Accumulation of docosahexaenoic acid-rich lipid in thraustochytrid Aurantiochytrium sp. strain T66: effects of N and P starvation and O2 limitation.
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.
Jakobsen
Anita N
AN
Department of Biotechnology, Norwegian University of Science and Technology, 7491, Trondheim, Norway. anita.n.jakobsen@hist.no
Aasen
Inga M
IM
Josefsen
Kjell D
KD
Strøm
Arne R
AR
D000818:Animals; D003470:Culture Media / Q000737:chemistry; D004281:Docosahexaenoic Acids / Q000737:chemistry / Q000378:metabolism*; D005057:Eukaryotic Cells / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008055:Lipids / Q000737:chemistry / Q000302:isolation & purification; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*
D003470:Culture Media; D005231:Fatty Acids, Unsaturated; D008055:Lipids; D004281:Docosahexaenoic Acids; D010758:Phosphorus; D009584:Nitrogen; D010100:Oxygen