The term "microalgae" is usually used in biotechnology in the broadest sense of the word for prokaryotic cyanobacteria and eukaryotic algae - unicellular and fibrous strains that are on the order of micrometers. It differs from macro algae (usually called seaweed) growing mainly in the seas, whose insoles reach a length of several meters. The smallest known microalgae is the single-celled marine cyanobacterium Prochlorooccus, which has an average of less than 1 micrometer.
Microalgae represent the oldest microorganisms that - more than 2.5 billion years ago - began to form the oxygen atmosphere of the Earth. They have evolved into a diverse
group of aquatic and soil species of unquestionable ecological importance, the distribution of which is incredible: they occur in all major ecosystems from cold polar regions to extremely acidic, alkaline or saline environments to hot springs and deserts. Microalgae perform photosynthesis and metabolic processes similar to higher plants, but have a significantly higher growth rate due to greater photosynthesis efficiency, very short reproductive cycles, simple cell structure with low demands on metabolic functions and competitive physiological processes (eg supportive development, flowering, fruit development, etc.).
Natural microalgae, phytoplankton, form the basis of the food chain. They grow in freshwater reservoirs, running waters and especially the seas, where they are responsible for almost half of global primary photosynthetic production. The result of the wide physiological diversity of microalgae species is the production of biomass containing various valuable substances (Table 1). Microalgae are their unique source - from raw biomass rich in proteins, oils, polysaccharides and antioxidants to valuable secondary metabolites with potential use in medicine.