Biomass composition
Microalgal biomass is composed mainly of proteins, lipids and carbohydrates, in proportions that depend on species and cultivation. Some, such as Spirulina, reach a very high protein content (≈60–70% of dry weight per FAO), while others stand out for their lipids or carbohydrates.
Added to this are high-value compounds: pigments (chlorophylls, carotenoids such as astaxanthin or beta-carotene, and phycobiliproteins such as phycocyanin), vitamins, minerals and polyunsaturated fatty acids. This richness underpins their applications in food, nutraceuticals, cosmetics and agriculture.
Primary and secondary metabolism
In primary metabolism, the microalga uses the energy and carbon fixed in photosynthesis to synthesise the cell's essential components: proteins, membrane lipids, storage carbohydrates and nucleic acids.
Secondary metabolism produces compounds that are not essential for growth but of great industrial interest, such as antioxidant carotenoids or certain fatty acids. Their synthesis is often triggered in response to specific environmental conditions.
How stress changes composition
Stress conditions —nutrient limitation (especially nitrogen), high light intensity or salinity— redirect metabolism toward the accumulation of storage or protective compounds.
Thus, nitrogen limitation favours lipid accumulation (of interest for biofuels), and high light induces carotenoids such as astaxanthin in Haematococcus or beta-carotene in Dunaliella. This principle is the basis of two-stage cultivation: first growth, then stress to accumulate the product.
FAQ
Mainly proteins, lipids and carbohydrates, plus pigments (chlorophyll, carotenoids, phycobiliproteins), vitamins, minerals and fatty acids; the proportions vary by species and cultivation.
Under nutrient limitation or high light, they redirect metabolism toward storage compounds (lipids) or protective ones (carotenoids such as astaxanthin), which is exploited in two-stage cultivation.
Sources
- Richmond, A. & Hu, Q. (eds.) (2013). Handbook of Microalgal Culture: Applied Phycology and Biotechnology. Wiley-Blackwell.
- Chisti, Y. (2007). Biodiesel from microalgae. Biotechnology Advances, 25(3), 294–306.
- Spolaore, P. et al. (2006). Commercial applications of microalgae. Journal of Bioscience and Bioengineering, 101(2), 87–96.
- Mata, T.M. et al. (2010). Microalgae for biodiesel production and other applications: A review. Renewable and Sustainable Energy Reviews, 14(1), 217–232.
Scientific outreach based on specialised literature. Scientific review: pending.
Other topics