A fermentation strategy for producing docosahexaenoic acid in Aurantiochytrium limacinum SR21 and increasing C22:6 proportions in total fatty acid

During the fermentation process, dissolved oxygen values and carbon-to-nitrogen ratios are critical factors influencing DHA productivity. This study employed an intermittent oxygen feeding method to maintain a 50% dissolved oxygen level and produced a dissolved oxygen fluctuation environment to facilitate both Aurantiochytrium limacinum SR21 growth and lipid accumulation. Study results indicated that at a 1.25 C:N ratio and medium composition of 100 g L−1 glycerol, 40 g L−1 yeast extract, and 40 g L−1 peptone, A. limacinum SR21 achieved biomass at 61.76 g L−1, lipid content at 65.2%, DHA concentration at 20.3 g L−1, and DHA productivity at 122.62 mg L−1 h−1, this result were better than most similar researches. Dissolved oxygen fluctuation environment also altered the fatty acid composition of A. limacinum SR21. In the late period of the fermentation process, C16:0 fatty acid ratios decreased significantly to below 5%, and C22:6 fatty acid ratios increased to 70%.