Accumulation of docosahexaenoic acid-rich lipid in thraustochytrid Aurantiochytrium sp. strain T66: effects of N and P starvation and O₂ limitation

• Published in: Applied microbiology and biotechnology Vol. 80; no. 2; pp. 297 - 306
• Main Authors: Jakobsen, Anita N, Aasen, Inga M, Josefsen, Kjell D, Strøm, Arne R
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.08.2008; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Animals; Applied Microbial and Cell Physiology; Aurantiochytrium; Biological and medical sciences; Biotechnology; Culture Media - chemistry; docosahexaenoic acid; Docosahexaenoic Acids - chemistry; Docosahexaenoic Acids - metabolism; Eukaryotic Cells - metabolism; Fatty acids; Fatty Acids, Unsaturated - metabolism; Fundamental and applied biological sciences. Psychology; Genes; Glycerol; Life Sciences; Lipid accumulation; Lipid extraction; Lipids; Lipids - chemistry; Lipids - isolation & purification; Microbial Genetics and Genomics; Microbiology; Nitrogen - metabolism; Nutrient starvation; Oxygen - metabolism; Phosphorus - metabolism; Ribosomal DNA; Studies; Taxonomy; Thraustochytrid; Lipid extraction; Lipid accumulation; Thraustochytrid; Docosahexaenoic acid; Nutrient starvation; Limitation; Lipids; Extraction; Aurantiochytrium Docosahexaenoic acid, Lipid accumulation· Lipid extraction, Nutrient starvation; n-3 fatty acid; Accumulation
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-008-1537-8

Aurantiochytrium sp. strain T66 was grown in batch bioreactor cultures in a defined glutamate- and glycerol-containing growth medium. Exponentially growing cells had a lipid content of 13% (w/w) of dry weight. A fattening of cells fed excess glycerol occurred in the post-exponential growth phase, after the medium was depleted of N or P. Lipid accumulation was also initiated by O₂ limitation (below 1% of saturation). N starvation per se, or in combination with O₂ limitation, gave the highest lipid content, i.e., 54% to 63% (w/w) of dry weight. The corresponding maximum culture density was 90 to 100 g/l dry biomass. The content of docosahexaenoic acid (22:6n-3) in N starved, well-oxygenated cells reached 29% (w/w) of total fatty acids but increased to 36% to 52% in O₂-limited cells, depending on the time span of the limitation. O₂-limited cells did not accumulate the monounsaturated fatty acids that were normally present. We inferred that the biological explanation is that O₂ limitation hindered the O₂-dependent desaturase(s) and favored the O₂-independent polyunsaturated fatty acid synthase. The highest overall volumetric productivity of docosahexaenoic acid observed was 93 mg/l/h. Additionally, we present a protocol for quantitative lipid extraction, involving heat and protease treatment of freeze-dried thraustochytrids.