Comparative analysis of DHA positional distribution and triacylglycerol molecular species in algal oil (Schizochytrium sp.) from different oil processing

This study aims to analysis the content and positional distribution of docosahexaenoic acid (DHA, 22:6 n-3) in algal oils (Schizochytrium sp.) using both Candida antarctica Lipase B (CAL-B)-catalyzed-transesterification combined with GC and 13C NMR. The triacylglycerol (TAG) molecular species in algal oils were also identified and quantified using LC-MS. The algal oils were from 3 kinds of oil processing including crude oil (CAO), liquid phase and solid phase oils from fractionation (LAO and SAO) as well as re-esterified triacylglycerol (rTAG). Algal oils contain 55%-97% polyunsaturated fatty acids (PUFAs) and 45%-80% DHA of the total oil; and DHA dominantly esterified at sn-2 position of glycerol backbone with the ratio of sn-2 DHA to total DHA ranged from 32% to 48%. A total of 42 TAGs were identified including 27 TAGs contained DHA, of which the 22:6/22:6/22:5 and 22:6/22:6/22:6 were the predominant species. The lipids containing DHA of algal oils are influenced by the fractionation processing. Compared with physical modified algal oils, rTAG has high DHA content (-80%, P < 0.05) but lower sn-2 DHA relative content (-32%, P < 0.05). This study provides an effective analysis scheme for high-PUFA-oils which will be used to develop novel functional oils.