Microalgae as a source of fatty acids

Microalgae are a very diverse group of organisms that consist of both prokaryotic and eukaryotic forms. Although most microalgae are phototrophic, some species are also capable of heterotrophic growth. Some species of microalgae can be induced to overproduce particular fatty acids through simple manipulations of the physical and chemical properties of the culture medium. As a result of the profound differences in cellular organization and growth modes and the ability to manipulate their fatty acid content, microalgae represent a significant source of unusual and valuable lipids and fatty acids. The utilization of microalgal lipids and fatty acids as food components requires that these organisms be grown at large scale under controlled conditions. Several growth systems have been developed for large scale growth of phototrophic microalgae using either natural sunlight or artificial light, but their lack of control of culturing parameters or their high cost of operation have limited their utility for the production of food products. Instead, large scale cultivation of heterotrophic microalgae using classical fermentation systems provides consistent biomass produced under highly controlled conditions at low cost. Microalgae contain many of the major lipid classes and fatty acids found in other organisms. However, they are also the principal producers in the biosphere of some polyunsaturated fatty acids, especially docosahexaenoic acid (DHA). The high DHA content found in some algae is currently being utilized to supplement infant formula to enable it to more closely resemble human breast milk. Thus, the commercialization of DHA from microalgae demonstrates the value of these organisms as a source of useful fatty acids.