Microalgae, the wonderful gift of nature
Bio-functional ingredients from microalgae
Antioxidants are the molecules of natural or synthetic origin that prevent, delay or neutralize the negative effects of oxidative stress caused by free radicals. Microalgae being photosynthetic organisms like that of higher plants generate free radicals during respiration and photosynthesis. They are therefore the richest natural source of antioxidants that nowadays received considerable commercial interests for health supplements. Human being generate free radicals only through respiration, but due to the modern life-style with improper diet may cause an imbalance between the levels of free-radicals and antioxidants required for disease-free health conditions. Microalgae are the resource for several types of water-soluble or lipid-soluble biomolecules with antioxidant activities and were proved to be useful health supplements. Usually, most of our required antioxidants are supplied through proper food intake and hence microalgal extracts or whole biomass can serve and antioxidants food supplement. Microalgal photosynthetic pigments such as Chlorophyll, carotenoids (astaxanthin, β-carotene, lutein, zeaxanthin, canthaxanthin) and phycobilipigments (phycocyanin, allophycocyanin and phycoerythrin present in red algae and cyanobacteria) have antioxidant activities and thus microalgae serve as natural antioxidant source. Microalgae also possess water soluble low molecular weight molecules including Mycosporine-like amino acids that have antioxidant activities.
Chlorophyll pigments
Chlorophyll-a is the major light harvesting pigment in microalgae and its content may be up to 5.6% of dry weight biomass. Chlorophyll-b (in chlorophyceae) and chlorophyll-c (in Bacillariophyceace and Rhodophyceaceae) are accessory light harvesting pigments present in microalgae at relatively very low quantities.
Phycocyanin
Phycocyanin, is the blue pigment of most cyanobacteria that serve as accessory photosynthetic pigment. Phycocyanin may reach upto 22% of dry weight biomass. Spirulina platensis is the richest natural source for commercial phycocyanin so far.
Allophycocyanin
Allophycocyanin is the deep blue colour protein pigment found in cyanobacteria and red algae. It has characteristic absorption peak at 650 nm and fluorescence peak at 660 nm. Maximum of 11% of dry weight biomass amount of allophycocyaninn was reported in Nostoc sp.
Phycoerythrin
Phycoerythrin (PE) is the red bilipigment found in red algae and in certain species of cyanobacteria. PE exists in various spectral forms with maximum absorption peak at 498 nm and is called phycourobilin, while maximum absorption peaks at 545 and 565 nm, is called phycoerythrobilin. PE may reach upto 8% of dry weight biomass.
Carotenoid pigments
Carotenoids are yellow, orange or red accessory pigments that help microalgae in trapping the light energy. Carotenoids also help preventing from photooxidative damages and from other stress environments. Freshwater microalga Haematococcus pluvialis is the richest natural source of carotenoid astaxanthin. Marine microalga Dunaliella salina is the richest natural source of β-carotene, followed by cyanobacterium Spirulina platensis. Other microalgae including cyanobacteria are potential source of various other types of carotenoids with antioxidant activities.
