Euglena gracilis is neither a plant nor an animal. It generates its energy from light and CO2 purely photoautotrophically or it assimilates a carbon source chemoheterotrophically and transforms its chloroplasts into proplastids resulting in an animal cell structure. E. gracilis is a unicellular protist with a length of about 50 μm and developed by secondary endosymbiosis. For this reason, the chloroplasts have three membranes instead of a double membrane with a positive effect on the lipid content. It has no cell wall and is therefore easily bioavailable to humans. Euglena produces large amounts of vitamin E α-tocopherol and the β-1,3-glucan paramylon in granule form and has a good amount of lipids. Thanks to its contractile vacuole, Euglena is able to grow in a wide pH range from around pH 1–11. Cultivation in the acidic range thus simplifies cultivation on a technical scale under axenic conditions and enhances the solubility of solids and trace elements.