Biochemical Composition of Euglena gracilis Cells during Mixotrophic Growth in the Presence of Various Organic Substrates

The general biochemical composition and profile of low molecular weight metabolites of euglena ( Euglena gracilis Klebs.) cells grown in a mixotrophic culture supplemented with 0.5% ethanol, glucose, butanol, glycine, or glycerol was studied. Ethanol and glucose significantly stimulated the growth of the Euglena culture and the accumulation of storage compounds (paramylon and wax esters) in the cells. Butanol also contributed to the division of euglena cells and increased biosynthesis of protein, mono- and disaccharides, carotenoids, and tocopherols. Glycine and glycerol were metabolized more slowly than other substrates, and they accumulated in E. gracilis cells along with their direct derivatives. Glycine did not stimulate the growth of the culture, but it caused the accumulation of paramylon, organic acids of the Krebs cycle, and nitrogen-containing metabolites (chlorophyll, free amino acids, and nitrogenous bases) in the cells. Apparently, glycine is equally effectively used by Euglena as an additional source of both carbon and nitrogen under the conditions of mixotrophy. Assimilation of glycerol was accompanied by the accumulation of wax esters and the amino acids proline and ornithine in Euglena cells. In general, the results obtained demonstrate the ability of Euglena to significantly rearrange its metabolism during the assimilation of organic substrates of various chemical nature. Our data can be used in the context of E. gracilis practical applications.