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In the present study, the total lipids from Schizochytrium sp. were ethylated, and ethyl esters (EE) enriched in C22:6n-3(DHA) were obtained through molecular distillation and converted to glyceride form via lipase-catalyzed glycerolysis under vacuum with activated clay as absorbents in non-solvent system. Total lipids were extracted from dry powder of Schizochytrium sp., which was followed by lipase catalyzed ethylation. EE with 83.04% DHA Downloaded by [North Carolina State University] at 08:41 30 March 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 was obtained through a three-stage procedure of molecular distillation. The effect of vacuum, temperature, reaction time, substrate ratio, and enzyme dosage on glycerolysis was investigated.Vacuum and increase in temperature had a positive effect on glycerolysis, and the increase in substrate ratio led to an increase in TAG content but a decrease in EE conversion. The adsorption of glycerol onto activated clay played a positive role in glycerolysis, and the operational stability of immobilized lipase. The conditions which gave the glycerides with more than 75% TAG were 60°C, 24h, 0.048mol EE, 0.016mol glycerol, 2.25g activated clay, and 3% Lipozyme435, and the immobilized lipase showed good operational stability in 10 batches of reactions with activated clay as absorbent.

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Using squalene as reaction medium was tried for the enzymatic synthesis of ether lipids rich in docosahexaenoic acid (DHA) via transesterification of alkylglycerols (AKG) obtained from shark liver oil and DHA-enriched ethyl esters (DHA-EE) from Schizochytrium sp. The effects of reaction time, temperature, molar ratio (AKG /DHA-EE), and enzyme dosage were investigated. DHA conversion of 74.47% was achieved for 48 hours of reaction at 60 C using a molar ratio of 1:2 and an enzyme dosage of 30% based on AKG in the presence of squalene with Lipozyme ® 435 (Novozymes, Tianjin, China) as the catalyst. With a high boiling point, squalene could act as a solvent without being vaporized from the reaction system under vacuum and improve the operational stability of immobilized lipase, which may be useful for enzymatic reactions under vacuum for lipid modification with byproducts of low boiling points.The scaled-up reactions were performed at 60 C for 48 hours with a Lipozyme 435 dosage of 30%, and the 138 J Am Oil Chem Soc J Am Oil Chem Soc (2020) 97: 135-140

A method of gas chromatography/mass spectrometry (GC/MS) was established to determine the fatty acids of Ulva pertusa Kjellm. The total lipids of Ulva pertusa Kjellm were extracted using Folch method, derivatized with HCl-CH3OH solution, and analyzed by GC/MS. The fragmentation patterns and mass spectrometry characteristics of saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids were analyzed and concluded by regular patterns of organic mass spectrometry. According to the database index and standard controls, twenty-four fatty acid components in Ulva pertusa Kjellm were identified, and the contents of 9,12,15-octadecatrienoic acid, 4,7,10,13-hexadecatetraenoic acid and 6,9,2,15-octadecatetraenoic acid accounted for 45.14% of the total fatty acids. The qualitative results of fatty acids in Ulva pertusa Kjellm show that it is very useful in identifying fatty acid methyl esters by characteristic ions, especially polyunsaturated fatty acid methyl esters.