Enrichment of DPAn‑6 and DHA from Schizochytrium sp. Oil by Low-Temperature Solvent Crystallization

The main objective of the present work was to increase the contents of n-6 docosapentaenoic acid (DPAn-6, C22:5n-6) and docosahexaenoic acid (DHA, C22:6n-3) from Schizochytrium sp. oil. Low-temperature solvent crystallization was carried out to effectively concentrate DPAn-6 and DHA by using oil (triglyceride, TAG) and free fatty acids (FFAs) as starting materials. Several variables, such as the fractionation temperature, type of solvent, FFA (TAG)/solvent ratio, and fractionation time, were investigated for optimization of the process. The optimum concentrations of DPAn-6 and DHA when using FFAs as the starting material were found to be 26.26 ± 0.06% and 64.81 ± 0.69%, respectively, with acetonitrile at a 1:5 FFA/solvent ratio (w/v) upon crystallization at −60 °C for 80 min, with corresponding yields of 53.58 ± 2.14% and 52.57 ± 2.09%. In the case of TAG, the best result was obtained with acetone at a 10% oil/solvent ratio (w/v) upon crystallization at −80 °C for 4 h. In this case, the concentrations of DPAn-6 and DHA were 21.50 ± 0.27% and 53.87 ± 0.67%, respectively, with corresponding yields of 61.34 ± 1.33% and 62.46 ± 1.33%.