# Sustainable Microalgae and Cyanobacteria Biotechnology
## 2 Applications of Biotechnology on Microalgae and Cyanobacteria Utilization
### High Valuable Compounds from Microalgae
#### Phycobiliproteins  
The major antennae component of cyanobacteria and red algae contain phycobilins (phycoerythrobilin, phycoyanobilin, and phycourobilin), which are packed into complex structures called phycobilisomes. These complexes are linked to photosynthetic membranes [34]. Phycobilisomes are linear tetrapyrroles with a magnesium atom attached. The wavelength absorption range of these accessory pigments is 500-650 nm, with colors ranging from blue-green to green, yellow, orange, and red. Phycobiliproteins, unlike chl proteins and carotenoid proteins, are water soluble, and the pigments are covalently bound to apoproteins. In general, cyanobacterial species have three important protein-pigment complexes that are covalently linked to chromophores: C-phycocyanin (PC, \(\Delta\)max 610-620 nm), allophycocyanin (APC, \(\Delta\)max 650-655 nm), and phycoerythrin (PE, \(\Delta\)max 540-570 nm) [35].  
Phycocyanin is a blue pigment that has important applications as a food supplement and a fluorescent biomedical marker in a variety of pharmaceutical applications. Phycocyanin is made up of a protein moiety (and apoprotein subunits) and bilin-type chromophores. Phycocyanin accounts for approximately 0.439 g/g of cyanobacteria biomass [36], but the concentration of phycocyanin in the cell is completely dependent on environmental growth conditions. Phycocyanin is thought to be an accessory pigment that absorbs light energy and transfers it to chlorophyll-a [35]. Phycocyanin has been proposed by several authors as a carbon storage material [37] or as a nitrogen source during nitrogen deficiency [38]. Some cyanobacteria species, such as _Calothrix_ sp. [39], _Oscillatoria_ sp., [40],Phormidium_ sp., [41], and _Synechocystis_ sp., have previously been proposed as a source for industrial production of phycocyanin [42].  
Previous research found that highly purified phycocyanin (PC) extracted from the thermophilic cyanobacterium Thermosynechococcus elongatus had anti-cancer activity against three cancer cell lines: colorectal adenocarcinoma, hepatocellular carcinoma, and mammary gland breast carcinoma. An in vitro assay demonstrated the cytotoxic effect against cancer cells, yielding these results [35]. In another study, the combination effect of PC and betaine also showed a good result on the growth of A549 lung cancer, with a decrease in cancer cell viability of up to 60% through in vivo studies [43]. Previous research revealed that this PC has two protein bands visible in SDS-PAGE analysis: -phycyocyanin (15 kDa) and \(\beta\)-phyocyanin (16.5 kDa) [35]. Another study found that using PC had an effective inhibitory effect on A53T\(\alpha\)-synuclein and A\(\beta\)40/42 fibril formation at low stoichiometric ratios [44]. Further research should be conducted to identify natural biomolecules that can be used to develop therapeutic aids for protein-related diseases characterized by an inadequacy in protein folding, such as cataracts, Alzheimer's disease, and Parkinson's disease [44].