# Biomolecules from Microalgae and Cyanobacteria: Applications and Market Survey
## 2 Microalgae
### Compositions and Technologies for Photoautotrophic Production of Microalgae and Cyanobacteria
#### 2.3.2 Photosynthetic Pigments  
Photosynthetic pigments of microalgae and Cyanobacteria are composed of chlorophyls, carotenoids, and phycobiliproteins (phycoerythrin, phycocyanin, and allophyco-cyanin). These three groups confer on microalgae their green, yellow/orange, and red/blue colors, respectively [62]. Natural pigments derived from microalgae and Cyanobacteria are of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy for photosynthesis but also play a role in photoprotective processes and display antioxidant, anticarcinogen, anti-inflammatory, antiobesity, antiangiogenic, and neuroprotective activities [24; 63]. Chlorophyls, which represent 0.5% to 1.5% of dry matter of microalgae and Cyanobacteria, are green, lipid-soluble pigments that play a major role in photosynthesis. They are tetra-pyrrolic macrocycles that are metalized by the presence of a complexed magnesium atom in their center and substituted by a phytyl chain, and they may be found in algae, higher plants, and Cyanobacteria.  
Chlorophyll a (Chl a) is present in all algae and has a major peak of light absorption at 683 \(\pm\) 20 nm due to the activity of photosystem II (PSII) and a second one at 700 to 750 nm due to both PSII and PSI [64]. This photosynthetic pigment is accompanied by accessory ones, including chlorophyls b, cl, c2 and d, phycobiliproteins, and carotenoids, which absorb at different wavelengths, thus expanding the spectrum of light-harvesting [20].  
Chlorophyll b, c, and d are variants of the Chl a found in green algae, brown algae, and Rhodophyta, respectively [65].  
Present as orange, red, or yellow colors, carotenoids (0.1% to 0.2% of dry matter) are responsible not only for the primary coloration of some algal groups but also for the mechanism of photosynthesis [66]. Carotenoids are chemically subdivided into deoxygenated carotenes, principally \(\beta\)-carotene, which is the most widely known of the carotenoids because of its antioxidant property as well as its dyeing power. Known as provvitamin A (precursor of vitamin A), \(\beta\)-carotene is mainly produced by the hypersaline species _Dunaliella salina_ (Chlorophyta), which can accumulate up to 98.5% of this compound in relation to its total carotenoids and about 13% of its dry biomass [39]. The second major group is the red oxygenated pigment. The freshwater chlorophyllceae _Haematococcus lacustris_ (Chlorophyta) is considered the primary source of astaxanthin as it was found to have the highest production on the industrial scale and can accumulate up to 81% of astaxanthin of its total carotenoids and about 7% of its dry weight [67, 68, 69]. This pigment is commercially produced from _Chlorella zofingiensis_, _Chlorococcus_ sp., and _Scendesmus_ sp. Astaxanthinis is described in the literature as having a higher antioxidant activity, health benefits, and dyeing power compared with those of \(\alpha\)- and \(\beta\)-carotenes, lutein and lycopene, canthaxanthin, and tocopherols [24, 39, 70]. Phycobiliproteins are colored (blue or red pigments) and water-soluble pigments organized in supramolecular complexes, called phycobilisomes, mainly present in Cyanophyta, Rhodophyta, Glaucophyta, and Cryptophyta. These complexes consist of 85% phycobiliproteins, of which 4 classes can be distinguished: allophycocyanin at the center of the complex, phycocyanin, followed by phycerythrin or phycoverythrocyanin at the level of the radiary projections. The characteristics of these pigments have been detailed by [PERSON] (1989) [71]. They absorb light in the visible region of 450-650 nm. They are used as natural colorants in the food, cosmetic, and pharmaceutical industries as substitutes for synthetic dyes. The species most commonly used for the production of phycobiliproteins are _Porphyridium_ sp. (Rhodophyta), _Arthrospira/Spirulina_ sp., and _Aphanizomenon flosaque_ (Cyanobacteria) [39, 70].