality of the functional unit and the efficiency of energy
transfer between different phycobiliproteins. Besides phycobiliproteins, cyanobacteria
contain another protein pigment, the orange carotenoid protein, that functions
photoprotectively and contains a carotenoid chromophore. Different isolation processes
follow the same principles but differ in the concentrations and types of reagents, the
intensity of lighting used in the growth of cyanobacteria and incubation time depending
on the purpose of use of the final product and the production volume. Because of their
diverse and specific fluorescent properties, phycobiliproteins can be used for many
biotechnological, medical, food and cosmetic purposes.
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